CN1993933B - wireless transmission method - Google Patents

Abstract

Retransmission control retransmission is performed using a packet having a lower priority than a multicast packet transmitted from a transmitting apparatus to a plurality of receiving apparatuses. A transmission device for performing wireless multicast reliably receives a packet. A sequence number higher than the MAC layer is assigned to a transmission end side for each bandwidth-guaranteed or priority-controlled MAC layer multicast packet, and each reception terminal side detects data loss by using the sequence number and requests retransmission by using a bandwidth other than the guaranteed bandwidth or a packet lower than the priority. The transmitting terminal retransmits the data packet using a frequency band other than the guaranteed frequency band or a data packet of the priority or less. Thus, when transmitting video, audio, and data to a plurality of receiving terminals using a bandwidth-guaranteed or priority-controlled MAC layer multicast packet, the plurality of receiving terminals can receive good video, audio, and data.

Description

wireless transmission method

technical field

In particular, the present invention relates to a wireless transmission method that uses retransmission processing to improve transmission reliability when using wireless technology to transmit image and sound data in multipoint transmission or broadcast transmission.

Background technique

As a conventional wireless transmission method, in order to improve the reliability of wireless multicast transmission, there is a method of repeatedly transmitting a multicast packet from the beginning (for example, refer to Patent Document 1). FIG. 55 shows a transmission time chart of the conventional wireless transmission device described in Patent Document 1. FIG.

In FIG. 55 , the vertical axis in the left column shows the terminal type, and the horizontal axis shows the time axis. 600 , 601 , 602 , 603 , 604 , and 605 are multicast packets simultaneously transmitted from the transmitting terminal to the first receiving terminal, the second receiving terminal, and the third receiving terminal object. 606 and 607 are unicast packets individually transmitted from the transmitting terminal to the first receiving terminal and the second receiving terminal object. 707 is a unicast packet for retransmitting the unicast packet 607 . 6061 is an Ack packet which is a confirmation of successful reception of the unicast packet 606 . 6072 is a Nack packet which is a reception failure acknowledgment of the unicast packet 607 . 7071 is an Ack packet which is a confirmation of successful reception of the retransmitted unicast packet 707 .

In the first half of the time chart, a multicast packet is simultaneously wirelessly multicast from the transmitting terminal to the first receiving terminal, the second receiving terminal, and the third receiving terminal. In the second half of the time chart, a unicast packet 606 is wirelessly unicasted from the transmitting terminal to the first receiving terminal, and a unicast packet 607 is wirelessly unicasted from the transmitting terminal to the second receiving terminal.

Next, the multicast and unicast operations of the wireless transmission device will be described using the above transmission timing chart.

Generally, in multicast, the receiving terminal does not return an Ack packet (or a Nack packet, which is a reception failure acknowledgment packet) of the MAC layer packet to the transmitting terminal. Therefore, in multicast transmission, retransmission control using Ack packets (or Nack packets) cannot be performed, and it is difficult to secure transmission reliability. In wired transmission, since the transmission quality is superior to that of wireless transmission, there may be practically no problem even if retransmission control using Ack packets (or Nack packets) is not performed, but in many cases, the wireless transmission path Multicast in is impractical due to the low quality of the transmission.

In order to improve this situation, in the wireless multicast transmission of the conventional wireless transmission device, a method of increasing the reception probability is adopted by repeatedly transmitting the multicast packets 600, 602, and 604 in the first half of the timing chart from the beginning. . In FIG. 55, multicast packets 600, 602, and 603 are repeatedly transmitted twice. The duplicate packets of multicast packets 600, 602, and 604 are 601, 603, and 605, respectively.

In FIG. 55 , the first receiving terminal failed to receive the multicast packet 600 in the first transmission, but received it correctly in the second transmission 601 . The same situation also occurs in the second receiving terminal, third receiving terminal, and broadcast packets 602, 603, 604, and 605.

Generally, if the probability of a receiving error in one transmission is set as Pe, then in n repetitions, the probability of at least one normal reception in n repetitions is P=1-Pe^n. If the normal reception probability is calculated when Pe=0.1, n=1, 2, 3, then

When n=1, P=1-0.1^1=0.9,

When n=2, P=1-0.1^2=0.99,

When n=3, P=1-0.1^3=0.999,

Use repeated transmissions to increase the probability of reception.

In the unicast transmission in the second half of the time chart, since the retransmission control using the Ack packet (or Nack packet) is usually performed, even if, for example, the second unicast packet (sending terminal → second receiving terminal) in FIG. 55 Transmission of the packet shown in ) fails to be received, and the reception probability can be increased by sending the retransmission packet 707 of the second unicast packet. In addition, whether the sending terminal has received the Nack packet 6072 or whether the Ack packet has not been received is used to determine the determination of retransmission. Finally, when the transmitting terminal receives the Ack packet 7071, the retransmission control ends.

Patent Document 1: Japanese Unexamined Patent Publication No. H10-173668 (pages 1-8, FIG. 6 )

However, in the above-mentioned conventional configuration, since the multicast packet or the broadcast packet is transmitted multiple times from the beginning, in order to increase the reception probability of the multicast packet or the broadcast packet, a huge amount of time proportional to the number of repetitions is required. Transmission band. In particular, when securing a transmission band in advance and transmitting packets in multicast or broadcast, it is necessary to secure a frequency band that is a multiple of the minimum number of repetitions of the transmission band required, and compress other packet transmission and reception bands.

Contents of the invention

The present invention solves the above conventional problems, and an object of the present invention is to provide a wireless transmission method that improves frequency band utilization efficiency and improves reception probability in wireless multicast or broadcasting.

In order to achieve the above object, the first invention is a wireless transmission method, which performs Mac layer multicast transmission or broadcast transmission between the sending terminal and the receiving terminal, wherein, the following steps are included:

On the sending terminal side, temporarily store a plurality of data groups higher than the MAC layer; assign sequence numbers for detecting data loss by the receiving terminal side to each of the plurality of data groups higher than the MAC layer; by band guarantee type or priority A high multicast or broadcast packet conveys data to which the sequence number is assigned;

On the receiving terminal side, temporarily store a plurality of received data groups including sequence numbers transmitted by multicast or broadcast packets of a band-guaranteed type or higher priority; In the group, using the serial number given by the sending terminal side, detecting a missing data group from the received data group; performing a resend request for the detected missing data group; and

On the sending terminal side, the sequence number is used to retransmit data higher than the MAC layer whose loss is detected on the receiving terminal side.

Invention effect

According to the above-mentioned wireless transmission method, it is possible to realize conventional low-quality wireless multicast transmission or broadcast transmission while keeping the frequency band utilization efficiency in a good state during band securing type or priority control type wireless transmission. Increased reliability.

Here, it is preferable to perform a step of retransmitting higher-level data than the MAC layer on the transmitting terminal side.

The transmission control of the retransmission data is performed with the same priority as, second, or lower priority than the multicast or broadcast packet of the band securing type or high priority.

In addition, it is preferable that on the transmitting terminal side, a step of retransmitting higher-level data than the MAC layer is performed.

It has a first sub-step of sending and resending data using unicast data packets; and a second sub-step of sending and resending data to a plurality of receiving terminals using multicast or broadcast data packets.

The first sub-step combines at least a part of a plurality of data groups higher than the MAC layer, and transmits the combined data using the unicast packet.

In addition, it is preferable that on the receiving terminal side, the step of requesting retransmission of the detected missing data group is the same as, or second, or less The priority of the resend request packet is controlled.

Preferably, on the receiving terminal side, the step of performing the retransmission request of the detected lost data group has the first substep, using unicast data packets, to send the retransmission request data; or the second substep, using multicast or broadcast Data packet, send and then send the request data.

Preferably, on the sending terminal side, when retransmitting data higher than the MAC layer, time limit is imposed on the retransmission.

On the transmitting terminal side, the step of retransmitting higher-level data than the MAC layer transmits retransmission request data including a plurality of sequence numbers of the detected missing data group using one unicast packet.

In addition, in the multicast method of the present invention, in a network communication system, stream data such as images or audio and asynchronous data such as Internet data are mixed and transmitted between a transmitting terminal and a plurality of receiving terminals. For each cycle of the communication cycle, set the stream transmission period in which the required transmission frequency band is secured in advance; and the asynchronous transmission period in which asynchronous data is transmitted,

During the streaming transmission period, the transmitting terminal multicasts and distributes stream data to a plurality of receiving terminals, and the receiving terminal judges the error of the received stream data, and if the stream data cannot be received correctly, during the asynchronous transmission period, it sends a message to the transmitting terminal A resend request of the streaming data is sent, and when the sending terminal receives the resending request from the receiving terminal, the streaming data is resent by multicast during the streaming transfer period of the next communication cycle.

Here, during asynchronous transmission, the transmitting terminal and all receiving terminals transmit asynchronous data after waiting for a time given by a product of a randomly selected natural number and a predetermined time before transmitting asynchronous data including a retransmission request.

Preferably said natural number randomly selected before sending a resend request is smaller than said natural number randomly selected before sending other asynchronous data.

The multicast communication method of the present invention is used by a transmitting terminal that multicasts distribution stream data to a plurality of receiving terminals, wherein, in each fixed cycle,

The multicast sending step is to send the stream data as a multicast packet; the delivery confirmation step is to confirm whether the distribution of the stream data to the receiving terminals is successful, and the result is obtained as a delivery confirmation result; and the retransmission step is, According to the result of the delivery confirmation, resend the stream data that failed to be distributed, and within the certain period, if the remaining time of the certain period is predicted to be less than a threshold, the sending terminal performs the transmission before the delivery confirmation step The step of the step ends, and the processing of the transmitting terminal moves to the next step.

Here, it is preferable that the resending step includes a multicast resending step for resending the stream data whose distribution failed by using multicasting, and the multicast resending step is within the certain period, the before the multicast sendout step described above.

Preferably, the resending step includes a unicast resending step of resending the stream data whose distribution failed by unicast, and the unicast resending step is within the certain period, the multiple The point transfer sending step and the delivery confirmation step are followed.

Preferably, said resending step includes a multicast resending step of resending said stream data whose distribution failed by multicasting; and a unicast resending step of resending all stream data whose distribution failed by unicasting. The retransmission of the stream data, the multicast retransmission step is performed first within the certain period, the multicast sending step is performed second, and the delivery confirmation step is performed third, the The unicast resending step is carried out fourthly, and when the predetermined period passes, the unicast resending step ends the processing and proceeds to the next processing of the predetermined period.

In addition, it is preferable that the multicast retransmission step preferentially retransmits the multicast data packets that have failed to be received by the communication devices of the slave stations. If the remaining time of a certain cycle is below the threshold, the retransmission is ended, and the unicast retransmission step gives priority to resending the multicast data packets with fewer communication devices in the sub-stations that failed to receive. When all the retransmissions of the streaming data are completed, or the certain period ends, the retransmission ends.

Here, the delivery confirmation step is a process of individually inquiring whether the distribution is successful to each of the plurality of sub-station communication devices by unicast, or collectively inquiring whether the distribution is successful by multi-cast to a plurality of the sub-station communication devices .

Here, it is preferable that the resending step includes a multicast resending step for resending the stream data whose distribution failed by using multicast, and the multicast resending step is the same as the multicast sending step It is carried out before the delivery confirmation step within the certain period, and if the remaining time of the certain period is below a threshold value, the delivery confirmation step is started.

Description of drawings

FIG. 1 is a time chart of a radio transmission device according to Embodiment 1-3 of the present invention.

FIG. 2 is a system diagram of a wireless transmission device according to Embodiment 1-4 of the present invention.

FIG. 3 is a timing chart of the wireless transmission device according to Embodiment 1 of the present invention.

FIG. 4 is a block diagram of a wireless transmitting terminal according to Embodiment 1-5 of the present invention.

Fig. 5 is a block diagram of a wired transmission unit according to Embodiment 1-5 of the present invention.

FIG. 6 is a structural diagram of a wired Ethernet packet according to Embodiment 1-4 of the present invention.

Fig. 7 is a state diagram of the memory according to Embodiment 1-4 of the present invention.

Fig. 8 is a block diagram of a wireless transmission unit according to Embodiment 1-5 of the present invention.

Fig. 9 is a block diagram of a buffer unit according to Embodiment 1-5 of the present invention.

Fig. 10 is a configuration diagram of a wireless multicast data packet according to Embodiment 1-5 of the present invention.

Fig. 11 is a block diagram of a wireless receiving terminal according to Embodiment 1-5 of the present invention.

Fig. 12 is a state diagram of the memory according to Embodiment 1-5 of the present invention.

Fig. 13 is a configuration diagram of a resend request packet according to Embodiment 1-5 of the present invention.

Fig. 14 is a configuration diagram of a retransmission packet according to Embodiment 1-5 of the present invention.

Fig. 15 is a timing chart of the radio transmission device according to Embodiment 1 of the present invention.

Fig. 16 is a timing chart of the wireless transmission device according to Embodiment 1 of the present invention.

Fig. 17 is a time chart of the radio transmission device according to Embodiment 1 of the present invention.

Fig. 18 is a time chart of the radio transmission device according to Embodiment 1 of the present invention.

FIG. 19 is a diagram showing the configuration of a receiving terminal according to Embodiment 2 of the present invention.

Fig. 20 is a diagram showing a configuration of a transmission timing adjustment unit in the receiving terminal.

FIG. 21 is a schematic diagram illustrating the timing of asynchronous data transmission during the asynchronous transfer period.

Fig. 22 is a time chart showing an example of a packet sequence in the wireless transmission device according to Embodiment 3 of the present invention.

Figure 23 is a state diagram of memory.

Fig. 24 is a diagram showing the structure of a resend request packet.

Fig. 25 is a timing chart of a wireless transmission device.

Fig. 26 is a diagram showing the structure of a retransmission packet.

Fig. 27 is a timing chart of a wireless transmission device.

Fig. 28 is a time chart of a wireless transmission device.

Fig. 29 is a timing chart of a wireless transmission device.

Fig. 30 is a timing chart of a wireless transmission device.

FIG. 31 is a schematic diagram illustrating a wireless multicast retransmission method according to Embodiment 5. FIG.

FIG. 32 is a diagram showing the configuration of a wireless network using the method shown in FIG. 31 .

FIG. 33 is a diagram showing the device configuration of the radio base station 100 .

Fig. 34 is a diagram showing the device configuration of a wireless substation.

FIG. 35 is a diagram showing the detailed configuration of the asynchronous data transmission buffer 340 of the wireless slave station.

FIG. 36 is a diagram showing an example of asynchronous data transmission timing in an asynchronous transfer period.

Fig. 37 is a time chart showing an example of a packet sequence in the wireless transmission device according to the sixth embodiment.

Fig. 38 is a diagram showing an example of a method of prioritizing packet transmission.

FIG. 39 is a diagram showing the configuration of a transmission buffer according to Embodiment 6. FIG.

Fig. 40 is a configuration diagram of a multicast communication system according to Embodiment 7.

FIG. 41 is a diagram showing the internal structure of the communication device 1431 of the master station.

FIG. 42 is a diagram showing the frame configuration of the wireless signal 1416.

FIG. 43 is a diagram showing the configuration of the buffer 14152 .

FIG. 44 is a diagram showing the configuration of the wireless unit 14155 .

Fig. 45 is a diagram showing the internal configuration of slave station communication devices 1432-1435.

Fig. 46 is a diagram showing the state of radio signals at time 1-5.

Fig. 47 is a configuration diagram showing a master station communication device according to Embodiment 8.

FIG. 48 is a diagram showing a system configuration assumed by Embodiment 9. FIG.

Fig. 49 is a diagram showing the configuration of the buffer of the second transmission terminal.

FIG. 50 is a flowchart illustrating operations performed by the buffer 14152.

FIG. 51 is a flowchart illustrating operations performed by the transfer confirmation processing unit 14156.

FIG. 52 is a flowchart illustrating the operation performed by the unicast retransmission processing unit 14157.

FIG. 53 is a flowchart illustrating the operation performed by the multicast retransmission processing unit 14158 .

FIG. 54 is a flowchart illustrating operations performed by the multicast distribution processing unit 14159.

Fig. 55 is a transmission time chart of a conventional wireless transmission device.

Symbol Description

(04-164202 first embodiment)

Detailed ways

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)

FIG. 1 is a time chart showing a basic packet sequence (sequence) of a wireless transmission device according to Embodiment 1 of the present invention.

[basic sequence]

Referring to Fig. 1, the basic idea of the present invention is explained first.

In FIG. 1 , 100 , 101 , and 102 denote 1st to Nth multicast packets simultaneously transmitted from a transmitting terminal to a first receiving terminal, a second receiving terminal, and a third receiving terminal. Numerals 103 and 104 denote a retransmission packet of the second packet and a retransmission packet of the Nth packet, respectively. 105 is other data packets. 300 and 301 are resend request packets for the receiving terminal to request resend when the receiving terminal fails to receive the multicast packet.

The time chart is divided into time slots, and alternately repeats the frequency band securing period and the frequency band non-reserving period as shown in the first secured band period→the first unsecured band period→the second secured band period.

During the reserved bandwidth period, the first multicast packet 100, the second multicast packet 101, . . . , the Nth multicast packet are transmitted from the transmitting terminal to the receiving terminal. During this period, since the frequency band to be used is allocated to the transmitting terminal in advance, the usable frequency band will not be reduced due to the interruption of other terminals. That is, during this period, packets other than the 1st to Nth multicast packets are not transmitted from other terminals, and this period is reserved for transmitting the 1st to Nth multicast packets.

The non-band secured period is a period in which each terminal participating in the network freely transmits packets, contrary to the aforementioned band secured period. Therefore, when a certain terminal intends to transmit a packet, it may not be able to transmit the packet because other terminals are transmitting, or the packet transmitted by itself may collide with the transmission packet of another terminal, and the packet transmission may not be possible.

It is necessary to transmit data at a constant rate during the frequency band guarantee period, for example, it is suitable for real-time transmission of images and sounds with the highest priority, and it is not necessary to transmit data at a constant rate during the frequency band guarantee period, which is suitable for low priority data transmission.

In the present embodiment, the following operation is performed, that is, the frequency band reserved period is used for the transmission of image and audio data, the frequency band reserved period is used for retransmission data and other data transmission, and the frequency band reserved period is used for retransmission in the frequency band reserved period. Failed to receive packets.

[overall composition]

Next, a hypothetical system form will be described with reference to FIG. 2 .

FIG. 2 is a system diagram of Embodiment 1 of the present invention.

In Fig. 2, 1 is an AV server, 2 is a wired Ethernet HUB, 3 is a first wireless sending terminal, 4 is a second wireless sending terminal, and 5 is a wired Ethernet connecting 1, 2, 3, and 4. 6 is the first wireless receiving terminal, 7 is the second wireless receiving terminal, 8 is the third wireless receiving terminal, 9 is the fourth wireless receiving terminal, 10 is the fifth wireless receiving terminal, and 11 is the sixth wireless receiving terminal.

The first wireless transmission terminal 3 has a parent-child relationship with the first wireless reception terminal 6 , the second wireless reception terminal 7 , and the third wireless reception terminal 7 to perform wireless communication using IEEE802.11 wireless LAN technology. That is, the first wireless transmitting terminal 3 is an AP (access point: master), and the first, second, and third wireless receiving terminals 6, 7, and 8 are STAs (stations: slave). In addition, the first, second, and third wireless reception terminals 6, 7, and 8 constitute a first multicast group 12 that receives the same multicast packet.

Similarly, the second wireless transmission terminal 4 has a parent-child relationship with the fourth wireless reception terminal 9 , the fifth wireless reception terminal 10 , and the sixth wireless reception terminal 11 to perform wireless communication using IEEE802.11 wireless LAN technology. That is, the second wireless transmission terminal 4 is an AP (access point: master), and the fourth, fifth, and sixth wireless reception terminals 9, 10, and 11 are STAs (stations: slaves). In addition, the fourth, fifth, and sixth wireless reception terminals 9, 10, and 11 constitute a second multicast group 13 that receives the same multicast packet.

Next, the operation of the transmission system configured as above will be described.

From the AV server 1 through the wired Ethernet 5, the image and sound data packets are input to the wired Ethernet HUB2. The wired Ethernet HUB 2 repeats (repeats) the input packets and distributes them to the first wireless transmission terminal 3 and the second wireless transmission terminal 4 . The wired Ethernet HUB 2 performs either an operation of repeating all input packets to all outputs or a switching operation of repeating only specific packets to a specific terminal. For example, in the case of switching operation, only the data packet transmitted to the first multicast group 12 is copied to the first wireless transmission terminal 3, and only the data packet transmitted to the second multicast group 13 is transmitted. The packet is copied only to the second wireless transmission terminal 4 .

The first wireless sending terminal 3 and the second wireless sending terminal 4 respectively receive the image and sound data distributed to the wireless receiving terminals under their own management from the wired Ethernet HUB2, and distribute to the wireless receiving terminals under their management by multicasting.

That is, in FIG. 2, all terminals (the first wireless receiving terminal 6, the second wireless receiving terminal 7, and the third wireless receiving terminal 8) managed by the first wireless transmitting terminal 3 belong to the first multicast group 12, so the first 1. The wireless transmission terminal 3 (12) receives the video and audio data packets of the first multicast group object, and distributes them to the first multicast group object. All terminals (the fourth wireless receiving terminal 9, the fifth wireless receiving terminal 10, and the sixth wireless receiving terminal 11) managed by the second wireless transmitting terminal 4 belong to the second multicast group 13, so the second wireless transmitting terminal 4 receives The video and audio data packets sent to the second multicast group 13 are distributed to the second multicast group object 13 .

FIG. 1 illustrates the basic idea of performing such wireless multicast distribution, and a more specific example of operation will be described below.

[Operation at the time of multicast distribution]

3 is a time chart showing an example of a packet sequence of the wireless transmission device according to Embodiment 1 of the present invention. In FIG. 3 , the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

In Fig. 3, 3001 is the Ack packet that transmits the acknowledgment of successful reception of the retransmission request packet 300 for the 1st transmission, 1031 is the Ack packet of the acknowledgment of the retransmission packet 103 that transmits the 2nd packet, and 1041 is the Ack packet that transmits the 2nd packet. The retransmission packet 104 of the N packet is an Ack packet for confirmation of successful reception.

In FIG. 3 , the transmitting terminal corresponds to the first wireless transmitting terminal 3 in FIG. 2 . In FIG. 2, there are two transmitting terminals, the first wireless transmitting terminal 3 and the second wireless transmitting terminal 4, but both of them operate in the same way, so no matter which one they correspond to, there will be no difference in description, so it corresponds to the first wireless transmitting terminal 4. 1 Wireless sending terminal 3. Similarly, in Fig. 3, the first receiving terminal corresponds to the first wireless receiving terminal 6 in Fig. 2, and in Fig. 3, the second receiving terminal corresponds to the second wireless receiving terminal 7 in Fig. 2, and in Fig. 3, the third The receiving terminal corresponds to the third wireless receiving terminal 8 in FIG. 2 .

[the first band securing period]

In the time chart 3 described above, first, the operation of the transmission terminal during the second frequency band reserved period will be described.

FIG. 4 shows the configuration of a transmitting terminal that transmits the first multicast packet 100, the second multicast packet 101, and the Nth multicast packet 102 during the first bandwidth reserved period.

[Configuration of sending terminal]

In Fig. 4, 14 is the input and output terminal of the data packet that input and output comes from wired Ethernet 5, and 15 is the wired transmission unit that carries out data packet sending and receiving by wired Ethernet 5, and 16 is the CPU of the internal unit of control sending terminal, 17 is a memory unit that stores data higher than the MAC layer, 18 is a wireless transmission unit that uses wireless to send and receive data packets, 19 is an internal bus that connects the CPU 16 and other units, and 20 is a first timer unit that measures operating time , 21 is an antenna for sending and receiving wireless data packets.

The wired Ethernet packet received from the wired Ethernet 5 via the input/output terminal 14 is first input to the wired transmission unit 15 . The wired transmission unit 15 is based on IEEE802.3, that is, the wired Ethernet standard, and performs the following operations: using the Ethernet MAC protocol, receives data packets from the wired Ethernet 5 and outputs them to the internal bus 19 .

[Structure of Priority Transmission Unit]

FIG. 5 is a block diagram showing the internal configuration of the wired transmission unit 15 . 22 is an input/output terminal, which performs input/output of packets based on wired Ethernet IEEE802.3. 23 is a wired physical layer signal processing unit, which performs modulation and demodulation of data packets transmitted by the wired Ethernet 5 . 24 is a MAC layer protocol processing unit, which processes the MAC protocol of the wired Ethernet 5 . 25 is a buffer unit that temporarily stores data input and output via the internal bus 19 . 26 is an input/output terminal, which is a connection terminal to the internal bus 19 .

The packet input from the input terminal 22 is input to the wired physical layer signal processing unit 23, and is converted into a MAC packet by modulation and demodulation of the wired Ethernet. The demodulated MAC data packet is input to the MAC layer protocol processing unit 24 .

[MAC packet]

FIG. 6 shows the configuration of an input MAC packet, which is composed of a MAC header, an IP header, a UDP header, transmission data, and an FCS (Frame Check Sum) from the beginning.

The beginning is the header of the data link layer, which is the MAC header. The MAC header is composed of a source MAC address, a destination MAC address, a higher protocol type, and the like, and indicates a source address in the MAC layer, a destination address in the MAC layer, and a higher protocol type, respectively.

IP (Internet Protocol) is generally used as the host protocol. The upper layer of the data link layer is the network layer, which includes the source IP address, destination IP address, upper protocol type, and the like. This network layer is a layer for routing data, and uses an IP address which is a dedicated address different from a MAC address. In the IP header, there is also a higher-level protocol type indicating a higher-level transport layer protocol type, but UDP is often used as a higher-level protocol for real-time transmission of images and sounds.

As shown in the figure, the UDP header is composed of the port number of the sending source and the port number of the destination, and is used to determine the virtual input and output destination of the data inside the terminal.

The actual transmission data is input to the UDP host, and a checksum (FCS) for checking the transmission error of the wired data packet is added at the end.

Such packets are output from the wired physical layer signal processing unit 23 and input to the MAC layer protocol processing unit 24 .

The MAC layer protocol processing unit 24 performs protocol processing for transmitting and receiving the MAC packet shown in FIG. 6 , and processing for determining whether the packet is addressed to the own terminal by using the previous destination MAC address, and receiving the packet by the own terminal. When the destination MAC address is addressed to the own terminal, the MAC header is removed to generate an upper data packet, which is input to the next buffer unit 25 .

The buffer unit 25 has a role of temporarily storing when the upper data packet input from the MAC layer protocol processing unit 24 is transmitted to the internal bus 19 via the input/output terminal 26 . When the CPU 16 completes the reception preparation and the internal bus 19 becomes available, the stored upper data packet is transferred to the CPU 16 .

When the CPU 16 receives the upper data packet, it first performs UDP/IP processing. That is, the IP address and UDP port are confirmed, and it is judged whether or not it is data to be wirelessly multicasted by the own terminal. If it is data to be wirelessly multicasted by the own terminal, a writing operation is performed to the memory unit 17 .

[Data storage in memory unit]

FIG. 7 is a memory state diagram showing a data storage state inside the memory unit 17. As shown in FIG. When the CPU 16 writes the high-order data packet into the memory unit 17, it assigns a serial number representing the order of the data to the head. Inside the memory unit 17, data is held in units of N (N is an integer equal to or greater than 1) whose number is the same as the transmission unit of the band securing period in the next wireless section.

As described above, the transmission band secured period and the band not secured period are alternately and periodically switched in the wireless section, but the N data groups shown in FIG. 7(a) are multicast during the first secured band period in FIG. 3 . Only the unit data of the data in which the reception error occurred is retransmitted during the first frequency band out-of-reserve period. After a certain period of time, the CPU 16 stores, in the memory unit 17 , the data with sequence numbers assigned to the beginnings of the subsequent N data from the N+1th to the 2*Nth before the second band securing period. Actually, the CPU 16 stores at least two or more sets of N data packet groups in the memory unit 17, and deletes unnecessary packets from the memory unit 17 after the wireless transmission during the out-of-band guarantee period and the retransmission control outside the band guarantee end. sent data.

Thereafter, the CPU 16 transfers the 1st to Nth data transmitted during the first band securing period to the wireless transmission unit 18 via the internal bus 19 . At this time, the CPU 16 performs appropriate UDP/IP processing as necessary, and transmits the sequence number from the payload of the UDP/IP packet. At this time, the CPU 16 newly adds an identifier indicating the type of data transferred by the payload to the beginning of the UDP/IP payload.

[Configuration of wireless transmission unit]

8 is a block diagram showing the internal structure of the wireless transmission unit 18, which consists of a timer input terminal 27, an input and output terminal 28, a buffer unit 29, a MAC processing unit 30, a second timer unit 31, a physical layer signal processing unit 32, The antenna 21 constitutes.

The buffer unit 29 is a buffer for wireless transmission, etc., and is set for when the wireless transmission timing arrives, the ratio of N sequence numbers+data stored on the memory unit 17 to be marked as a UDP/IP packet can be wirelessly transmitted at once. The upper data packet of the MAC layer is composed of a plurality of buffers having a storage capacity equal to or greater than the packet length of the wireless section.

Wireless transmission data input from CPU 16 via input/output terminal 28 is input to buffer unit 29 from internal bus 19 , and the block diagram of FIG. 9 shows the configuration of buffer unit 29 .

The buffer unit 29 is composed of an input and output terminal 33, a data sending and receiving unit 34, a sending buffer unit 35 for priority data, an output terminal 36 for priority data, a sending buffer unit 37 for normal data, an output terminal 38 for normal data, a transmission control The signal input and output terminal 39, the reception buffer unit 40, the input terminal 41 for the reception data, and the input and output terminal 42 for the reception control signal are constituted. Among them, the input and output terminals 33, the data transmission A receiving unit 34 , a transmission buffer unit 35 for priority data, an output terminal 36 for priority data, and an input/output terminal 39 for transmission control signals.

All or part of the wireless transmission data of the upper data packet input from the input and output terminal 33 is distributed to the priority data transmission buffer unit 35 through the data transmission and reception unit 34, and is transmitted through the priority data output terminal 36 according to the wireless transmission timing. Passed to the MAC processing unit 30.

The MAC processing unit 30 performs management of the band secured period/out of band secured period or MAC protocol processing, reads wireless transmission data from the buffer unit 29 at appropriate timing, and inputs it to the physical layer signal processing unit 32 .

In fact, the MAC processing unit 30 uses the second timer unit 31 provided inside to judge whether it is the band securing period, and during the band securing period, the buffer unit 29 is controlled using the input/output terminal 39 for sending control signals, and the priority data Data is read out from the transmit buffer unit 35 and transmitted. The timing of transferring data from the CPU 16 to the buffer unit is also determined by the control signal of the MAC processing unit 30 controlling the priority data buffer unit 35 and the data transmission and reception unit 34 via the transmission control signal input and output terminal 39 as a trigger. The CPU 16 transfers the data to the wireless transmission unit 18 when the data request is received.

The MAC processing unit 30 that has received the data performs wireless MAC packetization of the data, and FIG. 10 shows the configuration of the wireless packet. The determination of the bandwidth reservation period and transmission timing can also be determined by using the first timer unit 20 to input the same timing to the upper layer and the MAC layer.

[Structure of Wireless Packet]

The configuration of the wireless packet is a format in which the MAC header of the wired Ethernet packet previously shown in FIG. 6 is replaced with an IEEE802.11 wireless MAC header. The CPU 16 adds the above-mentioned identifier and serial number to the upper data transmitted to the wireless transmission unit 18 .

The wireless packet in this form is input to the physical layer signal processing unit 32 , and after being modulated by the physical layer signal processing unit 32 suitable for wireless transmission, it is wirelessly transmitted via the antenna 21 .

Through the above processing, the first to the Nth multicast packets are transmitted to the first to the third receiving terminals during the first frequency band reservation period in FIG. 3 .

[movement during period outside securing the first frequency band]

Next, in the timing chart 3, the operation of retransmission performed during the period outside of the reserved first frequency band will be described.

In FIG. 3 , multicast transmission is performed from the transmitting terminal to the receiving terminal during the first frequency band reserved period, but since the installation environments and receiving characteristics of the first to third receiving terminals are different, error occurrence conditions at the time of reception are different.

In FIG. 3 , the first multicast packet 100 has been successfully received by all receiving terminals, but the second multicast packet 101 has failed to be received only by the first receiving terminal. Similarly, only the third receiving terminal fails to receive the Nth multicast packet 102 .

Usually, in multicast transmission, since the MAC layer does not perform retransmission control using Ack packets (acknowledgment of successful reception), etc., the transmitting terminal cannot know whether the receiving terminal normally receives and multicasts packets. This is because if a plurality of receiving terminals unconditionally return Ack packets, useless use of the wireless frequency band due to collision of Ack packets in the wireless section and increase of the load of acknowledgment processing on the transmission side will occur. In addition, in order to retransmit and ensure the transmission quality, there has been a method of repeatedly transmitting the same multicast packet from the beginning. However, if this method is applied to the transmission of the frequency band guarantee, the originally required frequency band must be repeated, and it is necessary to ensure Since the frequency band is several times higher than that of the wired communication path, there are many problems of insufficient frequency band caused by wireless with a small transmission capacity.

[Transmission of resend request packet]

In this embodiment, the receiving terminal that failed to receive the multicast packet performs an operation of transmitting a retransmission request packet to the transmitting terminal object using the first out-of-band reserved period.

Only the first receiving terminal that failed to receive the second multicast packet 101 in the first bandwidth reserved period in FIG. 3 transmits the first resend request packet 300 to the sending terminal object using the first reserved bandwidth period. This time, in order to improve the transmission reliability of the resend request packet, a configuration of performing a resend request using a unicast packet will be described. If the sending terminal normally receives the first resend request packet 300, after returning the Ack packet 3001 as a confirmation of successful reception, refer to the content of the resend request packet 300, and use unicast to transfer the resend of the second packet The data packet 103 is sent to the first receiving terminal. When the first receiving terminal confirms the normal reception of the retransmission packet 103 of the second packet, it returns Ack 1031 to the transmitting terminal. Next, the operation of the terminal will be described in detail using diagrams.

[Structure of receiving terminal]

FIG. 11 is a block diagram showing the internal configuration of a receiving terminal. 16 is a CPU, 17 is a memory unit, 18 is a wireless transmission unit, 19 is an internal bus, and 20 is a first timer unit. These constituent elements are the same as the internal constituent elements of the transmitting terminal shown in FIG. 4 . In the following, when the same constituent elements as the preceding constituent elements are used, the description of the plurality of constituent elements will be omitted. 43 is an AV processing unit, which changes the image and sound data received through wireless into a displayable signal. 44 is a display unit which displays the output of the AV processing unit 43 .

The receiving terminal receives the 1st-Nth multicast data packets 100 , 101 , 102 via the antenna 21 . The first to Nth multicast packets 100 , 101 , and 102 are input to the wireless transmission unit 18 , and output to the internal bus 19 after undergoing a process opposite to the transmission.

The wireless transmission unit 18 has the same configuration as the transmission unit inside the transmitting terminal, and is configured as shown in FIG. 8 . The configuration of FIG. 8 has been described on the transmitting terminal side, so the description is omitted this time. In the wireless transmission unit 18, first, the modulation performed by the physical layer signal processing unit 32 at the time of transmission is demodulated, and the MAC packet shown in FIG. 10 is restored. The restored MAC packet is input to the MAC processing unit 30, and when the multicast address indicated by the MAC header is addressed to the broadcast group to which the own station belongs, the MAC header is removed and output to the buffer unit 29. The configuration of the buffer unit 29 is the same as that described on the transmission side shown in FIG. 9 . The send buffer system is operated when sending, but the receive buffer system is operated when receiving. The MAC-processed packet is input from the received data input terminal 41 and temporarily stored in the receive buffer unit 40 . In addition, at this time, the MAC processing unit 30 controls writing of received data into the receive buffer 40 via the control signal input/output terminal 42 . The data temporarily stored in the receiving buffer unit 40 is output to the internal bus 19 via the data transmitting and receiving unit 34 and the input and output terminals 33 and 28 , and then passed to the CPU 16 . At this time, the data transmitting/receiving unit 34 performs an operation of reading data from the receiving buffer unit 40 when the internal bus 19 is available and the CPU 16 can receive data. The CPU 16 that has received the data writes the received data into the memory unit 17. At this time, it judges whether it is a data packet that should be processed later according to the IP header, UDP header, and identifier in FIG. 6 . That is, the internal destination is judged using the IP header and UDP header, and whether it is multicast data to be stored in the memory is judged using the identifier.

[Data storage status in memory 17]

FIG. 12 shows the state of data storage inside the memory 17. As shown in FIG. The first to Nth multicast packet data are stored, and at this time, it is written in the memory unit 17 in a format that can determine which sequence number the packet data is missing. In this example, the position of the 1st-Nth multicast packet data on the memory is fixed in advance, and the sequence number + multicast packet data is appended to the beginning of the combination indicating whether the packet is received normally and written normally. identifier of the . That is, by referring to the inside of the memory unit 17, it can be determined which packet is missing among the 1st to Nth multicast packet groups transmitted during the band securing period. Based on the information stored in the memory unit 17, the CPU 16 judges that the data of the second multicast packet is lacking, generates a retransmission request packet 300, and prepares for transmission to the transmitting terminal. FIG. 13 shows the structure of the resend request packet 300. As shown in FIG. The CPU 16 stores, in the IP header and the payload of the TCP header, an identifier indicating that it is a resend request packet, and a sequence number of the packet for which a resend request is made. The resend request packet 300 is transferred to the wireless transmission unit 18 via the internal bus 19 . The wireless transmission unit 18 has the configuration shown in FIG. 8 as described above, and inputs the retransmission request packet 300 to the buffer unit 29 via the input/output terminal 28 . The buffer unit 29 is the structure of the above-mentioned FIG. 9, and the resend request data packet 300 input through the input and output terminal 33 is temporarily stored in the transmission buffer unit 37 for normal data through the data transmission and reception unit 34, and is transmitted through the output terminal for normal data. 38. Pass it to the MAC processing unit 30. At this time, the MAC processing unit 30 uses the built-in second timer unit 31 to determine the first frequency band out-of-guaranteed period, and if it becomes the first frequency band out-of-guaranteed period, the normal data buffer is controlled via the control signal input and output terminal 39. The unit 37 reads the retransmission request packet 300 from the buffer unit 37 for normal data. The read retransmission request packet 300 is subjected to modulation suitable for transmission by the physical layer signal processing unit 32 after the MAC header is added, and is unicast transmitted by the antenna 21 to the transmitting terminal. The bandwidth reservation period and the determination of the transmission timing can also be determined by using the first timer unit 20 to input the same timing to the upper layer and the MAC layer.

[Unicast operation of the sending terminal that received the resend request]

Upon receiving the retransmission request packet 300, the transmitting terminal returns an Ack packet 3001 to the first receiving terminal after confirming that the wireless packet has been received normally. When the first receiving terminal receives the Ack packet 3001, it waits for the retransmission of the packet for which the retransmission request was made.

When the transmitting terminal internally receives the resend request packet 300 via the antenna 21, it outputs the resend request packet to the internal bus 19 in the reverse process of the transmission.

The wireless transmission unit 18 at this time has the same configuration as the wireless transmission unit inside the transmitting terminal, and is configured as shown in FIG. 8 . The configuration of FIG. 8 has been described above, so the description thereof will be omitted. In the wireless transmission unit 18, first, the modulation performed by the physical layer signal processing unit 32 at the time of transmission is demodulated, and the MAC packet shown in FIG. 10 is restored. The restored MAC packet is input to the MAC processing unit 31 , and when the address shown in the MAC header is addressed to the own station, the MAC header is removed and output to the buffer unit 29 . The configuration of the buffer unit 29 is the same as that shown in FIG. 9 and previously described. The transmit buffer system is activated for transmission, and the receive buffer system is activated for reception. The MAC-processed packet is input from the received data input terminal 41 and temporarily stored in the receive buffer unit 40 . In addition, at this time, the MAC processing unit 30 controls writing of received data into the receive buffer 40 via the control signal input/output terminal 42 . The data temporarily stored in the receiving buffer unit 40 is output to the internal bus 19 via the data transmitting and receiving unit 34 and the input and output terminals 33 and 28 , and then passed to the CPU 16 . At this time, the data transmitting/receiving unit 34 performs an operation of reading data from the receiving buffer unit 40 when the internal bus 19 is available and the CPU 16 can receive data. The CPU 16 that has received the data writes the received data into the memory unit 17, and at this time, judges whether it is a data packet that should be processed later based on the IP header and the TCP header in FIG. 13 . When the identifier indicates a retransmission request, the CPU 16 confirms the subsequent packet sequence number and proceeds to preparations for transmitting the corresponding packet data. Since the data previously transmitted by multicast as shown in FIG. 7 is stored in the memory unit 17, the second multicast packet data in which a retransmission request is requested is retransmitted. That is, the retransmission packet 103 of the second packet in FIG. 3 is transmitted to the first receiving terminal.

FIG. 14 shows the structure of the retransmission packet 103, and the payload after the MAC header, IP header, and UDP header is composed of an identifier indicating that it is a retransmission packet, a sequence number, and data. This data part is the same as that of the second multicast packet that was first multicast transmitted.

The transmission process is the same as the procedure of multicast transmission during the first reserved period of the first frequency band. However, since the priority of the retransmission packet is lower than that of the first one, it is transmitted during the period outside the reserved first frequency band.

The CPU 16 transfers the retransmission packet data transferred during the first frequency band out-of-reserve period to the wireless transfer unit 18 via the internal bus 19 .

The wireless transmission data input from the CPU 16 via the internal bus 19 and the input/output terminal 28 is input to the buffer unit 29 .

The retransmission data of the second multicast data packet input from the input and output terminal 33 is distributed to the normal data transmission buffer unit 37 via the data transmission and reception unit 34, and is input through the normal data output terminal 38 according to the wireless transmission timing phase. to the MAC processing unit 30.

The MAC processing section 30 performs management of the band secured period/out of band secured period or MAC protocol processing, reads wireless transmission data from the buffer section 29 at an appropriate timing, and inputs it to the physical layer signal processing section 32 .

The MAC processing unit 30 may use the first timer unit 20 to input the same timing to the upper layer and the MAC layer, and determine an internally equipped band securing period or determine transmission timing. It is judged that it is a period when the frequency band is not secured. During the period when the frequency band is not secured, the buffer unit 29 is controlled using the transmission control signal I/O terminal 39, and the data is read from the normal data transmission buffer unit 37 and then unicasted. The timing at which data is transferred from the CPU 16 to the buffer unit is also determined by a control signal that the MAC processing unit 30 controls the normal data buffer unit 37 and the data transmission and reception unit 34 via the transmission control signal input and output terminal 39 as a trigger. When the CPU 16 receives a data request, it transfers the data to the wireless transmission unit 18 .

The MAC processing unit 30 that receives the data performs wireless MAC packetization of the data, and the wireless data packet is input into the physical layer signal processing unit 32, and after the physical layer signal processing unit 32 performs modulation suitable for wireless transmission, it is wirelessly transmitted through the antenna 21. send.

[Processing after packet resend: resend failed]

Through the above processing, the data of the resend request using the resend request packet 300 is sent to the first receiving terminal. The first terminal that has received the retransmission packet 103 of the second packet resent in this way returns the Ack packet 1031 as the reception confirmation packet to the transmitting terminal, and the re-reception of the failed packet is completed.

When the first receiving terminal fails to receive the retransmission packet 103 of the second packet, as shown in FIG. 15, the retransmission packet itself of the second packet may be retransmitted. In FIG. 15, 1032 is a Nack packet transmitted when the first terminal fails to receive the retransmission packet 103 of the second packet. In most cases, the Nack packet is not used. At this time, when the reception confirmation of the Ack packet cannot be performed within the predetermined time, the transmitting terminal determines that the first receiving terminal has failed to receive. 203 is a retransmission packet of the second packet, and its content is the same as that of the retransmission packet 103 of the second packet. If the data packet is successfully received, the Ack data packet 2031 is returned to the sending side, and retransmission is completed. If the number of retransmissions is unlimited, other terminals may not be able to use the period outside the reserved first frequency band, so it is preferable to limit the number of retransmissions. In addition, since the retransmission time itself during the period outside of the reserved first frequency band is used to suppress interference to other transmissions, it is more practical to set a retransmission time limit.

[Processing when multiple terminals fail to receive the same packet]

In Fig. 3 and Fig. 15, when the 3rd receiving terminal fails to receive the N multicast packet 102 as an example, the situation that the 1st receiving terminal fails to receive the 2nd multicast packet 101 is described, but as shown in Fig. 16, the 1st receiving terminal fails When the first receiving terminal and the second receiving terminal fail to receive the same second multicast packet 101, each retransmission and retransmission (103, 203, 104, 204) are all sent in the same way as the second multicast packet 101. The data.

[Transmission of resend packets, congestion of resend requests]

As shown in FIG. 17, before sending the resend data packet 103 of the second data packet and before sending the data packet 203 again, it is possible to send the third resend request 302. This is because the period outside the secured first frequency band is a period in which a terminal that intends to transmit a packet can freely transmit it, so it is not a problem although it may occur. In this case, the limit on the number of retransmissions or the time limit on retransmissions also applies.

[Priority of resend request]

In addition, FIG. 18 is an example of setting the priority of the retransmission request packet as the next priority of the 1st-Nth multicast packets 100, 101, 102. That is, the priority is set to be one level higher than that of other packets during the out-of-band reservation period. In this way, it is also possible to set a limit on the resend request time, so as to prevent resend requests or resend requests from being sent and resent without limit. In addition, since the sending terminal knows the arrival time of the resend request packet in advance, efficient internal processing can be performed.

In this way, when all the 1st to Nth multicast data packets are gathered in the memory unit 17 , the CPU 16 inputs these data to the AV processing unit 43 via the internal bus 19 . The AV processing unit 43 processes the input data and displays it on the display unit 41 .

In Fig. 3, the 3rd receiving terminal fails to receive the Nth multicast data packet, and the retransmission data packet 104, Ack1041 of the 2nd retransmission request data packet 301, Ack3011, N data packet carry out the same processing as above-mentioned processing, finish Resend for processing.

[Summary of the first embodiment]

According to the above configuration, there are: a memory unit for temporarily storing a multicast data group higher than the MAC layer; a sequence number assigning unit for assigning a sequence number for each of the multicast data groups to detect a lack of data on the receiving side; and a wireless transmission unit. , transmit the data assigned the sequence number by the band-guaranteed multicast packet; and the retransmission control unit uses the sequence number to retransmit the multicast data whose loss is detected by the wireless receiving side; it is performed by the upper layer of the Mac layer The retransmission control of the multicast data packet of the guaranteed bandwidth type, compared with the multicast data packet of the guaranteed bandwidth type, the retransmission control performs unicast retransmission with a lower priority, so the multicast data of the guaranteed bandwidth type can be transmitted with the highest priority. , the reception probability can be increased by using retransmission.

In addition, in this embodiment, retransmission processing of the retransmission request packet itself is not involved much, but retransmission processing may be performed.

(Embodiment 2)

This embodiment further focuses on the sequence in the period outside the reserved frequency band in the first embodiment. If the out-of-band guarantee period is entered, all receiving terminals and transmitting terminals can transmit necessary packets, but if each receiving terminal transmits at any time, packet collisions will occur on the network, and retransmission, retransmission, and repeated Send again...wait to repeat. The types of transmission packets include not only retransmission requests based on failure to receive stream data, but also various packets such as Internet site browsing request packets. Streaming data requires real-time performance, while other data packets, such as Internet browsing request packets, do not require real-time performance. It is necessary to prevent such non-real-time data packets from preempting the transmission path, and it is impossible to send data packets that require real-time performance.

Embodiment 2 improves this problem. The configuration for realizing this will be described below.

[Structure of receiving terminal]

FIG. 19 shows the configuration of a receiving terminal. The basic configuration is the same as that of the receiving terminal according to Embodiment 1 shown in FIG. 11 . The difference is that the receiving terminal of this embodiment includes normal data transmission buffers 51 . . . and transmission timing adjustment units 52 . . . The transmitting terminal is not shown, but has the same normal data transmission buffer and transmission timing adjustment means as the receiving terminal.

Normally, the data transmission buffers 51 ... have the number of priority classes of data packets required for transmission during out-of-band secured periods. The transmission timing adjustment units 52 . . . have as many normal data transmission buffers 51 .

Each transmission timing adjustment unit 52 ... is composed of a random number generator 521 , an upper limit value setting unit 522 , a counter 523 , a subtraction pulse generator 524 , and an AND circuit 525 as shown in FIG. 20 .

The random number generator 521 performs a process of generating a random number when receiving the notification of the end of the bandwidth reserved period. The end notification of the band secured period can be obtained from the second timer unit provided in the MAC processing unit, but in this embodiment, it is configured to be notified simultaneously from the transmitting terminal to the receiving terminal (see end notification 211 in FIG. 21 ). Upon receiving this notification, the random number generator 521 generates a random number once. Each random number generator 521 has an upper limit setting unit 522, corresponding to the priority level, becomes a specification specifying an upper limit, and generates a random number within a range of the set upper limit. The upper limit value is the smallest when the packet to be sent is a resend request packet. For example, if the counter initial setting value of the normal data transmission buffer other than the retransmission request is randomly selected from '1'-'32', the counter used to transmit the retransmission request is randomly selected from '1'-'8'. Usually the initial setting value of the counter of the data transmission buffer. The above-mentioned upper limit value is instructed to the upper limit setting unit 522 by the CPU in the terminal.

The random number generated by the random number generator 521 is set to the counter 523 . The counter 523 counts down the pulse generated by the subtraction pulse generator 524 from the set value when the gate of the AND circuit 525 is in an open state, and outputs a timing signal if it is 0. The timing signal is sent from the sending timing adjustment unit 52 to the corresponding sending buffer 51 through the data bus, and the data packets stored in the buffer are sent.

The AND circuit 525 is supplied with a signal representing an idle period in which no data packets flow in the network as a gate signal. Therefore, the countdown operation is performed only during idle periods. The state of the network is monitored by the wireless transmission unit 18, and a signal indicating an idle period is obtained from the wireless transmission unit 18. FIG. In addition, the subtraction pulse generator 524 generates clock pulses in the terminal by appropriate cycle frequency division.

[movement during out-of-band securing period]

FIG. 21 is a diagram showing an example of the normal data transmission timing during the period outside the bandwidth reservation. In FIG. 21 , numerals surrounded by circles indicate counter values of normal data transmission buffers of each wireless terminal (including a transmitting terminal and a receiving terminal). In addition, each counter value is counted down in the period T1 of each subtraction pulse. In the figure, time in the direction of the horizontal axis is schematically indicated for easy understanding of the countdown state, and the time T1 for countdown and the time required for sending a retransmission request or other normal data are shown differently from the actual length of time. Generally, the length of time required for data transmission is generally slightly longer than the period T1.

Also, for simplicity of description, it is assumed that each terminal has only one transmission buffer 51 and transmission timing adjustment unit 52 .

In FIG. 21 , when the transmitting terminal 3 broadcasts and transmits the end notice 211 of the reserved bandwidth period, it becomes an out-of-band reserved period thereafter. During the out-of-band secured period, the receiving terminal 7 must transmit a retransmission request 412 for the streaming data 312 , and the receiving terminal 8 must transmit a retransmission request 413 for the streaming data 313 . In addition, the transmitting terminal 3 must transmit the normal data 512 and the receiving terminal 6 must transmit the normal data 512 in addition to the retransmission request. Here, the transmitting terminal 3 and the receiving terminal 6 randomly select the upper limit setting value of the counter from '1'-'32', and the receiving terminals 7 and 8 randomly select from '1'-'8'.

As shown in the figure, the sending terminal 3 selects '12', the receiving terminal 6 selects '6', the receiving terminal 7 selects '3', and the receiving terminal 8 selects '7' as the initial setting value of the counter.

After entering the out-of-band guarantee period, it is confirmed that it is an idle period in which no other wireless terminal transmits a wireless frame to the wireless section, and the transmitting terminal 3 and each receiving terminal count down the counter by 1 every time the period of the subtraction pulse. It is determined to be an idle period by measuring the received power input from the antenna, and when the received power is equal to or less than a predetermined value, it is determined to be an idle period in which no radio frame is transmitted by another wireless terminal. When the transmitting terminal 3 and each receiving terminal count down the counter, first the counter of the receiving terminal 7 becomes 0, and the normal data transmission right is obtained. The receiving terminal 7 immediately transmits the retransmission request 102 to the wireless section when the counter reaches 0. At this moment, the counter values of the transmitting terminal 3 and the other receiving terminals 6, 8, and 80 are '9', '3', and '4', respectively.

While the receiving terminal 7 is transmitting the retransmission request 102, the transmitting terminal 3 and the receiving terminals 6, 8, and 80 do not count down the respective counters. When the receiving terminal 7 finishes sending the retransmission request 102, it becomes an idle period, and the sending terminal 3, the receiving terminals 6, 8, and 80 count down each counter again. Thereafter, when the counter becomes 0, the receiving terminal 6 acquires the right to transmit the normal data, and transmits the normal data 511 . By repeating the above operations, the receiving terminal 8 transmits the retransmission request 413, and the transmitting terminal 3 transmits the normal data 512 sequentially.

In the example shown in FIG. 21, after the receiving terminal 6 sends the normal data 511, the receiving terminal 8 sends a resend request 413. However, this is just an example, as long as the initial setting value of the counter acquired when sending a resend request is '1'-'8', and the initial setting value of the counter acquired when sending other normal data is '1'-'32', In probability, the resend request has priority over other asynchronous data to obtain the sending right, and is sent first. In addition, if the range of the initial setting value of the counter at the time of sending the resend request is set to '1'-'4', it can further be sent with priority over other normal data. However, if the acquisition range of the initial setting value of the counter is small, the state of the wireless transmission path is poor, and if transmission errors occur frequently, the number of terminals sending retransmission requests increases, and multiple wireless terminals take the same value as the initial value of the counter The probability increases, and when a plurality of wireless terminals transmit retransmission requests, a collision occurs. Therefore, the initial value range of the counter set when the retransmission request is transmitted is flexibly set in accordance with the situation of the wireless transmission path and the like.

As described above, by transmitting the retransmission request of stream data mixed with other normal data, the transmission terminal 3 can be notified of the retransmission request by effectively using the wireless frequency band.

(Embodiment 3)

This embodiment is an example in which Embodiment 1 is further developed. That is, in an actual transmission path, multiple transmission errors may occur, and in particular, the same receiving terminal fails to receive multiple packets. In Embodiment 1, at this time, it is possible to transmit for every packet that failed to receive the retransmission request. In this embodiment, when one receiving terminal fails to receive a plurality of packets in this way, the number of retransmission requests is completed only once.

Fig. 22 is a time chart showing an example of a packet sequence of the wireless transmission device according to Embodiment 3 of the present invention. In FIG. 22, the same reference numerals are attached to the same constituent elements as those in the previous timing charts of FIGS.

[Description of packet sequence]

In Fig. 22, 300 is the 1st resend request packet, 3001 is the Ack packet that transmits the 1st resend request packet 300's reception success confirmation, 103 is the resend packet of the 2nd packet, and 1031 is the resend packet of the 2nd packet. 2 Packet retransmission data packet 103 Ack packet for confirmation of successful reception, 1041 is Nack packet for confirmation of reception failure of retransmission data packet 104 for transmission of the Nth data packet, 204 is retransmission of the Nth data packet Packet 2041 is an Ack packet for confirming the successful reception of the retransmitted data packet 204 for transmitting the Nth data packet.

[Operation of sending terminal]

Next, the operation of the transmitting terminal will be described with reference to FIG. 22 .

In addition, the configuration of the transmitting terminal is shown in FIG. 4 , and since it has already been described, further description is omitted.

During the first bandwidth reserved period, the first to the Nth multicast packets are transmitted from the first to the third receiving terminal.

At this time, since the first to third receiving terminals have different installation environments and receiving characteristics, the error occurrence conditions at the time of reception are also different.

The first receiving terminal fails to receive the two packets of the first multicast packet 101 and the Nth multicast packet 102 . In addition, the first receiving terminal and the Nth receiving terminal failed to receive the Nth multicast packet 102 at the same time.

The receiving terminal performs an operation of transmitting a retransmission request packet to the transmitting terminal by utilizing the first frequency band out-of-reserve period.

During the first frequency band securing period, the first receiving terminal fails to receive the two packets of the second multicast packet 101 and the Nth multicast packet in the first to Nth multicast packets 100, 101, 102, The first retransmission request packet 300 is transmitted to the sending terminal object using the first reserved period of the frequency band. At this time, the retransmission requests of the two failed packets are described in the retransmission request packet. In order to improve the transmission reliability of the resend request packet, the present embodiment will also be described with a configuration in which the resend request is made using a unicast packet.

If the sending terminal normally receives the first resend request packet 300, after returning the Ack packet 3001 as a confirmation of successful reception, referring to the content of the resend request packet 300, first use unicast to send the resend request packet 300 to the second packet. The transmission packet 103 is transmitted to the first receiving terminal.

When the first receiving terminal confirms normal reception of the retransmission packet 103 of the second packet, it returns Ack 1031 to the transmitting terminal. Thereafter, the Nth multicast packet, which is the second reception failure packet, is transmitted to the first terminal.

Next, further detailed operations will be described using the drawings.

[Action of receiving terminal: Resend request]

The receiving terminal has the configuration shown in FIG. 11 , and receives the first to Nth multicast packets 100 , 101 , 102 via the antenna 21 . The first to Nth multicast packets 100 , 101 , and 102 are input to the wireless transmission unit 18 , and output to the internal bus 19 after undergoing a process opposite to the transmission.

The wireless transmission unit 18 has the configuration shown in FIG. 8 , and first demodulates the modulation performed by the physical layer signal processing unit 32 at the time of transmission, and restores the MAC packet shown in FIG. 10 . The restored MAC packet is input to the MAC processing unit 31, and when the broadcast address indicated by the MAC header is addressed to the broadcast group to which the own station belongs, the MAC header is removed and output to the buffer unit 29. The configuration of the buffer unit 29 is as shown in FIG. 9 and is the same as that explained on the transmitting side. The transmit buffer system is activated for transmission, and the receive buffer system is activated for reception. The MAC-processed packet is input from the received data input terminal 41 and temporarily stored in the receive buffer unit 40 . In addition, at this time, the MAC processing unit 30 controls writing of received data into the receive buffer 40 via the control signal input/output terminal 42 . The data temporarily stored in the receiving buffer unit 40 is output to the internal bus 19 via the data transmitting and receiving unit 34 and the input and output terminals 33 and 28 , and passed to the CPU 16 . At this time, the data transmission/reception unit 34 performs an operation of reading data from the reception buffer unit 40 when the internal bus 19 is available and the CPU 16 can receive data. The CPU 16 that has received the data writes the received data in the memory unit 17, but at this time, it is judged whether it is a data packet that should be processed later based on the IP header, UDP header, and identifier of FIG. 6 . That is, the internal destination is judged using the IP header and UDP header, and whether it is multicast data to be stored in the memory is judged using the identifier.

FIG. 23 shows the state of data storage inside the memory 17. As shown in FIG. The 1st-Nth multicast packet data is stored, and at this time, it is written in the memory unit 17 in a form that can determine which sequence number of the packet data is lost. In this example, the position of the 1st-Nth multicast packet data on the memory is fixed, and an identification indicating whether the packet is received normally and written normally is added to the beginning of the combination of sequence number + multicast packet data symbol. That is, by referring to the inside of the memory unit 17, it can be determined which packet is missing among the 1st to Nth multicast packet groups transmitted during the band securing period.

The CPU 16 makes preparations for judging the absence of the second multicast packet data and the N-th multicast packet data, and generates a retransmission request packet 300, and sends it to the transmitting terminal. FIG. 24 shows a configuration example of the retransmission request packet 300 . CPU16 memorizes in IP head, the payload part of TCP head and represents the identifier of retransmission request packet and the sequence number of the packet sequence number for retransmission request. The number n of data packets is stored before the data packet sequence, and n sequence numbers are stored thereafter.

The resend request packet 300 is transferred to the wireless transmission unit 18 via the internal bus 19 . The wireless transmission unit 18 inputs the resend request packet 300 to the buffer unit 29 via the input/output terminal 28 . The buffer unit 29 utilizes the data transmission and reception unit 34 to temporarily store the retransmission request packet 300 input through the input and output terminal 33 in the transmission buffer unit 37 for normal data, and transmits it to the MAC processing unit through the output terminal 38 for normal data. 30. At this time, the MAC processing unit 30 uses the built-in second timer unit 31 to determine the first frequency band out-of-guaranteed period, and if it becomes the out-of-first frequency band out-of-period, the normal data buffer is controlled via the control signal input/output terminal 39. The buffer unit 37 reads the retransmission request packet 300 from the buffer unit 37 for normal data. After the read retransmission request packet 300 is appended with a MAC header, it is modulated suitable for transmission by the physical layer signal processing unit 32, and is unicast by the antenna 21 and transmitted to the transmitting terminal. The bandwidth reservation period and the determination of the transmission timing can also be determined by using the first timer unit 20 to input the same timing to the upper layer and the MAC layer.

[Retransmission packet processing operation of the sending terminal]

After receiving the retransmission request packet 300, the transmitting terminal confirms that the wireless packet has been received normally, and then returns the Ack packet 3001 to the first receiving terminal. When the first receiving terminal receives the Ack packet 3001, it waits for retransmission of the packet for which the retransmission request was made.

4, when the resend request packet 300 is received via the antenna 21, the resend request packet is output to the internal bus 19 in the reverse process of the transmission.

The wireless transmission unit 18 has the configuration shown in FIG. 8 , and first, the physical layer signal processing unit 32 demodulates the modulation performed at the time of transmission, and restores the MAC packet shown in FIG. 24 . The restored MAC packet is input to the MAC processing unit 31 , and when the address indicated by the MAC header is addressed to the own station, the MAC header is removed and output to the buffer unit 29 . The transmit buffer system is activated for transmission, and the receive buffer system is activated for reception. The MAC-processed packet is input from the received data input terminal 41 and temporarily stored in the receive buffer unit 40 . In addition, at this time, the MAC processing unit 30 controls writing of received data to the receive buffer 40 via the control signal input/output terminal 42 . The data temporarily stored in the receiving buffer unit 40 is output to the internal bus 19 via the data transmitting and receiving unit 34 and the input and output terminals 33 and 28 , and passed to the CPU 16 . At this time, the data transmission/reception unit 34 performs an operation of reading data from the reception buffer unit 40 when the internal bus 19 is available and the CPU 16 can receive data. The CPU 16 that has received the data writes the received data into the memory unit 17, but at this time, it is judged from the IP header and the TCP header in FIG. 24 whether it is a data packet that should be processed later. After performing appropriate TCP/IP processing, the CPU 16 proceeds to the content confirmation action of the load. First, the identifier is confirmed, and when the identifier indicates a retransmission request of a plurality of packets, then the number of packets and the packet sequence number of the stored number are confirmed. After that, enter the preparation for sending corresponding multiple data packets. As shown in FIG. 7, the memory unit 17 stores the data previously transmitted by multicast, so the second multicast packet data and the Nth multicast packet data in which a retransmission request is requested are retransmitted separately. . That is, the retransmission packet 103 of the second packet in FIG. 22 is transmitted to the first receiving terminal object, and then the retransmission packet 104 of the Nth packet is transmitted to the first receiving terminal object. The resent data packet is shown in Figure 10.

The transmission process is the same as the first multicast transmission procedure during the first reserved frequency band period, but since the priority of the retransmission packet is lower than that at the beginning, it is transmitted during the period outside the first reserved frequency band.

The CPU 16 transfers the retransmission packet data transmitted during the first band out-of-band guarantee period to the wireless transmission unit 18 via the internal bus 19 .

The wireless transmission data input from the CPU 16 via the internal bus 19 and the input/output terminal 28 is input to the buffer unit 29 .

The buffer unit 29 distributes the retransmission data of the second multicast packet input from the input and output terminal 33 to the normal data transmission buffer unit 37 via the data transmission and reception unit 34, and outputs the data via the normal data transmission according to the wireless transmission timing. The terminal 38 is input to the MAC processing unit 30 .

The MAC processing section 30 performs band secured period/out-of-band secured period management or MAC protocol processing, reads wireless transmission data from the buffer section 29 at an appropriate timing, and inputs it to the physical layer signal processing section 32 .

The MAC processing unit 30 uses the second timer unit 31 provided inside to determine that it is the out-of-band guarantee period, and controls the buffer unit 29 using the input-output terminal 39 for the transmission control signal during the out-of-band guarantee period, from the normal data transmission buffer The data is read out in the device unit 37, unicast. At the timing of transferring data from the CPU 16 to the buffer unit, the MAC processing unit 30 also determines a control signal that controls the normal data buffer unit 37 and the data transmission/reception unit 34 via the transmission control signal input/output terminal 39 as a trigger. The CPU 16 transfers the data to the wireless transmission unit 18 when the data request is received. The bandwidth reservation period and the determination of the transmission timing can also be determined by using the first timer unit 20 to input the same timing to the upper layer and the MAC layer.

The MAC processing unit 31 that receives the data performs wireless MAC data packetization of the data, and the wireless MAC data packet is input to the physical layer signal processing unit 32, and after the modulation suitable for wireless transmission is performed by the physical layer signal processing unit 32, the wireless MAC data packet is transmitted through the antenna 21 wireless transmission. This transmission process is performed twice when the retransmission packet 103 of the second data packet is transmitted and when the retransmission data packet 104 of the Nth data packet is transmitted.

Through the above processing, a plurality of packet data of the retransmission request using the retransmission request packet 300 is transmitted to the first receiving terminal. The first terminal that has received the retransmission packet 103 of the 2nd packet and the retransmission packet 104 of the Nth packet in this way returns the Ack packet as the reception confirmation packet to the sending terminal, and ends Re-reception of packets that failed to be received.

When the first receiving terminal fails to receive the retransmission packet 104 of the Nth packet, as shown in FIG. 25, the retransmission packet itself of the second packet may be retransmitted. 204 is a retransmission packet of the Nth data packet, and its content is the same as that of the retransmission data packet 104 of the Nth data packet. If the data packet is successfully received, the Ack data packet 2041 is returned to the sending side, and the sending is completed again. If the number of retransmissions is unlimited, other terminals may not be able to use the period outside the reserved first frequency band, so it is preferable to limit the number of retransmissions. In addition, since the use of the retransmission time itself in the period outside the first frequency band reservation suppresses interference with other transmissions, it is more practical to set a retransmission time limit.

In addition, when retransmitting a plurality of data packets, a plurality of data may be combined and transmitted as in the retransmission data packet 107 of the second data packet+Nth data packet in FIG. 25 . As a result, head-out at the time of retransmission is reduced.

[Structure of resend packet]

The details of the resent data packet at this time are shown in FIG. 26 , and the payload part may also store the data packet number n, sequence number 1, data 1, sequence number 2, data 2, etc. after the identifier. This is combined at the moment when the CPU 16 generates the resend packet.

In this way, when all the 1st to Nth multicast data packets are gathered in the memory unit 17, the CPU 16 inputs these data to the AV processing unit 43 via the internal bus 19. The AV processing unit 43 processes the input data and displays it on the display unit 41 .

In FIG. 22, the third receiving terminal fails to receive the Nth multicast packet, and uses the second resend request packet 301, Ack3011, and the Nth packet's resend packet 104, Ack1041 to perform the same processing as in Embodiment 1. processing, complete the resend processing.

According to the above configuration, there are: a memory unit for temporarily storing a multicast data group higher than the Mac layer; a serial number assigning unit for assigning a serial number for each of the multicast data groups to detect a lack of data on the receiving side; and a wireless transmission unit. , the data assigned the sequence number is transmitted by the band-guaranteed multicast packet; and the retransmission control unit uses the sequence number to retransmit the multicast data whose loss is detected by the wireless receiving side, and is performed by the upper layer of the Mac layer The retransmission control of the bandwidth-secured multicast packet is performed with a lower priority than that of the bandwidth-secured multicast packet, so the bandwidth-secured multicast data can be transmitted with the highest priority. While the reception probability can be improved by using retransmission, when the terminal on the receiving side fails to receive multiple multicast packets during the same frequency band reservation period, since multiple packets are retransmitted with one retransmission request packet request, so the amount of resend request packets can be reduced. In addition, by sending a plurality of retransmission packets in combination, useless use of the frequency band for retransmission packets can be reduced.

In addition, in this embodiment, retransmission processing of the retransmission request packet itself is not involved, but retransmission processing may be performed.

In addition, in this embodiment, the configuration described in Embodiment 2 is adopted during the period when the frequency band is not secured, and when a plurality of receiving terminals and transmitting terminals transmit retransmission request packets or other normal packets, the transmission timing can be adjusted. .

(Embodiment 4)

In each of the above-mentioned embodiments, the transmission of the retransmission packet during the period outside the reserved bandwidth is performed by using unicast to transmit independently. Unicast distribution is inefficient at sending and resending packets. The present embodiment is a technique suitable for such a case.

Fig. 27 is a timing chart showing an example of a packet sequence of the wireless transmission device according to Embodiment 3 of the present invention. In FIG. 27 , the same reference numerals are used for the same components as those in the previous time chart, and part of the description is omitted.

[Description of packet sequence]

In Fig. 27, 300 is the 1st resend request packet, 3001 is the Ack packet that transmits the 1st resend request packet 300, and 302 is the 3rd resend request packet, and 3021 is the 3rd resend request packet. The transmission request packet 302 is an Ack packet for confirmation of successful reception, and 108 is a retransmission packet of the second packet.

In the wireless section, transmission is performed by periodically switching between a secured band period and an out-of-band secured period. During the first band reserved period, N data groups are multicasted, and during the first reserved band non-period, only the data in which a reception error occurred is retransmitted.

The multicast distribution operation during the bandwidth secured period is the same as that in the first embodiment above, and the packet numbers and receiving terminals that failed to be received are shown in FIG. its action.

During the first bandwidth secured period, the first receiving terminal and the second receiving terminal failed to receive the first multicast packet 101 . Therefore, each receiving terminal performs an operation of transmitting a retransmission request packet to the transmitting terminal using the first out-of-band reserved period.

The first receiving terminal and the second receiving terminal that failed to receive the multicast packet transmit the first retransmission request packet 300 and the third transmission request packet to the transmitting terminal individually using the first out-of-band reserved period. In order to improve the transmission reliability of the resend request packet, also in this embodiment, a configuration in which a resend request is made using a unicast packet is described. If the sending terminal normally receives the first resend request packet 300 and the 3rd resend request packet 302, then after returning the Ack packet 3001, 3002 as a successful confirmation of reception, refer to the two resend request packets 300, 302 content, it is judged that the two resend request packets have the same second packet data as the resend request. Thereafter, the second packet data is transmitted to the multicast group to which the first receiving terminal and the second receiving terminal both belong using the multicast packet.

[Operation of receiving terminal]

Regarding this operation, the operation of the terminal will be described in detail below with reference to the drawings.

The first and second receiving terminals have the configuration shown in FIG. The 1st to Nth multicast packets 100 , 101 , 102 are input to the wireless transmission unit 18 , and output to the internal bus 19 after undergoing a process opposite to that of transmission.

The wireless transmission unit 18 first demodulates the modulation performed by the physical layer signal processing unit 32 at the time of transmission, and restores the MAC packet shown in FIG. 10 . The restored MAC packet is input to the MAC processing unit 31, and when the broadcast address indicated by the MAC header is addressed to the broadcast group to which the own station belongs, the MAC header is removed and output to the buffer unit 29. The buffer unit 29 receives the MAC-processed packet and temporarily stores it in the receiving buffer unit 40 . In addition, at this time, the MAC processing unit 30 controls writing of received data to the receive buffer 40 via the control signal input/output terminal 42 . The data temporarily stored in the receiving buffer unit 40 is output to the internal bus 19 via the data transmitting and receiving unit 34 and the input and output terminals 33 and 28 , and passed to the CPU 16 . At this time, the data transmission/reception unit 34 performs an operation of reading data from the reception buffer unit 40 when the internal bus 19 is available and the CPU 16 can receive data. The CPU 16 that has received the data writes the received data in the memory unit 17, but at this time, according to the IP header, UDP header, and identifier of FIG. 6, the CPU 16 judges whether it is a data packet that should be processed later. That is, the internal destination is judged using the IP header and UDP header, and whether it is multicast data to be stored in the memory is judged using the identifier.

By referring to the data storage state inside the memory unit 17, it can be judged which sequence number the packet data is missing.

The CPU 16 makes preparations for judging that the data of the second multicast packet is lacking, generates a resend request packet 300 or 302, and sends it to the sending terminal object. The CPU 16 stores, in the IP header and the payload of the TCP header, an identifier indicating that it is a resend request packet, and a sequence number of the packet for which a resend request is made.

The resend request packet 300 or 302 is transferred to the wireless transmission unit 18 via the internal bus 19 . The wireless transfer unit 18 temporarily stores the retransmission request packet 300 in the buffer unit 37 for normal data in the buffer unit 29 , and passes it to the MAC processing unit 30 . The MAC processing unit 30 uses the built-in second timer unit 31 to determine the period outside the first frequency band guarantee, and if it becomes the period outside the first frequency band guarantee, it controls the buffer unit 37 for normal data via the control signal input and output terminal 39, The resend request packet 300 or 302 is read from the normal data buffer unit 37 . After the read retransmission request packet 300 or 302 is appended with a MAC header, it is modulated for transmission by the physical layer signal processing unit 32, and is unicast by the antenna 21 and transmitted to the transmitting terminal. The above processing is performed in the first receiving terminal for the resend request packet 300, and is performed in the second receiving terminal for the resend request packet 302.

[Operation of sending terminal]

After receiving the retransmission request packet 300, the transmitting terminal confirms that the wireless packet has been received normally, and then returns the Ack packet 3001 to the first receiving terminal. When the first receiving terminal receives the Ack packet 3001, it waits for retransmission of the packet for which the retransmission request was made. When the transmitting terminal that has received the retransmission request packet 302 confirms that the wireless packet has been received normally, it returns the Ack packet 3021 to the second receiving terminal. When the first receiving terminal and the second receiving terminal receive the Ack packets 3001 and 3021, respectively, they wait for retransmission of the second multicast packet for which a retransmission request was made.

When the transmitting terminal internally receives the resend request packet 300 or 302 via the antenna 21, it outputs the resend request packet 300 or 302 to the internal bus 19 in the reverse process of the transmission.

In the wireless transmission unit 18, first, the modulation performed by the physical layer signal processing unit 32 at the time of transmission is demodulated, and the MAC packet is restored. The restored MAC packet is input to the MAC processing unit 31 , and when the address indicated by the MAC header is addressed to the own station, the MAC header is removed and output to the buffer unit 29 . The buffer unit 29 inputs the MAC-processed packet from the received data input terminal 41 and temporarily stores it in the receive buffer unit 40 . In addition, at this time, the MAC processing unit 30 controls writing of received data into the receive buffer 40 via the control signal input/output terminal 42 . The data temporarily stored in the receiving buffer unit 40 is output to the internal bus 19 via the data transmitting and receiving unit 34 and the input and output terminals 33 and 28 , and passed to the CPU 16 . At this time, the data transmission/reception unit 34 performs an operation of reading data from the reception buffer unit 40 when the internal bus 19 is available and the CPU 16 can receive data. The CPU 16 that has received the data writes the received data into the memory unit 17, but at this time, it is judged based on the IP header and the TCP header whether it is a packet that should be processed later. When receiving a plurality of resend request packets requesting the same data for resend, the CPU 16 compares the contents thereof, and proceeds to preparation of packet data corresponding to multicast transmission. Since the data previously transmitted by multicast is stored in the memory unit 17, the second multicast packet data in which the retransmission request is requested is retransmitted by multicast. That is, the retransmission packet 108 of the second packet in FIG. 27 is transmitted to the multicast group to which the first receiving terminal and the second receiving terminal belong together.

The retransmission packet 108 is structured as shown in FIG. 10, and the payload part is composed of an identifier indicating that it is a retransmission packet, a sequence number, and data. This data part is the same as the second multicast packet data packet which is first multicast transmitted.

The transmission process is the same as the first multicast transmission procedure during the first reserved frequency band period, but since the priority of the retransmission packet is lower than that at the beginning, it is transmitted during the first out-of-band reserved period.

The CPU 16 transfers the retransmission packet data transmitted during the first band out-of-band guarantee period to the wireless transmission unit 18 via the internal bus 19 .

The wireless transmission data input from the CPU 16 via the internal bus 19 and the input/output terminal 28 is input to the buffer unit 29 .

The retransmission data of the second multicast data packet input from the input and output terminal 33 is distributed to the normal data transmission buffer unit 37 through the data transmission and reception unit 34, and is input to the transmission buffer unit 37 through the normal data output terminal 38 according to the wireless transmission timing. MAC processing unit 30 .

The MAC processing section 30 performs band secured period/out-of-band secured period management or MAC protocol processing, reads wireless transmission data from the buffer section 29 at an appropriate timing, and inputs it to the physical layer signal processing section 32 .

The MAC processing unit 30 uses the second timer unit 31 provided inside to determine that it is the out-of-band guarantee period, and controls the buffer unit 29 using the input-output terminal 39 for the transmission control signal during the out-of-band guarantee period, from the normal data transmission buffer The data is read out in the device unit 37, and multicast.

The timing at which data is transferred from the CPU 16 to the buffer unit is also determined by the control signal of the MAC processing unit 30 controlling the normal data buffer unit 37 and the data transmission and reception unit 34 via the transmission control signal input and output terminal 39 as a trigger. . The CPU 16 transfers the data to the wireless transmission unit 18 when the data request is received. The bandwidth reservation period and the determination of the transmission timing can also be determined by using the first timer unit 20 to input the same timing to the upper layer and the MAC layer.

The MAC processing unit 30 that receives the data performs wireless MAC data packetization of the data, and the wireless MAC data packet is input to the physical layer signal processing unit 32, and after the modulation suitable for wireless transmission is performed by the physical layer signal processing unit 32, the wireless MAC data packet is transmitted through the antenna 21 wireless transmission. In this way, the multicast transmission of the retransmission packet 108 of the second packet is performed.

Through the above processing, when retransmission of the same data is requested from two receiving terminals using retransmission request packets 300 and 302, it is transmitted to the first and second receiving terminals using multicast.

[Modification and application of this embodiment]

Since the retransmission data packet 108 of the second data packet is a data packet transmitted by a multicast data packet that does not use the Ack data packet, in the case of wanting to improve the reliability, it can also be sent repeatedly as shown in FIG. 28 .

In addition, as shown in the second multicast packet 101 in FIG. 29, even if there is only one receiving terminal that failed to receive, the request for another packet is written in the retransmission request packet (in FIG. In the case of 29, the first receiving terminal uses the first retransmission request packet 30 to request retransmission of the second multicast packet 101 and the Nth multicast packet 102.) In this case, it is also possible to use multicast to send The retransmission packet 108 of the second packet is repeatedly transmitted. If this method is used, the Nth multicast packet 102 in FIG. 29 does not wait for the reception of the retransmission request packets from other receiving terminals when a plurality of receiving terminals fail to receive the multicast packet 102 at the same time. When the request packet 300 is sent, the packet can be resent. Accordingly, the third receiving terminal can receive the necessary resend packet without sending the resend request packet.

In FIG. 29, the first resend request packet 300 is unicast, but by sending the first resend request packet 300 by multicast, other receiving terminals can know which data is requested to be resent by receiving terminals other than the own terminal. Accordingly, the CPU 16 can also perform the judgment of stopping the transmission of the retransmission request packet at the time when other receiving terminals can judge that the data requested by itself is requested.

The number of repetitions of the resend request packet in FIG. 28 and FIG. 29 can be appropriately determined by the CPU 16 according to the current situation according to the resend count of the past resend request packet.

The number of repetitions of the retransmission packet in FIG. 28 and FIG. 29 can be appropriately determined by the CPU 16 according to the current situation based on the number of retransmissions of the past retransmission packet.

In addition, as shown in FIG. 30, if all the packets that received the resend request are combined at the upper layer, and the resend packet of the second packet + the Nth packet of the multicast resend 110 is multicast, the resend packet is subtracted. Both the number of request packets and the number of retransmission packets can realize effective use of the frequency band. In this case, since the length of the multicast packet becomes longer, the probability of reception failure increases. A terminal that has failed in reception may retransmit the retransmission request 301 to reacquire a part of the data packet 100 (data packet 104). In this case, if the sending side unicasts the transmission, the reception probability can be increased.

In this way, if the 1st to Nth multicast data packets are all gathered in the memory unit 17 , the CPU 16 will input these data into the AV processing unit 43 via the internal bus 19 . The AV processing unit 43 processes the input data and displays it on the display unit 41 .

According to the above configuration, there are: a memory unit for temporarily storing a multicast data group higher than the MAC layer; a sequence number assigning unit for assigning a sequence number for each of the multicast data groups to detect a lack of data on the receiving side; and a wireless transmission unit. , the data assigned the sequence number is transmitted by the band-guaranteed multicast packet; and the retransmission control unit uses the sequence number to retransmit the multicast data whose loss is detected by the wireless receiving side, and is performed by the upper layer of the Mac layer The retransmission control of the bandwidth-secured multicast packet is performed with a lower priority than that of the bandwidth-secured multicast packet, so the bandwidth-secured multicast data can be transmitted with the highest priority. Retransmission can be used to improve the reception probability, and when multiple terminals on the receiving side fail to receive the same multicast packet during the same frequency band reservation period, the retransmission data can be resent by multicast, so the retransmission data can be reduced The amount of packets sent. In addition, by repeating multicast retransmission and retransmission of packets, the reception probability can be increased. When the first resend request packet is received, the multicast resend eliminates the need for other receiving terminals to transmit the resend request packet, thereby effectively utilizing the frequency band. In addition, it is also possible to effectively use the frequency band by transmitting and retransmitting packets in high-order link.

In addition, in this embodiment, retransmission processing of the retransmission request packet itself is not involved, but retransmission processing may be performed.

In addition, in this embodiment, the configuration described in Embodiment 2 is adopted during the period when the frequency band is not secured, and when a plurality of receiving terminals and transmitting terminals transmit retransmission request packets or other normal packets, the transmission timing can be adjusted. .

(Embodiment 5)

In Embodiment 4, the retransmission packet is distributed by multicast, and the distribution timing is during the out-of-band reservation period. In the case of multicast distribution, even if it does not transmit during the period when the band is not secured, it can be transmitted during the next period of band securing. The present embodiment adopts a configuration in which a retransmission packet is transmitted during the bandwidth reservation period of the next cycle. In addition, in the above-described embodiments, packets are transmitted and received by the transmitting terminal and the receiving terminal, but in this embodiment, as an example, a configuration in which packets are exchanged between a base station and a slave station is employed. Therefore, it should be noted that different terms are used from the above-described embodiments.

In addition, in this embodiment, the adjustment of the transmission timing described in Embodiment 2 is performed during the out-of-band reserved period. Please note that the description is repeated with Embodiment 2.

FIG. 31 is a schematic diagram for explaining the wireless multicast retransmission method of this embodiment, and FIG. 32 is a diagram showing the configuration of a wireless network to which the method of FIG. 31 is applied.

[Configuration of wireless network]

In FIG. 32, a wireless network 310 is composed of a wireless base station 100, a multicast group 111, a multicast group 112 consisting of wireless sub-stations 101-104, and wireless sub-stations 121, 122, and these devices are connected by a wireless LAN. In addition, the wireless base station 100 is connected to a server storing content such as images and music using a wired network such as Ethernet or a high-speed serial bus such as IEEE1394. The wireless sub-stations belonging to the multicast groups 111 and 112 can individually transmit and receive wireless frames with the wireless base station 100 in addition to receiving the wireless frames distributed by the multicast from the wireless base station 100 . The wireless substations 121 and 122 can communicate wirelessly with other wireless substations via the wireless base station 100 or directly. The radio base station 100 performs communication control of each radio sub-station at the transmission timing of these radio frames and the like.

[Configuration of wireless base station]

FIG. 33 is a diagram showing the device configuration of the radio base station 100 . The operation of the radio base station 100 will be described with reference to FIG. 33 .

In FIG. 33 , the input/output unit 320 is an interface with a wired network such as Ethernet or a high-speed serial bus such as IEEE1394, and exchanges stream data or asynchronous data with terminals connected thereto. The stream data transmission buffer 321 adds a stream data number and an error detection code to the stream data received by the input/output unit 320, converts it into a radio frame, and stores it. The stream data stored in the stream data transmission buffer 321 is transmitted from the transmission unit 324 to the wireless section during the stream transmission period.

The asynchronous data transmission buffer 322 adds an error detection symbol to the asynchronous data input from the input/output unit 320, converts it into a radio frame, and stores it. When sending asynchronous data with a priority order, the asynchronous data transmission buffer 322 is configured as shown in FIG. 35 . In FIG. 35 , the asynchronous data transmission buffer 340 is the same as the asynchronous data transmission buffer 322 in FIG. 33 . The asynchronous data transmission buffer 340 is composed of an asynchronous data distribution unit 341 and a plurality of transmission queues (1) 342 - (N) 344 . The asynchronous data distribution unit 341 distributes the asynchronous data received from the input and output unit 320 in priority order, and outputs them to the sending queues (1) 342-(N) 344, and the sending queues (1) 342-(N) 344 Store asynchronous data sequentially in priority order.

In FIG. 33 , the backoff control unit 323 prepares counters for each of the transmission queues (1) 342 - (N) 344 . In the case of storing asynchronous data in one of the sending queues (1) 342-(N) 344, a randomly selected natural number is inserted into the counter as an initial setting value, and during asynchronous transmission, at each specified time T1 Counting, when the counter reaches 0, the asynchronous data stored in the transmission queue is transmitted from the transmission unit 324 to the wireless section.

The transmitter 324 performs digital modulation such as multilevel phase modulation or multilevel quadrature amplitude modulation on streaming data or asynchronous data, converts it into a high-frequency analog signal, and transmits it from an antenna to a wireless section.

The receiving unit 325 converts the analog signal received from the antenna into a baseband digital signal, and performs digital demodulation. The error detection unit 326 detects whether there is no transmission error in the received data subjected to digital demodulation, and stores it in the reception buffer 327 if there is no error.

The reception buffer 327 judges the received data, and passes the received data to the retransmission control unit 328 if it is a retransmission request, and passes it to the input/output unit 320 if it is other data. Upon receiving the retransmission request, the retransmission control unit 328 instructs the stream data transmission buffer 321 to retransmit the instructed stream data.

[Configuration of Wireless Substation]

Fig. 34 is a diagram showing the device configuration of a wireless substation. The operation of the wireless slave station will be described using FIG.34.

In FIG. 34, the input/output unit 330 is an interface for exchanging stream data or asynchronous data. The stream data transmission buffer 331 adds a stream data number and an error detection code to the stream data input from the input/output unit 330, converts it into a radio frame, and stores it. The streaming data stored in the streaming data transmission buffer 331 is transmitted from the transmitting unit 334 to the wireless section under the control of the wireless base station 1100 during the streaming transmission period. A wireless substation that does not transmit streaming data does not need to have a streaming data transmission buffer 331 .

The asynchronous data transmission buffer 322 adds an error detection symbol to the asynchronous data input from the input/output unit 330 and the retransmission request input from the retransmission request unit 338 , converts them into radio frames, and stores them. FIG. 35 shows the detailed configuration of the asynchronous data transmission buffer 340 of the wireless sub-station similarly to the wireless base station. The asynchronous data transmission buffer 340 is the same as the asynchronous data transmission buffer 322 in FIG. 34 . The asynchronous data transmission buffer 340 is composed of the asynchronous data distribution unit 41 and a plurality of transmission queues (1) 342 - (N) 344 . The asynchronous data distribution unit 341 distributes the asynchronous data received from the input/output unit 330 and the retransmission request input from the retransmission request unit 338 in order of priority, and outputs them to transmission queues (1) 342 - (N) 344 . Here, if the priority order of the sending queue (1) 342 is the highest, then the resend request is stored in the sending queue (1) 342, and other asynchronous data are stored in the sending queue (2) 343-(N )344.

In FIG. 34 , the backoff control unit 333 prepares counters for each of the transmission queues (1) 342 - (N) 344 . In the case of storing asynchronous data in one of the sending queues (1) 342-(N) 344, a randomly selected natural number is inserted into the counter as an initial setting value, and during asynchronous transmission, at each specified time T1 Counting, when the counter reaches 0, the asynchronous data stored in the transmission queue is transmitted from the transmission unit 334 to the wireless section.

The transmitter 334 performs digital modulation such as multilevel phase modulation or multilevel quadrature amplitude modulation on streaming data or asynchronous data, converts it into a high-frequency analog signal, and transmits it from an antenna to a wireless section.

The receiving unit 335 converts the analog signal received from the antenna into a baseband digital signal, and performs digital demodulation. The error detection unit 326 detects whether there is no transmission error in the received data subjected to digital demodulation, and notifies the retransmission request unit 338 if there is a transmission error. If there is no transmission error, it is stored in the receive buffer 337 .

The receive buffer 337 judges the received data, if it is stream data, reconstructs the stream data in order of serial number, and transmits it to the input/output unit 320 . Since the retransmission request unit 338 notifies the radio base station 1100 of the serial number of the radio frame detected by the error detection unit 336 , a retransmission request frame is formed and stored in the asynchronous data transmission buffer 332 .

[action on wireless network]

The wireless network 110 constituted as above distributes the image content currently stored in the server 130 to the wireless sub-stations 101-104 belonging to the multicast group 111 via the wireless base station 100. The wireless base station 100 divides the image content into a plurality of stream data from the server 130 and receives it, adds a stream number to the received stream data, converts it into a wireless frame, and multicasts and distributes it to the multicast group 111 .

[Explanation of multicast method]

Here, the wireless multicast method when the wireless base station 100 wirelessly distributes streaming data to the wireless slave stations 101-104 belonging to the multicast group 111 will be described using FIG.31. In FIG. 31 , the vertical direction shows the passage of time from top to bottom, and the horizontal direction shows the transmission and reception status of wireless frames composed of streaming data and asynchronous data between wireless terminals. In the wireless multipoint transmission method of this embodiment, time is divided for each predetermined time period, and a stream transmission period corresponding to the frequency band securing period of the above-mentioned embodiment is set in each time period (corresponding to the frequency band securing period of the above-mentioned embodiment) band secured period) and an asynchronous transmission period (corresponding to the band secured period in the above-mentioned embodiment). During streaming, with the control from the wireless base station 100, the wireless base station 100 or any wireless sub-station transmits streaming data such as images or sounds that must be secured in advance in a wireless frequency band, and the wireless sub-station cannot freely transmit wireless frames. During asynchronous transmission, the radio base station 100 or any of the radio sub-stations transmits asynchronous data that does not require isochronism, such as Internet data, without control from the radio base station 100 .

[Action during streaming]

The length of time during streaming is determined by the amount of streaming data that must be transmitted within a specified time. However, if the wireless transmission path is not occupied during the streaming transmission period, the wireless base station 100 limits it to a predetermined time or less. The wireless base station 100 determines the time length of the streaming period according to the amount of streaming data transmitted from the server 130, broadcasts the transmission beacon 210 at the beginning of the time period, and notifies all wireless slave stations of the subsequent streaming period. In addition, the beacon 210 also includes the end time of one cycle, that is, the transmission time of the next beacon 220 . And, at the end of the streaming transmission period, the wireless base station 100 broadcasts and transmits the streaming transmission period end notification 211, and notifies all the wireless slave stations that the asynchronous transmission period will follow. The same applies to the next time period. At the beginning of the streaming period, the broadcast transmission beacon 220 is broadcast, and at the end of the streaming period, the broadcast transmission end notification 221 is broadcast. Afterwards, by repeating this operation, all wireless sub-stations can know the start and end of the stream transmission period and the asynchronous transmission period.

In addition, in FIG. 31, the end of the streaming transmission period is notified to all wireless sub-stations through the wireless base station 100 broadcast transmission end notification 211 and 221, but it is also possible to embed information on the end time of the streaming transmission period in the beacons 210 and 220 to notify Based on the end time information of the stream transmission period embedded in the beacons 210 and 220 for all wireless substations, the wireless substations perform operations during the asynchronous transmission period after that time.

During streaming, the wireless base station 100 converts the stream data divided and sent from the server 130 into wireless stream data 310-31N, and sequentially multicasts and distributes them to wireless sections. The radio base station 100 adds the sequence number and error detection code of the stream data when converting to the radio stream data. When the wireless substations 101-104 receive the stream data 310-31N, they perform an error check to see if there is no transmission error in the stream data 310-31N. In FIG. 31 , the wireless substation 102 detects a transmission error in the stream data 312 , and the wireless substation 103 detects a transmission error in the stream data 313 . Therefore, since the wireless substation 102 retransmits the streaming data 312 to the wireless base station 100 , preparations are made by creating a retransmission request frame embedding information that the streaming data 312 cannot be received normally, and sending it to the wireless base station 100 . The wireless substation 103 is the same, since it will retransmit the streaming data 313 to the wireless base station 100, it prepares to create a retransmission request frame embedding the information that the streaming data 313 cannot be received normally, and transmits it to the wireless base station 100.

In the above error detection confirmation, when the wireless slave station 102 detects an error in the stream data 312, it cannot be judged that the stream data 312 cannot be received normally. Therefore, since the wireless substation 102 normally receives the streaming data 311 and the streaming data 313 sequentially transmitted from the wireless base station 100, it can be known that the streaming data 312 is lost. The wireless substation 102 judges that a reception error is detected in the stream data 312 based on information such as loss of the stream data 312 and detection of an error in the stream data received in the order in which the stream data 312 was originally received.

[Operation during asynchronous transmission]

The above is the operation of the radio base station 100 and the radio slave stations 101-104 during the streaming transmission period. Next, the operation of the asynchronous transmission period after the radio base station 100 transmits the end notification 211 of the streaming transmission period will be described.

During asynchronous transmission, the wireless base station 100 and all other wireless substations belonging to the wireless network 10 transmit asynchronous data at their own transmission timing without being controlled by the wireless base station 100 . Here, since the wireless base station 100 or other wireless sub-stations transmit asynchronous data in disorder, the transmission start timing of the asynchronous data competes and collides in the wireless section, so a transmission error occurs.

Therefore, the radio base station 100 and all the radio sub-stations belonging to the network 10 individually hold counters for determining the transmission start timing. When it is necessary to send asynchronous data, the counter is randomly selected from the natural numbers within the predetermined range and set as the initial value. At each specified time T1, the counter is counted down by 1, and at the moment it is 0, the asynchronous data is sent. .

The range of the value set as the initial value of the counter can be statistically determined to be an optimal value according to the number of wireless terminals belonging to the network 10, the amount of asynchronous data transmitted in the wireless section, and the like. The predetermined time T1 is assumed to be longer than or equal to the time during which it can be confirmed whether or not another terminal has not transmitted a radio frame during T1.

In addition, the wireless substation has one or more asynchronous data sending buffers inside, and each asynchronous data sending buffer has the counter. A wireless substation requesting retransmission of stream data must have at least two asynchronous data transmission buffers. It is assumed that the counter initial setting value of the asynchronous data transmission buffer used to transmit the retransmission request among the plurality of reserved asynchronous data transmission buffers can take the maximum value of the range, which is higher than the counter initialization value of the other asynchronous data transmission buffers. The maximum value of the range where the setting value can be obtained is small. For example, if the initial setting value of the counter of the asynchronous data transmission buffer other than the resend request is randomly selected from '1'-'32', then the counter of the asynchronous data transmission buffer used to send the resend request is set The initial setting value is randomly selected from '1'-'8'.

FIG. 36 is a diagram showing an example of asynchronous data transmission timing in the asynchronous transfer period. In FIG. 36 , the numbers surrounded by circles represent the counter values of the asynchronous data transmission buffers of the respective wireless terminals. In addition, each counter value is counted every predetermined time T1. In Fig. 36, the countdown state of the counter is illustrated for easy understanding, so the time in the direction of the horizontal axis is schematically represented, the countdown time T1 and the time length required for resending requests or other asynchronous data transmissions and the actual time length different. Usually, the length of time required for asynchronous data transmission is much longer than the predetermined time T1.

In FIG. 36 , as described above, when the wireless base station 100 broadcasts the end notification 211 of the transmission stream transmission period, it becomes an asynchronous transmission period thereafter. During asynchronous transmission, the wireless substation 102 must send a resend request 412 for the stream data 312 , and the wireless substation 103 must send a resend request 413 for the stream data 313 . In addition to the retransmission request, the base station 100 must transmit the asynchronous data 512 and the wireless substation 101 must transmit the asynchronous data 511 . Here, the wireless base station 100 and the wireless sub-station 101 randomly select the counter initial setting value from '1'-'32', and the wireless sub-station from '1'-'8'. In Fig. 36, the wireless base station 100 selects '12', the wireless substation 101 selects '6', the wireless substation 102 selects '3', and the wireless substation 103 selects '7' as the initial setting value of the counter.

After entering the asynchronous transmission period, it is confirmed that it is an idle period in which other wireless terminals do not transmit wireless frames to the wireless section, and the wireless base station 100 and the wireless sub-stations 101-103 count down the counters by 1 at each time T1. The idle period is determined to be an idle period in which the received power input from the antenna is measured, and when the received power is equal to or less than a predetermined value, it is determined to be an idle period in which no other wireless terminal transmits a wireless frame. When the wireless base station 100 and the wireless sub-stations 101-103 count down the counters, the counter of the wireless sub-station 102 becomes 0 at first, and the right to transmit asynchronous data is obtained. The wireless slave station 102 transmits the retransmission request 102 to the wireless section immediately after the counter becomes 0. The counter values of the wireless base station 100, the wireless sub-station 101, and the wireless sub-station 103 at this time are '9', '3', and '4', respectively.

While the wireless substation 102 is transmitting the retransmission request 102, the wireless base station 100, the wireless substation 101, and the wireless substation 103 do not count down their respective counters. When the wireless substation 102 finishes sending the retransmission request 102, it becomes an idle period, and the wireless base station 100, the wireless substation 101, and the wireless substation 103 count down the respective counters again. Next, the wireless slave station 101 whose counter becomes 0 acquires the right to transmit the asynchronous data and transmits the asynchronous data 511 . By repeating the above operations, the wireless slave station 103 transmits the retransmission request 413, and the wireless base station 100 sequentially transmits the asynchronous data 512.

The asynchronous data 512 transmitted from the wireless base station includes an Ack response to the retransmission request transmitted from the wireless substation.

In the example shown in FIG. 36 , the wireless substation 103 transmits the retransmission request 413 after the asynchronous data 511 transmitted by the wireless substation 101 . However, this is just an example. As long as the initial setting value of the counter obtained when sending a resend request is '1'-'8', the initial setting value of the counter obtained when sending other asynchronous data is '1'-' 32', the resend request is probabilistically prioritized over other asynchronous data to obtain the sending right, and is sent first. In addition, if the range of the initial setting value of the counter when sending the resend request is set to '1'-'4', it can also be given priority over other asynchronous data transmissions. However, if the acquisition range of the initial setting value of the counter is reduced, the state of the wireless transmission path is poor, and if transmission errors occur frequently, the number of terminals sending retransmission requests increases, and multiple wireless terminals take the same value as the initial value of the counter. The probability of the value increases, and when a plurality of wireless terminals transmit retransmission requests, a collision occurs. Therefore, the range of the initial value of the counter set when the retransmission request is transmitted is flexibly set according to the situation of the wireless transmission path and the like.

As described above, by transmitting the retransmission request of stream data mixed with asynchronous data, it is possible to effectively use the radio frequency band to notify the radio base station 100 of the retransmission request.

[Action after the next cycle]

When the streaming transmission period and the asynchronous transmission period are regarded as one cycle and complete one cycle, the radio base station 100 broadcasts the transmission beacon 220 again, and becomes the streaming transmission period. In the preceding asynchronous transmission period, the radio base station 100 received a retransmission request 412 for the stream data 312 from the radio substation 102 , and received a retransmission request 413 for the stream data 313 from the radio substation 103 . Therefore, at the beginning of the streaming period, the radio base station 100 retransmits the stream data 312 and the stream data 313 in multicast. Since the stream data 312 has been normally received by the wireless slave stations other than the wireless slave station 102, even if the stream data 312 is received and retransmitted without error, it is discarded. Similarly, since the wireless slave stations other than the wireless slave station 103 have already received the stream data 313 normally, the stream data 313 retransmitted even if received without error is discarded. As described above, the retransmission of the stream data in which the transmission error occurred is completed.

In addition, in the example of FIG. 31, only one wireless substation cannot normally receive the stream 312 and the stream 313. Therefore, it is also possible to individually unicast and resend to the wireless substation that cannot normally receive it.

Hereafter, similarly, when the wireless substation 101 cannot normally receive the stream data 321 distributed by multicast during the streaming transmission period, it can also request retransmission by sending a retransmission request 421 to the wireless base station 100 during the asynchronous transmission period. Stream data 321 is sent.

By repeating the above operations, multicast retransmission of stream data can be performed.

Since the wireless base station 100 does not know the information that the streaming data is normally received from the wireless sub-stations 101-104, it is necessary to hold the streaming data. Therefore, when there is no request for retransmission of stream data from the wireless slave stations 101-104 within a predetermined time, the corresponding stream data is discarded. For example, if 300 milliseconds have elapsed since the first transmission of the stream data 311, it is determined to be discarded. At this time, the radio base station 100 must prepare a transmission buffer holding 300 milliseconds of streaming data. In addition, as another method, if the radio base station 100 does not receive a retransmission request from the radio sub-stations 101-104 during a predetermined period, all the stream data transmitted before the predetermined period are regarded as being normally received by the radio sub-stations 101-104. Stream data is discarded from the send buffer.

Through the above operations, it is possible to prevent the radio base station 100 from infinitely holding streaming data.

(Embodiment 6)

In Embodiment 1, the out-of-band guaranteed period is provided after the reserved in bandwidth period, and the retransmission request and the retransmission packet in response thereto are transmitted during this period. , It is also possible to multicast the distribution stream data. In this distribution, once the reception fails, a resend request can be made, and the resend of the failed packet is not delayed, and the purpose can be achieved. This embodiment shows an example in which such a band period and an out-of-band period are not provided.

Fig. 37 is a time chart showing an example of a packet sequence in the wireless transmission device according to the sixth embodiment.

[Description of packet sequence]

Components in FIG. 37 are the same as those in Embodiment 1 and the like, and therefore description thereof will be omitted. In addition, the configurations of the transmitting terminal and the receiving terminal are also the same as those described in Embodiment 1, so descriptions thereof are omitted here.

[explanation of priority]

The time chart in FIG. 37 does not distinguish between the band secured period and the band not secured period. Instead of distinguishing the above-mentioned periods, the data packets are transmitted and received preferentially during the frequency band securing period, and the data packet transmission itself is given priority.

Fig. 38 shows an example of a method with priority. 500 is the highest priority data packet, 501 is the second priority data packet, 502 is the third priority data packet, and 504 is the low priority data packet.

In FIG. 38 , the horizontal axis is the time axis, and the waiting time from the end of the busy period, that is, the period in which the previous wireless packet is transmitted, to the time when the packet can be transmitted varies depending on the priority of the packet. The highest priority data packet 500 can send a data packet after waiting for a short waiting time T1, the second priority data packet 501 can send a data packet after waiting for a second shortest waiting time T2, and the 3rd priority data packet 502 can wait for another short waiting time. The data packet is sent after the waiting time T3, and the data packet with the lowest priority 503 can be sent after waiting the longest waiting time T4. In this way, by controlling the transmission waiting time, it is possible to have transmission priority.

That is, as described with reference to FIG. 37, the transmitting terminal is not busy when the first multicast packet 100 has been transmitted, so the priority packets of each order start counting the waiting time. When time T1 is reached, if there is a first priority packet to be transmitted, the packet is transmitted. As a result, the transmitting terminal becomes busy. If the sending is finished, start counting the waiting time again. When the time T1 has elapsed, if there is a first priority packet to be transmitted, the transmission of the packet is started, and the state becomes busy. Next, whenever the sending data packet is finished, the waiting time is started to be calculated, and when the time T1 is reached, if there is a first priority data packet to be sent, then it is sent, if there is no first priority data packet, then it is not sent, Keep counting the time. Thereafter, when time T2 is reached, if there is a second priority packet to be transmitted, it is transmitted. If it does not exist, continue to calculate the waiting time, and when the time reaches T3, if there is a third data packet, then send it.

In this way, this embodiment does not set a period such as a band guarantee period, but by setting the waiting time in response to the priority, the data packet with a higher priority is sent preferentially, and after all the data packets of the higher priority are sent, the next order Priority data packets are sent, and the same transmission sequence is realized as during the band reservation period and during the non-band reservation period.

In the comparison between FIG. 3 and FIG. 37, the frequency band securing period in FIG. 3 is replaced with the first priority packet group in FIG. 37, and during this period, the first to Nth multicast packet groups are transmitted from the sending terminal to the receiving terminal. . When it ends, the resend request packet and the resend packet are transmitted from the second priority packet group. Non-priority packet groups are the next priority. These actions are repeated periodically.

In this embodiment, the 1st-Nth multicast packets are set as the first priority packets, and the resend request packet and the resend packet are set as the second priority packets, but the 1st-Nth multicast packets may also be set as the first priority packets. The Nth multicast packet is a priority packet of the first priority packet, the retransmission request packet is a second priority packet, and the retransmission packet is a priority packet of the third priority packet. At this time, since the priority is 3, the buffer unit included in the transmitting terminal has two transmission buffers as shown in FIG. 9 and cannot store the third packet. Therefore, the buffer unit 400 for low priority data and the output terminal 401 for low priority data are added to the transmission of the retransmission data packet which is the third priority data packet, and the transmission buffer configuration shown in FIG. 39 is adopted. The priority should just be 1st priority ≥ 2nd priority ≥ 3rd priority. In addition, the priority of the resend request packet and the priority of the resend packet may be reversed.

According to the above configuration, since the retransmission control uses the second priority packet to perform retransmission with a priority lower than that of the multicast packet, it is possible to transmit the multicast data with the highest priority while using the retransmission of the next priority to make the receiving The probability increases.

[Modification and application of this embodiment]

In addition, in this embodiment, retransmission processing of each unicast packet is not involved, but retransmission processing may be performed as a matter of course.

Also, in this embodiment, the length of the waiting time is set according to the priority, but as shown in Embodiment 2, a configuration may be adopted in which a random number below a different upper limit value is assigned according to the priority, and starting from this value Pulses such as count down clock pulses can be sent if they are zero.

In detail, each packet of the first priority packet group is assigned a random number with an upper limit of 3 or less, and each packet of the second packet group is assigned a random number with an upper limit of 7 or less. Each packet allocation upper limit value of the third packet group is a random number of 31 or less. Correctly, the random number is not allocated to the data packet but to the buffer storing the data packet, but for the sake of explanation, it is described as being allocated to the data packet. Each packet is counted down only while the network is not busy, and once it reaches zero, it starts sending.

Here, for the first priority packet group, the random number assigned to the second multicast packet 101 is counted down from the time when the transmission of the first multicast packet 100 is completed. The countdown of the random number assigned to the third multicast packet is performed simultaneously with the end of the transmission of the second multicast packet. That is, for the first priority packet group, counting down from the random number for the N+1th multicast packet starts when the transmission of the Nth multicast packet ends.

For the second packet group, for example, the countdown of the random number for the retransmission request packet starts from the time when the retransmission request is generated. In the case of a retransmission request of the first multicast packet, it starts from the time when the reception failure of the packet is detected. In the case of a resend packet, it starts from the time when the resend request is received. Similarly, the third priority packet group also starts from the time when the transmission of the packet is requested.

(Embodiment 7)

In most of the above-mentioned embodiments, the bandwidth secured period and the unsecured bandwidth period are repeated cyclically, and the data packets that failed to be transmitted are retransmitted during the unsecured bandwidth period or the next cycle secured bandwidth period. The period of cyclic repetition is assumed to be the length of time required for transmission and reception of the resend request packet and the resend packet. However, how many packets fail to deliver varies with the situation and is not necessarily the same for each cycle. There is no problem in a cycle with a small number of failed packets, but in a cycle with a large number of failed packets, the cycle is extended before all packets are sent in this cycle, or the cycle is not extended and sent in the next cycle, Or it is impossible to send any more and a new data packet is sent in the next cycle, and the countermeasure is not clear. This embodiment provides an answer at this point.

Next, this embodiment will be described.

[Configuration of multicast communication system]

Fig. 40 is a configuration diagram of a multicast communication system according to Embodiment 7 of the present invention.

In Fig. 40, 1401 is the master station, and 1402-1405 are child stations. They are all set within the home. The master station 1401 and the sub-station 1402 are set in the living room, and the sub-stations 1403-1405 are respectively set in the kitchen, children's room, and bedroom. 1411-1415 are high-definition television video and audio streams, and 1416 is a wireless signal based on IEEE802.11a, including the multicast distribution signal of the high-definition television video and audio stream 1411 . 1430 is a video and audio server that outputs the HDTV video and audio stream 1411 and is equipped inside the master station communication device 1401 . 1431 is a master station communication device that inputs the HDTV video and audio stream 1411 and outputs the IEEE802.11a-based wireless signal 1416 , and is equipped inside the master station 1401 . 1432-1435 are sub-station communication devices that input the wireless signal 1416 based on IEEE802.11a and output the high-definition television image and sound streams 1412-1415 respectively, and are equipped inside the sub-stations 1402-1405 respectively.

1442-1445 respectively input the high-definition television image and sound streams 1412-1415 and reproduce the high-definition television image and sound.

[Configuration of master station communication device]

41 is a diagram showing the internal structure of the master station communication device 1431, which consists of a buffer 14152, a wireless unit 14155, a delivery confirmation processing unit 14156, a unicast retransmission processing unit 14157, a multicast retransmission processing unit 14158, and a multicast retransmission processing unit 14158. The point transfer distribution processing unit 14159 is configured.

Here, the buffer 14152 is an element that temporarily stores audiovisual data packets. Wherein, since the failed data packets can be detected, the stored data packets correspond to the sequence numbers. The unicast resend processing unit 14157 and the multicast resend processing unit 14158 are functional parts that create packets that fail to be delivered and perform resend processing. The reason why two unicast retransmission processing units and multicast retransmission processing units are provided for retransmission processing will be described later. The terms of unicast and multicast have already been described in the previous embodiments, so the description is omitted here.

The multicast distribution processing unit 14159 is a functional part that performs processing for multicast distribution of new image packets stored in the buffer. The delivery confirmation processing unit 14156 is a section that confirms delivery of packets distributed by multicast to each slave station, receives a response packet, and detects which packet fails to be delivered. The wireless unit 14155 is a functional part that receives data packets from the above-mentioned processing units and transmits them to substations, or receives data packets from substations and transmits them to necessary processing units. A more detailed description of these parts will be described later, and each signal and data packet in FIG. 41 will be described first.

The audiovisual data packet 14101 is a packet received from the audiovisual server 1430, and stores the above-mentioned high-definition television audiovisual stream 1411 of a predetermined size in the payload.

The wireless transmission signal 14118 and the wireless reception signal are signals transmitted and received from the wireless unit 14155 and constitute the wireless signal 1416 based on IEEE802.11a.

FIG. 42 shows the frame configuration of the wireless signal 1416 based on IEEE802.11a. 14300 is a beacon, 14301 is a multicast signal, and 14302 is a unicast signal. The beacon 14300 is a wireless transmission signal 14118 in the wireless signal 1416 based on IEEE802.11a, and is a control block placed at the head of a frame. The multicast signal 14301 is the wireless transmission signal 14118 in the wireless signal 1416 based on IEEE802.11a, and consists of a signal related to the multicast distribution data packet 14112 and a signal related to the multicast retransmission data packet 14113 constitute.

The unicast signal 14302 is composed of a signal related to the delivery confirmation inquiry packet 14114 , a signal related to the delivery confirmation response packet 14110 , and a signal related to the unicast retransmission data packet 14115 . Wherein, the delivery confirmation inquiry data packet 14114 and the unicast retransmission data packet 14115 are the wireless transmission signal 14118 in the wireless signal 1416 based on IEEE802.11a, and the delivery confirmation response data packet 14110 is the wireless received signal 14119 in the wireless signal 1416 based on IEEE802.11a. As far as the unicast of the IEEE802.11a standard is concerned, since the receiving side returns an ACK when the reception is successful without error, the sending side Since the unicast signal 14302 is retransmitted when the ACK cannot be received, the wireless transmission signal 14118 and the wireless reception signal 14119 are mixed and used.

Here, the frame period (time from a certain beacon 14300 to the next beacon 14300) of the wireless signal 1416 based on IEEE802.11a is set to 1 second. In addition, the time required to send the beacon 14300 is much less than 1 second and can be ignored.

[Explanation of the composition of each part of the parent station]

Next, each functional part of Fig. 41 will be described in detail.

[buffer]

The buffer 14152 is composed of a sequence number generation unit 14201 , a combination unit 14202 , a storage unit 14203 , a search unit 14204 , and an extraction unit 14205 as shown in FIG. 43 in detail.

Synchronized with the audiovisual data packet sent from the server 1430, the sequence number generator 14201 generates a sequence number, and the combining portion 14202 adds the sequence number to the received audiovisual data packet, and stores it in the storage unit 14203 in sequence. The unit 14204 receives the serial number 103 sent from the unicast retransmission processing unit, the multicast retransmission processing unit, and the multicast distribution processing unit in the stored audiovisual data packet 14101, and then sends the serial number 103 from the storage unit 14203 A packet matching the serial number is searched, and if there is a matching packet, the fetching unit 14205 fetches it as the transmission data packet 14102 and outputs it to the requesting object.

In addition, although not shown in the figure, the transmission information 14105 about whether the stored audiovisual data packet 14101 has been transmitted or has not been transmitted, and the transmission information 14106 such as which slave communication device failed to transmit are input into the buffer 14152 each time. are stored and output as transmission delivery information 14104.

FIG. 50 is a flowchart illustrating the operation of the buffer 14152 described above. The rhombus block is the step of judging whether the condition is satisfied, and the rectangular block is the step of processing. The contents of judgment and processing are described in each block, so a series of processing can be understood by tracing them step by step from the beginning. Therefore, the above description of FIG. 50 is omitted here.

[wireless department]

As shown in FIG. 44 , the wireless unit 14155 is composed of a MAC processing unit 14161 , a physical processing unit 14162 , a timer 14163 , and a beacon generation unit 14164 .

The MAC processing unit 14161 and the physical processing unit 14162 perform processing on the MAC layer and the physical layer of IEEE802.11a as described in the previous embodiments. That is, a MAC header is added to the beginning of a data packet sent to the outside, and a MAC header is removed from a data packet received from the outside, and is transmitted to the delivery confirmation processing unit 14156 .

The packets sent to the outside are delivery confirmation query packets, multicast distribution data packets, multicast resend data packets, unicast resend data packets, and beacons. Packets other than beacons are sent from the delivery confirmation processing unit 14156 , the multicast distribution processing unit 14159 , the multicast resending processing unit 14158 , and the unicast resending processing unit 14157 . The beacon is generated by the built-in beacon generation unit 14164. The beacon generation unit 14164 controls the timing of generation by the timer 14163 . In this embodiment, it is set to 1 second. In addition, the beacon generating unit 14164 activates a beacon timing signal at the same time as the beacon is generated.

[Delivery Confirmation Processing Department]

Based on the above, the transfer confirmation processing unit 14156 performs the following three processes, which will be described based on the flowchart shown in FIG. 51 . The step numbers in parentheses correspond to the steps in Figure 51.

(1) When the beacon timing signal 14121 is activated (S511), the delivery confirmation inquiry packet 14114 destined for each slave communication device is output to the wireless unit 14155 (S512).

(2) Receive the delivery confirmation response packets 14110 sent from the slave station communication devices respectively from the wireless unit 14155 (S513), and extract the video and audio data packet 14101 indicating which slave station communication device received which sequence number 14103 failed. The information is written in the buffer 14152 as the transfer information 14106 (S514).

(3) When the process related to all delivery confirmation response packets 14110 ends (S515), the delivery information writing completion flag 14122 is activated (S516).

[unicast resend processing unit]

The unicast retransmission processing unit 14157 basically performs the following four processes, which will be described with reference to the flowchart in FIG. 52 .

(1) When the beacon timing signal 14121 is activated (S521), save the current time (S522). Assume that the moment at this time is A.

(2) Waiting for the activation of the transfer information writing completion flag 14122 (S523), calculate the remaining time of the frame according to the time at this time, the time A, and determine the upper limit of the number of unicast resends (S524).

(3) Based on the transmission delivery information 14104 from the buffer 14152, the serial number 14103 of the transmission data packet 14102 that failed to be delivered is obtained, and the serial number is assigned to the buffer (S525).

(4) Utilize the designation, take out the transmission data packet 14102 of transmission failure from the buffer 14152, add the address of the corresponding substation communication device according to the transmission transmission information 14104, and resend the data packet 14115 as unicast, Output to the wireless unit 14155 (S526). This is performed within the range below the upper limit of the number of unicast retransmissions (S526→525). At this time, the transmission data packets 102 are sequentially retransmitted to the wireless unit 14155 from the transmission data packets 102 whose number of the slave communication devices failed to be delivered. On the other hand, if the upper limit is exceeded, unicast retransmission is stopped, and the process returns to the beginning (S521).

Here, an example of upper limit calculation of the number of unicast retransmissions will be described. Let the beacon interval be 1 second. In addition, set the interval between when the beacon timing signal is activated and when the delivery information writing completion flag 14122 is activated, that is, from the beginning of the frame to the writing of the delivery information 14106 The time until the entry is completed is 900msec. The remaining time of the frame at this time is 100 msec. In addition, here, it is assumed that the time required for one packet transmission of the transmission data packet 14102 by unicast is 5 msec. At this time, the upper limit of the number of unicast retransmissions is 100 msec/5 (msec/packet)=20 packets. Therefore, in this example, the unicast resend processing unit 14157 sets the upper limit of the number of unicast resends to 20 packets. Here, the remaining time of a frame varies with each frame, so the upper limit of the number of unicast retransmissions is calculated for each frame.

[multicast resend processing section]

The multicast retransmission processing unit 14158 basically performs the following three processes, which will be described with reference to the flowchart in FIG. 53 .

(1) According to the beacon timing signal and delivery acknowledgment guarantee time, calculate the maximum usable time of intra-frame multicast retransmission, and determine the upper limit of the number of multicast retransmissions (S531).

(2) When the transfer information writing completion flag 122 is activated (S532), the register for counting the number of multicast retransmissions is reset (S533). This register is incremented by 1 every time a multicast retransmission data packet is output (S536). In addition, when the upper limit of the number of multicast retransmissions is reached (S534), the process is terminated, and the next delivery information writing completion flag is waited for activation (S532).

(3) In the state where the number of multicast retransmissions has not reached the upper limit value, by specifying the sequence number 14103 of the transmission data packet 14102 that failed to be delivered according to the transmission delivery information 14104, and taking it out from the buffer 152 The transmission data packet 102 that failed to be delivered is output to the wireless unit 14155 as the multicast retransmission data packet 113 with a multicast address attached (S535). At this time, the transmission data packets are sequentially transmitted from the transmission data packet of the number of slave station communication devices that failed to deliver.

Here, an example of the number of retransmissions of multicast packets will be described. The delivery confirmation guarantee time is a fixed value for ensuring the time required for delivery confirmation, and it is set as 10 msec here. If the beacon interval is set to 1 second, the maximum usable time for intra-frame multicast retransmission is 990 msec. Here, it is assumed that the time required for the transmission of one packet of the transmission data packet 14102 by multicast is 1 msec. At this time, the upper limit of the number of multicast retransmissions is 990 msec/1 (msec/packet)=990 packets. Therefore, in this example, the multicast retransmission processing unit 158 sets the upper limit of the number of multicast retransmissions to 990 packets. This value does not change for each frame as long as the frame period is changed or the delivery confirmation securing time is not changed.

[Multicast distribution processing section]

Next, the multicast delivery processing unit 14159 basically performs the following two processes.

(1) If the transfer information writing completion flag 14122 (S541) is activated, then after lsec (S542), by specifying the sequence number 14103 of the unsent transmission data packet 14102 according to the transmission transfer information 14104, from The buffer 14152 fetches the unsent transmission data packet 102, adds a multicast address, and outputs it to the wireless unit 14155 as the multicast distribution data packet 112 (S543-S547).

(2) Specifically, after S542, the beacon timing signal 14121, the delivery acknowledgment guaranteed time, and the multicast retransmission number 14117 are received from each unit, and the maximum available intra-frame multicast distribution is calculated. time, determine the upper limit of the number of multicast distributions (S543). An example is given to illustrate the determination of the upper limit. The delivery confirmation securing time is a fixed value for securing the time required for delivery confirmation, and here, as described above, it is set to 10 msec. In addition, assuming that the beacon interval is 1 second, the time required to transmit one packet of the transmission data packet 14102 by multicast is 1 msec. Here, if the multicast retransmission quantity 117 is assumed to be 500 packets, the maximum available time for intra-frame multicast distribution is (1 second-10msec-1 (msec/packet)*500 packets) = 490 msec. Therefore, in this example, the multicast distribution processing unit 14159 sets the upper limit of the number of multicast distributions to 490 packets. However, since the multicast retransmission quantity 14117 varies for each frame, the upper limit of the multicast distribution quantity is calculated for each frame.

(3) If the upper limit of the number of multicast distributions is determined, the register for counting the number of multicast distributions is reset (S544). Thereafter, the multicast distribution number is incremented by 1 every time a multicast distribution data packet is output, as in the previous multicast retransmission processing unit (S547). This is allowed within the range below the upper limit value of the number of multicast distributions (S545). If the upper limit is exceeded, the process is ended and the process waits until the next transfer information writing flag is activated (S541).

As described in the above example, distribution processing of a maximum of 490 packets per frame is allowed. Actually, if the number of unsent said transmit data packets 14102 stored in said buffer 14152 is less, then it is this number. For example, if the number of the unsent data packets 14102 is only 10 packets, 10 packets are distributed (S546). Afterwards, the corresponding audiovisual data packet 101 is sent and written into the buffer 14152 as the sending information 105 .

[Configuration of slave station communication device]

FIG. 45 is a diagram showing the internal configuration of the substation communication devices 1432-1435.

14201 is an image and sound data packet, 14202 is a data packet, 14206 is a reception message, 14210 is a delivery confirmation response packet, 14214 is a delivery confirmation inquiry packet, 14218 is a wireless transmission signal, and 14219 is a wireless reception signal. The video and audio data packets 14201 are the HDTV video and audio streams 1412-1415 themselves.

The wireless signal 1416 based on IEEE802.11a is composed of a wireless transmission signal 14218 and a wireless reception signal 14219 .

14252 is a buffer for receiving the data packet 14202 and the reception information 14206 and outputting the audiovisual data packet 14201 and the reception information 14206. The buffer 14252 sequentially stores the data packets 14202 according to the sequence numbers, and outputs them as the audiovisual data packets 14201 in order of the sequence numbers while removing the sequence numbers.

The buffer 14252 stores the stored data packets 14202 for each sequence number and outputs the reception information 14206 such as whether the storage is complete or not.

14255 is a wireless unit, which receives the wireless reception signal 14219 and the delivery confirmation response packet 14210, and outputs the delivery confirmation inquiry packet 14214 and the data packet 14202. The wireless unit 14255 outputs the delivery confirmation inquiry packet 14214 as the wireless transmission signal 14218 .

If the wireless reception signal includes an inquiry related to delivery confirmation, the wireless unit 14255 extracts this part, and outputs it as the delivery confirmation inquiry data packet 14214 . In addition, the basic functions of the wireless unit 14255 are the same as those of the wireless unit 14155 on the master station side, so the above description is omitted.

14256 is a delivery confirmation processing unit, which receives the reception information 14206 and the delivery confirmation inquiry packet 14214, and outputs the delivery confirmation response packet 14210. When the delivery confirmation processing unit 14256 receives the delivery confirmation inquiry data packet 14214, it refers to the received information 14206, checks the sequence number of the unstored data packet 14202, and uses this information as the delivery confirmation response data Package 14210 is output. For example, when the content of the delivery confirmation query data packet 14214 is 'from sequence number 100 to 200? ’ etc., store the content of the received information 14206, if it is ‘from sequence number 50 to 191 and from 193 to 199’, then remove the sequence number 192 and 200, and use the delivery confirmation response packet 14210 to return this situation.

[Operation of multicast communication system]

Next, the operation of the above configuration will be described.

In the parent station 1401, the internal video and audio server 1430 outputs a high-definition video and audio stream 1411, and the communication device 1431 of the parent station uses the wireless signal 1416 based on IEEE802.11a to perform multicast distribution.

The substations 1402-1405 respectively use the internal substation communication devices 1432-1435 to receive the wireless signal 1416, and use the TVs 1442-1445 to reproduce high-definition television images and sounds.

In this process, even if a large noise is applied to the wireless signal 1416, high-definition television images and sounds can be reproduced without problems.

Next, the operation inside the master station communication device 1431 inside the master station 1401 when a large noise is applied to the wireless signal 1416 will be described.

First, the operation before noise generation will be described.

[Moment 1: Before the noise occurs]

Let it be time 1. When the beacon timing signal 14121 is activated, the delivery confirmation processing unit 14156 outputs a delivery confirmation inquiry packet 14114 .

On the other hand, the wireless unit 14155 outputs the beacon 14300 when the beacon timing signal 14121 is activated. Thereafter, at time 0 before time 1, the multicast distribution data packet 14122 received from the multicast distribution processing unit 14159 is output as multicast 14301.

Thereafter, the wireless unit 14155 outputs the delivery confirmation inquiry packet 14114 received from the delivery confirmation processing unit 14156 this time (time 1) as a unicast 14302.

Thereafter, the wireless unit 14155 receives responses from the slave communication devices, and outputs them as unicast retransmission request packets 14302 and output as delivery confirmation response packets 14110 . At this time, since no noise occurs, the transmission does not fail, and no retransmission request is generated.

Thereafter, the processing of the unicast retransmission processing unit 14157 starts. However, when no noise occurs, delivery failure does not occur, and there is no transmission data packet 14102 to be retransmitted, so the unicast retransmission data packet 14115 is not generated.

At the same time, the processing of the multicast retransmission processing unit 14158 starts. However, when no noise occurs, delivery failure does not occur, and there is no transmission data packet 14102 to be retransmitted, so the multicast retransmission data packet 14113 is not generated.

After that, the process shifts to the processing of the multicast delivery processing unit 14159 . The audiovisual data packets that are the high-definition television audiovisual stream are sequentially stored in the buffer 14152 , so that unsent packets are output as the multicast distribution data packets 14112 .

In FIG. 46, (a) shows the state of the wireless signal 1416 at this time 1.

In the figure, 14300 is the beacon. 14310 is the multicast distribution data packet 14112 component. 14320 is the delivery confirmation inquiry packet 14114 component, which is a unicast packet. 14321 is the delivery confirmation response packet 14110 component, which is a unicast packet.

In the unicast of the IEEE802.11a standard, the receiving side returns an ACK if the reception is successful without error, and the sending side resends when the ACK cannot be received, so the delivery confirmation query packet component 14320 For the delivery confirmation response packet component 14321, both the wireless transmission signal 14118 and the wireless reception signal 14119 are used in confusion. Also, for convenience, the delivery confirmation inquiry packet component 14320 and the delivery confirmation response packet component 14321 are shown separately, but they may be used in confusion. For example, after exchanging the delivery confirmation query packet component 14320 and the delivery confirmation response packet component 14321 with the slave station communication device 1432, the delivery confirmation query packet may be sent to the slave station communication device 1433. Component 14320 is exchanged with Delivery Confirmation Response Packet Component 14321.

In (a) of FIG. 46, multicast distribution is performed without any problem.

[Moment 2: Noise occurs]

At time 2, noise occurs.

When the beacon timing signal 14121 is activated, the delivery confirmation processing unit 14156 outputs the delivery confirmation inquiry packet 14114 .

On the other hand, the wireless unit 14155 outputs a beacon 14300 at the time when the beacon timing signal 14121 is activated. Thereafter, the multicast distribution data packet 14112 received from the multicast distribution processing unit 14159 at the previous time (time 1) is output in multicast mode.

Thereafter, the wireless unit 14155 outputs the delivery confirmation inquiry packet 14114 received from the delivery confirmation processing unit 14156 this time (time 2) by unicast.

Afterwards, the wireless unit 14155 receives a reply from each substation communication device, and outputs it as a delivery confirmation response data packet 14110 . Due to the occurrence of noise, there is a transfer failure and a resend request occurs. Although delivery failure occurs in the delivery confirmation itself, since it is unicast, retransmission using ACK is no problem.

Thereafter, the processing of the unicast retransmission processing unit 14157 starts. Due to noise, delivery failure occurs, and there is a transmission data packet 14102 to be resent, so the unicast resend data packet 14115 is output. Here, a lot of noise occurs, and the exchange of the delivery confirmation inquiry packet 14114 and the delivery confirmation response packet 14110 takes time, and if there is no time left in the frame, this processing does not occur. If there is time left, the wireless unit 14155 receives the unicast retransmission data packet 14115 and outputs it in unicast mode.

At the same time, the processing of the multicast retransmission processing unit 14158 starts. A delivery failure occurs due to noise, and since there is the transmission data packet 14102 to be retransmitted, a multicast retransmission data packet 14113 is output. When a large amount of noise occurs and the number of the multicast retransmission data packets 14113 is large, the multicast retransmission data packets 14113 are limited to such an extent that the delivery acknowledgment securing time can be ensured within a frame. quantity.

After that, the process shifts to the processing of the multicast distribution processing unit 14159 . Since the audiovisual data packets are sequentially stored in the buffer 14152 , untransmitted packets are output as the multicast distribution data packets 14112 . However, when a large amount of noise occurs and the number of multicast retransmission data packets 14113 is large, the multicast distribution data is limited to the extent that the delivery confirmation guarantee time can be secured within a frame. The number of packets 14112. When the number of multicast retransmission data packets 14113 is limited, the number of multicast distribution data packets 14112 is suppressed to zero.

In FIG. 46, the state of the wireless signal 1416 at this time 2 is shown by (b). The same symbols are assigned to the same components as in (a).

14340 is noise. 14330 is the unicast resend data packet 14115 component.

By setting this 14330 at time 2, it can be seen that the state of delivery failure that occurred during multicast distribution can be restored by unicast retransmission. Among them, unicast retransmission is performed on each of the sub-station communication devices, which is inefficient. Therefore, when the influence of noise affects a large number of the sub-station communication devices, recovery does not end immediately. In this unicast retransmission, retransmission is performed starting from the data packets with fewer data packets of the slave station communication devices that failed to deliver. At the next time, it is effective in conjunction with multicast retransmission in which packets are retransmitted from the slave station communication devices that have failed in delivery. Specifically, when there are many transmission failures to specific slave communication devices, the unicast retransmission that enables further retransmission based on ACK is used to reliably perform retransmission to the specific slave communication devices that have many transmission failures. Sending, further retransmission based on ACK is not possible for other substation communication devices, but it can be resent to multiple substation communication devices in a unified manner, so the efficiency is high, and it can be efficiently and reliably carried out by multicast retransmission Recovery for delivery failures.

[Moment 3: Noise occurs]

Noise also occurs at the next time instant 3 .

When the beacon timing signal 14121 is activated, the delivery confirmation processing unit 14156 outputs the delivery confirmation inquiry packet 14114 .

On the other hand, the wireless unit 14155 outputs a beacon 14300 at the time when the beacon timing signal 14121 is activated. Thereafter, the multicast retransmission data packet 14113 received from the multicast retransmission processing unit 14158 at the previous time (time 2) and the multicast distribution processing unit 14113 are output by multicast. Section 14159 receives the multicast distribution data packet 14112.

Thereafter, the wireless unit 14155 outputs the delivery confirmation inquiry packet 14114 received from the delivery confirmation processing unit 14156 this time (time 2) by unicast.

Thereafter, the radio unit 14155 receives replies from each slave communication device, and outputs it as a delivery confirmation response packet 14110 . Due to the occurrence of noise, there is a transfer failure and a resend request occurs. Since the delivery confirmation itself is unicast, there is no problem in performing retransmission using ACK.

Thereafter, the processing of the unicast retransmission processing unit 14157 starts. Due to the occurrence of noise, delivery failure occurs and there is a transmission data packet 14102 to be resent, so a unicast resend data packet 14115 is output. However, when a large amount of noise occurs and the number of multicast retransmission data packets 14113 is large, this process is not performed because there is no time left in the frame. In the case of remaining time, the wireless unit 14155 receives the unicast retransmission data packet 14115 and outputs it as unicast.

At the same time, the processing of the multicast retransmission processing unit 14158 starts. A delivery failure occurs due to noise, and since there is the transmission data packet 14102 to be retransmitted, a multicast retransmission data packet 14113 is output. When a large amount of noise occurs and the number of the multicast retransmission data packets 14113 is large, the multicast retransmission data packets 14113 are limited to such an extent that the delivery acknowledgment securing time can be ensured within a frame. quantity.

Thereafter, the process shifts to the processing of the multicast delivery processing unit 14159 . Since new audiovisual data packets are sequentially stored in the buffer 14152 , unsent packets are output as the multicast distribution data packets 14112 . However, when a large amount of noise occurs and the number of multicast retransmission data packets 14113 is large, the multicast distribution data is limited to the extent that the delivery confirmation guarantee time can be secured within a frame. The number of packets 14112. When the number of multicast retransmission data packets 14113 is limited, the number of multicast distribution data packets 14112 is suppressed to zero.

(c) in FIG. 46 shows the state of the wireless signal 1416 at this time 3. The same symbols are assigned to the same components as (a) and (b).

In (c), 14331 is the multicast retransmission data packet 14113 component, which is a multicast signal. It can be seen from (c) that the state of delivery failure that occurred during multicast distribution is recovered by using multicast retransmission. This retransmission is performed not on the packet based on the delivery failure that occurred this time (time 3), but on the packet based on the delivery failure that occurred before the previous time (time 2). In this example, since delivery failure did not occur before time 1, it is retransmission of the packet based on the delivery failure that occurred at time 2.

At this time 3, the multicast distribution data packets 14112 originally seen at time 1 are not sent. This is because the number of multicast retransmission data packets 14113 in the processing of the multicast distribution processing unit 14159 at the previous time (time 2) was large, so the delivery confirmation time can be ensured within a frame. To a certain extent, limit the number of multicast distribution data packets 14112. As a result, at time 3, instead of not transmitting the multicast distribution data packets 14112 seen at time 1, the exchange of the delivery confirmation inquiry packet 14114 and the delivery confirmation response packet 14110 can be performed without any problem, and The multicast retransmission at the next time (time 4) is performed without any problem.

[Moment 4: No noise]

At the next instant 4, there is no noise. When the beacon timing signal 14121 is activated, the delivery confirmation processing unit 14156 outputs the delivery confirmation inquiry packet 14114 .

On the other hand, the wireless unit 14155 outputs the beacon 14300 when the beacon timing signal 14121 is activated. Thereafter, the multicast retransmission data packet 14113 received from the multicast retransmission processing unit 14158 at the previous time (time 3) and the multicast retransmission data packet 14113 received from the multicast distribution processing unit 14159 are output in multicast. Point transfer distribution data packet 14112.

Thereafter, the wireless unit 14155 outputs the delivery confirmation inquiry packet 14114 received from the delivery confirmation processing unit 14156 this time (time 4) by unicast.

Afterwards, the wireless unit 14155 receives a reply from each substation communication device, and outputs it as a delivery confirmation response data packet 14110 . Since no noise has occurred, there is an incomplete resend packet in the previous delivery failure, and a resend request is generated.

Thereafter, the processing of the unicast retransmission processing unit 14157 starts. Since there is no noise, there are uncompleted retransmission packets in past delivery failures, and there are transmission data packets 14102 to be retransmitted, so unicast retransmission data packets 14115 are output. However, even when the number of multicast retransmission data packets 113 is large, this process is not performed because there is no time left in the frame. In the case of remaining time, the wireless unit 14155 receives the unicast retransmission data packet 14115 and outputs it as unicast.

At the same time, the processing of the multicast retransmission processing unit 14158 starts. Noise has not occurred, but there were uncompleted retransmission packets in past delivery failures, and since there are transmission data packets 14102 that should be retransmitted, multicast retransmission data packets 14113 are output. When the number of multicast retransmission data packets 14113 is large, the number of multicast retransmission data packets 14113 is limited to the extent that delivery confirmation securing time can be secured within a frame.

Thereafter, the process shifts to the processing of the multicast delivery processing unit 14159 . Since the audiovisual data packets are sequentially stored in the buffer 14152, unsent packets are output as multicast distribution data packets 14112. However, when the number of multicast retransmission data packets 14113 is large, the number of multicast distribution data packets 14112 is limited to such an extent that delivery confirmation securing time can be secured within a frame.

(d) in FIG. 46 shows the state of the wireless signal 1416 at this time 4. The same symbols are assigned to the same components as (a), (b), and (c).

It can be seen from (d) that multicast retransmission is used to restore the delivery failure state that occurred during multicast distribution and multicast retransmission. This retransmission is performed not on the packet based on the delivery failure that occurred this time (time 4), but on the packet based on the delivery failure that occurred before the previous time (time 3). In this example, since delivery failure did not occur before time 1, it is retransmission of the packet based on the delivery failure that occurred at time 2 and time 3.

At time 4, the number of multicast distribution data packets 14112 originally seen at time 1 is not transmitted. This is because in the processing of the multicast distribution processing unit 14159 at the previous time (time 3), the number of multicast retransmission data packets 14113 was large, so the delivery confirmation securing time can be secured within the frame. , to limit the number of multicast distribution data packets 14112. As a result, at time 4, instead of not sending the number of multicast distribution data packets 14112 seen at time 1, the delivery confirmation inquiry packet 14114 and the delivery confirmation response packet 14110 can be exchanged without any problem. The multicast retransmission at the next time (time 5) is performed accordingly.

[Moment 5: No noise]

At the next moment 5, there is no noise.

When the beacon timing signal 14121 is activated, the delivery confirmation processing unit 14156 outputs the delivery confirmation inquiry packet 14114 .

On the other hand, the radio unit 14155 outputs a beacon 14300 when the beacon timing signal 14121 is activated. Thereafter, the multicast retransmission data packet 14113 received from the multicast retransmission processing unit 14158 at the previous time (time 4) and the multicast retransmission data packet 14113 received from the multicast distribution processing unit 14159 are output in multicast. Point transfer distribution data packet 14112.

Thereafter, the wireless unit 14155 outputs the delivery confirmation inquiry packet 14114 received from the delivery confirmation processing unit 14156 this time (time 5) by unicast.

Afterwards, the wireless unit 14155 receives a reply from each substation communication device, and outputs it as a delivery confirmation response data packet 14110 . Since no noise has occurred, there is an incomplete resend packet in the previous delivery failure, and a resend request is generated.

Thereafter, the processing of the unicast retransmission processing unit 14157 starts. Since there is no noise, there are uncompleted retransmission packets in past delivery failures, and there are transmission data packets 14102 to be retransmitted, so unicast retransmission data packets 14115 are output. Thereafter, the wireless unit 14155 receives the unicast retransmission data packet 14115, and outputs it as unicast.

At the same time, the processing of the multicast retransmission processing unit 14158 starts. Noise has not occurred, but there were uncompleted retransmission packets in past delivery failures, and since there are transmission data packets 14102 that should be retransmitted, multicast retransmission data packets 14113 are output.

After that, the process shifts to the processing of the multicast delivery processing unit 14159 . Since the audiovisual data packets are sequentially stored in the buffer 14152, untransmitted packets are output as the multicast distribution data packets 14112.

(e) in FIG. 46 shows the state of the radio signal 16 at this time 5. The same symbols are assigned to the same components as (a), (b), (c), and (d).

It can be seen from (e) that multicast retransmission is used to restore the delivery failure state that occurred during multicast distribution and multicast retransmission. With this, recovery is complete.

In (e), the multicast distribution data packet component 14310 is larger than what was originally seen at time 1. This is because in order to ensure delivery confirmation time, the amount that should have been obtained at the previous time (time 4) and the next time is restricted. Since the multicast distribution data packet 1411 was sent at time (time 3), a large number of unsent multicast distribution data packets 1411 remain in the buffer 14152 .

[Description of Operation and Effect of the Embodiment]

As described above, it can be seen that even if a large amount of noise occurs, it is necessary to ensure delivery confirmation time, and that good communication can be achieved by performing efficient multicast retransmission.

In addition, when delivery fails to a specific substation communication device, the multicast retransmission that can perform repeated retransmissions based on ACK is used to reliably resend the specific substation communication device with many delivery failures, and to other substations. The station communication device cannot perform multiple retransmissions based on ACK, but it is efficient because it retransmits multiple sub station communication devices collectively, and can efficiently and reliably recover delivery failures by using multicast retransmissions.

[Modification and application of this embodiment]

In this embodiment, the master station 1401 and the slave stations 1402-1405 are all set up in a home, but this may not be the case.

For example, it can be applied to systems that perform streaming, such as company lobbies, waiting rooms at stations, classrooms, study sessions, and laboratory venues, monitors for tour guides at exhibition locations, and image delivery systems in airplanes.

In addition, in this embodiment, the video and audio server 1430 outputs the high-definition television video and audio stream 11 , but this may not be the case.

The transmission rate of the physical layer of IEEE802.11a is a maximum of 54 Mbps, but in any case, in the case of high-definition television image and sound processing in the home, in the case of normal unicast transmission, the limit is one program, that is, one place. distribution. If this is applied to the technique of the present invention, although there is one program, it can be distributed to multiple places. This configuration is of course included in the scope of the present invention, but the present invention is not limited to this configuration.

For example, standard video and audio can also be processed, and multiple programs can be distributed to multiple locations. Multiple programs can also be distributed to the communication devices 1432-1435 of the substations, and any program can be provided to the subordinate TVs.

In addition, in the case of streaming, it is not limited to video and audio. For example, silent images, music data, or bidirectional game data may be used.

In addition, in this embodiment, IEEE802.11a wireless signals are handled, but this may not be the case.

At present, IEEE802.11a is widely popularized in the market, and there are still a large number of general-purpose IEEE802.11a wireless modules. This embodiment is characterized in that a general-purpose IEEE802.11a wireless module is used as the master station wireless unit 14155 or the slave station wireless unit 14255, and it can be realized by adding a new external configuration. Such an effect is obtained by processing IEEE802.11a wireless signals, and this configuration is of course included in the scope of the present invention, but the present invention is not limited to this configuration.

Noise is inevitable in wireless, as opposed to wired, where efforts are made to prevent noise. If this is the case, it is effective to secure the delivery confirmation time of the present invention and improve the effect of retransmission.

In addition, the present invention is also effective in an environment where noise occurs even if it is wired. Especially in severe noise environments such as CATV and power line communication (light line communication or PLC), it can be further effective. Therefore, the present invention is not limited to wireless.

In addition, in this embodiment, the beacon is placed at the head of the frame, but this may not be the case. This is based on the IEEE802.11a standard, and if other standards are used, it only needs to comply with the standard. In addition, in the calculation of the delivery assurance time, since the time related to the beacon is very small, it can be ignored, but of course it can also be taken into consideration. In addition, it is of course also possible to consider the case where a block is added to the frame.

In addition, in this embodiment, after the above-mentioned beacon, the transmission is performed in the order of multicast and unicast, but this may not be the case.

This is due to the association standard based on IEEE802.11a, the multicast communication cannot but be behind the beacon. This is because the slave communication device in the sleep mode also performs multicast communication, so even in the sleep mode, it is necessary to perform multicast communication after the beacon that becomes the operating state.

The case of using a general-purpose IEEE802.11a radio module corresponds to the case of transmitting by multicast or unicast after the beacon in this way, but the case of not using such a module does not need to consider this order. For example, after the beacon 300, it may be transmitted in the order of unicast and multicast.

Also, in this embodiment, among the multicast packets, packets related to multicast retransmission data packets and packets related to multicast distribution data packets are transmitted in the order of multicast packets, but this may not be the case.

With this configuration, since the earliest packet is transmitted first, the transmission can be completed before the buffer overflow occurs on the receiving side, so reliability can be improved even in an environment where a long burst error occurs. This configuration is also included in the scope of the present invention, but the present invention is not limited thereto. For example, it can also be configured according to the way of consideration: if the transmission to a plurality of the sub-station communication devices is completed, it is considered that the transmission to some of the sub-station communication devices has failed, and although it is an early data packet, it is communicated to a plurality of sub-stations. For the packets that have been transmitted by the device, the multicast distribution data packet that has not been transmitted to one slave communication device is prioritized. That is, it may be configured such that the packets related to the multicast retransmission data packet and the packets related to the multicast distribution data packet are considered together, and the distribution starts from the packet with the most slave communication devices whose transmission has not been completed.

In this embodiment, the frame period of the wireless signal based on IEEE802.11a is set to 1 second, but this may not be the case.

Since the overhead of beacon transmission and the like is reduced by increasing the frame period, there is room in the wireless transmission band. In this sense, it is better to increase the frame period.

On the other hand, if the frame period is increased, it will take time until the next multicast transmission starts, and the propagation delay will increase. In this sense, it is better to reduce the frame period.

In the case of processing high-definition television images using IEEE802.11a in this embodiment, according to the simulation, if the frame period is several hundred msec or more, the additional influence is small, and if the frame period is about several seconds, even if it is increased, Since the added influence basically does not change, it is realistic to set the frame period from several hundreds of msec to several seconds. However, an invention is not limited to this.

In addition, the frame period can also be reduced during initialization to shorten the switching time, and the frame period can be increased after initialization is completed.

In addition, in this embodiment, the buffer adds a sequence number to the audiovisual data packets and stores them sequentially. Also, if a unique number per packet is added to the audiovisual data packet as before, it is not necessary to add a new serial number if this is used as the serial number.

In addition, in the present embodiment, the buffer stores each time delivery information such as delivery failure to which slave communication device is input. This is because the present embodiment uses unicast retransmission in addition to multicast retransmission. It is also possible to set not to use unicast to resend, but to use only multicast to resend, and the delivery information is information such as whether there is or is not delivery failure. It is also possible to multicast and resend all the data packets with delivery failures. Alternatively, it may also be assumed that only multicast retransmission is used instead of unicast retransmission, and the delivery information is the number of slave station communication devices with delivery failures. In addition, for a data packet having a delivery failure, the multicast retransmission may be performed from the one with the larger number of slave station communication devices having a delivery failure.

In addition, in this embodiment, the radio unit on the master station side outputs a beacon timing signal, but this may not be the case. This is because it is necessary for the outside of the wireless unit to grasp the timing of the beacon in order to ensure delivery confirmation time within the frame. For example, the timing of independently generating a beacon outside the radio unit may be exchanged with the radio unit for correction. In addition, it is also possible to completely synchronize with the wireless unit using a clock or the like, and independently generate the timing of the beacon outside the wireless unit. In addition, the beacon and its timing may be independently generated outside the wireless unit based on the delivery confirmation response packet timing output by the wireless unit.

In addition, in the present embodiment, when the beacon timing signal is active, the delivery confirmation processing unit outputs the delivery confirmation inquiry packet destined for each slave station communication device, but this may not be the case.

The delivery confirmation processing unit may output the delivery confirmation inquiry packet before the wireless unit outputs the delivery confirmation inquiry packet component as a wireless transmission signal. Wherein, if it is to be sent before the activation of the beacon timing signal, it will be sent in the frame before the frame to be sent, so in this embodiment, if the beacon timing signal is activated, it will be sent. Based on the above reasons, as long as the delivery confirmation processing unit outputs the delivery confirmation to each slave station communication device before the wireless unit outputs the delivery confirmation inquiry packet component as a wireless transmission signal after the activation of the beacon timing signal. Just ask for the packet.

In addition, in the present embodiment, the delivery confirmation processing unit activates the delivery information writing completion flag when all the processes related to the delivery confirmation response packet are completed, but this may not be the case. Since the exchange of the delivery confirmation inquiry packet and the delivery confirmation response packet is unicast, retransmission based on ACK is performed, so the reliability is high, but even so, the exchange may fail. The maximum time may also be determined in advance, and if the time passes, the transfer information writing completion flag is activated. The delivery confirmation securing time may also be used as the maximum time.

In addition, in the present embodiment, a unicast resend processing unit is prepared to use unicast resend, but this may not be the case. Of course, the configuration using both multicast retransmission and unicast retransmission is also included in the scope of the present invention, but the present invention is not limited thereto.

Even if unicast resend is used to restore the delivery failure that occurred in multicast distribution, unicast resend resends each sub-station communication device one by one, and the efficiency is poor. Therefore, under the influence of noise on a large number of sub-stations If the communication device is affected, recovery will not end immediately. In this unicast retransmission, retransmission is performed starting from a packet with fewer slave station communication devices that failed to deliver. At the next time, it is effective in conjunction with multicast retransmission in which packets are retransmitted from the slave station communication devices that have failed in delivery. Specifically, when there are many transmission failures to specific sub-station communication devices, by using the unicast retransmission that can perform repeated retransmissions based on ACK, the specific sub-station communication devices with many transmission failures are surely retransmitted, Repeated retransmission based on ACK cannot be performed for other substation communication devices, but retransmission can be performed collectively for multiple substation communication devices, so the efficiency is high, and delivery failure can be recovered efficiently and reliably by using multicast retransmission .

In this way, in this embodiment, unicast retransmission starts from the data packets with fewer slave communication devices that failed to deliver, and multicast retransmission starts from data packets with more slave communication devices that failed to deliver. sent, and not quite. Regardless of the communication device of the slave station that failed in delivery, simply performing unicast retransmission or multicast retransmission from the earliest packet is effective, although the effect is reduced. In addition, among the data packets of the same number of slave communication devices that have failed in delivery, if the data packets are configured to be retransmitted from the earliest data packets, the transmission can be completed before the buffer on the receiving side overflows. In addition, data packets can also be divided into multiple groups in the order from early to late, starting from the early group, sequentially observing the number of sub-station communication devices in the group that fail to deliver, and then sending the data from the small number Packets are started, and multicast retransmission is started with a large number of packets. Thus, by making multicast retransmit a large number of data packets of the slave station communication devices responsible for delivery failures, and making unicast retransmit a small number of data packets of the slave station communication devices responsible for delivery failures, from early The data packet starts to be sent again, so that the transmission can be completed before the buffer on the receiving side overflows.

In addition, in the present embodiment, the time required for the transmission of one packet of the transmission data packet by unicast is 5 msec, but this may not be the case. In addition, the time required for the transmission of one packet of the transmission data packet by multicast is assumed to be 1 msec, but this may not be the case. These times can also be manually entered as fixed values from outside. It can also be measured automatically.

In addition, in the present embodiment, the multicast distribution processing unit starts processing after 1 msec when the transfer information writing completion flag is activated, but this may not be the case.

This is because by performing processing after the multicast retransmission processing unit, the multicast resend data packet that is preferentially transmitted by the wireless unit is preferentially created, and then the multicast distribution processing unit creates the The multicast distribution data packet sent by the wireless unit may be in another form as long as the above-mentioned processing can be realized. , if the transfer information writing completion flag is activated, the processing can be started after 2msec, or after 500μsec. In addition, it may be configured so that the multicast retransmission processing unit notifies the end of the processing. In addition, it may be configured such that the multicast distribution processing unit starts processing immediately when the transfer information writing completion flag is activated, even if the multicast retransmission data packet and the multicast distribution data packet are created almost at the same time, wireless The part is also output in the order of multicast resend data packets and multicast distribution data packets.

In addition, in this embodiment, FIG. 45 shows the internal configuration of the slave station communication device, but other configurations are also possible.

Other configurations are also possible as long as the delivery confirmation response packet having the same content as the delivery confirmation response packet is returned to the delivery confirmation inquiry packet having the same content as the delivery confirmation inquiry packet.

In addition, in the present embodiment, only the delivery confirmation processing unit is configured to create the delivery information, but this may not be the case. For example, since the unicast retransmission performed by the unicast retransmission processing unit is retransmission using ACK, it is a reliable retransmission. Therefore, when the retransmission by the unicast retransmission processing unit is judged as delivery failure, the unicast resend processing unit also creates the delivery information 106 . In addition, since the wireless unit receives the ACK directly, it can know whether the unicast retransmission is successful, so the wireless unit can generate the transfer information instead of the unicast retransmission processing unit.

In addition, in the present embodiment, the multicast distribution processing unit is configured to create transmission information, but this may not be the case. For example, the buffer may be configured to automatically add information to be transmitted when a data packet is read out.

In addition, in this embodiment, the multicast distribution processing unit calculates the maximum time available for multicast distribution within a frame based on the beacon timing signal, delivery confirmation guaranteed time, and the number of multicast retransmissions, and determines the multicast distribution time. Quantity upper limit. Based on the number of multicast resends, the time required for multicast resends is calculated, and the upper limit of the number of multicast distributions is determined. But that's not the case. The wireless unit actually performs multicast retransmission by wireless, so the time required for multicast retransmission can be grasped. Therefore, the time may be notified directly from the wireless unit.

In addition, in the present embodiment, the delivery confirmation securing time is fixed, but this may not be the case. For example, the delivery confirmation processing unit includes a delivery confirmation guaranteed time determination unit that determines a delivery confirmation guaranteed time, and when the frequency of delivery failure to a specific slave communication device is high based on the result of the delivery confirmation, the delivery confirmation guaranteed time The time is set to be large, and conversely, the delivery confirmation ensuring time is set to be small. According to this, when the frequency of delivery failure to a specific slave station communication device is high, the delivery confirmation time is large, and as a result, there is a lot of time left after the delivery confirmation is completed, and a more reliable method of performing retransmission based on ACK can be used. The unicast resend can be sure to resend to the specific substation communication device with high frequency of delivery failure. This configuration is also within the scope of the present invention.

In addition, in this embodiment, as a delivery confirmation, it is also possible to use unicast to individually inquire whether the distribution is successful or not to a plurality of slave station communication devices. With this configuration, the most important delivery confirmation can be performed in simple steps. This configuration is also within the scope of the present invention. But that's not the case.

For example, as a delivery confirmation, it is also possible to use multicast to ask a plurality of sub-station communication devices whether the distribution is successful or not. In this method, since multicast can be inquired at the same time, it can be inquired in a short time, so the time required for delivery confirmation is shortened, and the retransmission time is increased accordingly. This configuration is also within the scope of the present invention.

In addition, for example, as a delivery confirmation, it is also possible to use multicast to individually inquire whether the distribution is successful to a plurality of slave station communication devices, and for the slave station communication devices that have not received a reply, use unicast again to individually inquire. In this method, since multicast can be inquired at the same time and can be inquired in a short time, the time required for delivery confirmation is shortened, and the retransmission time is increased accordingly. Also, multicast cannot reliably perform retransmission by ACK, but by using unicast in combination, delivery confirmation can be reliably performed. This configuration is also within the scope of the present invention.

[Application of Embodiment 2]

In this embodiment, the configuration described in Embodiment 2 can also be adopted, and when a plurality of slave station communication devices and the master station communication device transmit delivery confirmation packets or other normal data packets by unicast, the transmission timing can be adjusted. adjustment.

(Embodiment 8)

This embodiment is similar to the seventh embodiment. The configuration is also the same as that described in the previous embodiment, as shown in FIG. 40 . Therefore, the description will not be repeated. The configuration that differs from the previous embodiment will be mainly described.

The communication device of the master station is structured as shown in FIG. 47. The difference from the device of the previous embodiment shown in FIG. Resend processing unit 14151.

The multicast distribution retransmission processing unit 14151 refers to the delivery information 14107 from the buffer 14152, designates the sequence number 14103 of the audiovisual data packet whose delivery has not been completed, thereby receives the transmission data packet 14102 from the buffer 14152, and appends After the multicast address, the retransmission data packet is distributed as a multicast and output to the wireless unit 14155 . In addition, the multicast distribution retransmission processing unit 14151 processes the distribution retransmission number at the time after subtracting the delivery confirmation ensured time from the frame period as the maximum retransmission retransmission number.

With this configuration, the multicast communication device of this embodiment can handle multicast retransmission and new multicast distribution in the same way, thereby simplifying the circuit. This point is a feature of the previous embodiment. Comparing FIG. 47 and FIG. 41, it can be seen that the circuit of this embodiment is simple. It is characterized in that the circuit scale is small, and at the same time, reliability can be improved in an environment where long pulse errors occur.

Various modifications and changes were described in the previous embodiment, but similar modifications and changes are possible in this embodiment.

(Embodiment 9)

The basic configuration of this embodiment is the same as that of the first embodiment, and is an example in which all substations in a group can communicate not only with the same transmission terminal but also with other transmission terminals.

Next, a system form assumed in this embodiment will be described with reference to FIG. 48 .

In FIG. 48, the same components as those in FIG. 2 have the same names and the same numbers.

1 is an AV server, 2 is a wired Ethernet HUB, 3 is a first wireless transmission terminal, 4 is a second wireless transmission terminal, and 5 is a wired Ethernet connecting 1, 2, 3, and 4. 6 is the first wireless receiving terminal, 7 is the second wireless receiving terminal, 8 is the third wireless receiving terminal, 9 is the fourth wireless receiving terminal, 10 is the fifth wireless receiving terminal, and 11 is the sixth wireless receiving terminal.

The first wireless transmitting terminal 3 has a parent-child relationship with the first wireless receiving terminal 6, the second wireless receiving terminal 7, and the third wireless receiving terminal 8, and performs wireless communication using IEEE802.11a wireless LAN technology. That is, the first wireless transmitting terminal 3 is an AP (access point: master), and the first, second, and third wireless receiving terminals 6, 7, and 8 are STAs (stations: slave). Similarly, the second wireless transmitting terminal 4 has a parent-child relationship with the fourth wireless receiving terminal 9, fifth wireless receiving terminal 10, and sixth wireless receiving terminal 11, and performs wireless communication using IEEE802.11a wireless LAN technology. That is, the second wireless transmission terminal 4 is an AP (access point: master), and the fourth, fifth, and sixth wireless reception terminals 9, 10, and 11 are STAs (stations: slaves).

The difference from the system of Figure 2 lies in the composition of the multicast groups. The first, second, third, and fourth wireless receiving terminals 6, 7, 8, and 9 constitute the first multicast group 12 for receiving the same multicast packet, and the fifth and sixth wireless receiving terminals 10, 11 constitute the receiving A second multicast group 13 of the same multicast packet. That is, the fourth wireless receiving terminal 9 that has no parent-child relationship with the first wireless transmitting terminal 3 is mixed in the first multicast group 12 . Seen from the second wireless transmitting terminal 4, wireless receiving terminals belonging to the first multicast group 12 and wireless receiving terminals belonging to the second multicast group are mixed under the own transmitting terminal. At this time, since the data distributed to the first multicast group 12 is not necessarily the same as the data distributed to the second multicast group, the second transmitting terminal 4 has the first The transmission buffers for two groups of transmission buffers (a), (b) for the multicast group 12 and transmission buffers (c), (d) for the second multicast group 13 correspond to Resend actions for both groups. In this case, any of the actions described in Embodiment 1 may be performed in plural at the same time.

According to this configuration, even when a plurality of multicast groups exist under the sending terminal, by having a plurality of sending buffers, the transmission reliability of all the multicast groups can be improved by retransmission processing.

In addition, broadcast data packets can also be used to replace the multicast data packets in any of the above-mentioned embodiments. In addition, all or part of the constituent elements of all the embodiments may be realized by a computer using a ROM and a program stored in the ROM.

Industrial availability

The wireless multicast technique of the present invention has the feature of using the priority of data packets, and is suitable for AV distribution etc. which require the highest priority multicast. In addition, it can also be applied to purposes such as data distribution.

Claims (7)

1. A wireless transmission method, between a sending terminal and a receiving terminal, carrying out MAC layer multipoint transmission or broadcast transmission, with the following steps: On the sending terminal side, temporarily store a plurality of data groups higher than the MAC layer; assigning sequence numbers for detecting data loss at the receiving terminal side to a plurality of data groups higher than the MAC layer; The data to which the sequence number is assigned is transmitted by a band-guaranteed or high-priority multicast or broadcast packet; Use a frequency band other than the above-mentioned guaranteed frequency band or a data packet below the above-mentioned priority to transmit data that needs to be retransmitted due to loss at the receiving end, On the receiving terminal side, temporarily store a plurality of received data groups including sequence numbers transmitted by multicast or broadcast packets of a band-guaranteed type or high priority; From among the plurality of received data groups stored higher than the MAC layer, using the sequence number given by the sending terminal side, detecting a missing data group from the received data groups; making a resend request of said detected missing data group; and On the sending terminal side, using the sequence number, retransmitting the data higher than the MAC layer that is detected to be lost on the receiving terminal side, Wherein, the step of resending higher-level data than the MAC layer includes: a first substep for sending and resending data using a unicast packet; or a second substep for using a multicast or broadcast packet , send and resend data to multiple receiving terminals, And, in the first sub-step, a plurality of data groups higher than the MAC layer lost at the receiving end are combined, and the combined data is transmitted using the unicast packet. 2. The wireless transmission method according to claim 1, characterized in that: On the receiving terminal side, perform the step of requesting retransmission of the detected lost data group, with the same priority as the band-secured or high-priority multicast or broadcast packet, or the same priority as above The second priority, which is one priority lower, or a priority lower than the above-mentioned second priority performs transmission control of the retransmission request packet. 3. The wireless transmission method according to claim 1, characterized in that: On the receiving terminal side, the step of performing the retransmission request of the detected lost data group includes: a first substep for sending retransmission request data using unicast data packets; or a second substep for using multipoint Transmit or broadcast data packets, send and send request data. 4. The wireless transmission method according to any one of claims 2 and 3, characterized in that: On the receiving terminal side, Receiving a multicast or broadcast packet containing resend request data, and judging whether it contains a resend request with the same lost data as its own, When the resend request data includes the request for the same lost data, stop the resend request for the same lost data. 5. The wireless transmission method according to claim 1, characterized in that: On the transmitting terminal side, the step of performing retransmission of data higher than the MAC layer limits the retransmission time. 6. The wireless transmission method according to claim 5, characterized in that: On the transmitting terminal side, the step of retransmitting higher-level data than the MAC layer transmits retransmission request data including a plurality of sequence numbers of the detected missing data group using one unicast packet. 7. The wireless transmission method according to claim 6, characterized in that: On the transmitting terminal side, the step of performing retransmission of data higher than the MAC layer imposes a time limit on the retransmission request.

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