JP2008167487A - Data transmission method and system using CSMA method - Google Patents

Abstract

The present invention provides a data transmission method and system using the CSMA method which can be applied even when ARQ transmission processing is used for error control.
Prior to transmission of one frame of transmission data, a random set time set by a standby time setting unit is made to wait, and no transmission from another wireless station is made by another station transmission detecting unit during this period. The transmission data 13 is transmitted in the state. On the other hand, for the reception of retransmission request signals (REQ1, REQ2) 16, 18 from the receiving radio station, the standby time setting unit 9 sets the standby time or transmits to other stations. The detection unit 8 performs processing without detecting the presence or absence of transmission by another wireless station.
[Selection] Figure 1

Description

  The present invention relates to a data transmission method and a system for performing communication using an ARQ (Automatic Repeat Request) transmission process on a radio channel in which a plurality of radio stations share the same frequency by the CSMA method.

  In the CSMA method, when a plurality of wireless stations share the same frequency and perform communication, it detects that another wireless station is transmitting by detecting a carrier sense or a synchronization signal in a wireless station other than the transmitting station. This is a multiple access method in which the transmission of its own station is prohibited while the transmission is detected to prevent collision. If all the other wireless stations can start transmitting immediately after transmission of the transmitting wireless station is completed, if there are multiple wireless stations that have been waiting for transmission, they are transmitted simultaneously. The collision will not be avoided. In order to prevent such a collision, each radio station independently performs random number generation processing and waits for the start of transmission for a time determined by the value of the random number at that time. However, the conventional CSMA scheme targets a transmission sequence in which only an ACK (Acknowledgement) response is made from a receiving station.

FIG. 3 is a transmission sequence diagram showing a conventional data transmission method based on the CSMA method (see, for example, Non-Patent Document 1). It is assumed that the plurality of radio stations A to E configuring the system are in a positional relationship in which the radio waves transmitted from other radio stations can be received. In this example, transmission data 22 and 23 that need to be transmitted to the wireless station C and the wireless station E are generated during transmission of the transmission data 21 from the wireless station A to the wireless station B. The transmission destination is wireless station D. After the transmission of the ACK signal 24 from the wireless station B is completed, the wireless station C and the wireless station E generate random numbers independent of each other, and wait for a waiting time t1 and a waiting time t2 proportional to the random numbers. After waiting time t1 and waiting time t2, respectively, detection processes 25 and 26 are performed by a method such as carrier sense to determine whether there is any other radio station transmitting. Here, since the standby time t1 of the wireless station C is shorter than the standby time t2 of the wireless station E, the detection processing 25 of the wireless station C determines that there is no transmission in another wireless station and the transmission data 22 Start sending. In the detection process 26 of the wireless station E, since it is determined that the wireless station C is transmitting, the wireless station C does not transmit and waits until the transmission of the ACK signal 27 from the wireless station D is completed. After the transmission of the ACK signal 27 of the wireless station D, the wireless station E generates a random number again and waits for a standby time t3 proportional to the random number. Thereafter, the wireless station E performs a process 28 for detecting the presence / absence of another transmitting station, but since there is no other transmission here, transmission of the transmission data 23 can be started.
IEEE 802.11

  However, the conventional data transmission method based on the CSMA method is intended for a transmission sequence in which only the ACK response is made from the receiving radio station, and one frame of transmission data is composed of a plurality of blocks, and each block has an error. If the error is detected by error detection performed for each block at the receiving wireless station, the transmission data of the block specified by the retransmission request signal returned from the receiving wireless station is transmitted on the transmitting side. A sequence such as ARQ transmission processing retransmitted from a radio station is not considered.

  An object of the present invention is to provide a data transmission method and system according to the CSMA method which can be applied even when ARQ transmission processing is used for error control.

  In order to achieve the above object, the present invention performs error detection for each block of transmission data received by a receiving radio station in a radio channel in which a plurality of radio stations share the same frequency by the CSMA method, and detects an error. In such a case, the retransmission request signal of the block is transmitted to the transmission side radio station, and the transmission side radio station that has received the signal transmits the transmission data of the corresponding block to the reception side radio station. In the data transmission method according to the method, the transmission side radio station detects the absence of transmission of another radio station after a randomly set waiting time at the start of transmission of one frame of transmission data. Data is transmitted, and the transmission data of the corresponding block is retransmitted without setting the waiting time for the retransmission request signal from the receiving radio station. It is characterized in.

  The present invention according to claim 2 detects an error by detecting an error for each block of transmission data received by a receiving radio station in a radio channel in which a plurality of radio stations share the same frequency by the CSMA method. In this case, the CSMA system has an ARQ data transmission unit that transmits a retransmission request signal of the block to the transmission-side radio station, and the transmission-side radio station that has received the signal transmits the transmission data of the corresponding block to the reception-side radio station. In the data transmission system according to the above, in the transmission side radio station, a standby time setting unit that sets a standby time when transmission data is generated, and other station transmission that detects that there is no transmission of other radio stations within this standby time A detection unit, an encoding unit that encodes the transmission data when the other station transmission detection unit detects that there is no transmission by another wireless station, and transmits the encoded transmission data A transmission unit, and a reception code determination unit that detects a retransmission request signal for requesting retransmission of transmission data of a block in which an error is detected in the reception-side wireless station, and the reception code determination unit detects the retransmission request signal when the retransmission request signal is detected Transmission data of a block corresponding to the retransmission request signal is transmitted from the transmission unit through the encoding unit without operating a standby time setting unit and the other station transmission detection unit.

  According to the data transmission method using the CSMA method according to the present invention, transmission of transmission data is performed in a state where it is detected that there is no transmission of another wireless station after a standby time randomly set prior to transmission of transmission data of one frame. On the other hand, the retransmission request signal can be transmitted without setting the standby time or detecting the presence / absence of transmission by another wireless station, so that other wireless stations are transmitting The transmission of the retransmission request signal and the retransmission data is efficient without causing any interference by starting transmission to the local station, without being interrupted by other stations until there is no error after the local station starts transmission. Can be realized.

  According to the data transmission system using the CSMA method according to the second aspect of the present invention, prior to transmission of one frame of transmission data, the other station transmission detection unit within the predetermined standby time determined by the standby time setting unit. The encoded transmission data is transmitted in a state where it is detected that there is no transmission of another radio station, but for the retransmission request signal detected by the reception code determination unit, the standby time setting unit and the other station transmission detection unit Since the transmission is performed without operating the other wireless station, it does not interfere with other wireless stations during transmission, and is interrupted by the other station until there is no error after the local station starts transmission. Therefore, efficient transmission of the retransmission request signal and the retransmission data can be realized.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a main part of a radio station of a data transmission system based on the CSMA scheme according to an embodiment of the present invention.
A plurality of radio stations employs ARQ transmission processing, for example, SR-ARQ (Selective Repeat type Automatic Repeat Request) on a radio line that shares the same frequency with the CSMA method, and the radio transmission apparatuses that constitute each radio station are: A transmission data memory 1 for storing transmission data, an encoding unit 2 that encodes transmission data composed of a plurality of blocks in one frame into a transmission signal that can detect errors for each block, and encoding for error detection A transmitter 3 that modulates and amplifies a carrier wave with a transmission signal and transmits, a receiver 4 that receives and amplifies and demodulates a received modulated wave and obtains an output corresponding to the received input level, and a transmitter 3 and a receiver by transmission and reception Transmission / reception switching unit 5 for switching the connection of the antenna 4 and decoding of the received signal demodulated by the receiving unit 4 The received code determination unit 6, the error detection unit 7 that detects the error of the demodulated data for each block, and the other station transmission that determines whether there is a station transmitting from the output corresponding to the reception input level of the reception unit 4 It has a detection unit 8, a standby time setting unit 9 for generating a random number at the start of data transmission and setting a random standby time determined by the random number, and a transmission control unit 10 for controlling the transmission / reception operation of the apparatus. .

  The details of the control of each component by the transmission control unit 10 will be described later, but at the time of the first transmission operation of transmission data, reception is performed in a state where it is detected that there is no transmission of other wireless stations after a randomly set waiting time. Transmission data is transmitted to the wireless station on the receiving side, but the transmission data of the corresponding block is retransmitted without setting a waiting time for the retransmission request signal from the receiving wireless station. Further, since the output from the receiving unit 4 to the other station transmission detecting unit 8 is an output corresponding to the received input level as described above, the received input level itself such as RSSI is shown.

FIG. 2 is a diagram of a transmission sequence of a data transmission system based on the CSMA scheme according to an embodiment of the present invention.
If one frame of transmission data 13 from the wireless station A to the wireless station B is generated, the transmission control unit 10 operates the standby time setting unit 9 before starting transmission of the transmission data 13 to generate a random number, A standby time t4 that is a random integer multiple of a fixed time proportional to the random number is set, and transmission is waited for. After the end of the waiting time t4, the transmission control unit 10 performs a process 15 for detecting whether or not there is a radio station transmitting by the other station transmission detection unit 8. As a result, when the other station transmission detection unit 8 has already detected the error-free signal (ER0) 14 from the wireless station C and determines that there is no wireless station that is transmitting because the transmission of the data transmission has been completed, 10 transmits the transmission data 13 to the encoding unit 2, and the transmission data 13 of one frame composed of a plurality of blocks is used as a transmission signal encoded so that an error can be detected for each block, and the transmission unit 3 modulates and amplifies the carrier wave. Then, transmission to the wireless station B is started.

  Here, the standby time t4 is obtained by multiplying the generated random number by a certain reference time, and the reference time is a time necessary for the carrier sense operation. For example, the response time and fluctuation of RSSI (level detection circuit) Although it is determined by the smoothing time, depending on the circuit configuration, it is generally considered to be about 20 to 50 symbols. The range of the random value varies depending on the probability that the transmission start time will collide, but if the number of radio stations is not too large, it may be about 10. Incidentally, in IEEE802.11, the initial condition is 15 (a random number in the range of 1 to 15 is generated).

  In the wireless station B that has received the transmission of the transmission data 13 from the wireless station A, the transmission data 13 input by the transmission control unit 10 through the reception code determination unit 6 is stored in the transmission data memory 1 and transmitted by the error detection unit 7. If the data 13 is detected for each block and it is detected that there is an error in any of the blocks, the retransmission request signal indicating that there is an error in the block to the wireless station A when reception of one frame is completed (REQ1) 16 is notified.

  When the reception code determination unit 6 of the wireless station A detects that the retransmission request signal (REQ1) 16 has been received, the transmission control unit 10 extracts again the transmission data of the block determined to have an error from the transmission data memory 1, After the encoding unit 2 performs the same process as described above, the data is retransmitted from the wireless station A to the wireless station B as retransmission data 17. In response to the transmission of the retransmission request signal (REQ1) 16 and the retransmission data 17 this time, the transmission control unit 10 does not operate the other station transmission detection unit 8 and the standby time setting unit 9, but sets a random standby time and others. The presence / absence of transmission by the wireless station is not detected.

  Further, when there is an error in the retransmission data 17, a retransmission request signal (REQ2) 18 corresponding to the error is returned from the wireless station B, and the transmission control unit 10 of the wireless station A that has received the retransmission request signal (REQ2) 18 similarly. The transmission data of the block corresponding to is retransmitted as retransmission data 19. Also for the transmission of the retransmission request signal (REQ2) 18 and the retransmission data 19 at this time, the transmission control unit 10 does not operate the other station transmission detection unit 8 and the standby time setting unit 9, and sets a random standby time. Does not detect the presence or absence of transmission by other radio stations.

  When the error detection unit 7 of the wireless station B determines that there is no error in the retransmission data 19, the wireless station B transmits a no error signal (ER0) 20 serving as a transmission end signal to complete the transmission. Thereafter, the next frame can be transmitted in the same manner. If there is no transmission data, the process returns to the standby state.

  Prior to the transmission of the transmission data 13 from the wireless station A, when the other station transmission detection unit 8 determines that there is a wireless station being transmitted, the transmission of the transmission data 13 is stopped and the transmission of the wireless station is completed. When the end of transmission of the radio station is detected, the operation returns to the operation before starting the transmission for operating the standby time setting unit 9, and the data in the transmission data memory 1 is read and sent to the encoding unit 2. Similar processing is performed.

  As described above, in the data transmission method using the CSMA method, transmission of the transmission data 13 is performed in a state in which transmission from another wireless station does not occur after a standby time randomly set prior to transmission of one frame of transmission data 13. On the other hand, for transmission of retransmission request signals (REQ1, REQ2) 16, 18 and retransmission data 17, 19 without setting a waiting time or detecting the presence or absence of transmission by other radio stations. Since it is implemented, transmission can be started immediately after the end code of each frame is generated, and it is efficient while preventing transmission of other radio stations from interrupting the sequence of the ARQ transmission processing method. Transmission can be realized.

  Further, in the data transmission system based on the CSMA method, the waiting time setting unit 9 waits for a certain period of time prior to transmission of one frame of transmission data 13, and the other station transmission detection unit 8 transmits data from other radio stations during that time. After confirming that the transmission data 13 is transmitted through the encoding unit 2, the reception code determination unit 6 receives the retransmission request signals (REQ1, REQ2) 16, 18 from the reception radio station and the retransmission data. When transmissions 17 and 19 are performed, the processing is performed without setting the standby time or detecting the presence or absence of transmission by other wireless stations, so that transmissions of other wireless stations are not performed during the sequence of the ARQ transmission processing method. Efficient transmission can be realized while preventing interruption.

  That is, when the data transmission system based on the conventional CSMA scheme shown in FIG. 3 is simply applied to the ARQ transmission processing scheme, the transmission side radio station to the reception side during transmission of transmission data from one radio station to another radio station. When transmission data to the wireless station is generated, the transmitting wireless station generates a random number in response to a response signal from the receiving wireless station and sets a standby time proportional to the random number. As described above, the transmitting wireless station generates a random number in response to the retransmission request signal from the receiving wireless station, and sets a waiting time according to the random number. For this reason, a standby time occurs for each retransmission request signal, and efficient data transmission cannot be performed. However, as described above, at the first transmission of one frame of transmission data, the standby time setting unit 9 and the encoding unit 2 are operated to generate a standby time. However, the standby time is set for the retransmission request signals (REQ1, REQ2). Since the setting unit 9 and the encoding unit 2 are not operated, it is possible to prevent other wireless stations from transmitting simultaneously and to perform efficient data transmission.

  In the data transmission system based on the CSMA system according to the present invention, the standby time t4 in FIG. 2 can be set as a standby time by adding a detection time in the other station transmission detection unit 8 to a time proportional to a random number.

It is a block block diagram which shows the principal part of the radio station of the data transmission system by the CSMA system by one embodiment of this invention. It is a time chart which shows the transmission sequence of the collision avoidance apparatus of the CSMA system by one embodiment of this invention. It is a time chart which shows the transmission sequence of the data transmission system by the conventional CSMA system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission data memory 2 Encoding part 3 Transmission part 6 Encoding part 7 Error detection part 8 Other station transmission detection part 9 Standby time setting part 10 Transmission control part 13 Transmission data 14 No error signal 16, 18 Retransmission request signal 17, 19 Resend data

Claims (2)

  Multiple wireless stations share the same frequency using the CSMA method, and perform error detection for each block of transmission data received by the receiving wireless station. If an error is detected, a retransmission request signal for that block is transmitted. In the data transmission method according to the CSMA method using the ARQ transmission process in which the transmission side wireless station that has transmitted and received the data to the side wireless station retransmits the transmission data of the corresponding block to the reception side wireless station. The station transmits the transmission data in a state where it is detected that there is no transmission of another wireless station after a randomly set waiting time at the start of the first transmission of transmission data of one frame, and from the receiving wireless station In response to the retransmission request signal, the transmission data of the corresponding block is retransmitted without setting the waiting time. Data transmission method.   Multiple wireless stations share the same frequency using the CSMA method, and perform error detection for each block of transmission data received by the receiving wireless station. If an error is detected, a retransmission request signal for that block is transmitted. In the data transmission system according to the CSMA system, which has an ARQ data transmission unit that retransmits transmission data of a corresponding block to the reception side radio station in the transmission side radio station that has transmitted to the reception side radio station and received it, the transmission side radio station A standby time setting unit that sets a standby time when transmission data is generated, an other station transmission detection unit that detects that there is no transmission of another wireless station within the standby time, and the other station transmission detection unit The encoding unit that encodes the transmission data when it is detected that there is no transmission by another radio station, the transmission unit that transmits the encoded transmission data, and the reception side radio station. A reception code determination unit that detects a retransmission request signal for requesting retransmission of transmission data of the detected block, and when the reception code determination unit detects the retransmission request signal, the standby time setting unit and the other station transmission A data transmission system according to the CSMA system, wherein transmission data of a block corresponding to the retransmission request signal is transmitted from the transmission unit through the encoding unit without operating a detection unit.

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