JP2005341031A - Wireless communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication method which quickly determines an optimum transfer rate or transmission power to communicate. <P>SOLUTION: The method comprises a step of adding power measuring symbols having a plurality of transfer speeds and amplification levels changed in a specified order to packets as following symbols of a signal unit used on the physical layer of a communication system having a hierarchical structure, sending the packets from the send side to the receive side, selecting the power measuring symbols in the packets one after another to detect the receiving condition at the receive side, retransmitting the detection result to the send side, determining an optimum transfer speed and amplification level at the send side, and repeating such steps mutually with switching over the send side and the receive side to determine an optimum transfer speed and transmission power (amplification level) with a less number of sending and receiving times of the packets to quickly make a radio communication. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention detects the reception status of a packet sent from the transmission side on the reception side and returns the detection result to the transmission side, thereby selecting the optimum transfer rate and amplification level on the transmission side and performing wireless communication. The present invention relates to a wireless communication method.

2. Description of the Related Art Conventionally, a wireless communication method has been known in which transmission efficiency is improved by grasping a necessary transfer rate and transmission power according to a communication environment or the like and optimizing the transmission rate (see, for example, Patent Document 1). ).
As a method for grasping the transfer rate and transmission power that can be transmitted in such wireless communication, for example, a procedure as shown in FIG. 5 can be used.
In the following description, an example in which the transmission side is an access point (AP) and the reception side is a station (ST) will be described.
First, in step 101) in FIG. 5, the AP side transmits a packet set at a low rate with the maximum transmission power to the ST. For example, in the IEEE802.11a standard, a modulated signal of 6 Mbps is transmitted. The ST side that received this packet measures the RSSI value (electric field strength) of the received signal at 102) in FIG. 5, and transmits this received RSSI value to the AP side at 103) in FIG.
In 104) to 106) of FIG. 5, the AP confirms the reception state of the ST, calculates how much dB transmission power is to be reduced from the present time, and in order to reduce the transmission power of the ST, Measure RSSI value (field strength). Thereby, in 107) and 108) in FIG. 5, the AP determines the transmission power that can be received by the ST, transmits the packet again with the transmission power, and returns the received RSSI value from the ST to the ST.
The ST that has received this confirms the reception state of the AP in 109) of FIG. 5, calculates in 110) of FIG. 5 how many dB the transmission power is reduced on the ST side, and in 111) of FIG. The packet is retransmitted according to the transmission power.

The procedure for lowering the transmission power of the AP and ST when the transfer rate is 6 Mbps is determined by the above procedure.
Therefore, next, the transfer rate is increased from 6 Mbps to 9 Mbps, and the procedures from 1) to 11) in FIG. 5 are repeated to determine the transmission power at the transfer rate of 9 Mbps. Such processing is performed in the order of 6 Mbps, 9 Mbps, 12 Mbps, 18 Mbps, 24 Mbps, 36 Mbps, 48 Mbps, and 54 Mbps, and finally the optimum transfer rate is determined.
JP 2003-3480952 A

However, in the above conventional method, since the packet communication procedure is repeated a plurality of times until the optimum transfer rate and transmission power are determined, it takes time to determine the optimum communication.
SUMMARY OF THE INVENTION An object of the present invention is to provide a wireless communication method capable of quickly determining an optimum transfer rate and transmission power and performing communication.

  In order to achieve the above-described object, the wireless communication method of the present invention selects a transfer rate from the transmission side to the reception side, transmits the packet, and detects the reception status of the packet transmitted from the transmission side on the reception side. Then, by returning the detection result to the transmission side, a wireless communication method for performing wireless communication by selecting an optimum transfer rate on the transmission side, wherein the transmission side sets a plurality of transfer rates in a predetermined order. The changed power measurement symbol is added in one packet and transmitted, and the reception side sequentially selects the power measurement symbol in the one packet to detect the reception status, and the detection result is It returns to the transmission side, and an optimal transfer rate is determined on the transmission side.

  According to the wireless communication method of the present invention, power measurement symbols in which a plurality of transfer rates are changed in a predetermined order are added and transmitted in one packet, and the power measurement symbols are sequentially selected and received. And the optimal transfer rate is determined based on the detection result, so that the optimal transfer rate and transmission power can be determined without sending and receiving many packets, improving communication efficiency and reducing communication time. There is an effect that can be achieved.

In the embodiment of the present invention, a power measurement symbol in which a plurality of transfer rates and amplification levels are changed in a predetermined order is added as a subsequent symbol of a signal unit used in a physical layer of a communication system having a hierarchical structure. The packet is transmitted from the transmission side to the reception side. The reception side sequentially selects the power measurement symbols in the packet to detect the reception status, returns the detection result to the transmission side, and determines the optimum transfer rate and amplification level on the transmission side.
By performing such a procedure by switching between the transmission side and the reception side, an optimum transfer speed and transmission power (amplification level) are determined by transmitting and receiving a small number of packets, and wireless communication is performed promptly.

FIG. 1 is an explanatory diagram showing an example of a communication procedure to which a wireless communication method according to an embodiment of the present invention is applied.
In this embodiment, as in the conventional example shown in FIG. 5, an example in which the transmission side is an access point (AP) and the reception side is a station (ST) will be described.
First, the AP side transmits to ST the packet in which the power measurement symbol, which is a feature of the present embodiment, is inserted in 1) of FIG. In this embodiment, according to a unique format obtained by modifying the IEEE802.11a standard to be described later, a transfer rate that changes stepwise in the order of 6 Mbps, 9 Mbps, 12 Mbps, 18 Mbps, 24 Mbps, 36 Mbps, 48 Mbps, and 54 Mbps, and each transfer rate. Correspondingly, a packet to which a power measurement symbol composed of a plurality of types of bit string data combined with amplification levels switched in three stages is added is transmitted. Details of the power measurement symbol will be described later.
The ST side that received this packet measures the RSSI value (electric field strength) of the received signal for each combination of the transfer rate and amplification level of the power measurement symbol in 2) of FIG. The received RSSI value is transmitted to the AP side. At the time of transmission, a power measurement symbol similar to that inserted in 1) of FIG. 1 is inserted into the packet and transmitted.

Next, in 4) to 6) in FIG. 1, the AP confirms the ST reception state for each combination of the transfer rate and the amplification level, calculates how much dB transmission power is to be reduced from the present time, and transmits the ST transmission power. In order to decrease the RSSI value, the RSSI value (electric field strength) of the signal received from the ST is measured for each combination of transfer rate and amplification level.
Thereby, in 7) and 8) in FIG. 1, the AP determines the transmission power that can be received by the ST, transmits the packet again with the transmission power, and returns the received RSSI value from the ST to the ST.
The ST that has received this confirms the reception status of the AP in 9) of FIG. 1, calculates in 10) of FIG. 1 how many dB the transmission power is reduced on the ST side, and in 11) of FIG. The packet is retransmitted according to the transmission power.
In the above, the reception state confirmation on the transmission side or the reception side is to determine whether or not the reception state is appropriate based on the bit error rate, for example.
By executing the above procedure, it is possible to check the reception status for each combination of transfer rate and amplification level in multiple stages inserted in the power measurement symbol, and determine the optimum transfer rate and amplification level. The subsequent communication can be performed.
Therefore, as in the conventional example shown in FIG. 5, it is possible to quickly determine the optimum communication conditions without repeating transmission / reception of packets whose transfer speed is switched in several steps, thereby shortening communication time and improving communication efficiency. It becomes possible.

Next, the signal format used in this embodiment will be described.
As described above, the present embodiment uses a unique format obtained by modifying the IEEE802.11a standard. Therefore, the current IEEE802.11a format will be described first, and then the power measurement symbol according to the present embodiment will be described. The insertion location and format of the will be described.
FIG. 2 is an explanatory diagram showing a symbol-added frame format based on the IEEE802.11a standard. Since this frame format is standardized by IEEE, only a brief description will be given here.
In FIG. 2, in the frame format according to IEEE802.11a, a PLCP preamble 21 is transmitted first.
This symbol is a fixed waveform signal for 16 μsec required for the reception synchronization processing of the radio packet signal, and is composed of 10 short preamble (24 Short preamble) 24 symbols and 2 long preamble (25 Long Preamble) 25 symbols. Composed.
Next, a symbol string called a signal (SIGNAL) unit 22 is transmitted. This signal part 22 includes the transfer rate and data length of the information data part 23 to be transmitted subsequently. The symbol 26 of the signal unit 22 is transmitted at the lowest 6 Mbps in order to reliably receive the packet.
Next, the information data part 23 is transmitted. The data 27 of the information data section 23 is modulated at a transfer rate defined by the signal unit 22, and is specifically transmitted at a transfer rate of 6 to 54 Mbps.

Next, a specific example of inserting a power measurement symbol, which is a feature of the present embodiment, by applying such a frame format according to IEEE802.11a will be described.
FIG. 3 is an explanatory diagram showing the insertion position of the power measurement symbol in the frame format. In addition, the same code | symbol is attached | subjected about the part similar to the element shown in FIG.
As shown in the figure, the present embodiment has a structure in which a power measurement symbol part 31 is added to the subsequent part of the signal part 22 shown in FIG.
It should be noted that the insertion location of the power measurement symbol is not limited to the example of FIG. 3 and can be inserted after the information data section 23, for example. In this case, the signal unit 22 defines where the power measurement symbol is inserted in the packet, and indicates the position, so that the signal unit 22 can be inserted in any position after the signal unit 22. .

FIG. 4 is an explanatory diagram illustrating a specific example of a transmission power measurement symbol in the present embodiment. In addition, the same code | symbol is attached | subjected about the part similar to the element shown in FIG.
In this example, three transmission power levels (amplification amplitude levels) are combined for each of eight transfer speeds of 54 Mbps, 48 Mbps, 36 Mbps, 24 Mbps, 18 Mbps, 12 Mbps, 9 Mbps, and 6 Mbps, depending on each transfer speed and the transmission power level. The symbol sequences are arranged in order, and the arrangement order shown in the figure is arranged in the order from the largest transmission power to the smallest transmission power in the order from the fastest transfer speed to the slowest pair.
Note that the arrangement order is not limited to this. For example, the arrangement order may be the order from the lowest transfer speed or the order from the largest transmission power.
However, if they are arranged in the order in which they are easy to receive, the first received symbol can be received almost certainly, and then the reception state gradually deteriorates, so that the reception state has reached its limit. The measurement sequence ends, and the transfer speed and transmission power level are determined. However, if they are arranged in an order that is difficult to receive, the first received symbol may not be received. After that, when the reception state gradually improves and reaches an appropriate reception state, the measurement sequence is terminated, and the transfer speed and the transmission power level are determined.
In the reception operation in this case, when a symbol for power measurement is detected, if a symbol with low transmission power is present in the packet, there is a possibility that the synchronization clock of the reception RF signal may be lost. It is effective to hold the frequency of the PLL circuit that controls the operation (clock) in order to maintain the clock synchronization state.

  As for the number of transmission power measurement symbols, a method of transmitting only one symbol and a method of transmitting a plurality of symbols can be used for the same transfer rate and the same transmission power level. Since it is impossible to measure the reception state based on the bit error rate, it is necessary to directly detect and determine the reception waveform itself, which complicates the circuit. Therefore, it is preferable to transmit a plurality of symbols. In this case, for example, a sufficient number of samples can be obtained by transmitting about 100 symbols and determining the error rate. It is possible to make an effective determination with a simple configuration.

When the reception state is detected using the transmission power measurement symbol shown in FIG. 4, first, in the section 41 shown in FIG. 4, a measurement symbol having a maximum transmission power value of 0 dBr is transmitted using a transfer rate of 54 Mbps. Next, in a section 42, a transmission power measurement symbol whose transmission power is reduced by, for example, −10 dBr from the maximum value is transmitted. Further, in section 43, a transmission power measurement symbol in which the transmission power is reduced by, for example, −20 dBr from the maximum value. Send. That is, in this example, at the transfer rate of 54 Mbps, three transmission power measurement symbols with the transmission power level lowered by 10 dBr are transmitted in order, and the reception state is detected on the reception side. Note that the transmission power measurement symbol in each section has a length of 4 μsec, and is composed of a head guard time portion and a data portion subsequent thereto.
Thereafter, the transfer power is switched, the measurement work is repeated for the same three types of transmission power, and it is determined which packet at which transfer rate can be received.

According to the present embodiment as described above, the following effects can be obtained.
(1) With a single transmission / reception, a value for reducing the transmission power at each transfer rate (for example, 6 Mbps to 54 Mbps in the case of IEEE802.11a) can be determined.
(2) With one transmission / reception, it is possible to measure the reception state of each transfer rate (for example, 6 Mbps to 54 Mbps), for example, the bit error rate.
(3) The number of packet exchanges can be reduced in the sequence between the AP and the ST, and the time until the value of the transmission power is determined can be shortened.
In addition, this invention is not limited to the above Example, A various deformation | transformation is possible in the range described in the claim of this invention.
For example, in the above-described embodiment, an example in which the frame format defined in IEEE802.11a is used has been described. However, for example, a format used in IEEE802.11b or other wireless communication may be used.
In the above-described embodiments, communication between the AP and the ST has been described as an example, but the present invention can be applied to communication between other terminals as well.

It is explanatory drawing which shows the example of a communication procedure to which the radio | wireless communication method by the Example of this invention is applied. It is explanatory drawing which shows the frame format of the symbol addition format based on the IEEE802.11a standard. FIG. 3 is an explanatory diagram showing an insertion position of a transmission power measurement symbol in the embodiment shown in FIG. 1 with respect to the format shown in FIG. It is explanatory drawing which shows the specific example of the symbol for transmission power measurement in the Example shown in FIG. It is explanatory drawing which shows the example of a communication procedure to which the conventional radio | wireless communication method is applied.

Explanation of symbols

  21... PLCP preamble, 22... Signal portion, 23... Information data portion, 24... Short preamble, 25 .. long preamble, 26.

Claims (17)

The transmission side selects the transfer rate from the transmission side to the reception side, transmits the packet, detects the reception status of the packet sent from the transmission side on the reception side, and returns the detection result to the transmission side, thereby transmitting the transmission side A wireless communication method for performing wireless communication by selecting an optimum transfer speed in
On the transmitting side, power measurement symbols in which a plurality of transfer rates are changed in a predetermined order are added and transmitted in one packet, and on the receiving side, power measurement symbols in the one packet are sequentially transmitted. Select to detect the reception status, return the detection result to the transmission side, and determine the optimum transfer speed on the transmission side,
A wireless communication method.   On the transmission side, a power measurement symbol in which a plurality of transfer rates and amplification levels are changed in a predetermined order is added and transmitted in one packet, and on the reception side, the power measurement symbol in the one packet is measured. 2. The wireless communication method according to claim 1, wherein the symbols are sequentially selected to detect the reception status, the detection result is returned to the transmission side, and the optimum transfer rate and amplification level are determined on the transmission side.   2. The wireless communication method according to claim 1, wherein the power measurement symbol is added to a subsequent symbol of a signal unit used in a physical layer of a communication system having a hierarchical structure.   The wireless communication method according to claim 1, wherein a transfer rate of the power measurement symbol changes stepwise.   The wireless communication method according to claim 1, wherein a transfer rate of the power measurement symbol is gradually changed.   The wireless communication method according to claim 2, wherein at least one of a transfer rate and an amplification level of the power measurement symbol changes stepwise.   The radio communication method according to claim 2, wherein at least one of a transfer rate and an amplification level of the power measurement symbol is gradually changed.   2. The radio communication method according to claim 1, wherein when receiving the power measurement symbol on the receiving side, the frequency of the PLL circuit that controls the operation of the receiving circuit is held.   The wireless communication method according to claim 1, wherein the power measurement symbol changes from a symbol having a high transfer rate to a symbol having a low transfer rate.   The radio communication method according to claim 1, wherein the power measurement symbol changes from a symbol having a low transfer rate to a symbol having a high transfer rate.   The wireless communication method according to claim 2, wherein the power measurement symbol changes from a symbol having a high transfer rate to a symbol having a low transfer rate.   The wireless communication method according to claim 2, wherein the power measurement symbol changes from a symbol having a low transfer rate to a symbol having a high transfer rate.   The radio communication method according to claim 2, wherein the power measurement symbol changes from a symbol having a high amplification level to a symbol having a low amplification level.   The radio communication method according to claim 2, wherein the power measurement symbol changes from a symbol with a low amplification level to a symbol with a large amplification level.   2. The wireless communication method according to claim 1, wherein the receiving side determines the suitability of the reception status by measuring the reception intensity and bit error rate of the power measurement symbol.   2. The wireless communication method according to claim 1, wherein the reception state detection operation using the power measurement symbol is terminated when an optimum transfer rate can be identified from the reception state detection result on the reception side.   3. The radio communication method according to claim 2, wherein the operation of detecting the reception status by the power measurement symbol is terminated when the optimum transfer rate and amplification level can be identified from the detection result of the reception status on the receiving side.

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