JP2007208830A - Radio relay method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible for a frame relay to be automatically performed by a third person's radio terminal located at most suitable position between transmitting and receiving radio terminals when performing communication between radio terminals located in areas where the mutual communication therebetween is impossible. <P>SOLUTION: A third person's radio terminal stores a buffer frames transmitted to a receiving-end radio terminal by a transmitting-end radio terminal. Reception waiting is performed for a reception recognition of response from the receiving-end terminal. When the reception recognition of response could not be received, after a given time has elapsed, the reception recognition of response of the frames is transmitted to the transmitting-end radio terminal in substitute for the receiving-end radio terminal depending on priority determined by the received power between the third person's radio terminal and the receiving-end radio terminal, and thereby the frames stored in the buffer are relayed. As a result, a radio terminal whose received power is stronger between itself and the receiving-end radio terminal is allowed to perform the relay to improve communication stability in relaying frames while to permit transmittable areas of radio communication to be easily extended. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In a wireless transmission system in which a plurality of wireless terminals that are not linked to each other coexist, the present invention enables a third party wireless terminal to automatically perform frame relay when direct communication is not possible between a transmission source wireless terminal and a destination wireless terminal. It is related with the wireless relay method which performs.

  In recent years, with the widespread use of wireless LAN terminals, it is common to connect to an Internet service provider via a wireless LAN base station from a wireless LAN slave station such as a notebook personal computer in order to access the Internet in a home or office. It is becoming. However, if there are many obstacles in the home or office and the wireless LAN slave station cannot communicate directly with the wireless LAN base station, the wireless LAN coverage area can be expanded by placing the wireless repeater at an appropriate position. is doing.

  As a wireless LAN standard, there is IEEE 802.11 (IEEE Std 802.11-1997 Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specification). In a wireless LAN defined by IEEE 802.11, a function for connecting wireless LAN base stations called WDS (Wireless Distribution System) is defined, and a wireless repeater can be configured by using this function. The counterpart wireless LAN base station has to be set manually, and installation of a wireless repeater has been extremely difficult for general users who have no knowledge of wireless LAN.

  On the other hand, there are standards such as MANET (Mobile Ad-hoc Network) as a technology for automatically performing routing such as setting of such connection destinations, but all use complicated routing technology. The cost is high and it cannot be easily introduced in ordinary households.

  Therefore, as a method of automatically performing wireless relay without performing complicated routing, there is one described in Patent Document 1.

  FIG. 4 is a diagram illustrating a configuration of a wireless network to which the wireless relay method disclosed in Patent Document 1 is applied. In FIG. 4, the wireless network includes one wireless base station 51 and a plurality of wireless slave stations 61, 71, and 81. Here, the wireless slave stations 61, 71, and 81 are under the management of the wireless base station 51, and are communicable with the wireless base station 51. Further, it is assumed that the wireless slave station 61 and the wireless slave station 71 are located at a distance from each other and cannot be directly communicated with each other.

  At this time, the operation when the wireless slave station 61 wants to directly communicate with the wireless slave station 71 will be described with reference to FIG. FIG. 5 is a schematic diagram for explaining a conventional wireless relay method. In FIG. 5, the timing at which the radio base station and each radio slave station transmit a frame is shown in time series in the horizontal axis direction.

  Although the data frame 200 is transmitted from the wireless slave station 61 to the wireless slave station 71, the wireless slave station 71 receives the data frame 200 because the wireless slave station 61 and the wireless slave station 71 are not within a communicable range. I can't. Since the wireless base station 51 is within the communicable range of the wireless slave station 61, the wireless base station 51 receives the data frame 200, analyzes the received data frame 200, and determines whether the destination address is addressed to its own address. Since the data frame 200 is addressed to the wireless slave station 71, the wireless base station 51 temporarily stores the data frame 200 in an internal buffer.

  The wireless slave station 71 that has not been able to receive the data frame 200 does not transmit an acknowledgment (ACK) frame to the wireless slave station 61. The wireless base station 51 waits for the acknowledgment response (ACK) waiting time T11 for the data frame 200 transmitted by the wireless slave station 61 to elapse, and then wirelessly transmits an ACK frame 210 for the data frame 200 to the wireless slave station 61. Transmit on behalf of the slave station 71.

  At this time, the transmission source address of the ACK frame 210 sets the address of the wireless slave station 71, and the wireless slave station 61 assumes that the ACK frame 210 is transmitted from the wireless slave station 71 and completes the transmission processing of the data frame 200.

Next, the radio base station 51 relays the data frame by transmitting the data frame 200 stored in the internal buffer to the radio slave station 71 as the data frame 211. Through the above operation, the wireless base station 51 relays the frame, thereby enabling communication between the wireless slave station 61 and the wireless slave station 71, which cannot perform direct communication.
JP 7-312597 A

  However, in the conventional wireless relay method, the frame relay is performed only by the wireless base station to which the wireless slave station belongs, and any wireless slave station that wants to communicate is within a range where it can communicate with the wireless base station. Must exist.

  Furthermore, when the wireless base station is installed at a location away from the wireless slave stations with which communication is desired, and relay processing must be performed in a state where the communication state between the wireless base station and the wireless slave station is poor However, there is a problem that the transmission efficiency is deteriorated.

  In order to solve this problem, if a wireless terminal that is not a wireless base station performs frame relay, a plurality of wireless terminals individually send back acknowledgments or frame frames unless a routing path is set in advance. In order to relay, there is a problem that the confirmation response or the relayed frame collides in the wireless section, or the relayed frame reaches a plurality of destinations.

  The radio relay method of the present invention solves the above-described conventional problem, and aims to perform frame relay not only in a radio base station but also in any radio terminal.

  In order to solve the above-described conventional problem, a wireless relay method of the present invention is performed between a source wireless terminal and a destination wireless terminal that are in a position where they cannot communicate with each other in a wireless network including a plurality of wireless terminals. The third party wireless terminal receives the frame transmitted from the transmission source wireless terminal to the destination wireless terminal, stores the frame in a buffer, waits for reception confirmation response from the destination terminal, and When the reception confirmation response cannot be received, the frame is relayed and retransmitted after the time determined according to the priority has elapsed.

  According to the wireless relay method of the present invention, it is possible to avoid collision of reception confirmation responses caused by a plurality of third party terminals transmitting reception confirmation responses at the same time, and to easily expand an area capable of wireless transmission. It becomes possible.

Embodiments of the present invention will be described below with reference to the drawings.
(Embodiment)
FIG. 1 is a diagram illustrating a configuration of a wireless network to which a wireless relay method according to an embodiment of the present invention is applied.

  In FIG. 1, the wireless network includes wireless terminals 11, 21, 31 and 41. A circle drawn around the wireless terminal indicates a range in which each wireless terminal can communicate. The communication area 10 is a range in which the wireless terminal 11 can communicate. A communication area 20 is a range in which the wireless terminal 21 can communicate. 30 indicates a range in which the wireless terminal 31 can communicate, and a communication area 40 indicates a range in which the wireless terminal 41 can communicate.

  In FIG. 1, since the wireless terminal 11 is in the communication area 30 and the communication area 40, it can communicate with the wireless terminal 31 and the wireless terminal 41, but is not in the communication area 20. Direct communication is not possible. Similarly, the wireless terminal 21 can communicate with the wireless terminal 31 and the wireless terminal 41, but cannot directly communicate with the wireless terminal 11, and the wireless terminal 31 does not communicate with the wireless terminal 11 and the wireless terminal 21. Although communication is possible, direct communication with the wireless terminal 41 is impossible, and the wireless terminal 41 can communicate with the wireless terminal 11 and the wireless terminal 21, but cannot directly communicate with the wireless terminal 31. is there.

  A sequence of frame transmission / reception when a data frame is transmitted from the wireless terminal 11 to the wireless terminal 21 in the wireless network configured as described above will be described. FIG. 2 is a schematic diagram for explaining the radio relay method according to Embodiment 1 of the present invention. In FIG. 2, the timing at which each wireless terminal transmits a frame is shown in time series in the horizontal axis direction.

  When the data frame 100 is transmitted from the wireless terminal 11 to the wireless terminal 21, the wireless terminal 31 and the wireless terminal 41 are within the communication area 10 of the wireless terminal 11 and receive the data frame 100. The wireless terminal 31 and the wireless terminal 41 analyze the received data frame 100 and determine whether the destination address is addressed to the own address. Since the data frame 100 is addressed to the wireless terminal 21, the wireless terminal 31 and the wireless terminal 41 store the data frame 100 in their relay buffers.

  Next, since the wireless terminal 21 is not in the communication area 10 of the wireless terminal 11, the data frame 100 cannot be received. Accordingly, the wireless terminal 21 does not transmit an acknowledgment (ACK) frame to the wireless terminal 11.

  Next, after the wireless terminal 31 and the wireless terminal 41 wait for the acknowledgment response (ACK) waiting time for the data frame 100 transmitted by the wireless terminal 11 to time out, the elapsed time of the back-off times T2 and T3 respectively determined Thereafter, an ACK for the data frame 100 is transmitted to the wireless terminal 11 instead of the wireless terminal 21. At this time, since the back-off period T2 of the wireless terminal 31 is shorter than the back-off period T3 of the wireless terminal 41, the wireless terminal 31 transmits a proxy ACK 110 to the wireless terminal 11.

  The transmission source address of the proxy ACK 110 sets the address of the wireless terminal 21, and the wireless terminal 11 completes the transmission process of the data frame 100 assuming that the ACK is transmitted from the wireless terminal 21. Here, a method for setting the back-off period determined by each wireless terminal that transmits the proxy ACK will be described. The back-off period is a period of waiting for transmission before transmitting a frame in order to avoid contention in the wireless section, and is set individually by the wireless terminal.

  For example, if the maximum back-off value is set to 15 in advance, the wireless terminal randomly selects an integer between 0 and 15 and multiplies the selected integer value by a unit time that is determined in advance. Set the initial value of. Therefore, since the wireless terminal starts to transmit a frame after a random transmission waiting time individually, the carrier sense is performed to confirm that the wireless section is in an idle state, and then the frame is transmitted. If it does, it can suppress that the collision of a frame generate | occur | produces in a radio area.

  At this time, if the maximum backoff value is set to a small value, the waiting time until the start of transmission is shortened stochastically, and the priority of proxy ACK transmission can be increased. Using this property, it becomes possible for a specific wireless terminal to preferentially transmit a proxy ACK to perform frame relay.

  Next, a priority determination method for preferentially transmitting a proxy ACK will be described with reference to FIG. FIG. 3 shows the configuration of the relay information management table managed by the wireless terminal 31 and the wireless terminal 41, respectively. The relay information management table includes a destination address and received power. The reception power may be measured when a frame is received from the destination terminal, or the measurement reception power may be measured by transmitting a measurement frame. In this way, the priority is determined based on the received power for each destination terminal measured in advance.

  Since the wireless terminal 31 and the wireless terminal 41 that can be relay terminals have already received frames from the transmission source wireless terminal 11, a wireless terminal having strong reception power with the wireless terminal 21 is used as a relay terminal. The stability of communication between the terminal and the destination wireless terminal is improved.

  In FIG. 3, the reception power obtained by the communication between the wireless terminal 31 and the wireless terminal 21 is −55 dBm, and the reception power obtained by the communication between the wireless terminal 41 and the wireless terminal 21 is − 60 dBm.

  Here, for example, if the maximum back-off value is set to 7 when the received power is −52 dBm to −57 dBm, and the maximum back-off value is set to 15 when the received power is −62 dBm to −57 dBm, the wireless terminal 31 is set. Determines a backoff waiting time between 0 and 7 with a maximum backoff value of 7, and the wireless terminal 41 determines a backoff waiting time between 0 and 15 with a maximum backoff value of 15. Accordingly, the wireless terminal 31 probabilistically has a transmission waiting time shorter than that of the wireless terminal 41, and the proxy ACK response can be transmitted preferentially.

  Note that the received power measurement may vary greatly depending on the state of the radio propagation environment, etc. Therefore, it is possible to use not only a single measurement but also a method of taking multiple measurements and taking the average. good.

  In the above example, the maximum back-off value is set according to the reception power between the third party radio terminal and the destination radio terminal. However, as another method, frame transmission between the third party radio terminal and the destination radio terminal is performed. The maximum backoff value may be determined according to the error rate. In this case, the maximum back-off value is set larger as the frame transmission error rate is higher.

  After transmitting the proxy ACK 110, the wireless terminal 31 transmits a transmission request (RTS: Request to Send) 111 to the wireless terminal 21 before relaying and retransmitting the data frame 100 stored in the relay buffer. After receiving the RTS 111, the wireless terminal 21 transmits a transmission request response (CTS: Clear to Send) 112.

  When receiving the CTS 112 from the wireless terminal 21, the wireless terminal 31 relays and retransmits the data frame 113 stored in the relay buffer. At this time, the transmission source address of the data frame 113 is transmitted using the address of the wireless terminal 11. The wireless terminal 21 that has normally received the data frame 113 transmits an ACK frame 114 to the wireless terminal 11 that is the transmission source of the data frame 113. The wireless terminal 31 receives this ACK frame 114 and completes the relay retransmission process for the data frame 113.

  With the above operation, the wireless terminal 11 and the wireless terminal 21 can transmit a data frame via the wireless terminal 31 without being aware of whether or not the other party is within the communicable range.

  In the present embodiment, the wireless terminal 31 serving as a relay station transmits RTS and CTS before transmitting a data frame because they are not in a communicable area and do not know the existence of the other party. This is to avoid contention between frames transmitted by wireless terminals that are hidden terminals in the wireless section. For this reason, information on a period during which the CTS 112, the data frame 113, and the ACK frame 114 are transmitted is inserted into the RTS 111 so that other wireless terminals cannot transmit frames during that period.

  In addition, information on a period T4 during which the data frame 113 and the ACK frame 114 are transmitted is inserted into the CTS 112 so that other wireless terminals cannot transmit frames during that period. The above operation is only an operation for avoiding a collision such as a data frame in a wireless section. When an environment in which a collision in a wireless section does not occur is assumed, a sequence for transmitting RTS 111 and CTS 112 is performed. May be omitted.

  In the first embodiment, the priority for returning the proxy ACK response is determined by the reception power between the relay terminal and the destination terminal, but the priority is determined by the transmission error rate between the relay terminal and the destination terminal. The degree may be determined, i.e., the maximum backoff value may be determined.

  In this embodiment, the proxy ACK 110 and the RTS 111 transmitted by the wireless terminal 31 are sequentially transmitted as separate frames. However, both the proxy ACK and the RTS are used as the same frame to the wireless terminal 11 and the wireless terminal 21. You may send it. As a result, it is possible to start relay retransmission of data frames in a shorter time than when transmitting as separate frames, and the probability of avoiding contention from other wireless terminals is increased.

  Note that the wireless terminal of the present invention is typically realized as an LSI which is an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include a part or all of them.

  The name used here is LSI, but it may also be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.

  Further, the method of circuit integration is not limited to LSI, and implementation with a dedicated circuit or a general-purpose processor is also possible. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used. Alternatively, a configuration in which a processor is controlled by executing a control program stored in a ROM in hardware resources including a processor and a memory may be used.

  Further, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. Biotechnology can be applied.

  The wireless relay method according to the present invention is useful as a wireless repeater that relays to a station that cannot directly communicate with an access point in a wireless LAN system in a home or office. Further, it is useful as a frame relay method between wireless terminals in a wireless transmission system in which a plurality of wireless terminals that are not linked to each other are mixed, for example, an ad hoc wireless network or a multihop wireless network.

The figure which shows the structure of the wireless network in Embodiment 1 of this invention. Schematic diagram for explaining a radio relay method according to Embodiment 1 of the present invention. Relay information management table managed by the wireless terminal according to Embodiment 1 of the present invention The figure which shows the structure of the conventional wireless network Schematic diagram for explaining an example of a conventional wireless relay method

Explanation of symbols

10, 20, 30, 40 Wireless terminal communicable area 11, 21, 31, 41 Wireless terminal 51 Wireless base station 61, 71, 81 Wireless slave station 100, 200 Data frame 110 Proxy ACK frame 111 RTS frame 112 CTS frame 113 Relay data frame 114 ACK frame 210 ACK frame 211 Relay data frame

Claims (7)

A wireless relay method in which a third party wireless terminal relays and retransmits a frame between a source wireless terminal and a destination wireless terminal that are in a position where they cannot communicate with each other in a wireless network including a plurality of wireless terminals. ,
The third party wireless terminal is
Receiving a frame transmitted by the source wireless terminal to the destination wireless terminal;
Storing the frame in a buffer;
Waiting to receive a reception confirmation response from the destination terminal;
And a step of relaying and retransmitting the frame after elapse of a time determined according to a priority when the reception confirmation response cannot be received. The step of relaying and resending the frame includes:
Transmitting a reception confirmation response of the frame to a transmission source wireless terminal;
The wireless relay method according to claim 1, further comprising: transmitting the frame to a destination wireless terminal. The step of relaying and resending the frame includes:
Transmitting a transmission request to the destination wireless terminal;
The radio relay method according to claim 2, further comprising a step of receiving a transmission request response from the destination terminal.   The wireless relay method according to claim 1, wherein the priority is determined according to received power from the destination wireless terminal.   The wireless relay method according to claim 1, wherein the priority is determined according to a frame transmission error rate with the destination wireless terminal. The third party wireless terminal transmits a transmission request from the third party wireless terminal to the destination wireless terminal before relaying and resending the accumulated frame; and
The wireless relay method according to claim 1, further comprising: a step of transmitting a transmission request response by the destination wireless terminal that has received the transmission request.   The third party wireless terminal transmits a reception confirmation response transmitted on behalf of the destination wireless terminal and a transmission request transmitted to the destination wireless terminal as the same frame. Wireless relay method.

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