JP2010199998A - Radio communication system, relay station device and radio communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication system in which throughput is improved more when performing network coding with a relay station device. <P>SOLUTION: When the relay station device R receives a data frame 105 addressed to a radio station B from a radio station A, in a radio communication system, a plurality of frames are continuously transmitted/received at high-priority short frame intervals (SIFS 106, 702), the plurality of frames including at least an ACK frame 701 from the relay station device to each radio station and a coding data frame 703 generated by arithmetically processing exclusive OR with the data frame 105 and a data frame, addressed to the radio station A, in a storage means of the relay station device. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a radio communication system, a relay station apparatus, and a radio communication method for relaying radio communication between radio stations using a relay station apparatus.

  Wireless communication has been increasing in frequency and bandwidth toward higher speed communication. In a system having the same configuration as the current wireless communication system, a higher transmission power is required for the transmission station. Therefore, a relay station (or relay station apparatus; AP (Access Point)) is provided for the purpose of reducing the transmission power of each wireless station. Research and development of a multi-hop wireless communication network having () is underway (see, for example, Non-Patent Document 2). On the other hand, a network coding technique that can reduce the number of packets to be transmitted by coding data to a plurality of destinations at a relay station has attracted attention (see, for example, Non-Patent Document 3). In particular, network coding is experimentally implemented in a wireless LAN (Local Area Network) system, and its characteristics are evaluated (for example, see Non-Patent Document 4). However, a technique for realizing an optimal media access control method when network coding is applied is a future technical problem.

  In addition, results of applying network coding to wireless LAN systems that employ CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) for all wireless stations have been reported ( For example, refer nonpatent literature 4). As a result, network coding has been reported to improve throughput. In contrast, wireless relay network coding using Slotted ALOHA has been shown to improve throughput by controlling the transmission probability of a relay station (see, for example, Non-Patent Documents 1 and 5). Further, in wireless multi-hop networks using RTS / CTS (Request To Send; Clear To Send; reception ready), a method of reducing control packets during handshake has been proposed (for example, Non-Patent Document 6). reference).

Tomoya Hirano, Daisuke Umehara, Satoshi Tano, Masahiro Morikura, Takatoshi Sugiyama, “Examination of Relay Control Method for Wireless Relay Slotted ALOHA Network Coding System”, IEICE Technical Report RCS2008-83, pp.181-186, August 2008 F. A. Tobagi, “Analysis of a two-hop centralized packet radio network − Part II: Carrier sense multiple access,” IEEE Trans. Commun., Vol. COM-28, no. 2, pp. 208−216, Feb. 1980 R. Ahlswede et al., “Network information flow,” IEEE Trans. Inform. Theory, vol. 46, no. 4, pp. 1204-1216, July 2000 S. Katti et al., “XOR's in the air: Practical wireless network coding,” Proc. ACM SIGCOMM 2006, pp. 243-254, Sep. 2006 D. Umehara et al., “Throughput analysis of wireless relay slotted ALOHA systems with network coding,” Proc. IEEE Globecom 2008, 5 pages, Nov./Dec. 2008 C-K. Toh et al., “MARCH: A medium access control protocol for multihop wireless ad hoc networks,” Proc. MILCOM 2000, pp. 512−516, Oct. 2000

  As described above, in a multi-hop wireless communication network having a relay station, network coding techniques are being studied in order to improve throughput. A combination of CSMA / CA and network coding technology is also being considered. However, conventional CSMA / CA did not consider optimization in combination with network coding technology.

  Note that in the wireless communication system according to the present invention, data is transmitted and received after being divided into fixed units. This unit of data division is called a packet or a frame. In the present application, hereinafter, this data division unit is referred to as a frame. Also, the frames are classified into three types: management frames, control frames, and data frames. The management frame includes a beacon frame and an authentication frame. The control frame includes an ACK frame (Acknowledgment, response confirmation frame), an RTS frame (transmission request frame), a CTS frame (reception ready frame), and the like. The data frame is used for transferring user data.

  The present invention has been made in consideration of the above circumstances, and includes a relay station apparatus that performs radio relay between radio stations, and is based on a frame unit based on CSMA / CA (carrier sensing multiple access method with collision avoidance function) It is an object of the present invention to provide a radio communication system, a relay station apparatus, and a radio communication method that can further improve throughput when network coding is performed by a relay station apparatus in a radio communication system that transmits and receives radio signals. .

  In order to solve the above-described problem, the invention according to claim 1 is a relay station apparatus that performs radio relay between radio stations, and a first that transmits and receives radio signals via the relay station apparatus when radio waves cannot reach each other. A wireless communication system including a second wireless station and a second wireless station, wherein the first wireless station, the second wireless station, and the relay station device are based on a carrier sensing multiple access scheme with a collision avoidance function. The first radio station or the second radio station transmits a transmission request frame before transmitting a data frame, and receives a reception ready frame as a response to the transmission request frame. A data frame is transmitted when received, and when the relay station apparatus receives a data frame addressed to the second radio station from the first radio station, the relay station apparatus, the first radio station, and Between the second radio stations, a control frame from the relay station device toward at least one of the first radio station and the second radio station, and the first radio station received by the relay station device From the second radio station to the second radio station and the data frame addressed to the first radio station from the second radio station in the storage unit of the relay station device by performing an exclusive OR operation process. A wireless communication system characterized by continuously transmitting and receiving a plurality of frames including at least a generated coding data frame at short frame intervals with high priority.

  According to a second aspect of the present invention, when the relay station apparatus receives a data frame addressed to the second radio station from the first radio station, the relay station apparatus transmits the first radio station to the second radio station. When the addressed data frame is not in the storage unit of the relay station device, the response signal to the first radio station including transmission request information to the second radio station is continuously received at the short frame interval. An acknowledgment frame is transmitted to the first radio station and the second radio station, a data frame addressed to the first radio station is received from the second radio station, and stored in the storage means Storing the exclusive OR of the data frame addressed to the second radio station from the first radio station and the data frame addressed to the first radio station from the second radio station in the storage means. Before coding data frame generated by calculation processing And transmitting toward the the first radio station and the second radio station.

  According to a third aspect of the present invention, when the relay station apparatus receives a data frame addressed to the second radio station from the first radio station, the relay station apparatus receives the first radio station from the second radio station. When the addressed data frame is in the storage means of the relay station device, the response signal to the first radio station including the transmission request information to the second radio station is continuously received at the short frame interval. A certain acknowledgment frame is transmitted to the first radio station and the second radio station, and a data frame addressed to the second radio station from the first radio station and the second frame in the storage means are transmitted. A coding data frame generated by performing an exclusive OR operation with a data frame addressed to the first radio station from two radio stations is directed to the first radio station and the second radio station. It is characterized by transmitting.

  According to a fourth aspect of the present invention, when the relay station apparatus receives a data frame addressed to the second radio station from the first radio station, the relay station apparatus receives the first radio station from the second radio station. When the addressed data frame is in the storage means of the relay station apparatus, an acknowledgment frame is continuously transmitted to the first radio station at the short frame interval, and is sent to the second radio station. Transmitting a transmission request frame, receiving a reception preparation completion frame from the second wireless station as a response to the transmission request frame, and thereafter, transmitting a data frame addressed to the second wireless station from the first wireless station; A coding data frame generated by performing an exclusive OR operation with the data frame addressed to the first radio station from the second radio station in the storage means is generated with the first radio station and the second radio station. Radio stations And transmitting toward the.

  According to a fifth aspect of the present invention, there is provided a relay station apparatus that performs radio relay between radio stations, a first radio station that transmits and receives radio signals via the relay station apparatus that cannot transmit radio waves to each other, and a second radio station A relay station device in a wireless communication system including a wireless station, wherein the relay station device is in frame units between the first wireless station and the second wireless station based on a carrier sensing multiple access scheme with a collision avoidance function. When a transmission request frame is received from the first wireless station or the second wireless station, a reception preparation completion frame is sent to the wireless station as a response to the transmission request frame. Transmitting, receiving a data frame transmitted from the radio station in response to the reception preparation completion frame, and receiving a data frame addressed to the second radio station from the first radio station, A control frame from the relay station device to at least one of the first radio station and the second radio station between the station device, the first radio station, and the second radio station; and the relay station A data frame addressed to the second radio station from the first radio station received by the device and a data frame addressed to the first radio station from the second radio station in the storage means of the relay station device. A relay station apparatus characterized by continuously transmitting and receiving a plurality of frames including at least a coding data frame generated by performing an exclusive OR operation process at short frame intervals with high priority.

  According to a sixth aspect of the present invention, there is provided a relay station apparatus that performs radio relay between radio stations, a first radio station that transmits and receives radio signals via the relay station apparatus that cannot receive radio waves, and a second radio station. A wireless communication method in a wireless communication system comprising a wireless station, wherein the first wireless station, the second wireless station, and the relay station device are based on a carrier sensing multiple access scheme with a collision avoidance function. When the first radio station or the second radio station transmits a transmission request frame before transmitting a data frame and receives a reception preparation completion frame as a response to the transmission request frame When the relay station apparatus receives a data frame addressed to the second radio station from the first radio station, the relay station apparatus, the first radio station, and the Between the two radio stations, the control frame from the relay station device to at least one of the first radio station and the second radio station, and the first radio station received by the relay station device from the first radio station A data frame addressed to the second radio station and a data frame addressed to the first radio station from the second radio station in the storage means of the relay station device are generated by performing an exclusive OR operation process. A wireless communication method characterized by continuously transmitting and receiving a plurality of frames including at least a coding data frame at short frame intervals with high priority.

  According to the present invention, when the relay station apparatus receives a data frame addressed to the second radio station from the first radio station, control from the relay station apparatus to the first radio station and the second radio station is performed. A frame, a data frame addressed to the second radio station from the first radio station received by the relay station device, and a data frame addressed to the first radio station from the second radio station in the storage means of the relay station device A plurality of frames including at least a coding data frame generated by performing an exclusive OR operation process are continuously transmitted and received at a short frame interval having a high priority, so that a standby state is set for collision avoidance and the like. Time can be reduced compared to the conventional case. Therefore, the throughput can be improved compared to the conventional case.

  Also, transmission is performed by transmitting an acknowledgment frame that is a response signal to the first radio station including transmission request information to the second radio station, to the first radio station and the second radio station. It is possible to omit a part of the request frame or the reception preparation completion frame. Therefore, the throughput can be further improved.

1 is a block diagram illustrating an embodiment of a wireless communication system according to the present invention. It is a schematic diagram showing a frame flow by CSMA / CA using RTS / CTS as the background art of the present invention. FIG. 3 is a schematic diagram illustrating an example of a frame flow in the relay station apparatus R illustrated in FIG. 1. 4 is a flowchart showing a processing flow in relay station apparatus R of FIG. 1 corresponding to the frame flow shown in FIG. 3. FIG. 7 is a schematic diagram illustrating another example of a frame flow in the relay station apparatus R illustrated in FIG. 1. 6 is a flowchart showing a processing flow in relay station apparatus R of FIG. 1 corresponding to the frame flow shown in FIG. 5. Characteristic diagram to show the degree of bias between radio stations of data frames relayed by relay stations when combining CSMA / CA using network coding technology and CSMA / CA using RTS / CTS and CSMA / CA not using RTS / CTS It is. It is a comparison figure of the throughput of the conventional CSMA / CA system (CSMA / CA) and the control system (RIT and RIT / TH) in the embodiment of the present invention.

  Embodiments of a wireless communication system according to the present invention will be described below with reference to the drawings. A radio communication system 1 shown in FIG. 1 includes a relay station device R, a radio station A, and a radio station B. The relay station device R is a device that performs wireless relay between the wireless stations A and B. The radio station A and the radio station B are radio stations that cannot transmit and receive radio waves and transmit and receive radio signals via the relay station device R. That is, wireless station A and wireless station B are in a hidden terminal relationship. Hereinafter, the relay station device R, the wireless station A, and the wireless station B may be referred to as a transmitting station or a receiving station.

  The relay station apparatus R shown in FIG. 1 includes a communication control apparatus 11 for transmitting and receiving radio signals, and a storage apparatus (storage means) 12 for storing data frames received from the radio stations A and B. I have. In this case, the storage device 12 has a buffer A13 for storing data frames addressed to the radio station A received from the radio station B, and a buffer B14 for storing data frames addressed to the radio station B received from the radio station A. And have.

  Further, the wireless station A has a communication control circuit 21 for transmitting and receiving wireless signals, and a storage device 22 having a buffer 23 for storing a data frame transmitted to the wireless station B via the relay station device R. It has. The radio station B includes a communication control circuit 31 for transmitting and receiving radio signals, and a storage device 32 having a buffer 33 for storing a data frame transmitted to the radio station B via the relay station device R. ing.

  With the above configuration, the relay station apparatus R of FIG. 1 stores the data frame 41 addressed to the radio station B received from the radio station A in the buffer B14, and then reads out the data frame 41 at a predetermined timing to the radio station B. On the other hand, after the data frame 42 addressed to the radio station A received from the radio station B is temporarily stored in the buffer A13, it is read out at a predetermined timing and transmitted to the radio station A, thereby relaying the radio signal. In this case, the data included in the data frame 41 is “a”, and the data included in the data frame 42 is “b”.

  At that time, when the relay station apparatus R receives the data frame 41 (data “a”) addressed to the radio station B from the radio station A, the relay station apparatus R stores the data frame 42 (addressed to the radio station A from the radio station B in the buffer A13). When the data “b”) exists, the data frame 41 and the data frame 42 are subjected to an exclusive OR operation process to generate a coding data frame 43. Then, the generated coding data frame 43 is transmitted (broadcast) toward the radio station A and the radio station B. Further, when the relay station apparatus R receives the data frame 42 (data “b”) addressed to the radio station A from the radio station B, the relay station apparatus R stores the data frame 41 (data) addressed to the radio station B from the radio station A in the buffer B14. If “a”) exists, the data frame 42 and the data frame 41 are subjected to an exclusive OR operation to generate a coding data frame 43. Then, the generated coding data frame 43 is transmitted (broadcast) toward the radio station A and the radio station B. When the data in the data frame 41 is “a” and the data in the data frame 42 is “b”, the data in the coding data frame 43 is “a xor b” (in this specification, the exclusive OR is “ xor ”, but in FIG. 1, it is represented by a symbol with“ + ”in“ ◯ ”).

  On the other hand, the wireless station A stores the data frame 41 transmitted to the buffer 23 when the data frame 41 (data “a”) addressed to the wireless station B is transmitted to the relay station apparatus R. When the coding data frame 43 (data “a xor b”) is received from the relay station apparatus R, an exclusive OR operation process is performed on the data frame 41 and the coding data frame 43 in the buffer 23, and wireless communication is performed. The data “b” of the data frame 42 transmitted from the station B to the wireless station A is decoded. That is, the data “b” is obtained by the calculation process of a xor (a xor b) = b. The wireless station B stores the data frame 42 transmitted to the buffer 33 when the data frame 42 (data “b”) addressed to the wireless station A is transmitted to the relay station device R. When the coding data frame 43 (data “a xor b”) is received from the relay station apparatus R, an exclusive OR operation process is performed on the data frame 42 and the coding data frame 43 in the buffer 33, and wireless communication is performed. The data “a” of the data frame 41 transmitted from the station A to the wireless station B is decoded. That is, the data “a” is obtained by the calculation process of b xor (a xor b) = a.

  On the other hand, when the relay station apparatus R receives the data frame 41 (data “a”) addressed to the radio station B from the radio station A, the relay station apparatus R stores the data frame 42 (data) addressed to the radio station A from the radio station B in the buffer A13. When there is no "b"), the data frame 41 is temporarily stored in the buffer B14. Then, the relay station apparatus R generates a data frame 45 including the data “a” in the data frame 41 stored in the buffer B14 after a predetermined standby time has elapsed, and transmits the data frame 45 to the radio station B. Further, when the relay station apparatus R receives the data frame 42 (data “b”) addressed to the radio station A from the radio station B, the relay station apparatus R stores the data frame 41 (data) addressed to the radio station B from the radio station A in the buffer B14. When "a") does not exist, the data frame 42 is temporarily stored in the buffer A13. Then, the relay station apparatus R generates a data frame 44 including the data “b” in the data frame 42 stored in the buffer A13 after a predetermined standby time has elapsed, and transmits the data frame 44 to the radio station A.

  The waiting time is set to increase the probability that a state in which the coding data frame 43 can be generated by receiving data from both the radio station A and the radio station B will occur. If this waiting time is long, the probability that coding is possible increases. However, if the standby time is increased, the transmission delay of data placed in the standby state is increased. Therefore, it is desirable to set the standby time to an appropriate value. The set value of the standby time can be set using, for example, a simulation result. In this embodiment, by providing an appropriate waiting time, it is possible to suppress a decrease in throughput, which is a problem particularly in a non-uniform traffic environment, and to compensate for a data frame transmission delay when using a network coding technique. become. Furthermore, in an environment where uneven traffic occurs, even in a non-coding state, the buffer capacity of the relay station apparatus R can be increased by transmitting a non-coded data frame with a high probability when a predetermined waiting time is exceeded. There is an effect that it is not necessary to consume a large amount.

  In addition, the radio station A, radio station B, and relay station apparatus R of this embodiment shown in FIG. 1 use carrier sensing multiplexing with a collision avoidance function using a transmission request frame (RTS frame) and a reception preparation completion frame (CTS frame). Radio signals are transmitted and received in frame units based on the access method (CSMA / CA). CSMA / CA made it so that the transmitting station senses that no other transmitting station is transmitting the radio signal (that is, the carrier) before transmitting the radio signal in order to avoid the collision of the radio signal. Access method. In addition, CSMA / CA using RTS / CTS senses radio signals transmitted from other transmitting stations when radio waves cannot reach each other between radio stations A and B, as in this embodiment. This is CSMA / CA with a countermeasure function for the case where there is a transmitting station that cannot perform (ie, there is a hidden terminal problem). The RTS frame is a control frame that is transmitted in order to make a transmission request (a request to transmit a frame) by a transmitting station that intends to transmit a radio signal. This RTS frame includes the address of the transmitting station of the RTS frame, the address of the receiving station, the required period (duration), and the like. The CTS frame is a control frame that is transmitted when the receiving station specified by the receiving station address of the RTS frame completes preparation for reception. The CTS frame includes the address of the transmitting station of the CTS frame and the address of the receiving station of the CTS frame. When the RTS frame is transmitted from the wireless station A or the wireless station B to the relay station apparatus R and the CTS frame is received from the relay station apparatus R, the data station is transmitted so that the transmitting station Even when radio signals from the transmitting station cannot be detected, signal collision can be avoided.

  An ACK frame that is another control frame is a frame used for an acknowledgment when the frame is normally received. The ACK frame includes the address of the receiving station. The data frame for transferring user data includes a receiving station address (destination address), a transmitting station address (source address), an address of the relay station device R, user data to be transmitted, and the like. A data frame can be transmitted to a plurality of receiving stations by setting a broadcast address set in advance as a receiving station address of the data frame.

  The transmission timing in this embodiment is determined according to the CSMA / CA binary slot exponent backoff algorithm. Also. The radio stations A and B and the relay station device R use the same channel (frequency band). Therefore, one station cannot receive two or more frames simultaneously. Since there is no interference between the radio stations A and B, the other radio station can receive the frame of the relay station apparatus R even when one radio station is transmitting a frame. The radio stations A and B and the relay station apparatus R each have a single omnidirectional antenna and cannot transmit and receive frames simultaneously.

  As described above, the wireless communication system according to the present embodiment is a combination of network coding technology and access control technology based on CSMA / CA using RTS / CTS. The wireless communication system of the present embodiment employs a configuration that is characteristic of a frame flow in wireless relay, thereby improving frame efficiency when combining both technologies, that is, throughput. Hereinafter, the frame flow employed in the present invention will be described with reference to FIGS. However, FIG. 2 shows a technology as a background for comparing and explaining the configuration characterized by the present invention shown in FIGS. 3 and 5.

  FIG. 2 is a schematic diagram showing a time-series arrangement of frames transmitted and received by the relay station apparatus R in the same wireless communication system configuration as FIG. FIGS. 2A and 2B both show the operation when the RTS frame is transmitted from the wireless station A and correctly received by the relay station apparatus R. However, FIG. 2A shows a case where there is no data frame addressed to the radio station A from the radio station B in the relay station apparatus R. FIG. 2B shows a data frame addressed to the radio station A from the radio station B to the relay station apparatus R. Shows the behavior when there is.

  In each figure, blocks indicated by dotted lines are frames or time intervals transmitted / received by the relay station apparatus R at a time when the radio stations A and B and the relay station apparatus R may compete with each other. That is, these frames cannot always be transmitted and received at this time.

  A block shaded by a diagonal line rising to the right is SIFS (Short Inter Frame Space), and a block shaded by the diagonal line to the right is DIFS (Distributed Inter Frame Space). For example, in the IEEE 802.11 standard, priority control by IFS (Inter Frame Space) is defined. In CSMA, carrier sense is performed between a predetermined IFS time assigned to each transmitting station and a random time called back-off from when the transmission signal is lost. A transmitting station that has not sensed the radio signal continuously obtains the right to transmit the radio signal. Priority control is performed by defining multiple types of IFS lengths. Three types of IFS are defined: SIFS and DIFS, and PIFS (Point coordination function IFS; polling frame interval). Of these, IFS has the shortest SIFS and the highest priority (highest). It is set as an interval before transmitting an ACK frame. PIFS has the following priorities and is used for centralized control. The DIFS is the IFS having the longest priority and the low priority (lowest). Used for distributed control.

  When the relay station apparatus R shown in FIG. 2A does not have a data frame addressed to the radio station A from the radio station B, the RTS frame 101 is first transmitted from the radio station A to the relay station apparatus R and received by the relay station apparatus R. Is done. Next, the CTS frame 103 is transmitted from the relay station apparatus R to the radio station A with the SIFS 102 placed. Next, the radio station A transmits the data frame 105 with the SIFS 104, and the relay station apparatus R receives it. The relay station apparatus R puts the SIFS 106 and transmits an ACK frame 107 indicating that the data frame 105 has been normally received to the wireless station A, and the wireless station A receives this. Thereafter, after the DIFS 108 and a delay time called back-off consisting of a random number of slot times 109, 110, 111, and 112 have elapsed, the relay station apparatus R transmits the RTS frame 113 to the radio station B. The wireless station B that has received the RTS frame 113 transmits the CTS frame 115 to the relay station apparatus R with the SIFS 114 placed. The relay station apparatus R transmits the data frame 117 generated based on the data frame 105 received from the wireless station A with the SIFS 116 placed, to the wireless station B.

  When the relay station apparatus R shown in FIG. 2B has a data frame addressed from the radio station B to the radio station A, first, the RTS frame 101 is transmitted from the radio station A to the relay station apparatus R and received by the relay station apparatus R. Is done. Next, the CTS frame 103 is transmitted from the relay station apparatus R to the radio station A with the SIFS 102 placed. Next, the radio station A transmits the data frame 105 with the SIFS 104, and the relay station apparatus R receives it. The relay station apparatus R puts the SIFS 106 and transmits an ACK frame 107 indicating that the data frame 105 has been normally received to the wireless station A, and the wireless station A receives this. Thereafter, after the DIFS 108 and the backoff (delay time) consisting of a random number of slot times 109, 110, 111, 112,... Have elapsed, the relay station apparatus R sends the RTS frame 201 to the radio station B. Send. The wireless station B that has received the RTS frame 201 transmits the CTS frame 203 to the relay station apparatus R with the SIFS 202 in place. The relay station apparatus R sets the SIFS 204, and the data frame 205 generated by exclusive ORing the data frame 105 received from the wireless station A and the stored data frame from the wireless station B to the wireless station A. Is transmitted to the wireless station A and the wireless station B by broadcast.

  2A and 2B, after the relay station apparatus R receives the data frame 107 from the wireless station A and transmits the ACK frame 107, the DIFS 108 and a random number of data are transmitted. There is a time during which the relay station apparatus R, which has a delay time called back-off consisting of the slot times 109, 110, 111, 112,.

  FIG. 3 is a schematic diagram showing a time-series arrangement that is characterized by the present invention of frames transmitted and received by the relay station apparatus R in the configuration of the wireless communication system shown in FIG. FIG. 3A and FIG. 3B both show the operation when the RTS frame is transmitted from the radio station A and correctly received by the relay station apparatus R. However, FIG. 3A shows a case where there is no data frame addressed to the radio station A from the radio station B in the relay station apparatus R. FIG. 3B shows a data frame addressed to the radio station A from the radio station B to the relay station apparatus R. Shows the behavior when there is. In FIG. 3, the same reference numerals are used for the same components as those in FIG.

  2, the blocks indicated by dotted lines in FIG. 3 indicate frames or time intervals transmitted / received by the relay station apparatus R at times when the radio stations A and B and the relay station apparatus R may compete with each other. It is. That is, these frames cannot always be transmitted and received at this time. Also, the block shaded with a diagonal line rising to the right is SIFS.

  When the relay station apparatus R shown in FIG. 3A does not have a data frame addressed to the radio station A from the radio station B, the RTS frame 101 is first transmitted from the radio station A to the relay station apparatus R and received by the relay station apparatus R. Is done. Next, the CTS frame 103 is transmitted from the relay station apparatus R to the radio station A with the SIFS 102 placed. Next, the radio station A transmits the data frame 105 with the SIFS 104, and the relay station apparatus R receives it. The relay station apparatus R puts the SIFS 106 and transmits an ACK frame 107 indicating that the data frame 105 has been normally received to the wireless station A, and the wireless station A receives this. Thereafter, a predetermined waiting time (WAIT) 302 occurs after SIFS 301. Then, after the standby time 302 has elapsed, the relay station device R transmits the RTS frame 303 to the wireless station B. The wireless station B that has received the RTS frame 303 transmits the CTS frame 305 to the relay station apparatus R with the SIFS 304 placed. The relay station apparatus R transmits the data frame 307 generated based on the data frame 105 received from the wireless station A with the SIFS 306 to the wireless station B.

  When the relay station apparatus R shown in FIG. 3B has a data frame addressed to the radio station A from the radio station B, the RTS frame 101 is first transmitted from the radio station A to the relay station apparatus R and received by the relay station apparatus R. Is done. Next, the CTS frame 103 is transmitted from the relay station apparatus R to the radio station A with the SIFS 102 placed. Next, the radio station A transmits the data frame 105 with the SIFS 104, and the relay station apparatus R receives it. The relay station apparatus R puts the SIFS 106 and transmits an ACK frame 107 indicating that the data frame 105 has been normally received to the wireless station A, and the wireless station A receives this. Thereafter, after the SIFS 401 has elapsed, the relay station apparatus R transmits the RTS frame 402 to the radio station B. The wireless station B that has received the RTS frame 402 transmits the CTS frame 404 to the relay station apparatus R with the SIFS 403 placed. The relay station apparatus R sets the SIFS 405, and generates a coding data frame generated by exclusive ORing the data frame 105 received from the wireless station A and the stored data frame from the wireless station B to the wireless station A. 406 is transmitted to the wireless station A and the wireless station B by broadcast.

  In this way, in the cases shown in FIGS. 3A and 3B, it is possible to perform access control using only SIFS as IFS and not using DIFS or the like. Further, carrier sense by backoff is not always necessary. In addition, when transmission of a coding data frame by network coding shown in FIG. 3B is possible, a control frame and coding are continuously performed at SIFS intervals without generating a contention interval (block indicated by a dotted line). Data frames can be transmitted and received.

  4 is a flowchart showing a processing flow in relay station apparatus R of FIG. 1 corresponding to the frame flow shown in FIG. The processing flow of FIG. 4 shows the flow of processing when the relay station apparatus R in the carrier sense state transmits or receives a radio signal or detects a radio signal collision state. When the relay station apparatus R transmits data (DATA) (“transmission” in step S101), the relay station apparatus R transmits an RTS frame to the radio station A or B (step S102). The relay station apparatus R waits for a maximum predetermined timeout time (Timeout) and a CTS frame is transmitted from the wireless station A or B (step S103), and when the CTS frame is transmitted before the timeout time elapses. Receives it (step S104). Next, the relay station apparatus R transmits a data frame to the radio station A or B (step S105). If the radio station A or B normally receives the ACK frame from the radio station A or B, the relay station apparatus R receives this (step S106). Next, a predetermined standby time is set (step S107), and the relay station apparatus R returns to the carrier sense state.

  On the other hand, when the RTS frame (corresponding to the RTS frame 101 in FIG. 3) is received from the radio station A or B by the relay station apparatus R in the carrier sense state (from “Reception” to Step S108 in Step S101), the relay station apparatus R Sends SITS (corresponding to SIFS102) and transmits a CTS frame (corresponding to CTS frame 103) to the wireless station A or B (step S109). Then, the relay station apparatus R puts SIFS (corresponding to SIFS 104) and receives a data frame (corresponding to the data frame 105) from the radio station A or B (step S110). When receiving data normally, the relay station apparatus R places SIFS (corresponding to SIFS 106) and transmits an ACK frame (corresponding to ACK frame 107) to the radio station A or B (step S111). Here, when coding is possible, that is, when data to be coded is stored in the buffer A13 or B14 (“Y” in step S112), the relay station apparatus R puts SIFS (corresponding to SIFS401), An RTS frame (corresponding to the RTS frame 402) is transmitted to the wireless station B or A (step S113). When the relay station apparatus R receives SITS (corresponding to SIFS403) and receives a CTS frame (corresponding to CTS frame 404) from the wireless station B or A (step S114), the relay station apparatus R is compatible with SIFS (SIFS405). ) And a coding data frame (corresponding to the coding data frame 406) is transmitted to the radio stations A and B (step S115). Next, a predetermined standby time is set (step S107), and the relay station apparatus R returns to the carrier sense state. If coding is not possible (in the case of “N” in step S112), relay station apparatus R sets a predetermined waiting time (corresponding to waiting time (WAIT) 302) (step S107), and then enters the carrier sense state. Return.

  In addition, when a collision of transmission signals is detected in the carrier sense state (in the case of “collision” in step S101), or when a timeout time elapses after RTS frame transmission during data transmission (in the case of “Y” in step S103) The predetermined standby time is set (step S107), and the relay station apparatus R returns to the carrier sense state.

  In this way, when the relay station apparatus R transmits and receives a radio signal according to the frame flow of FIG. 3 (that is, the flow of FIG. 4), if coding is possible, transmission of the coding data frame is performed immediately (that is, at SIFS intervals). Can be performed (a series of processes in steps S108 to S115 in FIG. 4).

  FIG. 5 is a schematic diagram showing another time-series arrangement of frames that are transmitted and received by the relay station apparatus R in the configuration of the wireless communication system shown in FIG. 5 (a), 5 (b), and 5 (c) all show operations when the RTS frame is transmitted from the wireless station A and is correctly received by the relay station apparatus R. FIG. However, FIG. 5A shows a case where the relay station apparatus R has no data frame addressed from the wireless station B to the wireless station A, and the wireless station B has no transmission data. When there is no data frame addressed to the wireless station A from B and there is transmission data to the wireless station B, FIG. 5C shows the operation when the relay station apparatus R has a data frame addressed to the wireless station A from the wireless station B. Show. In FIG. 5, the same reference numerals are used for the same components as those in FIG.

  2, the blocks indicated by dotted lines in FIG. 5 indicate frames or time intervals transmitted / received by the relay station apparatus R at times when the radio stations A and B and the relay station apparatus R may compete with each other. It is. That is, these frames cannot always be transmitted and received at this time. Also, the block shaded with a diagonal line rising to the right is SIFS.

  When the relay station apparatus R shown in FIG. 5A has no data frame addressed from the wireless station B to the wireless station A and there is no transmission data in the wireless station B, the RTS frame 101 is first transmitted from the wireless station A to the relay station apparatus R. It is transmitted and received by the relay station device R. Next, the CTS frame 103 is transmitted from the relay station apparatus R to the radio station A with the SIFS 102 placed. Next, the radio station A transmits the data frame 105 with the SIFS 104, and the relay station apparatus R receives it. The relay station apparatus R places the SIFS 106 and transmits an ACK frame 501 to the wireless station A and the wireless station B, and the wireless station A and the wireless station B receive it.

  This ACK frame 501 has the frame configuration defined in the present embodiment, and indicates that the data frame 105 has been normally received by the wireless station A and also indicates a transmission request to the wireless station B. It is assumed that information (transmission request information) is included. The ACK frame 501 includes, for example, the address of the receiving station that receives the ACK frame 501 (in this case, the address of the receiving station A and the address of the receiving station B). In addition, by using the position in the frame including the address and other additional information, it becomes possible to identify the destination address of the acknowledgment response and the destination address of the transmission request information among the addresses of the plurality of receiving stations. It shall be.

  A predetermined waiting time (WAIT) 504 occurs after SIFS 502 after the ACK frame 501 is transmitted. Then, after the standby time 504 has elapsed, the relay station device R transmits the RTS frame 504 to the wireless station B. The wireless station B that has received the RTS frame 504 places the SIFS 505 and transmits the CTS frame 506 to the relay station apparatus R. The relay station apparatus R transmits the data frame 508 generated based on the data frame 105 received from the wireless station A with the SIFS 507 to the wireless station B.

  When there is no data frame addressed from the wireless station B to the wireless station A in the relay station apparatus R shown in FIG. 5B and there is transmission data in the wireless station B, the RTS frame 101 is first transmitted from the wireless station A to the relay station apparatus R. It is transmitted and received by the relay station device R. Next, the CTS frame 103 is transmitted from the relay station apparatus R to the radio station A with the SIFS 102 placed. Next, the radio station A transmits the data frame 105 with the SIFS 104, and the relay station apparatus R receives it. The relay station apparatus R places the SIFS 106 and transmits an ACK frame 601 to the radio station A and the radio station B, and the radio station A and the radio station B receive this. Similar to the ACK frame 501, the ACK frame 601 indicates that the data frame 105 has been normally received by the wireless station A and includes information for indicating a transmission request to the wireless station B. . Thereafter, after SIFS 602 has elapsed, the wireless station B transmits a data frame 603 addressed to the wireless station A to the relay station apparatus R, and the relay station apparatus R receives and stores the data frame 603. The relay station apparatus R sets the SIFS 604 and generates the exclusive OR of the data frame 105 received from the radio station A and the stored data frame from the radio station B to the radio station A (data frame 603). The coding data frame 605 is transmitted to the wireless station A and the wireless station B.

  When the relay station apparatus R shown in FIG. 5C has a data frame addressed to the radio station A from the radio station B, the RTS frame 101 is first transmitted from the radio station A to the relay station apparatus R and received by the relay station apparatus R. Is done. Next, the CTS frame 103 is transmitted from the relay station apparatus R to the radio station A with the SIFS 102 placed. Next, the radio station A transmits the data frame 105 with the SIFS 104, and the relay station apparatus R receives it. The relay station apparatus R places the SIFS 106 and transmits an ACK frame 701 to the wireless station A and the wireless station B, and the wireless station A and the wireless station B receive this. Like the ACK frames 501 and 601, the ACK frame 701 indicates that the data frame 105 has been normally received by the wireless station A and includes information for indicating a transmission request to the wireless station B. It is out. Thereafter, after the SIFS 702 has elapsed, the relay station device R generates the exclusive OR of the data frame 105 received from the wireless station A and the stored data frame from the wireless station B to the wireless station A. The coding data frame 703 is transmitted to the wireless station A and the wireless station B.

  In this way, in the cases shown in FIGS. 5A, 5B, and 5C, it is possible to perform access control using only SIFS as IFS and not using DIFS or the like. Further, carrier sense by backoff is not always necessary. In addition, when transmission of a coding data frame by network coding shown in FIGS. 5B and 5C is possible, without generating a contention section (block indicated by a dotted line), continuously at SIFS intervals, Control frames, data frames, and coding data frames can be transmitted and received.

  5B and 5C, transmission / reception of control frames corresponding to the RTS frame 402 and the CTS frame 404 before transmission of the coding data frame 406 shown in FIG. 3 can be omitted. This can further improve the frame efficiency.

  FIG. 6 is a flowchart showing a processing flow in the relay station apparatus R of FIG. 1 corresponding to the frame flow shown in FIG. The processing flow in FIG. 6 shows a processing flow when the relay station apparatus R in the carrier sense state transmits or receives a radio signal or detects a radio signal collision state. When the relay station apparatus R transmits data (DATA) (“transmission” in step S201), the relay station apparatus R transmits an RTS frame to the radio station A or B (step S202). The relay station apparatus R waits for a maximum predetermined timeout time (Timeout) and a CTS frame is transmitted from the wireless station A or B (step S203), and when the CTS frame is transmitted before the timeout time elapses. Receives it (step S204). Next, the relay station apparatus R transmits a data frame to the radio station A or B (step S205). If the radio station A or B normally receives the ACK frame from the radio station A or B, the relay station apparatus R receives this (step S206). Next, a predetermined standby time is set (step S207), and the relay station apparatus R returns to the carrier sense state.

  On the other hand, when the relay station apparatus R in the carrier sense state receives an RTS frame (corresponding to the RTS frame 101 in FIG. 5) from the radio station A or B (from “Reception” to Step S208 in Step S201), the relay station apparatus R Puts SIFS (corresponding to SIFS102) and transmits a CTS frame (corresponding to CTS frame 103) to radio station A or B (step S209). Then, relay station apparatus R places SIFS (corresponding to SIFS 104) and receives a data frame (corresponding to data frame 105) from radio station A or B (step S210). When receiving data normally, the relay station apparatus R places SIFS (corresponding to SIFS 106) and transmits an ACK frame (corresponding to ACK frame 501, 601 or 701) to the radio stations A and B (step S211). . Here, when coding is possible, that is, when data to be coded is stored in the buffer A13 or B14 (“Y” in step S212), the relay station apparatus R puts SIFS (corresponding to SIFS702), A coding data frame (corresponding to the coding data frame 703) is transmitted to the radio stations A and B (step S213). Then, a predetermined standby time is set (step S207), and the relay station apparatus R returns to the carrier sense state.

  On the other hand, when coding is not possible ("N" in step S212), when the relay station apparatus R receives the data frame (corresponding to the data frame 603) from the wireless station B or A with SIFS (corresponding to SIFS 602) ( In step S214, from “Y” to step S215), the relay station apparatus R puts SIFS (corresponding to SIFS 604) and transmits a coding data frame (corresponding to the coding data frame 605) to the radio stations A and B (step S213). ). Then, a predetermined standby time is set (step S207), and the relay station apparatus R returns to the carrier sense state.

  On the other hand, when coding is not possible ("N" in step S212), when the relay station apparatus R does not receive a data frame from the radio station B or A with SIFS (corresponding to SIFS502) ("N" in step S214) ”), A predetermined standby time (corresponding to the standby time 503) is set (step S207), and the relay station apparatus R returns to the carrier sense state.

  In addition, when a collision of transmission signals is detected in the carrier sense state (in the case of “collision” in step S201), or when a timeout time has elapsed after RTS frame transmission during data transmission (in the case of “Y” in step S203) The predetermined standby time is set (step S207), and the relay station apparatus R returns to the carrier sense state.

  As described above, when the radio signal is transmitted / received in the relay station apparatus R according to the frame flow of FIG. 5 (that is, the flow of FIG. 6), the coding data frame is transmitted immediately (that is, at SIFS intervals) if coding is possible. (A series of processes in steps S208 to S213 in FIG. 6 or a series of processes in steps S208 to S212, S214, S215, and 213). Further, according to the frame flow of FIG. 5 (or the flow of FIG. 6), compared with the frame flow of FIG. 3 (or the flow of FIG. 4), the procedure for transmitting / receiving the RTS / CTS frame is greater when coding data frames are transmitted. Can be omitted. Further, according to the frame flow of FIG. 5 (or the flow of FIG. 6), a data transmission request to the wireless station A or B can be made immediately (that is, at SIFS intervals) according to the situation.

  In summary, as described with reference to FIGS. 3 to 6, the present embodiment is configured so that the relay station apparatus R, the radio station A (first radio station), and the radio station B (second radio station) Control frames (RTS frame 402, CTS frame 404, ACK frame 601 and ACK frame 701) from the relay station apparatus R to the radio stations A and B, and the radio received by the relay station apparatus R Exclusively between data frame 105 addressed from station A to wireless station B and data frame addressed to wireless station A from wireless station B in the storage means (storage device 12) of relay station apparatus R (such as those corresponding to data frame 603) A plurality of frames including at least coding data frames (coding data frames 406, 605, and 703) generated by performing a logical OR operation process at a short frame interval (SIFS) having a high priority. A wireless communication system characterized by transmitting and receiving (that is, without interposing back-off or DIFS).

  Next, the operation characteristics of the embodiment of the wireless communication system shown in FIG. 1 will be described with reference to FIGS. Each figure is an example using the IEEE 802.11 54 Mbps mode as the line speed. FIG. 7 shows the result of confirming how much deviation occurs in the flow of data frames between the relay station apparatus R and the radio station A or between the relay station apparatus R and the radio station B. For comparison, FIG. 7 shows both characteristics when using CSMA / CA as an access control method and when using CSMA / CA using RTS / CTS as in the present embodiment. The horizontal axis in FIG. 7 represents the ratio of data frames from the transmitting station A to the transmitting station B in the data frames transmitted by the relay station apparatus R, and the vertical axis represents the frequency distribution. It can be seen that the distribution using the RTS / CTS indicated by the solid line is more concentrated around the ratio = 0.5 than the distribution when the RTS / CTS indicated by the broken line is not used. That is, by using RTS / CTS, it can be seen that one-way communication can be prevented (that is, two-way communication is maintained), and the opportunity for network coding to be increased.

  On the other hand, FIG. 8 is a characteristic diagram for comparing the case where the frame flow characteristic of the present invention shown in FIGS. 3 and 5 is used with the case where the frame flow shown in FIG. 2 is used. 8 uses the frame flow shown in FIG. 2 (shown as CSMA / CA), uses the frame flow shown in FIG. 3 (shown as RIT), and uses the frame flow shown in FIG. Showed the throughput (shown as RIT / RH). In each case, a comparison was made between when network coding techniques were combined (open rectangles) and when no network coding techniques were used (shaded rectangles). RIT is an abbreviation for Relay Immediate Transmission, and RH is an abbreviation for Reduced Handshake.

  As shown in FIG. 8, it can be seen that when the network coding technique is combined with RIT and when the network coding technique is combined with RIT / RH, the throughput is improved as compared with the other.

  Thus, the relay control method using RTS / CTS in the configuration of the present embodiment can prevent one-way communication by RTS / CTS and increase network coding opportunities (from FIG. 7). As a result, the coding gain (the effect of coding) when the random access CSMA / CA is implemented in the relay station apparatus R can be improved (from the presence or absence of the CSMA / CA network coding (NC) in FIG. 8). . Further, by transmitting the relay data frame transmitted from the relay station apparatus R with the highest priority, further coding gain is expected (from RIT in FIG. 8). Further, further coding gain can be obtained by reducing handshaking by transmitting the CTS and ACK functions in one control packet (RIT / RH in FIG. 8).

  The embodiment of the present invention is not limited to the above. For example, the number of relay station apparatuses R and radio stations A and B can be appropriately increased. Further, the relay station device R and the radio stations A and B may be configured to be incorporated in other electronic devices, for example. Also, the access control method is not limited to the name CSMA / CA, but other functions may be provided as long as it is a multiple access method having the same function, that is, priority control based on frame intervals and collision avoidance function based on carrier sensing. Even if it is a thing, it is thought that it is applicable. In addition, in the frame flows shown in FIGS. 2 and 3, the names of control frames such as RTS frames, CTS frames, and ACK frames, and frame intervals such as SIFS are not limited to the above, but to solve the hidden terminal problem. It is considered possible to use a frame including other information as long as it has information indicating a control frame, a signal transmission right request, and a response indicating whether or not the signal is transmitted.

  Further, the relay station device R, the radio station A, and the radio station B described above can be configured with a computer system inside or inside an electronic device to be combined. The processing related to the network coding described above is stored in a computer-readable recording medium in the form of a program, and the above processing may be performed by the computer reading and executing the program. it can. Here, the computer-readable recording medium means a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. Alternatively, the computer program may be distributed to the computer via a communication line, and the computer that has received the distribution may execute the program.

  The relationship between the description of the scope of claims and each frame flow in the embodiment is as follows. Claim 1 corresponds to each frame flow. Claim 2 corresponds to the frame flow described with reference to FIG. Claim 3 corresponds to the frame flow described with reference to FIG. Claim 4 corresponds to the frame flow described with reference to FIG.

  R ... Relay station device, A, B ... Wireless station, 12 ... Storage device, 13 ... Buffer A, 14 ... Buffer B, 106, 401, 403, 405, 602, 604, 702 ... SIFS, 402 ... RTS frame, 404 ... CTS frame, 601, 701 ... ACK frame, 603 ... data frame, 406, 605, 703 ... coding data frame.

Claims (6)

Wireless communication comprising a relay station device that performs wireless relaying between wireless stations, and a first wireless station and a second wireless station that transmit and receive wireless signals via the relay station device that cannot reach each other A system,
The first radio station, the second radio station, and the relay station apparatus perform radio signal transmission / reception in frame units based on a carrier sensing multiple access scheme with a collision avoidance function,
The first radio station or the second radio station transmits a transmission request frame before transmitting a data frame, and transmits a data frame when a reception ready frame is received as a response to the transmission request frame.
When the relay station apparatus receives a data frame addressed to the second radio station from the first radio station, the relay station apparatus, the first radio station, and the second radio station perform the relay. A control frame directed from the station apparatus to at least one of the first radio station and the second radio station, and a data frame addressed to the second radio station from the first radio station received by the relay station apparatus And a coding data frame generated by performing an exclusive OR operation process on the data frame addressed to the first radio station from the second radio station in the storage means of the relay station device. A wireless communication system, wherein frames are continuously transmitted and received at short frame intervals with high priority. When the relay station apparatus receives a data frame addressed to the second radio station from the first radio station, the data frame addressed to the first radio station is transmitted from the second radio station to the relay station. When not in the storage means of the device, continuously at the short frame interval,
Transmitting an acknowledgment frame that is a response signal to the first radio station including transmission request information to the second radio station to the first radio station and the second radio station;
Receiving a data frame addressed to the first radio station from the second radio station and storing it in the storage means;
An exclusive OR operation process is performed on the data frame addressed to the second radio station from the first radio station and the data frame addressed to the first radio station from the second radio station in the storage means. The wireless communication system according to claim 1, wherein the coding data frame generated by the transmission is transmitted to the first wireless station and the second wireless station. When the relay station apparatus receives a data frame addressed to the second radio station from the first radio station, the data frame addressed to the first radio station is transmitted from the second radio station to the relay station. When in the storage means of the device, continuously at the short frame interval,
Transmitting an acknowledgment frame that is a response signal to the first radio station including transmission request information to the second radio station to the first radio station and the second radio station;
An exclusive OR operation process is performed on the data frame addressed to the second radio station from the first radio station and the data frame addressed to the first radio station from the second radio station in the storage means. The wireless communication system according to claim 1 or 2, wherein the coding data frame generated by the transmission is transmitted to the first wireless station and the second wireless station. When the relay station apparatus receives a data frame addressed to the second radio station from the first radio station, the data frame addressed to the first radio station is transmitted from the second radio station to the relay station. When in the storage means of the device, continuously at the short frame interval,
Sending an acknowledgment frame towards the first radio station;
Transmitting a transmission request frame to the second wireless station;
Receiving a reception ready frame from the second radio station as a response to the transmission request frame;
An exclusive OR operation process is performed on the data frame addressed to the second radio station from the first radio station and the data frame addressed to the first radio station from the second radio station in the storage means. The wireless communication system according to claim 1, wherein the coding data frame generated by the transmission is transmitted to the first wireless station and the second wireless station. Wireless communication comprising a relay station device that performs wireless relaying between wireless stations, and a first wireless station and a second wireless station that transmit and receive wireless signals via the relay station device that cannot reach each other A relay station device in the system,
Between the first radio station and the second radio station, radio signals are transmitted and received in frame units based on a carrier sensing multiple access scheme with a collision avoidance function,
When a transmission request frame is received from the first wireless station or the second wireless station, a reception preparation completion frame is transmitted to the wireless station as a response to the transmission request frame, and the reception preparation completion frame is received. Receive the data frame transmitted from the radio station,
When a data frame addressed to the second radio station is received from the first radio station, the relay station device, the first radio station, and the second radio station are connected to each other from the relay station device. A control frame for at least one of the first radio station and the second radio station, a data frame addressed to the second radio station from the first radio station received by the relay station device, and the relay station device A plurality of frames including at least a coding data frame generated by performing an exclusive OR operation with the data frame addressed to the first wireless station from the second wireless station in the storage means A relay station apparatus characterized by continuously transmitting and receiving at high short frame intervals. Wireless communication comprising a relay station device that performs wireless relaying between wireless stations, and a first wireless station and a second wireless station that transmit and receive wireless signals via the relay station device that cannot reach each other A wireless communication method in a system, comprising:
The first radio station, the second radio station, and the relay station apparatus perform radio signal transmission / reception in frame units based on a carrier sensing multiple access scheme with a collision avoidance function,
The first radio station or the second radio station transmits a transmission request frame before transmitting a data frame, and transmits a data frame when a reception ready frame is received as a response to the transmission request frame.
When the relay station apparatus receives a data frame addressed to the second radio station from the first radio station, the relay station apparatus, the first radio station, and the second radio station perform the relay. A control frame directed from the station apparatus to at least one of the first radio station and the second radio station, and a data frame addressed to the second radio station from the first radio station received by the relay station apparatus And a coding data frame generated by performing an exclusive OR operation process on the data frame addressed to the first radio station from the second radio station in the storage means of the relay station device. A wireless communication method characterized by continuously transmitting and receiving frames at short frame intervals with high priority.

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