JP5492662B2 - Radio relay system, relay station apparatus, and radio relay method - Google Patents

Description

  The present invention relates to a radio relay system, a relay station apparatus, and a radio relay method using network coding.

  In recent years, network coding (NC) technology aimed at improving the throughput of multi-hop communication has attracted attention. In the network coding technology, a plurality of information sequences are linearly encoded in a relay station on a network that performs multi-hop relay, and then a plurality of multicast communication and unicast communication are multiplexed to a plurality of end stations that are destination nodes. Transmit and perform decoding operations at each terminal station. Thereby, the throughput can be improved as compared with the case where network coding is not used.

  In a multi-hop wireless network using network coding, throughput is improved by utilizing the broadcast capability of wireless communication and network coding. The node acting as a relay station encodes information frames received from a plurality of terminal stations with a linear code and relays the information frame to a target terminal station. The terminal station that has received the information frame encoded by the linear code from the relay station node uses the information frame received from the other node or the information frame held by itself to perform the same processing on the encoded information frame. The original information can be obtained by decoding with a linear code.

  Hereinafter, as a specific example, a conventional wireless network coding technique will be described by giving an Alice & Bob topology, which is a typical multi-hop wireless topology to which the network coding technique can be applied. Hereinafter, performing coding of network coding on a certain information frame is referred to as NC coding, and decoding of an information frame coded by network coding is referred to as NC decoding. In the NC encoding and NC decoding, an exclusive OR (XOR) for each bit of information frames is used. In addition, a network-encoded information frame is described as an encoded information frame, and in order to clearly distinguish an encoded information frame from an unencoded information frame, an information frame that is not NC-encoded is referred to as native information. It is described as a frame.

  FIG. 6 is a diagram illustrating a configuration of the Alice & Bob topology. In the wireless multi-hop topology shown in the figure, node A (node-A) and node B (node-B), which are end stations at both ends, exchange information with each other via node R (node-R), which is a relay station. Consider the case of interaction. The purpose of this topology is that the node A and the node B transmit information held by themselves as an information frame using a radio channel and receive an information frame from a terminal station as a counterpart. All nodes share a single frequency channel, and each node has one modulation / demodulation circuit and one omni antenna. That is, while a certain node transmits an information frame, all other nodes do not transmit the information frame at the same time.

  FIG. 7 shows a communication procedure in the Alice & Bob topology when the network coding technique is not used. The communication procedure when the network coding technique is not used is as follows.

(1) At time T1, node A transmits information frame A, which is a native information frame, to node R. Node R receives information frame A.
(2) At time T2, the node R transmits the information frame A to the node B. Node B receives information frame A.
(3) At time T3, node B transmits information frame B, which is a native information frame, to node R. Node R receives information frame B.
(4) At time T4, the node R transmits the information frame B to the node A. Node A receives information frame B.

  Since the above-described procedure is necessary, four time slots are required for node A and node B to exchange information with each other.

  On the other hand, FIG. 8 shows a communication procedure in the Alice & Bob topology when the network coding technique is used. The communication procedure when using the network coding technique is as follows.

(1) At time T1, node A transmits information frame A, which is a native information frame, to node R. Node R receives information frame A.
(2) At time T2, node B transmits information frame B, which is a native information frame, to node R. Node R receives information frame B.

(3) At time T3, the node R performs NC coding on the information frame A and the information frame B to generate a coded information frame X. The node R broadcasts the generated encoded information frame X to the node A and the node B. The node A obtains the information frame B by performing NC decoding using the information frame A transmitted at time T1 and the encoded information frame X received at time T3. Similarly, node B obtains information frame A by performing NC decoding using information frame B transmitted at time T2 and encoded information frame X received at time T3.

  By performing the above procedure, the required number of time slots is three. Comparing the case where the network coding technique is not used and the case where the network coding technique is used, by applying the network coding technique, the number of time slots consumed by the node A and the node B for exchanging information becomes 3/4. That is, the throughput increase effect (this is referred to as “NC gain”) by the application of the network coding technique is 4/3 of the reciprocal thereof (see, for example, Patent Document 1).

JP 2009-206778 A

  In a multi-hop wireless system to which network coding technology is applied, it is possible to further reduce the number of required time slots by simultaneously transmitting modulated frames, that is, modulated information frames, to relay stations by multiple end stations. It is. However, in the prior art, it is assumed that all nodes are equipped with omni antennas. When the relay station simultaneously receives modulation frames from a plurality of terminal stations, the modulation frames interfere with each other, and demodulation is performed. It was impossible to do.

  The present invention has been made in view of such circumstances, and the object of the present invention is to perform wireless transmission that can efficiently transmit and receive information frames and increase system throughput in wireless relay to which network coding technology is applied. A system, a relay station apparatus, and a wireless relay method are provided.

In order to solve the above-described problem, the present invention provides a radio relay system having a relay station apparatus and a plurality of terminal station apparatuses, wherein the relay station apparatus is a terminal station directional antenna of the plurality of terminal station apparatuses. The terminal device provided opposite to each other, receiving an information frame wirelessly from a terminal directional antenna of the terminal device facing the device, and facing an encoded information frame obtained by network-coding a plurality of information frames A plurality of directional antennas that are wirelessly transmitted to the terminal station directional antennas, and information frames received by the corresponding directional antennas from the terminal devices. A plurality of demodulation units to be demodulated, and a network that encodes information frames demodulated by each of the plurality of demodulation units to generate a coded information frame A workpiece coding unit, a modulation unit modulates the encoded information frames, wherein the network encoder unit has generated a distribution unit for outputting the encoded information frame, wherein the modulator is corrected by modulating the plurality of directional antennas, wherein Instructing the network encoding unit to generate an encoded information frame using an information frame targeted for network encoding among the information frames demodulated by each of the plurality of demodulation units, and A control unit that instructs the distribution unit to output encoded information frames modulated by the modulation unit to the plurality of directional antennas facing the terminal directional antenna of the terminal device that is the destination ; The terminal device receives an encoded information frame transmitted from the directional antenna facing the relay station device. A terminal station directional antenna; a key storage unit that stores a key information frame used for decoding a coded information frame; a terminal station demodulator that demodulates a coded information frame received by the terminal station directional antenna; A wireless relay system comprising: a network encoding / decoding unit that decodes the encoded information frame demodulated by a station demodulating unit with a key information frame read from the key storage unit.

Further, the present invention is the relay station device in a radio relay system having a relay station device and a plurality of terminal station devices, provided facing each of the terminal station directional antennas of the plurality of terminal station devices, An information frame is received wirelessly from a terminal directional antenna of the terminal device facing the terminal, and an encoded information frame obtained by network encoding a plurality of information frames is transmitted to the terminal directional antenna of the terminal device facing the terminal. A plurality of directional antennas that transmit by radio, a plurality of demodulation units that are provided corresponding to each of the plurality of directional antennas, and that the corresponding directional antennas demodulate information frames received from the terminal device; A network encoding unit for generating an encoded information frame by performing network encoding on an information frame demodulated by each of the plurality of demodulation units; A modulation unit serial network coding section modulates the generated encoded information frame, and a distribution unit for outputting the encoded information frame, wherein the modulator is corrected by modulating the plurality of directional antennas, each of the plurality of demodulator are Instructs the network encoding unit to generate an encoded information frame using an information frame that is a network encoding target among demodulated information frames, and the terminal station that is a destination of the information frame that is a network encoding target And a control unit that instructs the distribution unit to output the encoded information frame modulated by the modulation unit to the plurality of directional antennas facing the terminal directional antenna of the apparatus. It is a station device.

Further, the present invention is the relay station apparatus described above, wherein an error detection unit that performs error detection of each information frame demodulated by each of the plurality of demodulation units, and among the information frames demodulated by each of the plurality of demodulation units, instructs to the network coding unit to generate encoded information frame with a plurality of information frames of the network coded an error is not detected in the error detection unit, a network coding error is not detected The distribution unit outputs the encoded information frame modulated by the modulation unit to the plurality of directional antennas facing the terminal directional antenna of the terminal device that is the destination of the plurality of information frames of interest. And a control unit for instructing.

Further, the present invention is a radio relay method for the relay station apparatus in a radio relay system having a relay station apparatus and a plurality of terminal station apparatuses, facing each of the terminal station directional antennas of the plurality of terminal station apparatuses. A plurality of directional antennas provided to receive information frames wirelessly transmitted from the terminal device, and a demodulator provided corresponding to each of the plurality of directional antennas includes the receiving process. A demodulating process for demodulating an information frame received from the terminal device by the directional antenna corresponding to the demodulating unit, and a network encoding target among the information frames demodulated by each of the plurality of demodulating units in the demodulating process an instruction step of instructing to generate encoded information frame using information frames, each of the plurality of demodulator are in the demodulation process Of the tone information frame, and the network coding process for generating an encoded information frame network coded information frames indicated in the instruction process by network coding, coding is generated in the network coding process A modulation process for modulating an information frame, and a code modulated in the modulation process to the plurality of directional antennas facing the terminal directional antenna of the terminal device that is a destination of the information frame to be network encoded A control process for instructing to output a coded information frame , a distribution process for outputting the encoded information frame modulated in the modulation process to the plurality of directional antennas instructed in the control process, and the plurality of directivities The encoded antenna outputs the encoded information frame output in the distribution process. The arm is a radio relay method characterized by and a transmission process to wirelessly transmit to the opposing said plurality of terminal equipment in the terminal directional antennas.

According to the present invention, in a wireless relay system to which a network coding technique is applied, a relay station can easily receive and demodulate modulation frames from a plurality of terminal stations simultaneously, and the transmission timings of the plurality of terminal stations can be set in time. Therefore, it is not necessary to separate each other, so that the system throughput can be increased.
Further, according to the present invention, it is possible to easily solve the hidden terminal problem between terminal stations that occurs when the wireless relay system is a multi-hop wireless system operating with CSMA / CA (carrier sense multiple access / collision avoidance). . In other words, the terminal station transmits an information frame to the relay station when it determines that the communication path is empty, but if the other terminal stations are outside the signal reachable range, the other terminal stations There is a case where the information frame is transmitted without recognizing that the information frame is transmitted. Even if such a situation occurs, the relay station of the present invention can normally receive information frames received simultaneously from a plurality of terminal stations, and the received information frames are encoded by NC encoding. An information frame can be generated and transmitted to the terminal station.

It is a figure which shows the communication procedure of the radio relay system by the 1st Embodiment of this invention. FIG. 3 is a functional block diagram of a relay station according to the same embodiment. It is a functional block diagram of the terminal station by the embodiment. It is a functional block diagram of the relay station by 2nd Embodiment. It is a functional block diagram of the terminal station by the embodiment. It is a figure which shows the structure of Alice & Bob topology. A communication procedure in the Alice & Bob topology when the network coding technique according to the prior art is not used is shown. The communication procedure in the Alice & Bob topology when the network coding technique according to the prior art is used is shown.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is a diagram showing a communication procedure in the wireless relay system according to the first embodiment of the present invention. The radio relay system according to the present embodiment includes a plurality of terminal stations 1 and one relay station 2. Hereinafter, the N terminal stations 1 (N is an integer of 2 or more) will be referred to as terminal stations 1-1, 1-2,. This figure shows a case where the radio relay system of the present embodiment is applied to an Alice & Bob topology, which is a two-hop radio relay system using network coding (hereinafter also referred to as “NC”) technology. Two terminal stations 1 of 1-1 and 1-2 are described.

  In the wireless relay system shown in the figure, the terminal stations 1-1 and 1-2 that are both the receiving station apparatus and the transmitting station apparatus communicate with each other via the relay station 2 that is the relay station apparatus. I do. Each terminal station 1 and the relay station 2 are assumed to be time slot synchronized, and each of the terminal stations 1-1 and 1-2 includes one directional antenna 10 directed to the relay station 2, and the relay station 2 Directional antennas 20-1 and 20-2 directed to the directional antennas 10 of the terminal stations 1-1 and 1-2 are provided.

  Hereinafter, the m-th transmission timing in the entire system is represented as time Tm. Also, performing network coding encoding is described as “NC encoding”, and decoding an information frame encoded by network coding is described as “NC decoding”. An information frame that is not NC-encoded is a “native information frame”, an information frame that is NC-encoded is “encoded information frame”, and an information frame that is required for NC-decoding the encoded information frame is “key” “Information frame”.

(1) At time T1, the terminal station 1-1 modulates the information frame F1, which is a native information frame, to the relay station 2, and the terminal station 1-2 modulates the information frame F2, which is a native information frame, to the relay station. To 2 at the same time. The relay station 2 simultaneously receives the modulated information frame F1 by the directional antenna 20-1 and the modulated information frame F2 by the directional antenna 20-2. The relay station 2 generates an encoded information frame X by NC encoding information frames F1 and F2 obtained by demodulating the modulation frames received from the terminal stations 1-1 and 1-2. For the NC encoding, for example, an exclusive OR (XOR) for each bit of information frames is used.

(2) At time T2, the relay station 2 modulates the encoded information frame X generated at time T1 and broadcasts it to the terminal stations 1-1 and 1-2 by the directional antennas 20-1 and 20-2. Send. The terminal station 1-1 demodulates the modulation frame received by the directional antenna 10, uses the information frame F1 transmitted by itself at time T1 as a key information frame, and performs NC decoding of the encoded information frame X obtained by demodulation. To obtain the information frame F2. Similarly, the terminal station 1-2 also demodulates the modulation frame received by the directional antenna 10, and uses the information frame F2 itself transmitted at time T1 as the key information frame, and obtains the encoded information frame obtained by demodulation. NC decoding of X is performed to obtain an information frame F1. In NC decoding, exclusive OR of information frames is used as in NC encoding.

  As described above, since a plurality of terminal stations 1 can transmit information frames to the relay station 2 at the same time, the number of time slots required for exchanging information between the terminal stations 1 can be reduced. .

  FIG. 2 is a block diagram illustrating a configuration of the relay station 2 according to the present embodiment. The relay station 2 includes a directional antenna 20-1 to 20-n, a transmission / reception switching circuit group 21 including transmission / reception switching circuits 21-1 to 21-n, a demodulation circuit group 22 including demodulation circuits 22-1 to 22-n, A network encoding circuit (hereinafter referred to as “NC circuit”) 23, a storage circuit 24, a modulation circuit 25, and an N distribution circuit 26 are included (n is an integer of 2 or more).

  Each of the N directional antennas 20-1 to 20-n faces the directional antenna 10 of one terminal station 1, and wireless transmission is performed by outputting an input modulation frame to a space as an antenna. At the same time, a modulated frame transmitted wirelessly from the terminal station 1 is received. The transmission / reception switching circuits 21-1 to 21-n perform switching according to transmission / reception timings of signals scheduled in advance. Each transmission / reception switching circuit 21-i (i = 1 to n) outputs the modulation frame received by the directional antenna 20-i to the demodulation circuit 22-i at the time of signal reception, and N distribution circuit 26 at the time of signal transmission. The distributed modulation frame is output to the directional antenna 20-i. The transmission / reception switching circuits 21-1 to 21-n output inputs from the directional antennas 20-1 to 20-n to the demodulation circuits 22-1 to 22-n using a circulator circuit, and an N distribution circuit. 26 may be output to the directional antennas 20-1 to 20-n.

  Each demodulation circuit 22-i (i = 1 to n) demodulates the modulation frame received by the directional antenna 20-i and output from the transmission / reception switching circuit 21-i, and the native information frame obtained by the demodulation is displayed. Output to the NC circuit 23. The NC circuit 23 NC-codes the native information frame output from the demodulation circuits 22-1 to 22-n to generate an encoded information frame, and outputs the encoded information frame to the storage circuit 24. The storage circuit 24 stores the encoded information frame generated by the NC circuit 23. The modulation circuit 25 modulates the encoded information frame output from the storage circuit 24 to generate a modulation frame. The N distribution circuit 26 distributes the modulation frame generated by the modulation circuit 25 to the directional antennas 20-1 to 20-n.

  Next, the operation of the wireless relay system of this embodiment will be described. Here, for the sake of simplicity, it is assumed that the directional antenna 20-i (i = 1 to n) faces the directional antenna 10 of the terminal station 1-i.

(1) At time T1, the terminal station 1-i (i = 1 to n) simultaneously transmits a modulation frame obtained by modulating the information frame Fi that is a native information frame. The directional antenna 20-i (i = 1 to n) of the relay station 2 receives the modulation frame of the information frame Fi transmitted from the terminal station 1-i at the same time and without mutual interference. The transmission / reception switching circuit 21-i (i = 1 to n) of the relay station 2 switches the output destination of the directional antenna 20-i to the demodulation circuit 22-i. The transmission / reception switching circuit 21-i (i = 1 to n) outputs the modulation frame received by the directional antenna 20-i to the demodulation circuit 22-i, and the demodulation circuit 22-i includes the directional antenna 20-i. The received modulation frame is demodulated to obtain an information frame Fi. Since the modulation frames of the information frames F1 to Fn received simultaneously do not interfere with each other, they can be demodulated simultaneously. The demodulation circuit 22-i (i = 1 to n) outputs the information frame Fi obtained by the demodulation to the NC circuit 23. The NC circuit 23 generates an encoded information frame X by NC encoding the information frames F1 to Fn, and writes it into the storage circuit 24.

(2) At time T2, the storage circuit 24 of the relay station 2 outputs the stored encoded information frame X to the modulation circuit 25. The modulation circuit 25 modulates the encoded information frame X output from the storage circuit 24 and outputs it to the N distribution circuit 26. The N distribution circuit 26 distributes the modulation frame of the encoded information frame X to the transmission / reception switching circuits 21-1 to 21-n. The transmission / reception switching circuit 21-i (i = 1 to n) outputs the modulation frame of the encoded information frame X distributed by the N distribution circuit 26 to the directional antenna 20-i, and the directional antenna 20-i The modulation frame of the encoded information frame X is broadcast to the opposite terminal station 1-i.
When the terminal station 1-i (i = 1 to n) receives the modulation frame transmitted from the relay station 2 by the directional antenna 10, the terminal station 1-i demodulates the received modulation frame and obtains the encoded information frame X obtained by the demodulation. Is decrypted with a key information frame to obtain a desired information frame.

  Thereafter, the wireless relay system repeatedly executes (1) to (2) described above.

  The case where there are two terminal stations 1 will be described using the Alice & Bob topology two-hop wireless relay system shown in FIG. 1 as an example.

  FIG. 3 is a block diagram showing a configuration of the terminal station 1 when the present embodiment is applied to the Alice & Bob topology. The terminal station 1 has the same configuration as the conventional terminal station except that a directional antenna is provided instead of the omni antenna. The terminal station 1 includes a directional antenna 10, a modulation circuit 11, a storage circuit 12, a transmission / reception switching circuit 14, a demodulation circuit 15, and a network coding / decoding circuit (hereinafter referred to as “NC decoding circuit”) 16. Is done.

  The modulation circuit 11 modulates a native information frame input from an upper layer or the like. The storage circuit 12 stores a key information frame such as a native information frame input to the modulation circuit 11. The transmission / reception switching circuit 14 performs switching according to the transmission / reception timing of signals scheduled in advance. The transmission / reception switching circuit 14 outputs the modulation frame output from the modulation circuit 11 to the directional antenna 10 at the time of signal transmission, and outputs the modulation frame received by the directional antenna 10 to the demodulation circuit 15 at the time of signal reception. The transmission / reception switching circuit 14 may output the input from the modulation circuit 11 to the directional antenna 10 and output the input from the directional antenna 10 to the demodulation circuit 15 using a circulator circuit. The directional antenna 10 performs radio transmission by outputting the modulation frame input via the transmission / reception switching circuit 14 to a space as an antenna, and receives the modulation frame wirelessly transmitted from the relay station 2. The demodulation circuit 15 demodulates the modulation frame received by the directional antenna 10 and output from the transmission / reception switching circuit 14. The NC decoding circuit 16 uses the key information frame read from the storage circuit 12 to NC-decode the encoded information frame demodulated by the demodulation circuit 15.

The wireless relay system of this embodiment to which the Alice & Bob topology is applied operates as follows.
(1) At time T1, the terminal station 1-1 transmits the modulation frame of the information frame F1 through the directional antenna 10. At the same time, the terminal station 1-2 transmits the modulation frame of the information frame F2 through the directional antenna 10. Specifically, the modulation circuit 11 of the terminal station 1-i (i = 1, 2) modulates the information frame Fi input from an upper layer or the like, and the storage circuit 12 stores the information frame Fi. The information frame Fi modulated by the modulation circuit 11 of the terminal station 1-i is output to the directional antenna 10 via the transmission / reception switching circuit 14, and is transmitted by radio.

  At the same time as the demodulation circuit 22-1 of the relay station 2 demodulates the modulation frame received by the directional antenna 20-1 to obtain the information frame F1, the demodulation circuit 22-2 receives the reception of the directional antenna 20-2. The information frame F2 is acquired by demodulating the modulation frame. The NC circuit 23 generates an encoded information frame X by NC encoding the information frame F1 demodulated by the demodulation circuit 22-1 and the information frame F2 demodulated by the demodulation circuit 22-2, and writes the encoded information frame X in the storage circuit 24.

(2) At time T2, the modulation circuit 25 of the relay station 2 modulates the encoded information frame X output from the storage circuit 24, and the N distribution circuit 26 transmits the modulation frame of the encoded information frame X to the transmission / reception switching circuit. It distributes to 21-1, 21-2. The directional antenna 20-1 receives the modulation frame input via the transmission / reception switching circuit 21-1, and the directional antenna 20-2 receives the modulation frame input via the transmission / reception switching circuit 21-2. The modulation frame is broadcast to the terminal station 1-2.

  The terminal stations 1-1 and 2 receive the modulation frame transmitted from the relay station 2 by the directional antenna 10, and the received modulation frame is input to the demodulation circuit 15 via the transmission / reception switching circuit 14 and demodulated. The NC decoding circuit 16 of the terminal station 1-1 NC-decodes the encoded information frame X demodulated by the demodulation circuit 15 using the information frame F1 read from the storage circuit 12, and obtains an information frame F2. -2 NC decoding circuit 16 NC-decodes the encoded information frame X demodulated by the demodulation circuit 15 using the information frame F2 read from the storage circuit 12 to obtain an information frame F1.

  When there are three or more terminal stations 1, each terminal station 1 includes a directional antenna facing the terminal station 1 that transmits a native information frame used as a key information frame in addition to the directional antenna 10. When all the terminal stations 1 transmit the modulated native information frame to the relay station 2 at the same time, each terminal station 1 stores the native information frame transmitted by the terminal station, and is used as a key information frame. A modulation frame is received from another terminal station 1 that transmits the information frame, and a native information frame obtained by demodulation is stored. When each terminal station 1 demodulates the modulation frame received from the relay station 2 to obtain an encoded information frame, each terminal station 1 performs NC decoding using the stored native information frame as a key information frame.

[Second Embodiment]
Subsequently, a second embodiment of the present invention will be described. In the first embodiment, the relay station 2 simultaneously receives and demodulates native information frames transmitted from N terminal stations 1 at the reception timing, and then receives N native information frames obtained by demodulation. An encoded information frame is generated by NC encoding. However, if the native information frame demodulated by the relay station 2 includes an erroneous native information frame, the terminal station 1 may not be able to normally NC-decode the encoded information frame. Therefore, in the second embodiment, the relay station performs NC encoding using only the native information frame that can be normally received, and generates an encoded information frame. Therefore, the terminal station 1 transmits a native information frame on which error detection encoding has been performed to the relay station 2, and the relay station 2 can detect a bit error with respect to a demodulation result of the received native information frame. Hereinafter, the difference from the first embodiment will be mainly described.

  FIG. 4 is a block diagram showing the configuration of the relay station 2a according to this embodiment. In this figure, the same parts as those in the relay station 2 according to the first embodiment shown in FIG. The relay station 2a shown in FIG. 4 is different from the relay station 2 of the first embodiment in that a storage circuit group 31 including storage circuits 31-1 to 31-n, an error detection circuit 32, and a control unit 33 are provided. In other words, an NC circuit 23 a is provided in place of the NC circuit 23, and an N distribution circuit 26 a is provided in place of the N distribution circuit 26.

  The storage circuit 31-i (i = 1 to n) stores the native information frame demodulated by the demodulation circuit 22-i. The error detection circuit 32 reads out the native information frame demodulated by the demodulation circuit 22-i from the storage circuit 31-i, performs error detection, and outputs the result to the control unit 33. The control unit 33 receives the error detection result of the native information frame demodulated by the demodulation circuits 22-1 to 22-n from the error detection circuit 32, and converts the encoded information frame using only the normally demodulated native information frame. The NC circuit 23a is instructed to generate, and the N distribution circuit 26a is instructed to the directional antennas 20-1 to 20-n facing the terminal station 1a that is the destination of the normally demodulated native information frame by the modulation circuit 25. Instructs to distribute the encoded information frame modulated by. The NC circuit 23a performs NC encoding using the native information frame instructed by the control unit 33, and generates an encoded information frame. The N distribution circuit 26 a distributes the modulation frame output from the modulation circuit 25 to the directional antennas 20-1 to 20-n instructed by the control unit 33.

Next, the operation of the wireless relay system of this embodiment will be described.
(1) At time T1, as in the first embodiment, the terminal stations 1a-i (i = 1 to n) simultaneously wirelessly transmit the modulation frame of the information frame Fi. However, the information frame Fi is subjected to error detection coding, and the modulation frame includes frame identification information for specifying the information frame Fi. For error detection coding, for example, a CRC (Cyclic Redundancy Check) code or the like can be used. When the relay station 2a demodulates the modulation frame received from the terminal stations 1a-i (i = 1 to n) as in the first embodiment, the information frame Fi obtained by the demodulation and the frame identification of the information frame Fi Information is stored in the memory circuit 31-i.

(2) At time T2, the storage circuit 31-i (i = 1 to n) of the relay station 2a outputs the information frame Fi demodulated by the demodulation circuit 22-i and the frame identification information of the information frame Fi. The error detection circuit 32 performs error detection on the information frame Fi output from the storage circuit 31-i (i = 1 to n), and outputs an error detection result to the control unit 33. When the control unit 33 recognizes a normally demodulated information frame Fk (k is an integer of 1 to n) from the error detection result, the NC circuit performs NC encoding using the normally demodulated information frame Fk. 23a and distributes the modulation frame to the directional antenna 20-k 'facing the terminal station 1a-k' (k 'is an integer not less than 1 and not more than n) that is the destination of the normally demodulated information frame Fk The N distribution circuit 26a is instructed to do so. The terminal station 1a as the destination may be determined in advance corresponding to the terminal station 1a that is the transmission source of the native information frame, or may be acquired from the destination information set in the native information frame.

  In accordance with an instruction from the control unit 33, the NC circuit 23a encodes an encoded information frame using only the normally demodulated information frame Fk among the information frames F1 to Fn output from the storage circuits 31-1 to 31-n. When X is generated, the encoded information frame X and the frame identification information of the information frame Fk are output. The modulation circuit 25 modulates the encoded information frame X output from the NC circuit 23 a and outputs it to the N distribution circuit 26. The modulation frame of the encoded information frame X generated by the modulation circuit 25 includes NC encoded information indicating that it is an NC encoded information frame and frame identification information of the information frame Fk. The N distribution circuit 26a distributes the modulation frame of the encoded information frame X to the directional antenna 20-k 'in accordance with the instruction from the control unit 33. The directional antenna 20-k 'broadcasts the modulation frame input via the transmission / reception switching circuit 21-k' to the opposite terminal station 1a-k '.

  The terminal station 1a-k ′ receives the modulation frame transmitted from the relay station 2a by the directional antenna 10 and demodulates the received modulation frame. Since the NC encoded information is added to the demodulated information frame, the terminal station 1a-k ′ selects the key information frame based on the frame identification information of the information frame Fk added to the encoded information frame. Then, the encoded information frame is NC-decoded using the selected key information frame to obtain a desired information frame.

  In the above (2), when there is only one information frame Fk demodulated normally, the following process (2 ') is performed.

(2 ′) When the control unit 33 of the relay station 2a determines from the error detection result that there is only one information frame Fk that is normally demodulated, the NC circuit 23a is not subjected to NC encoding, and the information frame Fk Is directly output to the modulation circuit 25 and the N distribution circuit 26a is instructed to distribute the modulation frame to the directional antenna 20-k ′ corresponding to the terminal station 1a-k ′ that is the destination of the information frame Fk. . The NC circuit 23a outputs the information frame Fk to the modulation circuit 25, and the N distribution circuit 26a outputs the information frame Fk modulated by the modulation circuit 25 to the directional antenna 20-2. The modulated information frame Fk is transmitted by radio from the directional antenna 20-k ′.
The terminal stations 1a-k ′ demodulate the modulation frame received from the relay station 2a. Since NC encoded information is not added to the information frame obtained by demodulation, NC decoding is not performed.

  The case where the terminal station 1 is replaced with the terminal station 1a of the present embodiment and the relay station 2 is replaced with the relay station 2a of the present embodiment, taking the two-hop wireless relay system of the Alice & Bob topology shown in FIG. 1 as an example. To do.

  FIG. 5 is a block diagram showing the configuration of the terminal station 1a according to this embodiment. In this figure, the same parts as those of the terminal station 1 according to the first embodiment shown in FIG. The terminal station 1a shown in FIG. 5 is different from the terminal station 1 of the first embodiment in that a control unit 17 is provided, a modulation circuit 11a is provided instead of the modulation circuit 11, and an NC An NC decoding circuit 16a is provided instead of the decoding circuit 16.

  The modulation circuit 11a performs error detection encoding and modulation of the native information frame. When the received information frame is NC-encoded, the control unit 17 instructs the storage circuit 12 to output a key information frame, instructs the NC decoding circuit 16a to perform NC decoding, and receives the received information frame. Is not NC encoded, the storage circuit 12 is instructed not to output the key information frame, and the NC decoding circuit 16a is instructed not to perform NC decoding. The NC decryption circuit 16a performs NC decryption on the encoded information frame demodulated by the demodulation circuit 15 using the key information frame output from the storage circuit 12 in accordance with an instruction from the control unit 17, and the obtained native information frame is obtained. Output to the upper layer or the like, or output the demodulated native information frame to the upper layer or the like as it is.

The wireless relay system of this embodiment to which the Alice & Bob topology is applied operates as follows.
(1) At time T1, the terminal station 1a-1 stores the information frame F1 in the storage circuit 12, and transmits the modulation frame of the information frame F1 output from the modulation circuit 11a by the directional antenna 10. At the same time, the terminal station 1a-2 stores the information frame F2 in the storage circuit 12, and transmits the modulation frame of the information frame F2 output from the modulation circuit 11a by the directional antenna 10. Similar to the relay station 2 of the first embodiment, the demodulation circuit 22-1 of the relay station 2a demodulates the modulation frame received by the directional antenna 20-1, and the demodulation circuit 22-2 is directional antenna 20-2. Demodulates the received modulation frame. The modulation circuit 22-1 writes the information frame F1 obtained by demodulation and the frame identification information of the information frame F1 to the storage circuit 31-1, and the modulation circuit 22-2 includes the information frame F2 obtained by demodulation, The frame identification information of the information frame F2 is written into the storage circuit 31-2.

(2) At time T2, the error detection circuit 32 of the relay station 2a performs error detection on the information frames F1 and F2, and outputs an error detection result to the control unit 33. If the control unit 33 determines that both the information frames F1 and F2 have been demodulated normally, the control unit 33 instructs the NC circuit 23a to perform NC encoding using the information frames F1 and F2, and instructs the N distribution circuit 26a to transmit a directional antenna. Instructs 20-1 and 20-2 to distribute the modulation frame. The NC circuit 23a generates an encoded information frame X using the information frames F1 and F2, adds the frame identification information of the information frames F1 and F2, and outputs the frame to the modulation circuit 25. The modulation frame of the encoded information frame X generated by the modulation circuit 25 is output to the directional antennas 20-1 and 20-2 by the N distribution circuit 26a and transmitted by broadcast.

  The demodulation circuit 15 of the terminal stations 1a-1 and 1a-2 demodulates the modulation frame received by the directional antenna 10 from the relay station 2a, and the control unit 17 performs NC encoding on the demodulated encoded information frame X. Since the information is added, the NC decoding circuit 16a is instructed to perform NC decoding, and the key information frame is determined based on the frame identification information of the information frames F1 and F2 added to the encoded information frame X. . The control unit 17 of the terminal station 1a-1 instructs the storage unit 12 to output the information frame F1 transmitted by the local station specified by the frame identification information, and the NC decryption circuit 16a uses the information frame F1 as the key information. Using as a frame, the demodulated encoded information frame X is NC-decoded to obtain an information frame F2. Further, the control unit 17 of the terminal station 1a-2 instructs the storage unit 12 to output the information frame F2 transmitted by the own station, which is specified by the frame identification information, and the NC decoding circuit 16a selects the information frame F2. An information frame F1 is obtained by NC decoding the demodulated encoded information frame X, which is used as a key information frame.

  In the above (2), when only one of the information frames F1 and F2 is normally demodulated and an encoding error is detected in the other, the following process (2 ') is performed.

(2 ′) For example, when the control unit 33 of the relay station 2a recognizes that the information frame F1 is normally demodulated from the error detection result and a coding error is detected in the information frame F2, the information is sent to the NC circuit 23a. Instructs the N distribution circuit 26a to output the frame F1 without NC encoding, and instructs the N distribution circuit 26a to output the modulation frame to the directional antenna 20-2 corresponding to the terminal station 1a-2 that is the destination of the information frame F1. To do. As a result, the modulated information frame F1 is wirelessly transmitted from the directional antenna 20-2. The demodulation circuit 15 of the terminal station 1a-2 demodulates the modulation frame received by the directional antenna 10 from the relay station 2a, and the control unit 17 does not add NC encoded information to the demodulated information frame. The NC decoding circuit 16a is instructed not to perform NC decoding. The NC decoding circuit 16a of the terminal station 1a-2 outputs the information frame F1 output from the demodulation circuit 15 to the upper layer or the like as it is.

  In the present embodiment, all the terminal stations 1a-1 to 1a-n simultaneously transmit native information frames at time T1, but some of the terminal stations 1a-1 to 1a-n simultaneously transmit native information frames. The terminal stations 1a-1 to 1a-n can all transmit native information frames at different times. The relay station 2 obtains a transmission opportunity after receiving native information frames from all of the terminal stations 1-1 to 1-n.

  When there are three or more terminal stations 1, each terminal station 1 includes a directional antenna facing the terminal station 1 that transmits a native information frame used as a key information frame, in addition to the directional antenna 10. When all the terminal stations 1 transmit the modulated native information frame to the relay station 2 at the same time, each terminal station 1 stores the native information frame transmitted by the terminal station and its frame identification information, as well as key information. A modulation frame is received from another terminal station 1 that transmits a native information frame used as a frame, and a native information frame and its frame identification information obtained by demodulation are stored. When each terminal station 1 demodulates the modulation frame received from the relay station 2 to obtain an encoded information frame, the terminal station 1 selects a key information frame from the stored native information frames based on the added frame identification information. Is selected and NC decoding is performed.

[Third Embodiment]
In the second embodiment, information frames received from all terminal stations are targeted for NC encoding at transmission timings from relay stations that are scheduled in advance. At each transmission timing, only some of the native information frames are subject to NC encoding. For example, at a certain transmission timing of the relay station, an encoded information frame is generated from information frames received from the terminal stations 1a-1, 1a-2, and at the next transmission timing of the relay station, the terminal stations 1a-3, 1a- 4 is scheduled to generate an encoded information frame from the information frame received from 4. Hereinafter, differences from the second embodiment will be described.

  The configuration of the relay station of this embodiment is the same as that of the relay station 2a of the second embodiment shown in FIG. The wireless relay system of this embodiment operates as follows.

(1) At time T1, the relay station 2a stores the information frame Fi transmitted from the terminal stations 1a-i (i = 1 to n) in the storage circuit 31-i as in the second embodiment. . Note that information frames may not be received from all the terminal stations 1a as long as the information frames that are subject to network coding are received at least at the transmission timing of the next relay station 2a.

(2) At time T2, the control unit 33 of the relay station 2a transmits the information frame to the storage circuit 31-j storing the NC encoding target information frame Fj (j is an integer of 1 to n). Direct output. An NC encoding target information frame at each transmission timing is stored in the control unit 33 in advance. The error detection circuit 32 detects an error in the information frame Fj output from the storage circuit 31-j and outputs the error detection result to the control unit 33. When the control unit 33 recognizes a normally demodulated information frame Fk (k is an integer not less than 1 and not more than n) among the information frames Fj from the error detection result, the control unit 33 uses the normally demodulated information frame Fk. Output to the NC circuit 23a to be encoded, and N distribution to distribute the modulation frame to the directional antenna 20-k ′ corresponding to the terminal station 1a-k ′ that is the destination of the normally demodulated information frame Fk Instruct the circuit 26a.
The subsequent operation of the relay station 2a is the same as in the second embodiment. The operation when there is only one information frame Fk demodulated normally is the same as in the second embodiment.

  For example, in a wireless relay system including three or more terminal stations 1a, an information frame F1 addressed to the terminal station 1a-2 from the terminal station 1a-1 Is sent. Transmission of information frames from the terminal stations 1a-1 and 1a-2 may be performed simultaneously or at different times. At the transmission timing of the relay station 2a, when the control unit 33 determines that the native information frame received from the terminal stations 1a-1 and 1a-2 is the NC encoding target at this transmission timing, the error detection circuit 32 The error detection results of the information frames F1 and F2 are received. When there is no error in both the information frames F1 and F2, the control unit 33 instructs the NC circuit 23a to generate an encoded information frame using these information frames, and the directional antennas 20-1 and 20-2. The N distribution circuit 26a is instructed to distribute the encoded information frame that is modulated into the N distribution circuit 26a. The encoded information frame X generated by the NC circuit 23a and modulated by the modulation circuit 25 is simultaneously transmitted to the terminal station 1a-1 by the directional antenna 20-1 and to the terminal station 1a-2 by the directional antenna 20a-2. Is done.

  Further, for example, when the wireless relay system is an X topology in which an information frame addressed to the terminal station 1a-2 from the terminal station 1a-3 and a packet addressed to the terminal station 1a-1 are transmitted from the terminal station 1a-4, The station 1a-1 receives the information frame F3 addressed to the terminal station 1a-2 transmitted from the terminal station 1a-3 to the relay station 2a by an antenna different from the directional antenna 10, and stores it as a key information frame in the storage circuit 12. The terminal station 1a-2 stores the information frame F4 addressed to the terminal station 1a-1 transmitted from the terminal station 1a-4 to the relay station 2a by an antenna different from the directional antenna 10 and receives it as a key information frame. Store in the memory circuit 12. In the transmission timing of the relay station 2a, when the control unit 33 determines that the native information frame received from the terminal stations 1a-3 and 1a-4 is the NC encoding target at this transmission timing, the storage circuit 31-3 The error detection results of the output information frame F3 and the information frame F4 output from the storage circuit 31-4 are received from the error detection circuit 32. When there is no error in the information frames F3 and F4, the control unit 33 instructs the NC circuit 23a to generate an encoded information frame using these information frames, and the terminal station 1a that is the destination of the information frame F4 N distribution circuit 26a to distribute the modulated encoded information frame to the directional antenna 20-1 facing -1 and the directional antenna 20-2 facing the terminal station 1a-2 that is the destination of the information frame F3. To instruct. The encoded information frame X generated by NC encoding the information frames F3 and F4 is modulated by the modulation circuit 25, and then transmitted to the terminal station 1a-1 by the directional antenna 20-1, and by the directional antenna 20-2. It is simultaneously transmitted to the terminal station 1a-2. The terminal station 1a-1 decodes the encoded information frame X with the information frame F3 to obtain the information frame F4, and the terminal station 1a-2 decodes the encoded information frame X with the information frame F4 to obtain the information frame F3. To get.

According to the embodiments of the present invention described above, in the wireless relay to which the network coding technique is applied, the relay station uses the directional antennas facing the directional antennas of the plurality of terminal stations to simultaneously prevent the plurality of relay stations from interfering with each other. The native information frame is received from each terminal station, demodulated in each demodulation circuit provided corresponding to each directional antenna, and the demodulated native information frames are NC-encoded. The encoded information frame generated by the NC encoding is modulated by the modulation circuit at the transmission timing of the relay station, and is transmitted by broadcast through a directional antenna facing each of the plurality of terminal stations. Therefore, it is not necessary to separate the transmission timings of a plurality of terminal stations by time, so that the system throughput can be increased.
Further, according to the second and third embodiments, the relay station stores the native information frame before NC encoding in the storage circuit corresponding to each demodulation circuit, so that the reception of the native information frame is performed. It is possible to perform flexible NC encoding in accordance with the error situation and the situation of the retained information frame at the terminal station.

Further, according to the present embodiment, it is possible to easily solve the hidden terminal problem between terminal stations that occurs when the system is a multi-hop wireless system operating with CSMA / CA (carrier sense multiple access / collision avoidance).
CSMA / CA is a medium access control method adopted in a wireless local area network (LAN). Specifically, CSMA / CA is a method for avoiding contention when a plurality of users access the same channel, and is adopted in IEEE 802.11. Since a wireless LAN has a weak transmission signal, it cannot be detected even if a collision of signals flowing through the same channel occurs. CSMA / CA is a system that constantly monitors the transmission status so that such a collision does not occur. Each terminal station confirms that the communication channel is continuously available for a certain period of time and then transmits data. If the data is correctly received, a signal called ACK (Acknowledge) is returned from the receiving side. When the ACK signal is returned, it is determined that the data transfer has been established. If no ACK signal is returned, it is determined that a collision has occurred and data is transmitted again.
Further, the hidden terminal problem is, for example, when two nodes, node A and node B, are hidden from each other (out of the signal reachable range) and both transmit data simultaneously, This is a problem that data collision occurs because data arrives simultaneously from node A and node B. Since node A and node B are hidden from each other, node A has no way of knowing whether node B is currently transmitting data. Similarly, from node B, there is no way of knowing whether node A is currently transmitting data. Therefore, the node A and the node B may transmit data to the receiving node C at the same time.

  In other words, the terminal station transmits an information frame to the relay station when it determines that the communication path is empty, but if the other terminal stations are outside the signal reachable range, the other terminal stations There is a case where the information frame is transmitted without recognizing that the information frame is transmitted. Since the relay station of this embodiment can receive information frames from a plurality of terminal stations at the same time, even if such a situation occurs, it receives information frames normally received from a plurality of terminal stations at the same time, and receives the received information frames. An encoded information frame that is NC-encoded using the frame can be generated and transmitted to the terminal station. Therefore, the terminal station obtains a transmission opportunity when no information frame is transmitted from the relay station, and the relay station obtains a transmission opportunity when no information frame is transmitted from any terminal station. Good.

  The terminal stations 1 and 1a and the relay stations 2 and 2a have a computer system inside. The modulation circuits 11, 11a, the storage circuit 12, the demodulation circuit 15, the NC decoding circuits 16, 16a, and the control unit 17, the demodulation circuit group 22, the NC circuits 23, 23a, the storage circuit 24, the modulation circuit 25, The operation processes of the storage circuit group 31, the error detection circuit 32, and the control unit 33 are stored in a computer-readable recording medium in the form of a program, and the computer system reads and executes this program. The above processing is performed. The computer system here includes a CPU, various memories, an OS, and hardware such as peripheral devices. The modulation circuit 11, the demodulation circuit 15, the demodulation circuit group 22, and the modulation circuit 25 may be realized by dedicated hardware.

Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used.
The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory in a computer system serving as a server or a client in that case, and a program that holds a program for a certain period of time are also included. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.

1, 1-1, 1-2... Terminal station (terminal station apparatus)
10. Directional antenna (terminal station directional antenna)
11 ... Modulation circuit 12 ... Storage circuit (key storage unit)
13 ... Amplifier circuit 14 ... Transmission / reception switching circuit 15 ... Demodulation circuit (terminal demodulator)
16... NC decoding circuit (network encoding / decoding unit)
2, 2a ... Relay station (relay station device)
20-1 to 20-n Directional antenna 21 Transmission / reception switching circuit group 21-1 to 21-n Transmission / reception switching circuit 22 Demodulation circuit group (demodulation unit)
22-1 to 22-n... Demodulation circuit 23, 23a... NC circuit (network coding unit)
24 ... Memory circuit 25 ... Modulation circuit (modulation unit)
26, 26a ... N distribution circuit (distribution unit)
31: Memory circuit groups 31-1 to 31-n: Memory circuit 32: Error detection circuit (error detection unit)
33 ... Control unit

Claims (4)

A wireless relay system having a relay station device and a plurality of terminal devices,
The relay station device
Provided facing each of the terminal directional antennas of the plurality of terminal devices, receiving information frames wirelessly from the terminal directional antennas of the facing terminal devices, and encoding the plurality of information frames by network coding A plurality of directional antennas that wirelessly transmit the encoded information frames to the terminal directional antennas of the terminal device facing each other;
A plurality of demodulation units that are provided corresponding to the plurality of directional antennas, respectively, and the corresponding directional antennas demodulate information frames received from the terminal device;
A network encoding unit for generating an encoded information frame by performing network encoding on an information frame demodulated by each of the plurality of demodulation units;
A modulation unit for modulating the encoded information frame generated by the network encoding unit;
A distribution unit that outputs the encoded information frame modulated by the modulation unit to the plurality of directional antennas ;
Instructing the network encoding unit to generate an encoded information frame using an information frame targeted for network encoding among the information frames demodulated by each of the plurality of demodulation units, and the information frame targeted for network encoding A control unit that instructs the distribution unit to output the encoded information frame modulated by the modulation unit to the plurality of directional antennas facing the terminal directional antenna of the terminal device that is a destination of ,
The terminal device is
A terminal directional antenna that receives an encoded information frame transmitted from the directional antenna facing the own station of the relay station device;
A key storage unit for storing a key information frame used for decoding an encoded information frame;
A terminal demodulation unit that demodulates the encoded information frame received by the terminal directional antenna;
A network encoding / decoding unit that decodes the encoded information frame demodulated by the terminal demodulation unit with a key information frame read from the key storage unit;
A wireless relay system characterized by that. The relay station apparatus in a radio relay system having a relay station apparatus and a plurality of terminal stations,
Provided facing each of the terminal directional antennas of the plurality of terminal devices, receiving information frames wirelessly from the terminal directional antennas of the facing terminal devices, and encoding the plurality of information frames by network coding A plurality of directional antennas that wirelessly transmit the encoded information frames to the terminal directional antennas of the terminal device facing each other;
A plurality of demodulation units that are provided corresponding to the plurality of directional antennas, respectively, and the corresponding directional antennas demodulate information frames received from the terminal device;
A network encoding unit for generating an encoded information frame by performing network encoding on an information frame demodulated by each of the plurality of demodulation units;
A modulation unit for modulating the encoded information frame generated by the network encoding unit;
A distribution unit that outputs the encoded information frame modulated by the modulation unit to the plurality of directional antennas;
Instructing the network encoding unit to generate an encoded information frame using an information frame targeted for network encoding among the information frames demodulated by each of the plurality of demodulation units, and the information frame targeted for network encoding A control unit that instructs the distribution unit to output the encoded information frame modulated by the modulation unit to the plurality of directional antennas facing the terminal directional antenna of the terminal device that is the destination of
A relay station apparatus comprising: An error detection unit that performs error detection of an information frame demodulated by each of the plurality of demodulation units;
Of the information frames demodulated by each of the plurality of demodulation units, the network encoding unit generates an encoded information frame using a plurality of information frames to be encoded in the network in which no error is detected in the error detection unit The modulation unit is connected to the plurality of directional antennas facing the terminal directional antenna of the terminal device that is the destination of the plurality of information frames to be encoded in the network in which no error is detected. A controller that instructs the distributor to output a modulated encoded information frame;
The relay station apparatus according to claim 2, further comprising: A radio relay method for the relay station apparatus in a radio relay system having a relay station apparatus and a plurality of terminal stations,
A reception process in which a plurality of directional antennas provided facing each of the terminal directional antennas of the plurality of terminal devices receive information frames wirelessly transmitted from the terminal devices;
A demodulating unit provided for each of the plurality of directional antennas, a demodulating process for demodulating an information frame received from the terminal device by the directional antenna corresponding to the demodulating unit in the receiving process;
An instruction process for instructing to generate an encoded information frame using an information frame to be network encoded among information frames demodulated by each of the plurality of demodulation units in the demodulation process;
A network coding process for generating a coded information frame by performing network coding on a network coding target information frame indicated in the instruction process among information frames demodulated by each of the plurality of demodulation units in the demodulation process;
A modulation process for modulating the encoded information frame generated in the network encoding process;
Instructing the plurality of directional antennas facing the terminal directional antennas of the terminal device that is the destination of the information frame to be encoded to output the encoded information frames modulated in the modulation process. Control process,
A distribution process of outputting the encoded information frame modulated in the modulation process to the plurality of directional antennas instructed in the control process ;
A transmission process in which the plurality of directional antennas wirelessly transmit the encoded information frames output in the distribution process to terminal directional antennas of the plurality of terminal devices facing each other;
A wireless relay method comprising:

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