JP2015136010A - Device, system, method and program for radio communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio communication system capable of improving communication quality without damaging real time when performing multi-hop communication in both directions.SOLUTION: In a radio communication system communicating on a route including a first end radio communication device, one or a plurality of relay radio communication devices and a second end radio communication device, different protocols are applied between upward and downward directions on the route. Each radio communication device performs multi-hop communication using a protocol according to a communication direction. One of the end radio communication devices to be a transmission source and each relay radio communication device respectively include: retransmission function units for trying to retransmit the same packet for a plurality of number of times and retransmission suspension function units for suspending retransmission when a next hop radio communication device receives a packet transmitted to the farther radio communication device.

Description

  The present invention relates to a wireless communication device, a wireless communication system, a wireless communication method, and a wireless communication program. For example, communication is performed between a plurality of in-vehicle wireless devices (a roadside wireless device may be included as some wireless devices). It can be applied to a vehicle network system to be performed.

  Since the position of the in-vehicle wireless devices constituting the vehicle network changes as the vehicle travels, communication between the in-vehicle wireless devices often fails. Various methods have been proposed as methods for shortening the recovery time at the time of communication disconnection or improving communication quality (see Patent Documents 1 to 9).

  Patent Document 1 and Patent Document 2 describe a method of duplicating a path to reduce time required for path rediscovery after a link failure and switching to a sub path when the main path is disconnected. The technology described in Patent Literature 1 and Patent Literature 2 is multi-hop communication between a server and a terminal, and the communication status is confirmed in the server. Further, in the case of guarantee type communication, since the communication state can be confirmed on the server by returning an Ack (reception response), the communication quality can be improved by the techniques described in Patent Document 1 and Patent Document 2. However, the techniques described in Patent Document 1 and Patent Document 2 are not suitable for broadcast communication or best effort communication in wireless ad hoc communication without a base station (corresponding to a server).

  Patent Documents 3 and 4 describe a method of obtaining an alternative route in advance in order to reduce the time for finding a new route after the route is disconnected. In the technologies described in Patent Document 3 and Patent Document 4, a time from when the route is found to be changed to the alternative route is generated. In guarantee type communication such as TCP, the communication quality is higher than the real-time property. Therefore, the techniques described in Patent Document 3 and Patent Document 4 are applicable. However, for example, in best-effort communication that emphasizes real-time performance over communication quality, such as voice data, since Ack is not returned, it is difficult to immediately detect communication disconnection, and control for confirming route disconnection is confirmed. It depends on the frequency of packet transmission. That is, if the control packet is frequently transmitted, the traffic of the control information increases, and if the frequency of occurrence of the control information is lowered to reduce the traffic, the delay of the disconnection confirmation is increased.

  Patent Document 5 (paragraphs “0005” to “0007”) describes a method of deleting unused terminals from the route information when the wireless mesh network is duplicated. However, this is a method of managing unused ends by a base station, and is not suitable for an ad hoc network in which each terminal operates in an autonomous and distributed manner.

  Patent Document 6 describes a multi-hop relay communication method using inter-vehicle communication. This description technique is a method for determining whether or not to relay in order to suppress traffic because the number of relays increases when there are many vehicles at the intersection.

  Patent Document 7 describes a method of improving communication quality by transmitting the same packet a plurality of times when performing broadcast transmission. However, the technique described in Patent Document 7 does not consider the multi-hop function. Since the communication quality of an ad hoc network depends on the number of peripheral terminals and the amount of traffic, it is necessary to transmit only the maximum number of retransmissions in order to perform broadcast communication.

  Patent Document 8 (Claim 8 of the present invention, paragraph “0031”) describes a function of stopping retransmission after a packet is transmitted if the same packet is relayed and transferred from the next hop destination. Further, it is described that the above-described function can be used for a unidirectional or bidirectional communication mode.

  However, the technology described in Patent Document 8 does not work effectively in a multi-hop environment where hidden terminals exist. Hereinafter, this problem will be described with reference to FIG. Now, as shown in FIG. 8, it is assumed that bidirectional communication is performed between the terminal N1 and the terminal N5 via the terminals N2 to N4. Further, the communication range of each of the terminals N1 to N5 is assumed to be the next hop destination. In such a situation, it is assumed that transmission of an uplink packet from the terminal N2 to the terminal N3 and transmission of a downlink packet from the terminal N4 to the terminal N3 are performed simultaneously. Since the upstream packet and the downstream packet are packets according to the same protocol, the terminal N3 cannot receive the upstream packet or the downstream packet due to packet collision, and the terminal N3 is a terminal N4 or terminal that is the next hop destination. Relay transfer cannot be performed toward N2. As a result of the terminal N3 not relaying and transferring, the terminal N2 and the terminal N4 transmit packets for the maximum number of retransmissions. Patent Document 8 describes that the above-described retransmission control function can be used for bidirectional communication, but as described above, it is recognized that bidirectional communication is possible in an environment where a hidden terminal exists. hard. Although detailed description is avoided, when the timing at which the terminal N2 tries to transmit a packet to the terminal N3 and the timing at which the terminal N3 tries to transmit a packet to the terminal N2 are simultaneous, the exposed terminals that are in a waiting state. Problems arise.

  As a countermeasure method for such a problem in Patent Document 8, a method of dividing the uplink communication from the terminal N1 to the terminal N5 and the downlink communication from the terminal N5 to the terminal N1 into time divisions can be considered. However, with this countermeasure method, the real-time property is newly impaired, and it is necessary to always always perform time division. There is a problem of how division control is performed in an autonomous and distributed manner.

  The paragraph describing the purpose of Patent Document 9 “provides a multimedia communication device capable of communicating high-quality multimedia information even on a transmission line with poor transmission quality such as a wireless transmission line without impairing real-time performance” It is described that it is determined whether or not to perform retransmission control depending on whether or not there is an error in received information. However, the technology described in Patent Document 9 does not impair real-time performance if multimedia information is transmitted only on one side. However, when bidirectional communication is performed, if the channel is shared, the reverse direction is achieved. It may affect the real-time nature of transmission.

JP 2005-354626 A Japanese Patent Laid-Open No. 10-190670 Japanese Patent Laid-Open No. 2004-23440 JP 2004-282270 A JP 2008-294944 A JP 2008-219409 A JP 2006-295476 A JP-T-2004-513530 JP-A-8-65278

  As described above, all of the conventional techniques are not applicable techniques when performing multi-hop communication in both directions, and have problems such as deterioration of real-time performance and communication quality deterioration due to a hidden terminal problem. And there was much room for improvement.

  Therefore, there is a demand for a wireless communication device, a wireless communication system, a wireless communication method, and a wireless communication program that can improve communication quality without impairing real-time performance when performing bi-directional multi-hop communication.

  According to a first aspect of the present invention, there is provided a wireless communication system that performs communication on a route including a first end wireless communication device, one or more relay wireless communication devices, and a second end wireless communication device. Further, different protocols are applied in the downlink direction, and each of the wireless communication devices performs multi-hop communication with a protocol corresponding to the communication direction.

  Here, any of the end wireless communication devices serving as a transmission source and each of the relay wireless communication devices retransmits the same packet multiple times, and the next-hop wireless communication device further performs wireless communication beyond It is preferable to provide a retransmission stop function unit that stops retransmission when a packet transmitted to the apparatus is received.

  According to a second aspect of the present invention, there is provided the wireless communication system according to any one of the elements of a wireless communication system that performs communication via a route including the first end wireless communication device, the one or more relay wireless communication devices, and the second end wireless communication device. In the wireless communication device to which the device corresponds, the wireless communication system applies different protocols to the route in the uplink direction and the downlink direction, and performs protocol selection to execute multi-hop communication with a protocol according to the communication direction It is provided with a functional part.

  Here, when the wireless communication apparatus receives a retransmission function unit that tries to retransmit the same packet a plurality of times and a packet transmitted by the next-hop wireless communication apparatus to a further wireless communication apparatus, the retransmission is stopped. It is preferable to provide a stop function unit.

  According to a third aspect of the present invention, there is provided a wireless communication method for performing communication on a route including a first end wireless communication device, one or more relay wireless communication devices, and a second end wireless communication device. Further, different protocols are applied in the downlink direction, and each of the wireless communication devices performs multi-hop communication processing with a protocol corresponding to the communication direction.

  Here, any of the end wireless communication devices and the relay wireless communication devices that are the transmission sources try to retransmit the same packet a plurality of times, and the next-hop wireless communication device further transmits to the next wireless communication device. When the received packet is received, it is preferable to stop the retransmission.

  A wireless communication program according to a fourth aspect of the present invention is any one of elements of a wireless communication system that performs communication via a route including a first end wireless communication device, one or more relay wireless communication devices, and a second end wireless communication device. The computer mounted in the wireless communication device to which the wireless communication device corresponds corresponds to a protocol corresponding to a communication direction in which different protocols are assigned to the route in the uplink direction and the downlink direction. It functions as a protocol selection function unit.

  Here, when the above-described computer further receives a retransmission function unit that tries to retransmit the same packet multiple times, and a packet transmitted by the next-hop wireless communication device to the wireless communication device further ahead, the retransmission stop that stops retransmission It is preferable to function as a functional unit.

  According to the present invention, it is possible to realize a wireless communication device, a wireless communication system, a wireless communication method, and a wireless communication program that can improve communication quality without impairing real-time performance when performing bi-directional multi-hop communication.

It is a block diagram which shows the detailed structure of the radio | wireless terminal of 1st Embodiment. It is a block diagram which shows schematic structure of the radio | wireless terminal of 1st Embodiment. It is explanatory drawing which shows the outline | summary of the retransmission control in the radio | wireless communications system of 1st Embodiment. 3 is a flowchart illustrating an outline of reception and relay operations by the wireless terminal according to the first embodiment. 4 is a flowchart illustrating a subroutine for each protocol of reception and relay operations by the wireless terminal according to the first embodiment. It is drawing explaining the influence which selection of the timeout time which starts retransmission in the radio | wireless terminal of 1st Embodiment has on transmission required time. It is explanatory drawing which arranged the characteristic etc. of the retransmission control method of 1st Embodiment. 10 is an explanatory diagram of a problem of the conventional technique described in Patent Document 8. FIG.

(A) First Embodiment Hereinafter, a first embodiment of a wireless communication device, a wireless communication system, a wireless communication method, and a wireless communication program according to the present invention will be described with reference to the drawings.

  The wireless communication system according to the first embodiment is a wireless multi-hop network, where there is no wireless communication device corresponding to a control station, and each wireless communication device autonomously communicates with a nearby wireless communication device. It is a network. In addition, each wireless communication device of the first embodiment is intended for a device whose position changes frequently, such as an in-vehicle device.

(A-1) Configuration of First Embodiment FIG. 2 is a block diagram showing a schematic configuration of a radio communication device (hereinafter referred to as a radio terminal) constituting the radio communication system of the first embodiment. 1 is a block diagram illustrating a detailed configuration of a wireless terminal.

  In FIG. 2, a wireless ad hoc network 10 is configured by a plurality of wireless terminals 100-1 to 100-4 (four are shown in FIG. 2).

  Each of the wireless terminals 100-1 to 100-4 includes an omnidirectional antenna 101-1 to 101-4, a PHY (physical) layer transmitting / receiving unit 102-1 to 102-4, and a MAC (medium access control) layer transmitting / receiving unit. 103-1 to 103-4 and network control units 104-1 to 104-4. Omnidirectional antenna 101 (101-1 to 101-4), PHY (physical) layer transceiver 102 (102-1 to 102-4), MAC (medium access control) layer transceiver 103 (103-1 to 103) -4) The detailed configuration of the network control unit 104 (104-1 to 104-4) is shown in FIG.

  The omnidirectional antenna 101, the PHY layer transmission / reception unit 102, and the MAC layer transmission / reception unit 103 are similar to those according to a conventional autonomous distributed communication method (for example, CSMA / CA (Carrier Sense Multiple Access Avidity Aidance) method). Detailed description thereof is omitted. In the case of the first embodiment, the MAC layer transmission / reception unit 103 (reception configuration) receives not only received information obtained by disassembling received packets but also received power information (for example, RSSI). Value) is also given as a kind of received information.

  The network control unit 104 (104-1 to 104-4) performs network layer and transport layer processing (for example, route selection and associative control). For example, the network control unit 104 can be configured as hardware such as a dedicated integrated circuit, or can be configured as software such as a CPU and a program executed by the CPU (wireless communication program of the embodiment). In any case, any configuration method can be functionally represented in FIG.

  In the case of the first embodiment, a communication protocol (hereinafter referred to as an uplink protocol) applied in one of the two directions (there is no server or management node, but hereinafter referred to as an uplink direction), One feature is that a communication protocol (hereinafter referred to as a downlink protocol) applied to the other of the two directions (hereinafter referred to as a downlink direction) is different.

  Here, the communication protocol represents a communication system that does not interfere with each other, and the upstream protocol and the downstream protocol are, for example, a 5.8 GHz band wireless communication system, a 2.4 GHz band wireless communication system, a 700 MHz band wireless communication system, and the like. One of the following applies.

  In addition to the difference in communication method, the routing protocol may be different between the upstream protocol and the downstream protocol.

    For example, as a routing protocol for an ad hoc network, an OLSR (Optimized Link State Routing) protocol, a TBRPF (Topology Dissociation Forward RSR protocol, a DSDV (Destination Sequencing Protocol), and a DSDV (Destination Protocol) (Fishey State Routing Protocol) protocol, IARP (Intrazone Routing Protocol) protocol, IERP (Interzone Routing Protocol) protocol Col, ZRP (Zone Routing Protocol) protocol, AODV (Ad Hoc Demand Vector Algorithm) protocol, DSR (Dynamic Source Routing Protocol) protocol, BRP (The Bordecast Protocol protocol) protocol type active protocol routine, etc. However, any of these protocols can be applied as the routing protocol in the upstream protocol and the downstream protocol.

  As illustrated in FIG. 1, the wireless terminals 100 (100-1 to 100-4) transmit an uplink protocol omnidirectional antenna 101U, a downlink protocol omnidirectional antenna 101D, an uplink protocol PHY layer transmission unit 102US, and an uplink protocol MAC layer transmission. 103US, uplink / downlink protocol PHY layer receiving unit 102UDR, uplink / downlink protocol MAC layer receiving unit 103UDR, downlink protocol PHY layer transmitting unit 102DS, downlink protocol MAC layer transmitting unit 103DS, hub (HUB) 110, and network control unit 104.

  The uplink protocol omnidirectional antenna 101U transmits and receives radio signals according to the uplink protocol, and the downlink protocol omnidirectional antenna 101D transmits and receives radio signals according to the downlink protocol.

  The uplink protocol PHY layer transmission unit 102US executes PHY layer transmission processing according to the uplink protocol, and the downlink protocol PHY layer transmission unit 102DS executes PHY layer transmission processing according to the downlink protocol. is there. The uplink / downlink protocol PHY layer receiving unit 102UDR executes PHY layer reception processing regardless of the uplink protocol and the downlink protocol.

  The uplink protocol MAC layer transmission unit 103US executes MAC layer transmission processing (for example, packet assembly, packet transmission) according to the uplink protocol, and the downlink protocol MAC layer transmission unit 103DS performs MAC processing according to the downlink protocol. The layer transmission process is executed. The uplink / downlink protocol MAC layer receiving unit 103UDR executes reception processing (for example, packet reception, packet decomposition) of the MAC layer regardless of the uplink protocol and the downlink protocol.

  The uplink protocol MAC layer transmitter 103US, the uplink protocol MAC layer receiver 103UDR, and the downlink protocol MAC layer transmitter 103DS are connected to the network controller 104 via the hub 110.

  For example, when the upstream protocol and the downstream protocol are separated by using the time axis channel with the same protocol, or when a dedicated interface is used for the upstream protocol and the downstream protocol, the hub 110 can be eliminated. .

  As shown in FIG. 1, the network control unit 104 includes a transmission information buffer 105A, a reception information buffer 105B, a control packet generation unit 106, a multihop control unit 107, a peripheral terminal monitoring unit 108, and a local terminal information unit 109. Note that a GPS receiving unit 111, an upper layer processing unit 112, and the like are provided in association with the network control unit 104.

  The transmission information buffer 105A is a buffer that temporarily stores transmission information, and the reception information buffer 105B is a buffer that temporarily stores reception information. As the transmission information, for example, application data output from the upper layer processing unit 112, control packets generated by the control packet generation unit 106, route information output from the multihop control unit 107 inserted into various packets, various packets The own terminal information output from the own terminal information unit 109 to be inserted into the terminal can be exemplified. As received information, for example, application data to be given to the upper layer processing unit 112, information to be relayed to the multi-hop control unit 107, information for collating whether the received destination node to be given to the own terminal information unit 109 is the own terminal, A control packet that enables the peripheral terminal monitoring unit 108 to recognize wireless terminals existing in the vicinity, information inserted therein, and the like can be exemplified.

  Application packets and control packets that are given to the transmission information buffer 105A and buffered are made into packets according to the uplink protocol or the downlink protocol according to the transmission direction by the generation unit. When the transmission information buffer 105A also has a packet generation function, it generates a packet according to the uplink protocol or the downlink protocol corresponding to the transmission direction. Similarly, since a reception packet according to the uplink protocol or the downlink protocol arrives at the reception information buffer 105B, the reception information buffer 105B can cope with both the uplink protocol and the downlink protocol.

  The control packet generator 106 generates a control packet that is applied to path construction and supplies it to the transmission information buffer 105A. In FIG. 1, the transmission information buffer 105 </ b> A is described as an image in which all information of the control packet is completed. However, necessary information from the multihop control unit 107 and the own terminal information unit 109 is transferred to the control packet generation unit 106. Then, the control packet generator 106 may give a control packet complete with all the information to the transmission information buffer 105A.

  The control packet generator 106 generates a control packet periodically, for example, when management information of the peripheral terminal monitor 108 is updated or when application data to be transmitted is generated. Identification information (ID) on the network of the wireless terminal 100 is inserted into the source address of the control packet, and an address value representing broadcast, multicast or unicast is inserted into the destination address. That is, the control packet of the first embodiment is broadcast, multicast or unicast.

  The multihop control unit 107 performs control so that multihop communication can be performed. That is, the multi-hop control unit 107 performs multi-hop communication based on information of the wireless terminal 100 (own terminal information) in the own terminal information unit 109, information (for example, link-specific received power information) in the peripheral terminal monitoring unit 110, and the like. And which route is used for multi-hop communication.

  In the case of the first embodiment, the multi-hop control unit 107 also confirms whether a route such as a transmission route or a relay route is an uplink direction or a downlink direction, and applies an uplink protocol in the case of the uplink direction. Each part is controlled, and each part is controlled to apply the downlink protocol in the case of the downlink direction.

  The peripheral terminal monitoring unit 108 is a part that collects and manages information related to peripheral wireless terminals from the received control packet. The management information is, for example, information on the network configuration (node, link), received power information when a packet is transmitted / received via the link, and an information update time is also given as appropriate. The received power information may be a received power value, may be a link cost obtained by converting the received power value so that it can be applied when evaluating a path, or may be both a received power value and a link cost. good.

  The own terminal information unit 109 holds information related to the wireless terminal 100 (for example, an address or position information on the network). The own terminal information unit 109 acquires the position information from the GPS receiving unit 111 and updates it as needed. The position information is inserted into, for example, a control packet, an application packet (also called a data packet), or a dedicated position information exchange packet for exchanging position information.

(A-2) Operation of First Embodiment Next, a multihop communication operation in the wireless communication system (wireless multihop network) of the first embodiment will be described.

  FIG. 3 is an explanatory diagram illustrating an outline of retransmission control in the wireless communication system according to the first embodiment, and illustrates uplink retransmission control. Although illustration of downlink retransmission control is omitted, it is the same as uplink retransmission control except for the difference in the applied protocol.

  In the example of FIG. 3, the wireless terminal 100-1 is the transmission source and the wireless terminal 100-4 is the destination, and packets are transmitted in the order of the wireless terminals 100-1, 100-2, 100-3, and 100-4. It is assumed that the route is constructed in advance by a known method, for example, a routing protocol such as the AODV protocol. Each wireless terminal 100-1, 100-2, 100-3, 100-4 exists only in the same communication area as the adjacent wireless terminal. In such a case, as described above, the communication quality is greatly deteriorated if the bidirectional operation is performed with the same protocol due to the hidden terminal problem.

  The wireless communication system 10 of the first embodiment applies a multi-hop method using a multi-protocol. Each wireless terminal 100-1, 100-2, 100-3, 100-4 receives not only packets addressed to itself but also other packets. At this time, it is determined whether the next-hop wireless terminal has transmitted the relay packet to the next-hop wireless terminal. If the relay packet is not transmitted within the specified time, the packet is transmitted again. Repeat this a predetermined number of times. However, since only the wireless terminal that transmits the relay packet to the end wireless terminal (destination wireless terminal) does not have the next-hop wireless terminal, the transmission is always repeated a predetermined number of times.

  Hereinafter, a specific example will be described with reference to FIG. A case where the radio terminal 100-1 transmits to the radio terminal 100-4 using an uplink protocol will be described.

  Assume that the wireless terminal 100-1 transmits a packet of the wireless terminal 100-4 to the wireless terminal 100-2. In FIG. 3, P (x → y) _z is a packet for direct transmission / reception between the wireless terminal 100-x and the wireless terminal 100-y, and indicates that the number of transmissions is the zth. In the example of FIG. 3, in the first transmission from the wireless terminal 100-1 to the wireless terminal 100-2, the wireless terminal 100-2 cannot receive a packet, and the wireless terminal 100-1 waits for a predetermined time. Since the packet from the wireless terminal 100-2 to the wireless terminal 100-3 could not be received, the second packet transmission is performed (P (1 → 2) _2). After the wireless terminal 100-1 transmits the packet twice, the wireless terminal 100-2 can receive the packet and transmits the relay packet toward the wireless terminal 100-3 (P (2 → 3) _1). . When the wireless terminal 100-1 receives this packet, the subsequent packet is not retransmitted. Therefore, the wireless terminal 100-1 can view the relay packet from the wireless terminal 100-2 to the wireless terminal 100-3 as Ack, and the maximum number of retransmissions (n1) that is predetermined in advance by intercepting the relay packet. Never send a packet of minutes.

  If the wireless terminal 100-3 can receive the packet in the first transmission of the relay packet of the wireless terminal 100-2, the wireless terminal 100-4 is the end wireless terminal because the next-hop wireless terminal 100-4 is the end wireless terminal. -3 transmits a packet a predetermined number of times n2 (n2 = 3 in FIG. 3) (P (3 → 4) _1 to P (3 → 4) _1). When the wireless terminal 100-2 receives the first transmission packet from the wireless terminal 100-3 to the wireless terminal 100-4, the subsequent packet is not retransmitted. Since the wireless terminal 100-3 transmits the packet for the specified number of times n2, in many cases, the wireless terminal 100-4 can receive the packet with any number of transmission times.

  Although not shown, unlike the method M1, the wireless terminal 100-4 that is the end wireless terminal may return an Ack, and the immediately preceding wireless terminal 100-3 receives the Ack. Therefore, retransmission of subsequent packets is not executed (method M2). In this case, the wireless terminal 100-3 does not need to perform the packet transmission operation n2 times for each relay.

  FIG. 4 is a flowchart showing an outline of reception and relay operations by the wireless terminal 100.

  When receiving a packet or generating a packet that needs to be transmitted while waiting for packet processing, the wireless terminal 100 checks the protocol of the relay packet or the packet from which the wireless terminal 100 is a transmission source (step S100). If the protocol of the processing target packet is an upstream protocol, the process proceeds to a subroutine for the upstream protocol (step S101). If the protocol of the processing target packet is a downstream protocol, the process proceeds to a subroutine for the downstream protocol (step S102). When it returns, it returns to the packet processing waiting state.

  In FIG. 4, the method is described in which the upstream protocol and the downstream protocol are operated in one sequence flow. However, bidirectional communication is possible without interfering with each other in the upstream protocol and the downstream protocol. You may make it let it. For example, if the carrier frequency and time-sharing allocation time are changed between uplink and downlink, downlink can be determined without determining the protocol, and the processing flow in each direction can be executed.

  Similar processing is executed for both the uplink protocol subroutine and the downlink protocol subroutine except for the difference in the applied protocol. FIG. 5 is a flowchart showing detailed processing in the subroutine for the upstream protocol or downstream protocol.

  When the process proceeds to an uplink protocol or downlink protocol subroutine, the wireless terminal 100 determines whether or not real-time characteristics are required for a transmission event that occurs at the transmission source or relay source of the wireless terminal 100 (step S200).

  In the example of FIG. 5, a case where the UDP type communication (best effort type communication) is handled as requiring real-time performance is shown. For example, priority control is performed in a wireless LAN, and queues for transmission are divided into high and low priority queues in access category mapping (assignment). This mapping may be used to determine whether or not to perform retransmission control for each queue. The relay packet may be sorted according to whether it is a UDP packet (best effort communication) or whether it depends on an access category mapping queue.

  If the real-time property is not required, the wireless terminal 100 performs TCP communication, non-retransmission control type best effort communication, and the like, although details are omitted (step S209).

  If it is determined that the real-time property is high, the wireless terminal 100 confirms that the packet needs to be transmitted (step S201), performs the packet transmission process (step S202), and then stores the transmitted packet information in the buffer. Temporarily save (step S203). For example, if a packet that is received and intended to be relayed is a packet that the terminal does not need to relay (for example, a packet transmitted by the previous or next node), or the terminal is a destination packet. It is determined that packet transmission is unnecessary.

  After the packet is transmitted, the wireless terminal 100 monitors whether the packet transmitted from the wireless terminal of the next hop has been transmitted before the timeout time t_out set for the wireless terminal of the next hop has been exceeded ( Steps S204 and S205). 2 and 3, if the wireless terminal is the wireless terminal 100-2, the wireless terminal 100-2 is connected to the next-hop wireless terminal 100-3. 4, whether or not the packet is transmitted within the time-out time t_out set from the time of transmission by itself is monitored. The built-in timer performs the time measurement. For example, the time from when the wireless terminal 100-1 transmits a packet until the wireless terminal 100-2 receives the packet and when the wireless terminal 100-2 transmits the relay packet to the wireless terminal 100-3 is denoted by Δt. Then, the timeout time t_out is set to a time longer than this time Δt.

  When the time counts out, the wireless terminal 100 transmits the packet temporarily stored in the buffer again (step S206), and then whether or not the number of transmissions reaches a preset maximum number by this packet transmission. Is determined (step S207). Although not clearly shown in FIG. 5, there is provided a transmission number counter (which may be a hardware counter or a software counter) that counts up for each transmission.

  If the number of transmissions has not reached the preset maximum number, the wireless terminal 100 returns to step S204 described above, and transmits the packet transmitted from the wireless terminal of the next hop from the wireless terminal to the wireless of the next hop. It is monitored whether or not the transmission has occurred before the timeout time t_out set for the terminal is exceeded.

  When it is confirmed that the packet transmitted from the wireless terminal of the next hop has been transmitted before the timeout time t_out set for the wireless terminal of the next hop has been exceeded (Yes in step S204), the number of transmissions is When the preset maximum number of times is reached (Yes in step S207), the wireless terminal 100 deletes the packet information temporarily stored in the buffer (step S208), and then returns to the main routine.

  In the example of FIG. 5, a case has been shown in which it is determined whether or not the UDP counter communication (best effort communication) or whether or not to perform the above-described retransmission control according to the priority of the transmission queue. Instead, it may be determined whether to perform retransmission control according to the reception power intensity in the reverse direction. For example, when the wireless terminal 100-1 transmits to the wireless terminal 100-2 using the uplink protocol, the received power intensity when the wireless terminal 100-1 transmits the downlink protocol from the wireless terminal 100-2 to the wireless terminal 100-1 The wireless terminal 100-1 performs retransmission control when the received power strength of the downlink protocol is close to the reception sensitivity (lower limit value that is regarded as reception), and the received power strength is sufficiently high. In this case, it may be determined that retransmission control is not performed. Specifically, if the reception sensitivity is −95 dBm, retransmission control may not be performed if the received power is −80 dBm or higher, and retransmission control may be performed if the received power is lower than −80 dBm. The numerical values described here are specific examples, and are not limited to the above numerical values.

  FIG. 6 is a diagram for explaining the influence of the selection of the timeout time Δt for starting retransmission on the required transmission time.

  FIG. 6A corresponds to the flowchart of FIG. 5, and the timeout time Δt1 described in FIG. 6 is equal to the timeout time t_out used in the description of FIG.

  Although the packet was transmitted from the wireless terminal 100-1, but did not reach the wireless terminal 100-2, it is transmitted again after the timeout time Δt1. In the example of FIG. 6A, the second time is in the timeout state, and the wireless terminal 100-2 can receive the packet by the third transmission, and transmits the relay packet toward the wireless terminal 100-3. Although the packet transmitted from the wireless terminal 100-2 to the wireless terminal 100-3 is not addressed to the wireless terminal 100-1, it can be recognized that the wireless terminal 100-1 has received and transmitted. To stop. Thus, by using the packet transmitted by the next hop wireless terminal instead of Ack, the number of retransmissions can be autonomously changed from moment to moment according to the communication quality between the respective wireless terminals. The timeout Δt1 is longer than the time until the wireless terminal 100-2 performs packet transmission while performing carrier sense. That is, the retransmission timing scheme shown in FIG. 6A is a scheme for determining whether or not to retransmit while confirming whether or not the next-hop wireless terminal transmits.

  On the other hand, the method shown in FIG. 6B is a modified embodiment of the first embodiment, in which retransmission is performed after a timeout Δt2 shorter than the timeout Δt1, and the next hop destination relays sequentially. It does not check whether it has been sent or not. As a result, the end-to-end delay time can be shortened. If the relay packet from the next hop can be received before transmitting the maximum number of retransmissions, the retransmission is stopped. This eliminates the need to transmit the maximum number of retransmissions each time. The method shown in FIG. 6B does not include step S204 in FIG. 5, and monitors whether or not the next hop destination has relayed transmission using a subroutine separate from FIG. The packet information temporarily stored in the buffer is deleted by the processing step corresponding to step S208 provided in a separate subroutine.

  Unlike the first embodiment, assuming that the transmission interval when resending n times for each transmission is Δt3, if the transmission interval Δt3 is not significantly shortened such that Δt2> Δt3, the required transmission time will be It will be long.

(A-3) Effect of First Embodiment According to the first embodiment, a packet from the wireless terminal is detected as a next-hop wireless terminal by detecting whether or not the next-hop wireless terminal has transmitted. It is possible to check whether or not the packet has been received, and improve the communication quality by performing retransmission processing without repeatedly transmitting the packet a predetermined number of times each time it is necessary to transmit the packet. It becomes possible. That is, communication quality can be improved without impairing real-time performance.

  The effects described above will be described by taking the arrangement of wireless terminals as shown in FIG. 2 as an example.

  When the data communication is UDP communication (best effort communication), it is unknown at the transmission source whether or not the destination has been reached. If the path is duplicated in consideration of communication quality, if two-way communication is performed between the wireless terminal 100-1 and the wireless terminal 100-4 and the protocol is divided up and down, four protocols are required. In practice, protocol allocation is difficult. Also, as described in Patent Document 7, if retransmission is always performed a predetermined number of times, each wireless terminal will transmit the maximum number of retransmissions each time. As shown in FIG. 3, when the route from the source terminal to the destination terminal is 3 hops, (a) when there is no retransmission, it is necessary to transmit a total of 3 packets by one-way communication. When transmitting only the number of retransmissions (here, 5) (Patent Document 7), it is necessary to transmit a total of 3 × 5 = 15 packets in one-way communication. (C) As shown in FIG. According to the method of the first embodiment, a total of 2 + 1 + 3 = 6 packets can be transmitted in one-way communication, and deterioration of real-time property can be suppressed while deterioration of communication quality due to retransmission is suppressed.

(B) Arrangement of Features of First Embodiment and Modified Embodiment As described above, it is determined whether or not the next hop destination has transmitted using different protocols for uplink and downlink of the route, and retransmitted. By performing the control, it is possible to suppress the deterioration of the uplink / downlink communication quality without impairing the real-time property in the reverse direction. The retransmission control method according to the first embodiment will be described in an organized manner with reference to FIG.

  FIG. 7A shows whether or not to perform retransmission control depending on whether or not the best-effort type, whether the priority control is high or low, and whether or not the reception power strength of the protocol in the reverse direction is higher or lower than the reception sensitivity. It is a summary. Each method is as described in the operation section described above. A specific example of retransmission control is shown in FIG. 3 as described above.

  From these facts, the features of the retransmission control method according to the first embodiment can be summarized as shown in FIG. Since uplink and downlink are divided by multi-protocol, even if traffic increases due to retransmission, no interference occurs in the reverse direction, and the communication quality in the reverse direction is not affected (No. 1). Also, by using different protocols for uplink and downlink, each wireless terminal can perform retransmission control independently for uplink and downlink in an autonomous distributed manner (No. 2). By making the multi-protocol in the uplink and downlink, it is not necessary to operate the same application at the same time, and it is possible to cope with different applications in the uplink and downlink, that is, different retransmission control (No. 3). . Further, it is not necessary to have the same transmission rate and the same modulation scheme in uplink and downlink (No. 4).

  When performing retransmission control, it is not necessary to perform an Ack reply to determine whether to continue or stop retransmission depending on whether or not the next hop destination has performed multi-hop transfer, and packet transmission is substantially one-way communication. (No. 5).

  These are very different from the technology described in Patent Document 8.

(C) Other Embodiments The wireless communication system of the present invention can be used for a vehicle network in which a wireless device is mounted on a vehicle and communication is performed between the vehicles. In general, the present invention can also be applied to autonomous decentralized ad hoc network wireless communication.

100: wireless terminal (wireless communication device),
101 ... Omnidirectional antenna, 101U ... Uplink protocol omnidirectional antenna, 101D ... Downlink protocol omnidirectional antenna,
102 ... PHY (physical) layer transceiver, 102US ... uplink protocol PHY layer transmitter, 102DS ... downlink protocol PHY layer transmitter, 102UDR ... uplink protocol PHY layer receiver,
103 ... MAC (medium access control) layer transmission / reception unit, 103US ... uplink protocol MAC layer transmission unit, 103DS ... downlink protocol MAC layer transmission unit, 103UDR ... uplink and downlink protocol MAC layer reception unit,
104 ... Network control unit, 105A ... Transmission information buffer, 105B ... Reception information buffer, 106 ... Control packet generation unit, 107 ... Multi-hop control unit, 108 ... Peripheral terminal monitoring unit, 109 ... Own terminal information unit,
110: Hub (HUB).

According to a first aspect of the present invention, there is provided a wireless communication system that performs communication on a route including a first end wireless communication device, one or more relay wireless communication devices, and a second end wireless communication device. And different protocols in the downlink direction, and each of the wireless communication devices performs multi-hop communication with a protocol corresponding to the communication direction, and any one of the end wireless communication devices serving as a transmission source and each of the relay wireless communication devices The apparatus includes a retransmission function unit that attempts to retransmit the same packet multiple times, and a retransmission stop function unit that stops retransmission when the next-hop wireless communication apparatus further receives a packet transmitted to the wireless communication apparatus of the next hop. end wireless communication device of any of the destination, upon receiving a packet addressed to itself, and transmits a response to the effect that has received the packet

According to a second aspect of the present invention, there is provided the wireless communication system according to any one of the elements of a wireless communication system that performs communication via a route including the first end wireless communication device, the one or more relay wireless communication devices, and the second end wireless communication device. In the wireless communication device to which the device corresponds, the wireless communication system applies different protocols to the route in the uplink direction and the downlink direction, and performs protocol selection to execute multi-hop communication with a protocol according to the communication direction A functional unit , a retransmission functional unit that tries to retransmit the same packet a plurality of times, and a retransmission stop functional unit that stops retransmission when the next-hop wireless communication device further receives a packet transmitted to the wireless communication device of the next hop. If the packet is addressed to one of the end wireless communication devices as the transmission destination, and if a packet addressed to itself is received, a response indicating that the packet has been received. And transmitting a.

According to a third aspect of the present invention, there is provided a wireless communication method for performing communication on a route including a first end wireless communication device, one or more relay wireless communication devices, and a second end wireless communication device. and apply different protocols downlink, each wireless communication device is a multi-hop communication process a row of Umono a protocol corresponding to the communication direction, either end the wireless communication device and each of which is a source The relay wireless communication device tries to retransmit the same packet multiple times, and when the next-hop wireless communication device further receives a packet transmitted to the next wireless communication device, the relay wireless communication device stops the retransmission and either becomes the transmission destination. When the end wireless communication apparatus receives a packet addressed to itself, the end wireless communication apparatus transmits a response indicating that the packet has been received .

A wireless communication program according to a fourth aspect of the present invention is any one of elements of a wireless communication system that performs communication via a route including a first end wireless communication device, one or more relay wireless communication devices, and a second end wireless communication device. The computer mounted in the wireless communication device to which the wireless communication device corresponds corresponds to a protocol corresponding to a communication direction in which different protocols are assigned to the route in the uplink direction and the downlink direction. A protocol selection function unit , a retransmission function unit that attempts to retransmit the same packet multiple times, and a retransmission stop function unit that stops retransmission when a packet transmitted by the next-hop wireless communication device to a further wireless communication device is received. If the packet is addressed to one of the end wireless communication devices that is the transmission destination, if the packet addressed to itself is received, the packet is received. Characterized in that to function as a reception response transmission function unit which transmitted a response to the effect.

In FIG. 2, a wireless communication system 10 is configured by a plurality of wireless terminals 100-1 to 100-4 (four are shown in FIG. 2).

Assume that the wireless terminal 100-1 transmits a packet of the wireless terminal 100-4 to the wireless terminal 100-2. In FIG. 3, P (x → y) _z is a packet for direct transmission / reception between the wireless terminal 100-x and the wireless terminal 100-y, and indicates that the number of transmissions is the zth. In the example of FIG. 3, the first transmission from the radio terminal 100-1 to the wireless terminal 100-2, wireless terminal 100-2 can not receive the packet, the radio terminal 100-1 is waiting the provisions Time Since the packet from the wireless terminal 100-2 to the wireless terminal 100-3 could not be received, the second packet transmission is performed (P (1 → 2) _2). After the wireless terminal 100-1 transmits the packet twice, the wireless terminal 100-2 can receive the packet and transmits the relay packet toward the wireless terminal 100-3 (P (2 → 3) _1). . When the wireless terminal 100-1 receives this packet, the subsequent packet is not retransmitted. Therefore, the wireless terminal 100-1 can view the relay packet from the wireless terminal 100-2 to the wireless terminal 100-3 as Ack, and the maximum number of retransmissions (n1) that is predetermined in advance by intercepting the relay packet. Never send a packet of minutes.

For these reasons, the features of the retransmission control method according to the first embodiment, can be summarized as in Figure 7 (b). Since uplink and downlink are divided by multi-protocol, even if traffic increases due to retransmission, no interference occurs in the reverse direction, and the communication quality in the reverse direction is not affected (No. 1). Also, by using different protocols for uplink and downlink, each wireless terminal can perform retransmission control independently for uplink and downlink in an autonomous distributed manner (No. 2). By making the multi-protocol in the uplink and downlink, it is not necessary to operate the same application at the same time, and it is possible to cope with different applications in the uplink and downlink, that is, different retransmission control (No. 3). . Further, it is not necessary to have the same transmission rate and the same modulation scheme in uplink and downlink (No. 4).

Claims (12)

In a wireless communication system that communicates via a path including a first end wireless communication device, one or more relay wireless communication devices, and a second end wireless communication device,
A wireless communication system, wherein different protocols are applied to the route in the uplink direction and the downlink direction, and each of the wireless communication devices performs multi-hop communication with a protocol corresponding to the communication direction.   Any one of the end wireless communication apparatuses and each relay wireless communication apparatus that are the transmission source transmits a retransmission function unit that tries to retransmit the same packet multiple times, and a wireless communication apparatus of the next hop further transmits to the wireless communication apparatus ahead The wireless communication system according to claim 1, further comprising: a retransmission stop function unit that stops retransmission when a received packet is received.   The retransmission function unit confirms whether or not the next-hop wireless communication apparatus has further transmitted to the next wireless communication apparatus within a specified time, and retransmits the packet on condition that a predetermined time has elapsed. The wireless communication system according to claim 2.   The retransmission function unit retransmits a packet on the condition that a predetermined time has elapsed without confirming whether or not the next-hop wireless communication device has transmitted to the next wireless communication device within a specified time. The wireless communication system according to claim 2. A wireless communication device to which any one of the wireless communication devices that are elements of a wireless communication system that communicates via a path including the first end wireless communication device, the one or more relay wireless communication devices, and the second end wireless communication device In
The wireless communication system applies different protocols to the route in the upstream and downstream directions,
A wireless communication apparatus comprising a protocol selection function unit that executes multi-hop communication with a protocol according to a communication direction. A retransmission function unit that attempts to retransmit the same packet multiple times;
The wireless communication device according to claim 5, further comprising: a retransmission stop function unit that stops retransmission when the next-hop wireless communication device further receives a packet transmitted to a wireless communication device ahead of the next-hop wireless communication device.   The retransmission function unit confirms whether or not the next-hop wireless communication apparatus has further transmitted to the next wireless communication apparatus within a specified time, and retransmits the packet on condition that a predetermined time has elapsed. The wireless communication apparatus according to claim 6.   The retransmission function unit retransmits a packet on the condition that a predetermined time has elapsed without confirming whether or not the next-hop wireless communication device has transmitted to the next wireless communication device within a specified time. The wireless communication apparatus according to claim 6. In a wireless communication method for communicating via a path including a first end wireless communication device, one or more relay wireless communication devices, and a second end wireless communication device,
A wireless communication method, wherein different protocols are applied to the route in the uplink direction and the downlink direction, and each of the wireless communication devices performs multihop communication processing with a protocol corresponding to the communication direction.   Any of the end wireless communication devices and the relay wireless communication devices that are the transmission sources try to retransmit the same packet a plurality of times, and the packets transmitted by the next-hop wireless communication device to further wireless communication devices The wireless communication method according to claim 9, wherein retransmission is stopped upon reception. A wireless communication device to which any one of the wireless communication devices that are elements of a wireless communication system that communicates via a path including the first end wireless communication device, the one or more relay wireless communication devices, and the second end wireless communication device The computer installed in
A wireless communication program that functions as a protocol selection function unit that executes multi-hop communication with a protocol corresponding to a communication direction to which different protocols are assigned in the uplink direction and the downlink direction for the route. The above computer
A retransmission function unit that attempts to retransmit the same packet multiple times;
12. The wireless communication program according to claim 11, wherein when the next-hop wireless communication device receives a packet transmitted to a wireless communication device further ahead, the wireless communication device is caused to function as a retransmission stop function unit that stops retransmission.

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