JP6519217B2 - Wireless communication apparatus, wireless communication method and wireless communication system - Google Patents

Description

  The present invention relates to a wireless communication device, a wireless communication method, and a wireless communication system, and can be applied to, for example, a wireless device and a system mounted on a vehicle forming an ad hoc network.

  Conventionally, there is inter-vehicle communication in which, for example, vehicle radios mounted on vehicles temporarily form an ad hoc network, and multihop relays information between the vehicle radios. Although the ad hoc network configuration may change from time to time due to the mobility of the vehicle, improvement of communication quality of multi-hop relay between vehicle radios is required even in such an environment.

  The technique described in Patent Document 1 solves the problem that there is a branch in the relay route of wireless multi-hop relay, and if periodic intermittent transmission is applied, frame relaying is delayed at the branch point and the relay efficiency is reduced. is there. The technology described in Patent Document 1 is a multi-hop with a branch point, (1) a radio channel reservation step of temporarily stopping transmission of a part of peripheral nodes, (2) reserved by the radio channel reservation step A period setting step of setting a transmission cycle when the start point node intermittently transmits a transmission frame on the wireless channel, (3) A transmission of the start point node on the reserved wireless channel in the transmission cycle set in the period setting step A method is described for relay forwarding using a frame relay step of intermittently transmitting frames.

  According to Patent Document 2, in a multihop communication network in which a plurality of communication terminal devices having data to be collected sequentially repeat data transfer, the communication terminal device does not transmit or relay for each packet, but a start point node The method of dividing the route from the node to the end node into several clusters and collectively transmitting the clusters is described.

  According to Patent Document 3, any one of a plurality of terminals constituting a wireless LAN is a transmission node of a traffic transmission source, a transmission destination terminal of traffic is a reception node, and a plurality of other terminals or base stations are transmission nodes to a reception node. The present invention relates to a multi-hop wireless LAN system that transmits traffic as a relay base station node that relays traffic to the network. In the technology described in Patent Document 3, a plurality of MAC transfer paths are set, and branch relay base station nodes that distribute traffic from transmitting nodes to different multi-hop wireless paths, and traffic from different wireless paths are bundled in the MAC layer A technique is described which comprises combining and relay base station nodes that are thereby regenerated and transmitted to receiving nodes.

  Patent Document 4 describes a method of performing relaying by using a repeater function when relaying, and further removing interference when transferring a received signal.

  Patent Document 5 describes a method of performing congestion notification and cancellation processing between a station-side communication device and a subscriber-side communication device. In this method, the determination as to whether or not congestion occurs is made based on whether or not the buffer is empty.

  Patent Document 6 describes a method in which, in data communication between a parent station and a node, the parent station centrally manages the transmission right of each node using polling to perform relay processing.

  Patent Document 7 describes a method of selecting a parent device and a method of selecting a parent device in a star-connected ad hoc wireless network.

  Patent Document 8 describes, in a communication method between an information center and a ship, a method for enabling an information center to obtain and monitor the position of a mobile station and to increase the radio wave utilization factor.

  Patent Document 9 describes a method of performing distributed processing by providing a blockade avoiding function in a network of interconnected networks for parallel processing.

JP, 2006-319787, A JP 2006-295813 A JP, 2006-229328, A JP 2007-180597 A JP 2000-69163 A JP 2004-158965 A JP, 2008-113354, A JP, 2008-131520, A JP-A-8-147250

Masahiro Morikura, Shuji Kubota ed., "Revised version 802.11 high-speed wireless LAN textbook", Impress, 2005

  However, in multi-hop communication between vehicle radios, it is required to reduce deterioration in communication quality due to hidden terminals.

  FIG. 2 is an explanatory view for explaining the problem to be solved by the present invention. In FIG. 2A, for example, in a service area of about 2 km 2, a vehicle wireless device (represented as “vehicle” in FIG. 2) mounted on a mobile vehicle is a temporary ad hoc network. It shows how it is being formed. In FIG. 2 (A), vehicles 1, 3, 5, 7, 9 are vehicle radios serving as transmission sources or destinations, and vehicles other than vehicles 1, 3, 5, 7, 9 use multi-protocol. It is a vehicle radio that performs multi-hop relay. Communication from the vehicle 1 to the vehicles 3, 5, 7, 9 is "down", and communication in the reverse direction is "up".

  FIG. 2 (B) shows downlink throughput characteristics, and FIG. 2 (C) shows uplink throughput characteristics. In the case of downlink, there is little degradation due to the influence of hidden terminals, and the throughput characteristics are stable. On the other hand, in the case of uplink, the influence of the hidden terminal is large, small fluctuations in throughput are observed, and the throughput temporarily drops. In the case of downlink, the source traffic is large and the destination traffic volume is small. On the other hand, in the case of uplink, traffic is small at the source and traffic is large at the destination. Further, in random access control, as shown in FIG. 3, communication deterioration is reduced by using, for example, an RTS (Request To Send) / CTS (Clear To Send) function (Non-Patent Document 1).

  As described above, in a temporarily formed ad hoc network, at a branch point where the relay route of multi-hop communication branches off, there is a possibility that frame relay delay or relay efficiency may be reduced, and the communication quality by the hidden terminal may be degraded. Things can happen.

  The technique described in Patent Document 1 solves the problem that there is a branch in the relay route of wireless multi-hop relay, and if periodic intermittent transmission is applied, frame relaying is delayed at the branch point and the relay efficiency is reduced. is there. However, according to the technology described in Patent Document 1, the start point node transmits Beacon to the end point node, and the end point node returns Ack to the start point node. Also, when using Beacon or Ack, the channel capacity is used accordingly. In addition, when multi-hop is applied, the throughput is reduced to 1 / n (n is the number of hops). Therefore, if the technology described in Patent Document 1 is applied as it is, the vehicle radio device located at the branch point of the multi-hop relay route becomes a bottleneck.

  As in the technology described in Patent Document 2, it is possible to reduce overhead such as a MAC header by transmitting each cluster. However, when applying real-time characteristics such as voice to applications that require the multi-hop end-to-end packet delay time, it is also necessary to consider the delay time due to clustering in Patent Document 2. The audio information differs depending on the system of the codec, but it is necessary to transmit and receive about 10 to 100 bytes of information within 20 to 100 msec, for example. Therefore, for example, in the network topology as shown in FIG. 2, if the vehicle intervals (vehicle radio equipment intervals) are spaced apart by about several hundred meters, only the vehicle radio equipment of the next hop destination is in the communication range, and clustering and clustering The effect of delivery is thin, but rather, the degradation of communication quality due to delay is greater.

  The technology described in Patent Document 3 can not be applied as it is because the relay base station is essential, and since there is no redundant path in a star topology in which a single path is connected.

  Although the technology described in Patent Document 4 performs relay transfer of a received signal by removing radio interference, the technology described in Patent Document 4 can not be applied because it relates to signal processing of a physical layer (PHY layer). .

  In the technology described in Patent Document 5, the distinction between the station-side communication device (child station side) and the subscriber-side communication device (master station side) is determined in advance and does not have a multi-hop function, so It can not be applied. Also, since the network topology formed by the mobile radio of the mobile vehicle is not always fixed, the technology described in Patent Document 5 can not be applied as it is.

  Although the technique described in Patent Document 6 describes a method using polling, it can not be applied as it is because the parent station and the node are predetermined.

  The technology described in Patent Document 7 switches the master station according to the remaining battery time, and can not solve the stagnation of frame relay at the branch point of the relay path of multihop communication and the reduction in relay efficiency.

  The technology described in Patent Document 8 is a communication method between an information center and a ship, that the wireless terminal is always in a fixed state, only communication between a master station and a slave station, and has no multihop function. Therefore, it can not be applied as it is.

  Therefore, there is a need for a wireless communication device, a wireless communication method, and a wireless communication system capable of reducing deterioration of communication quality due to the influence of a hidden terminal when performing multi-hop communication between wireless devices configuring an ad hoc network. There is.

In order to solve such a problem, a wireless communication apparatus according to a first aspect of the present invention is a wireless communication apparatus that configures an ad hoc network and performs multi-hop communication with another wireless communication apparatus, in the ad hoc network. a route search processing means for performing a route search processing, on the basis of the route search processing unit route search results throughput decreased cause of determination results determined using by, from the autonomous distributed communication, located branch point of a plurality of paths And control means for performing transmission processing by switching to centralized management type communication in which the wireless communication device serving as the master station is the master station, and the control means is a master station serving as the transmission source or destination of the own device. With reference to the accumulated amount holding unit for holding the accumulated amount of data to be transmitted acquired from the source slave station and the accumulated amount holding unit, the transmission timing to the slave station having a large accumulated amount A higher priority grayed, and having a transmission timing controller for transmitting a downlink signal in each path according to their priorities.

A wireless communication method according to a second aspect of the present invention is a wireless communication method for forming an ad hoc network and performing multi-hop communication with another wireless communication device, wherein the route search processing means determines the route in the ad hoc network. It performs processing, control means, based on the route search processing unit route search results throughput decreased cause of determination results determined using by-free lines from the autonomous distributed communication, you located at the branch point of the plurality of paths There line transmission processing is switched to the centralized communication to the communication device with the master station, the control means, from the slave station device itself when the master station to the source or destination, to the destination or source of each path The acquired accumulated amount of data to be transmitted is held in the accumulated amount holding unit, and the priority of transmission timing to a slave station with a large accumulated amount is increased with reference to the accumulated amount holding unit, and the priority order is set. And transmitting a downlink signal in each path according to.

A wireless communication system according to a third aspect of the present invention is a wireless communication system for forming an ad hoc network and performing multi-hop communication with a plurality of wireless communication devices, wherein the plurality of wireless communication devices are paths in the ad hoc network. a route search processing means for performing a search process, on the basis of the route search processing unit route search results throughput decreased cause of determination results determined using by, from the autonomous distributed communication, you located at the branch point of the plurality of paths the radio communications apparatus and a control means for performing transmission processing by switching to a centralized communication to the master station, a wireless communication device determines that the master station device itself as a source or destination, the destination or the route The accumulated amount of data to be transmitted, acquired from the slave station serving as the transmission source, is held in the accumulated amount holding unit, and transmission to the slave station with a large accumulated amount is performed with reference to the accumulated amount holding unit. A higher priority timing, and transmits the downlink signal to each path according to their priority.

  According to the present invention, when multi-hop communication is performed between radios configuring an ad hoc network, it is possible to reduce the deterioration of communication quality due to the influence of a hidden terminal.

It is a functional block diagram which shows the functional structure of the radio | wireless machine which concerns on 1st Embodiment. It is an explanatory view explaining the subject which the present invention tends to solve. It is explanatory drawing explaining the RTS / CTS function at the time of random access control. It is a block diagram which shows the hardware constitutions of the radio | wireless machine which concerns on 1st Embodiment. It is an explanatory view explaining the change timing of the communication method concerning a 1st embodiment. FIG. 7 is an explanatory diagram for explaining communication timing in the case of centralized management communication in the first embodiment. It is an explanatory view explaining information required for change concerning a 1st embodiment. It is a flowchart which shows the processing operation in the vehicle radio | wireless machine which concerns on 1st Embodiment. It is an explanatory view explaining uplink and downlink asymmetric communication concerning a 2nd embodiment. It is a flowchart which shows a processing operation when a master station transmits a packet to each path | route by centralized management communication which concerns on 2nd Embodiment. It is explanatory drawing explaining the method to which the master station which concerns on 2nd Embodiment judges uplink and downlink asymmetric communication. It is a figure which shows the network topology of the communication system which concerns on 3rd Embodiment (the 1). It is a figure which shows the network topology of the communication system concerning 3rd Embodiment (the 2). It is a flowchart which shows the process of the transmission source terminal at the time of the autonomous distributed communication which concerns on 4th Embodiment, and a receiving side terminal.

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

  In the first embodiment, a case where the present invention is applied to a wireless communication apparatus that is mounted on a mobile vehicle and that employs multi-hop communication will be exemplified.

(A-1) Configuration of First Embodiment (A-1-1) Overall Configuration of Network Communication System The basic configuration of a network communication system (network) according to the first embodiment is the same as that of the prior art. Since it can be configured, it will be described with reference to FIG.

  In FIG. 2A, the network communication system 10 according to the first embodiment performs multi-hop communication between vehicle radios mounted on a plurality of vehicles. The information communicated by the vehicle wireless device may include, for example, various contents such as an audio signal, image information, moving image information, data and the like. In the following description and drawings, for convenience of explanation, a vehicle radio device mounted on a vehicle will be referred to as a vehicle.

  The topology of the network can be changed as appropriate according to the mobility of the vehicle. In FIG. 2A, for example, in the service area of about 2 km square, the ad hoc formed temporarily between the vehicle radios It shows the configuration of the network. In addition, the distance between the vehicle radios is assumed to be about several hundred meters. In FIG. 2 (A), the vehicles 1, 3, 5, 7, 9 are vehicle radios serving as the transmission source or destination, and the vehicles 2, 4, 6, 8 perform multi-hop relay using multiprotocol. It is a vehicle radio that performs.

  In FIG. 2 (A), the vehicle 1 is located at a position (branch point) at which the relay route of the multihop communication branches off. That is, it is assumed that the vehicle wireless device of the vehicle 1 is at a position where relay transfer is performed with the adjacent vehicle wireless devices on each route of the plurality of branched relay routes.

  Further, in FIG. 2A, each of the vehicles 1 to 9 has a multi-protocol function of performing multi-hop communication in the uplink direction and the downlink direction using a plurality of protocols. As described above, by using different protocols in the upstream direction and in the downstream direction, it is possible to reduce the degradation of communication quality in bi-directional multi-hop communication.

  Here, various types of protocols can be widely applied to the two types of protocols, and, for example, 700 MHz band wireless communication and 5.8 GHz band wireless communication being considered in inter-vehicle communication are assumed. Further, for example, different channels that do not interfere with each other may be allocated to uplink and downlink in the IEEE 802.11 based Wi-Fi wireless device. Furthermore, any wireless communication protocol that does not cause interference with each other may be used. In addition, although each vehicle 1-9 illustrates the case where two types of protocols are used in this embodiment, the number of the protocol to be used is not limited to this.

(A-1-2) Internal Configuration of Wireless Device FIG. 4 is a configuration diagram showing a hardware configuration of the wireless device according to the first embodiment. FIG. 4 shows the hardware configuration and relationship between two radios 100 and 200 that communicate with each other.

  FIG. 1 is a functional block diagram showing a functional configuration of the wireless device 100 according to the first embodiment. FIG. 1 shows the functional configuration of the wireless device 100 as a representative of the wireless device, and shows the correspondence between the hardware shown in FIG. 4 and the functions of the wireless device 100.

  Since each of the wireless device 100 and the wireless device 200 has the same or corresponding hardware configuration and functions, the configuration of the wireless device 100 will be representatively described below.

  In FIG. 4, the wireless device 100 includes a protocol 1 omnidirectional antenna unit 101A, a protocol 2 omnidirectional antenna unit 101B, a protocol 1 wireless unit 102A, a protocol 2 wireless unit 102B, an L3 switch (layer 3 switch) 103, and a network control unit. And 104 has a GPS device 105.

  In FIG. 1, the wireless device 100 includes a protocol 1 omnidirectional antenna unit 101A, a protocol 2 omnidirectional antenna unit 101B, a protocol 1_PHY_Tx 121, a protocol 1 transmitter 122, a protocol 1 and 2 _PHY_Rx 123, a protocol 1 and 2 receiver 124, and a protocol. 2_PHY_Tx 125, protocol 2_PHY_Tx 126, L3 Switch 103, network control unit 104, GPS device 105, and upper layer 130.

  Protocol 1_PHY_Tx 121, protocol 1 transmission unit 122, protocol 1 and 2_PHY_Rx 123, protocol 1 and 2 reception unit 124, protocol 2_PHY_Tx 125 and protocol 2_PHY_Tx 126 are processes in protocol 1 radio unit 102A and radio unit 102B.

  The protocol 1 omnidirectional antenna unit 101A captures an incoming radio wave, and supplies an electrical signal converted according to one of the two types of protocols (protocol 1) to the protocol 1 wireless unit 102A.

  The protocol 2 omnidirectional antenna unit 101B captures an incoming radio wave, and provides the protocol 1 wireless unit 102A with an electrical signal converted according to the other protocol (protocol 2) of the two types of protocols.

  The protocol 1 wireless unit 102A analyzes the signal from the protocol 1 omnidirectional antenna unit 101A, and performs reception processing such as packet reception or packet decomposition and analysis. Also, the protocol 1 wireless unit 102A assembles a packet including transmission information (transmission data) from the L3 switch 103 and performs transmission processing of the transmission packet.

  The protocol 2 wireless unit 102B analyzes the signal from the protocol 2 omnidirectional antenna unit 101B, and performs reception processing such as packet reception or packet decomposition and analysis. Also, the protocol 2 wireless unit 102 B assembles a packet including transmission information (transmission data) from the L3 switch 103 and performs transmission processing of the transmission packet.

  As described above, the wireless device 100 performs uplink and downlink multihop communication in a multiprotocol. Therefore, the wireless device 100 includes an omnidirectional antenna unit and a wireless unit according to each of the protocols 1 and 2 in order to perform transmission / reception processing according to two types of protocols. When three or more protocols are used, an antenna unit and a radio unit may be provided according to the number of protocols.

  The L3 Switch 103 is provided between the network control unit 104 and the protocol 1 wireless unit 102A and the protocol 2 wireless unit 102B, and is between the network control unit 104 and the protocol 1 wireless unit 102A and the protocol 2 wireless unit 102B. Data exchange is performed via the L3 switch 103.

  The GPS device 105 acquires position information from GPS satellites in order to recognize position information of the own terminal, and provides the network control unit 104 with position information of the own terminal.

  The upper layer 130 performs predetermined application processing based on the information acquired from the network control unit 104. The upper layer 130 provides the network control unit 104 with information to be transmitted to other vehicle radios.

  The network control unit 104 controls inter-vehicle communication employing multi-hop communication. As shown in FIG. 1, the network control unit 104 includes a control unit 111, a reception information IF unit 112, an own terminal information unit 113, a data temporary buffer 114, and a transmission information IF unit 115.

  The reception information IF unit 112 provides the control unit 111 with the reception information received via the L3 switch 103. Further, the reception information IF unit 111 provides the transmission information IF unit 115 with reception information to be transferred to another wireless device, and gives reception information to the upper layer 130 as needed.

  The transmission information IF unit 115 receives the control of the control unit 111 and gives the L3 switch 103 transmission information to be transmitted by another wireless device.

  The own terminal information unit 113 acquires position information (GPS information) of the own terminal acquired by the GPS device 105, transmits the position information of the own terminal to the control unit 111, and transmits information for including the position information. It is given to the IF unit 115.

  The data temporary buffer 114 temporarily holds data to be transmitted from the upper layer 130. The control unit 111 manages the amount of data held in the data temporary buffer 114. In this embodiment, although the case where the data temporary buffer 114 is provided in the network control unit 104 is shown, it may be provided as an intermediate layer between the network control unit 104 and the upper layer 130.

  The control unit 111 is a processing unit that controls the network of the wireless device 100, and functionally includes a peripheral terminal monitoring unit, a routing table change / update unit, a multiprotocol selection unit, a multihop control unit, and a transmission timing control unit. .

  The peripheral terminal monitoring unit monitors the other radios by obtaining the number of other radios, address information, and the like based on the information including the position information acquired from the other radios located around the own terminal. Do.

  The routing table change / update unit confirms the status of the peripheral terminal by the peripheral terminal monitoring unit, performs routing processing according to a predetermined routing protocol, and creates or updates the routing table. Therefore, all received packets from other wireless devices are supplied to the control unit 111 of the network control unit 104. Such a configuration makes it possible to cope with the use of a plurality of protocols. Here, the routing protocol is not particularly limited, and various protocols can be widely applied. For example, as a routing protocol, AODV (Ad hoc On-Demand Distance Vector), OLSR (Optimized Link State Routing), DYMO (Dynamic MANET On-demand), DSR (Dynamic Source Routing), etc. can be applied.

  The multi-protocol selection unit refers to the routing table generated by the routing table change / update unit to determine whether the information transfer destination is in the uplink or downlink direction in the network topology, and the judgment result is Select the protocol to use accordingly.

  The multi-hop control unit controls multi-hop communication with reference to the routing table created by the routing table change / update unit.

  The transmission timing control unit performs communication control by switching to either autonomous distributed communication or centrally managed communication according to the position of the own terminal on the communication path with reference to the routing table. Also, when the own terminal functions as a parent station to perform centralized management communication, the transmission timing control unit controls transmission timing to the downstream for each route, thereby transmitting uplink information from each route. Control the timing.

  The transmission timing control unit checks the position of the own terminal on the communication path of the multihop communication with reference to the routing table in order to determine whether it functions as the parent station or the other vehicle radio. That is, the transmission timing control unit determines whether the own terminal belongs to any one of the master station, the end terminal, and the relay terminal. Here, the master station is a vehicle wireless device in which the own terminal is located at the position of a branch point at which a communication path of multi-hop communication branches off (position where a plurality of communication paths overlap).

  Further, the transmission timing control unit refers to the routing table and controls the own terminal as a master station if the own terminal is located at the overlapping position of a plurality of communication paths. At this time, when the own terminal is a master station, the transmission timing control unit determines whether the conditions for switching timing between autonomous distributed communication and centralized management communication are satisfied, and the conditions for switching timing are satisfied. When there is a switch, the switching change from the autonomous distributed communication to the centrally managed communication, or the switching change from the centrally managed communication to the autonomous distributed communication is performed.

  FIG. 5 is an explanatory diagram for explaining the switching timing of the communication method according to the first embodiment. FIG. 5 (A) shows an example of switching timing for switching from autonomous distributed communication to centralized management communication, and FIG. 5 (B) shows an example of switching timing for switching from centralized management communication to autonomous distributed communication.

  The transmission timing control unit controls the communication system to be centrally managed communication or autonomous distributed, when the own terminal is a master station and any of the conditions illustrated in FIG. 5 (A) or 5 (B) is satisfied. Switch to type communication.

  Typically, multi-protocol capabilities are used to transmit data to each vehicle radio in autonomous distributed communication. However, for example, when the number of communication routes increases, the load on the vehicles located at the branch point is increased, so that the vehicle at the branch point of the route becomes the master station and is switched to the centralized control type.

  As illustrated in FIG. 5A, (1) when the number of communication paths increases to a predetermined value or more, (2), for example, when the route discovery time is longer than a specified length when used for a routing algorithm of AODV. , (3) When the reception throughput has become less than the predetermined value, (4) When the reception throughput has become less than the specified value, etc., the transmission timing control unit changes from autonomous distributed type to centralized management type. Switch.

  As illustrated in FIG. 5A, (11) when the number of communication paths becomes equal to or less than the predetermined value, (12) when a specified time has elapsed after switching from the autonomous distributed type to the centralized control type, (13) When the reception throughput recovers to a predetermined value or more, (14) when the reception throughput recovers to a predetermined value or more, the transmission timing control unit switches from centralized management communication to autonomous distributed communication.

  The End terminal is a vehicle wireless device that exists at the end (end) of the route and can communicate with only one other vehicle wireless device. The relay terminal is a vehicle wireless device that is present along the route and can communicate with a plurality of other vehicle wireless devices. In this case, the transmission timing control unit performs the communication method according to the instruction of the master station, and for example, transmits transmission data by centralized management communication when there is a request for switching to centralized management communication from the master station; When there is a cancellation request for centrally managed communication from the master station, transmission data is transmitted by autonomous distributed communication.

(A-2) Operation of First Embodiment Next, the processing operation in the network communication system 10 according to the first embodiment will be described in detail with reference to the drawings.

  Here, first, definitions of terms used for processing operations in the network communication system 10 according to the first embodiment will be described.

  "Protocol" is a communication protocol used for each of the uplink and downlink. The downward direction is communication from the vehicle 1 to the vehicles 3, 5, 7, 9. The upward direction is communication from the vehicles 3, 5, 7, 9 to the vehicle 1. Upstream and downstream use different protocols, and in FIG. 2A, the downstream direction is protocol 1 and the upstream direction is protocol 2.

  “Down” is a direction of communication from a vehicle with overlapping routes (ie, a vehicle at a branch point) to an end terminal of the route that can communicate with only one vehicle. For example, in FIG. 2A, the communication from the vehicle 1 to the vehicles 3, 5, 7 and 9 is downward.

  The "up" is in the opposite direction to the down. The end of the route, which is the direction of communication from the End terminal that can communicate with only one vehicle, to the terminal to which the route is connected (ie, the vehicle at the junction).

  The “route 1” is a route of communication (downlink) from the vehicle 1 (transmission source) to the vehicle 3 (destination) and communication (uplink) from the vehicle 3 (transmission source) to the vehicle 1 (destination). At this time, the vehicle 2 is a relay transfer vehicle.

  The “route 2” is a route of communication (downlink) from the vehicle 1 (transmission source) to the vehicle 5 (destination) and communication (uplink) from the vehicle 5 (transmission source) to the vehicle 1 (destination). At this time, the vehicle 4 is a relay transfer vehicle.

  The “route 3” is a route of communication (downlink) from the vehicle 1 (transmission source) to the vehicle 7 (destination) and communication (uplink) from the vehicle 7 (transmission source) to the vehicle 1 (destination). At this time, the vehicle 6 is a relay transfer vehicle.

  The “route 4” is a route of communication (downlink) from the vehicle 1 (transmission source) to the vehicle 9 (destination) and communication (uplink) from the vehicle 9 (transmission source) to the vehicle 1 (destination). At this time, the vehicle 8 is a relay transfer vehicle.

  The “autonomous distributed communication” refers to a communication scheme in which each vehicle autonomously confirms the surrounding communication status and transmits it. For example, as the autonomous distributed communication, a carrier sense multiple access (CSMA) scheme or the like can be applied.

  In "centrally managed communication", the route is overlapping in the downward direction, and the vehicle located at the position corresponding to the route branch point becomes the master station (vehicle 1 in Fig. 2A), and the master station performs communication processing A communication method that transmits while centrally managing After receiving the down information, the vehicles at the End terminal (vehicles 3, 5, 7 and 9 in FIG. 2A) transmit the up information. At this time, different protocols are used for uplink and downlink. By this multi-protocol, it is possible to suppress interference between uplink and downlink. Although an example using a plurality of protocols has been described here, interference may be suppressed by using different channels in the same protocol in uplink and downlink.

  The "End terminal vehicle" is a vehicle radio that exists at the very end (end) of the route and can communicate with only one other vehicle radio.

  The "types of terminals constituting the vehicle network" mean the following. In autonomous distributed communication, a vehicle radio corresponding to a transmission source and a destination is referred to in order not to perform centralized management in a master station. For example, in FIG. 2A, vehicles 1, 3, 5, 7 and 9 are transmission sources and destinations. The remaining vehicles 2, 4, 6 and 8 are vehicle radios that perform multi-hop relay. In the centralized control type communication, a vehicle radio corresponding to the master station is required, and in the star type (vehicle arrangement as shown in FIG. 2A), the vehicle 1 existing at the center of the star type is the master station. Vehicles 3, 5, 7 and 9 are slave stations to the master station. The remaining vehicles 2, 4, 6 and 8 are vehicle radios that perform multi-hop relay as in the autonomous distributed communication.

(A-2-1) Description of Processing Operation of Communication Timing in Centralized Management Communication FIG. 6 is an explanatory diagram for explaining communication timing in the case of centralized management communication in the first embodiment.

  FIG. 6A shows a network topology assumed here, which is the same as the configuration of FIG. Vehicles 1, 3, 5, 7, 9 are vehicle radios of a packet source or destination, and vehicles 2, 4, 6, 8 are relay relays of the packets.

  The vehicle 1 is a master station since it is located at a branch point of the communication route, and the network configuration of FIG. 6A has a star topology centered on the vehicle 1. Further, the vehicle 1 confirms that the conditions of the switching timing illustrated in FIG. 5 are satisfied, and performs packet transmission in a centralized management type.

  FIG. 6B is an explanatory diagram for explaining transmission timing of centralized management communication.

  In FIG. 6 (B), the vehicle 1 which is a parent station transmits packets to the routes 1, 2, 3 and 4 in order using the protocol 1 in the downward direction of each route. At this time, the transmission timing control unit of the vehicle 1 (master station) refers to the routing table, and transmits a packet including the address information of the vehicle radio set as the relay destination and destination of the routes 1, 2, 3 and 4, respectively. Transmit per route in multi-hop. For example, in FIG. 6B, the vehicle 1 uses the protocol 1 in the downward direction of the route 1 using information including the address information (vehicle 2_Tx) of the vehicle 2 and the address information (vehicle 3_Tx) of the vehicle 3 To send. Also, at a predetermined interval time, the vehicle 1 transmits downlink information of the route 2, downlink information of the route 3, and downlink information of the route 4.

  Although FIG. 6 (B) describes the case where the vehicle 1 transmits in order to the routes 1, 2, 3, 4, the transmission order is not particularly limited. For example, the routes 4, 2,. The order of 1 and 3 or the like may be used. In addition, when the transmission time of the downlink information of one route is set as a predetermined time, the vehicle 1 allocates a plurality of continuous transmission times for the same route, such as the routes 1, 1, 2, 3, 2, 4, and so on. May be sent. This is because, for example, the transmission data amount held by the vehicle 3 that is the transmission source of the route 1 holds data exceeding the data amount that can be transmitted in one transmission time, or, for example, When the vehicle 1 holds an amount of data for which the amount of data to be transmitted to a certain vehicle 3 exceeds the amount of data that can be transmitted in one transmission time, the continuous relay time is allocated to the route 1 for rapid relaying. The transfer can be made.

  Vehicles 2, 4, 6, 8 functioning as relay terminals for each route relay and forward packets received from vehicle 1 to vehicles 3, 5, 7, 9 as destinations, and the final destination of each route Send to The downlink throughput characteristic at this time holds a stable value as shown in FIG. 2 (B).

  In the vehicles 3, 5, 7, 9 which are destinations of the respective routes, the transmission timing control unit transmits data in the uplink direction using the protocol 2 in accordance with the timing at which the data in the downlink direction is received. That is, the vehicles 3, 5, 7, 9 hold the transmission information generated from the upper layer in the data temporary buffer 114, and the transmission timing control unit of the vehicles 3, 5, 7, 9 receives the down information. , Transmit the data held in the temporary data buffer 114.

  Here, since different protocols are used in the uplink direction and the downlink direction, for example, the vehicle 1 transmits the information of “route 2 downlink” without waiting for the completion of “route 1 uplink” communication. Is possible.

  In addition, since the vehicles 3, 5, 7, 9 transmit uplink packets after receiving the downlink packets, the timing of downlink packet transmission functions as a sort of polling right. Therefore, it is not necessary for the vehicle 1, which is a master station, to transmit a packet for giving polling rights to vehicles of each destination.

(A-2-2) Switching Process Between Autonomous Distributed Communication and Centrally Managed Communication The master station located at the branch point of the communication path judges whether or not the conditions for switching timing are satisfied. Switching from autonomous distributed communication to centrally managed communication, or switching from centrally managed communication to autonomous distributed communication.

  FIG. 7 is an explanatory view for explaining information necessary for switching according to the first embodiment. FIG. 7A is an explanatory diagram for explaining a packet format including switching information.

  As shown in FIG. 7A, the switching beacon transmitted by the master station to each vehicle includes a PR (preamble) and UW (unique word) portion and a header information portion, as in the general packet format, The switching information is included in the overhead of the header information (the hatched portion in FIG. 7A). In addition, switching information is described in the overhead of header information, and in multi-hop relaying, relay is performed as it is without changing the header information part. Therefore, as shown in FIG. 7A, data packets transmitted by vehicles other than the master station include information having the same content as the header information of the switching beacon. The header information includes, as with normal header information, a transmission source ID, a destination ID, a relay transmission ID, a relay destination ID, a Seq number (sequence number), a type, a time stamp, and the like.

  FIG. 7 (B) is an example of information showing information necessary for switching when the master station transmits, and FIG. 7 (C) is an example of information showing information necessary for switching when the slave station transmits data. It is.

  As shown in FIGS. 7B and 7C, the switching information includes (b1) a parent station identification flag, (b2) a switching request flag, (b3) a communication method flag, and (b4) a transmission start timing flag, (B5) There is information such as the number of continuously transmittable packets, and (b6) buffer accumulation amount.

  (B1) The master station identification flag is a flag for identifying whether the transmission source of the packet is the master station. For example, 1-bit information can be used, and is "1" (see FIG. 7B) in the case of the parent station and "0" in the case of other than the parent station (see FIG. 7C).

  (B2) The switching request flag normally performs autonomous distributed communication. Therefore, the switching request is a switching request from the autonomous distributed type to the centralized management type. For example, 2 bits of information can be used for the switching request flag, "00" at no change, "01" at switching request, "10" at switching cancellation request, and "11" for spare. .

  (B3) The communication method flag is a flag for confirming the communication method currently in use. For example, in the case of centralized management communication (denoted as "centralized" in FIG. 7), it is "01", and in the case of autonomous distributed communication, it is "10".

  (B4) The transmission start timing flag is a flag for recognizing the timing that can be transmitted by the end terminal vehicle in order to transmit a plurality of packets to one route. For example, if the End terminal vehicle receives a packet addressed to itself from the parent station after a predetermined time (for example, several tens of msec to several seconds), this transmission start timing flag is not present. Also, it becomes possible to cope. Since the elapsed time varies depending on the number of paths and the number of multihops, it can be determined by simulation evaluation and examination on the desk.

  (B5) The number of continuously transmittable packets is determined in advance to what extent the number of quantized levels can be several levels. It is possible to transmit one packet for uplink and one packet for one route, and to sequentially change to the next route without the packet.

  For example, level 1 is defined as up to 10, level 2 up to 50, level 3 up to 100, and level 4 up to 500. The numerical values described here are an example. In this embodiment, the number of continuously transmittable packets is exemplified. However, the number of packets is not limited to the number of packets, and may be defined by a transmittable allowable time. Also in this case, since the time is different depending on the packet length and the number of multi-hops, specific numerical values are determined from simulation evaluation and desk study.

  (B6) The buffer accumulation number is information described by the End terminal vehicle, and indicates the buffer accumulation number held in the data temporary buffer 114 of the End terminal vehicle. The parent station preferentially switches paths in descending order of the buffer accumulation amount included in the packet received from the slave station.

(A-2-3) Method of Determining Whether or Not a Parent Station Each vehicle radio refers to the created routing table, and when the own terminal is located at a branch point of a plurality of communication paths, Act as a station. In the case of a star topology, the master station is determined by determining whether it is located at the center of the star topology.

  In some cases, a plurality of vehicle radios may be determined as a master station, but in that case, any one of the vehicle radios functions as a master station. For example, it may be made to function as a master station which transmitted the switching beacon which makes a master station identification flag "1" earlier than other vehicle radios.

(A-2-4) Uplink and Downlink Transmission Method Switching from autonomous distributed communication to centrally managed communication or switched from centrally managed communication to autonomous distributed communication with reference to FIGS. 6 and 7 Hereinafter, the timing of the switching function will be described.

  FIG. 7 shows a packet format in which information necessary for overhead is added to perform the switching function. FIG. 7A shows a packet format.

  First, the communication method in the normal state is determined to be autonomous distributed communication, so that the switching request is a switching request from autonomous distributed communication to centralized management communication, and cancellation of switching request is centralized management. It is possible to recognize that it is a request for switching from communication to autonomous distributed communication.

  The switching request and switching cancellation are transmitted by being included in a short packet length format (switching Beacon) not including the data area.

  In FIG. 6A, since the relay vehicle is included between the vehicle 1 as the master station and each of the vehicles 3, 5, 7, and 9 as the End terminal vehicles, the master station is not a broadcast but a unit vehicle. Send Switch Beacon for each route by cast. By this, it is possible to suppress the packet collision by the hidden terminal at the time of relaying.

  Here, although the case where the parent station transmits switching Beacon on each route by unicast is illustrated, for example, if it is clear that the parent station does not relay based on the routing result (link cost), the parent The station may transmit the switching beacon by broadcast. More specifically, when the control unit 111 determines that there is no relay up to the end terminal vehicle from the link cost such as the number of hops of each route and response time by the routing processing by the control unit 111, switching is performed by broadcast. You may send Beacon.

  In FIG. 6 (A), when the End terminal vehicle receives the switching beacon, the End terminal vehicle stops autonomous packet transmission. The timing at which the End terminal vehicle can transmit is the downstream protocol (or channel), after receiving information addressed to itself, after confirming the surrounding communication situation in the uplink by Carrier Sense (CSMA), the example shown in FIG. 7A. Send data packets.

  For example, in FIG. 6A, in the case where multi-hop packet communication is performed on the downstream communication channel in the order of route 1, 2, 3, 4 from the parent station, the uplink has an End-to-End packet arrival delay time. Communication can be performed in the order of paths 1, 2, 3, and 4 with timing delayed to some extent. By communicating with different protocols (or different channels within the same protocol) for uplink and downlink, communication can be suppressed between uplink and downlink even in a hidden terminal environment while suppressing interference. Become.

  In addition, as described above, the End terminal vehicle becomes a sort of polling right by providing a rule to transmit an uplink packet after receiving a downlink packet, and the master station makes a packet for giving a polling right. There is no need to send.

  When the parent station that is the transmission source or the End terminal vehicle transmits a plurality of packets, the parent station and the End terminal vehicle confirm that the next hop destination has relayed the packet transmitted by itself, and then the next packet Send At this time, although a packet relay-transferred by the next hop destination is not addressed to the own terminal, by intentionally receiving it, it is possible to suppress packet collision at the time of multi-hop relay.

  Specifically, the example of the path 1 in FIG. 6A will be described. For example, the master station (vehicle 1) needs to continuously transmit a plurality of packets 1, 2 and 3 to the end terminal vehicle (vehicle 3), and the vehicle 3 transmits packets 4, 5 and 6 to the vehicle 1 It shall be. In this case, the following downlink processing and uplink processing are performed.

(A) Down process
[Step 1] The vehicle 1 transmits a packet 1 addressed to the vehicle 3.
[Step 2] After the vehicle 1 intercepts that the vehicle 2 has relayed the packet 1 in multihop, the vehicle 1 transmits the next packet 2 to the vehicle 2.
[Step 3] Also for the packet 3, the vehicle 1 transmits the packet 3 in the same manner as Step 1 and Step 2.
[Step 4] The vehicle 1 repeats Step 1 to Step 3 for the next route.
In the above example, the Ack is not returned, but the vehicle 1 may transmit the next packet after receiving the Ack from the vehicle 2 which is the next hop destination. At this time, although Ack is in the reverse direction of packet transmission, it is possible to distinguish between downlink and uplink by using the same protocol as downlink or by using a channel different by the same protocol.

  Although the above is the down process, the up process is as follows.

(B) Upstream processing
[Step 1] The vehicle 3 receives a packet from the vehicle 1 (master station) that is the transmission source. The transmission start timing flag ((b3) in FIG. 7B) in the packet is confirmed, and it can be recognized that transmission is possible.
[Step 2] The vehicle 3 transmits the packet 4 to the vehicle 1.
[Step 3] After the vehicle 3 intercepts that the vehicle 2 has relayed the packet 4 in multi-hop, the vehicle 3 transmits the packet 5 to the vehicle 2.
[Step 4] Also for the packet 6, the vehicle 3 transmits the packet 6 in the same manner as Step 2 and Step 3.
[Step 5] The vehicle 3 is in a standby state.
Although the above shows an example in which Ack is not returned, the next packet may be transmitted after receiving Ack from the next hop destination. At this time, Ack is in the reverse direction of the packet transmission direction, but uses the same protocol as downlink, or uses the same protocol different channel. By doing this, transmission and reception related to data communication in the downlink direction can be separated from protocol 1 and transmission and reception related to data communication in the uplink direction can be separated from protocol 2 and interference between uplink and downlink can be suppressed.

(A-2-5) Switching Timing Process of Autonomous Distributed Communication, Centrally Managed Communication The master station switches from autonomous distributed communication to centralized communication, using the conditions of switching timing illustrated in FIG. Also, it is determined whether to return from centralized communication to autonomous distributed communication.

  Note that only one of the conditions illustrated in FIG. 5 may be set in advance, or a plurality of some or all of the conditions in FIG. 5 may be set in advance. In the latter case, the master station may switch the communication method when any one of the conditions is satisfied.

  FIG. 5A shows an example of the switching timing condition from the autonomous distributed communication to the centralized communication, and FIG. 5B shows an example of the condition of the switching timing from the centralized communication to the autonomous distributed communication.

  As a switching timing trigger from the autonomous distributed communication to the centrally managed communication shown in FIG. 5A, it is changed when the number of paths becomes a predetermined value or more. Specifically, from the autonomous distributed type, the vehicle 1 serving as a master station (see FIG. 6A) always recognizes some of the number of routes based on the routing table. If it becomes a numerical value (for example, about 6) prescribed in advance, it changes from autonomous distributed communication to centralized communication.

  As another method, for example, if AODV is used as a routing protocol, autonomous distributed communication may be changed to centralized communication if route discovery time becomes equal to or longer than a predetermined time. Although the case where the routing protocol is AODV is illustrated, another routing protocol (OLSR, DYMO, DSR, etc.) may be applied, and even in that case, the routing results of various routing protocols may be used. Good.

  Furthermore, as another method, if the End-to-End packet arrival time becomes equal to or more than a predetermined value, it may be changed from an autonomous distributed type to a centrally managed type. End-to-End delay time contains a time stamp (time stamp is the time of transmission) to be embedded in the packet, and the time stamp (transmission time) is compared with the time received on the receiving side, and the time difference is End Calculate to-End packet delay time.

  As another method, when the reception throughput becomes lower than a predetermined value, it may be changed from the autonomous distributed type to the centralized control type. The predetermined values described above are determined from simulation evaluation or desktop design.

  The switching timing trigger from the centrally managed communication to the autonomous distributed communication shown in FIG. 5B can also be switched by a method corresponding to the trigger of the trimming method of FIG. 5A.

(A-3) Process in Vehicle Wireless Device FIG. 8 is a flowchart showing the processing operation in the vehicle wireless device according to the first embodiment.

  Each vehicle constantly acquires position information of its own terminal by the GPS device 105, and transmits a packet including the position information of its own terminal to surrounding vehicles. Also, each vehicle performs routing processing according to a predetermined routing protocol, and constantly creates and updates a routing table.

  Each vehicle refers to the routing table to determine whether its own terminal is a parent station (S101).

  At this time, processing is divided into processing when the own terminal is an End terminal vehicle (S121 to S125), processing when the own terminal is a relay vehicle (S126, S127), and processing (S102 to S117) when the own terminal is a master station .

  For the reason that the number of routes is small, the number of multi-hops is small, the traffic is low, etc., all vehicles are performing transmission / reception processing in an autonomous distributed manner unless they are switched to centralized management.

  In FIG. 8, after a series of processes, the process returns to the process of determining whether each vehicle is a master station (port “A”) or the process of determining whether each vehicle is a master station or not, Processing (ports “B”, “C”, “D”). This is because different vehicles may become parent stations due to changes in topology, and therefore, condition α (detection of topology change in routing protocol) is attached. As this condition α, a routing protocol considered in an ad hoc network (for example, AODV, OLSR, DYMO, DSR, etc.) can be used.

(A-3-1) Processing Flow of End Terminal Vehicle When it is determined that the own terminal is an End terminal vehicle in S101, autonomous distributed communication or centrally managed communication is determined according to the switching beacon from the parent station ( S121).

  In the autonomously distributed communication, the End terminal vehicle performs packet transmission while using the CSMA method to check the communication status of peripheral terminals (S122). Since this CSMA method (access control method) can apply the existing access control method used by wireless LAN etc., it omits detailed explanation here. The End terminal vehicle that has transmitted the packet determines whether the condition α is satisfied, and transits to the state of the port “A” or “B” (S123).

  In addition, when the End terminal vehicle communicates in the autonomous distributed type, when the switching request is received by the switching beacon from the master station, the transmission by the autonomous distributed communication is temporarily stopped. Thereafter, when a downstream communication packet (switching beacon) whose source is the parent station is received, it is determined from the overhead information whether or not the own station can transmit, and it is determined that the own station can transmit. While performing carrier sense using the CSMA method (while confirming the communication status of the peripheral terminal), transmission of data packets is started (S124). The End terminal vehicle that has transmitted the packet determines whether the condition α is satisfied, and transits to the state of the port “A” or “B” (S125).

(A-3-2) Processing flow of relay terminal vehicle In S101, when it is determined that the own terminal is a relay terminal vehicle of multi-hop transfer, the packet is relayed after receiving the packet (switching Beacon) from the master station. If it is necessary to relay, it is relayed to the destination, and if it is not necessary, the received packet is discarded (124). At this time, whether or not to relay the received packet is determined with reference to the routing table.

  The relay processing by the relay terminal vehicle also operates according to the routing protocol, and for example, a method under consideration by a wireless LAN of IEEE 802.11 system or the Internet Engineering Task Force (IETF) Shall follow).

  The relay terminal vehicle that has performed the packet relay judges whether or not the condition α is satisfied, and transits to the state of port “A” or “C” (S127).

(A-3-3) Buffer Accumulation Status Collection of Each Vehicle In S101, when the own terminal is a parent station, the parent station collects the buffer accumulation status held in the data temporary buffer 114 of each vehicle ( S110). Here, the process of collecting the buffer accumulation state in S110 will be described.

  In order for the master station to understand the buffer accumulation status of each End terminal vehicle, the End terminal vehicle always writes information on the buffer accumulation amount of its own station in the overhead and transmits it regardless of the autonomous distributed type or centralized management type. .

  Also, regardless of the autonomous distributed type and centralized management type, the master station holds buffer accumulation amounts from each End terminal vehicle in a buffer accumulation amount table for each End terminal vehicle. When the master station switches to the centralized management type, it refers to the buffer storage amount table and enables data transmission from the End terminal vehicle having a large buffer storage amount with priority. That is, the master station sequentially transmits downlink information from the route of the End terminal vehicle having a large buffer storage amount. As a result, uplink information can be transmitted to the parent station in order from the End terminal vehicle having a large buffer storage amount.

  Further, the master station may periodically refer to the buffer accumulation amount table to adjust the order of switching paths and the allocation time. The time for periodically referring to the buffer accumulation amount table may be, for example, several tens of msec to several tens of seconds. This numerical value may be set to a similar value with reference to parameters related to the routing protocol (e.g., Neighbor Hold Time, Topology Hold Time, Active Route Timeout, Hello Interval, etc.). Alternatively, it may be determined with reference to simulation evaluation and desktop design.

  Note that FIG. 8 exemplifies the case where the master station collects the buffer accumulation amount of each vehicle before switching to the centralized management type. This is because, immediately after the switching of the communication system, the routes are changed equally to all routes and in order so that each End terminal vehicle can transmit equally, and immediately after the switching, buffer storage of End terminal vehicles is performed. It is to monitor the quantity. After the predetermined time has elapsed, the master station may set the priority of the transmission timing in the downlink direction according to the buffer accumulation amount of each vehicle, and change each route according to the priority. Also in this case, the master station periodically refers to the buffer storage amount table to change the priority of transmission timing in the downlink direction.

(A-3-4) Processing Flow of Master Station When the own terminal is a master station in S101, as described above, the situation of the buffer accumulation amount of each vehicle is collected (S110). At this time, the parent station refers to the above-mentioned buffer accumulation amount table and prioritizes the transmission timing in the down direction of each route according to the buffer accumulation amount of each End terminal vehicle.

  Next, the master station determines whether the communication scheme is in use of autonomous distributed communication (S102). If the current communication scheme is autonomous distributed communication, the process proceeds to S103, and if not, the process proceeds to S111.

  In S103, the master station checks whether or not a change to centrally managed communication is necessary using the conditions of the switching timing in FIG. 5A (S103, S109). Then, if the conditions for switching timing in FIG. 5A are not satisfied and there is no need to change to centralized communication, the master station continuously performs autonomous distributed communication to transmit a packet (S104). ). Then, after packet transmission, the master station determines whether the condition α is satisfied, and transitions to the state of the port “A” or “D” (S105).

  On the other hand, if the master station determines in S103 that the conditions for switching timing shown in FIG. 5A are satisfied and it is determined that change to centralized management communication is necessary, the master station determines A Beacon packet including a switching request is transmitted to the End terminal vehicle in order to stop the autonomous distributed communication (S106). At this time, the master station relays all at once under an environment where relay terminal vehicles on each route can become hidden terminals, and does not use broadcast communication but protocol 1 on each route in order to suppress the occurrence of packet collisions. Use unicast communication.

  Thereafter, the parent station refers to the buffer accumulation amount table to increase the priority of the transmission timing to the end terminal vehicle having a large buffer accumulation amount, and transmits the downlink packet to each route according to the priority (S107). As a result, each End terminal vehicle confirms the communication status in the vicinity after transmitting the downlink packet, and transmits the uplink packet.

  Here, the parent station refers to the buffer accumulation amount table to determine whether or not there is a buffer accumulation amount of the destination End terminal vehicle, and if there is a buffer accumulation amount of the End terminal vehicle, the buffer A downstream packet including dummy data of a data length corresponding to the storage amount is transmitted. This is because, when the buffer accumulation amount of the End terminal vehicle is large, the number of upstream packets increases or the upstream packet transmission time becomes long. Then, not only uplink packets from the route but also uplink packets from other routes are simultaneously received by the parent station, and the parent station may become a bottleneck. Therefore, the master station distributes the traffic between the routes by transmitting a downlink packet including dummy data of a data length according to the buffer accumulation amount of the End terminal vehicle.

  Also, after the transmission processing for each path is completed, the parent station checks whether there is a change in topology, and returns to port "A" or "D" (S108).

  In S102, when the current communication method is centralized management type, the master station confirms whether or not the change to the autonomous distributed communication is necessary using the condition of the switching timing of FIG. 5 (B) (S111) , S117). Then, if the conditions for switching timing in FIG. 5B are not satisfied and there is no need to change to autonomous distributed communication, the master station continuously performs centralized communication and transmits a packet (S113). ). Then, after packet transmission, the master station determines whether the condition α is satisfied, and transitions to the state of the port “A” or “D” (S113).

  On the other hand, if the master station determines in S111 that the conditions for switching timing shown in FIG. 5B are satisfied, and determines that it is necessary to change to autonomous distributed communication, the master station sets each route In response, a Beacon packet including a switching release message is transmitted (S114). Each vehicle, including the parent station, switches to autonomous distributed communication, and each vehicle performs packet transmission while performing carrier sensing using the CSMA method (S115). Then, after packet transmission, the master station (vehicle) determines whether the condition α is satisfied, and transits to the state of the port “A” or “D” (S116).

(A-4) Effects of First Embodiment As described above, according to the first embodiment, communication in two-way multi-hop communication is performed by performing communication using different protocols for uplink and downlink. It is possible to reduce the deterioration of quality.

  Further, according to the first embodiment, the vehicle radio set located at a branch point (branch point) of a plurality of communication paths of multi-hop communication becomes a master station, and if necessary, centralized control type By switching to the communication method, in multi-hop communication, it is possible to disperse traffic at bottleneck points where communication concentrates, and to reduce deterioration of communication quality.

  Furthermore, according to the first embodiment, at the time of centralized management communication by the parent station, the parent station sequentially transmits downlink packets for each route, and the End terminal vehicle transmits uplink packets after receiving the downlink packets. By this, it is possible to perform the same function as the polling function, to disperse the traffic at the bottleneck point where communication concentrates, and to reduce the deterioration of communication quality.

(B) Second Embodiment Next, a second embodiment of a wireless communication apparatus, a wireless communication method, and a wireless communication system according to the present invention will be described in detail with reference to the drawings.

(B-1) Configuration of Second Embodiment The configurations and operations of the communication system and the vehicle radio of the second embodiment are basically the configurations of the communication system and the vehicle radio according to the first embodiment. And identical to the operation. Therefore, the second embodiment will be described with reference to FIGS. 1 to 8 according to the first embodiment.

  In the second embodiment, the function of the transmission timing control unit of the control unit 111 of the vehicle wireless device 100 is different from that of the first embodiment.

  The transmission timing control unit of the second embodiment adjusts the time allocated for each route based on the amount of upstream traffic and the amount of downstream traffic in centralized management communication.

(B-2) Operation of Second Embodiment The processing operation of the vehicle radio apparatus according to the second embodiment is also basically the same as that of the first embodiment.

  FIG. 9 is an explanatory diagram for explaining uplink and downlink asymmetric communication according to the second embodiment. FIG. 9A shows the case of downlink only (or downlink is the mainstream of data), and FIG. 9B shows the case of uplink only (or uplink (or uplink is data mainstream).

  As shown in FIG. 9A, when the downstream is the main stream, the vehicle 1 serving as the parent station transmits sequentially to each route without considering the buffer storage amount of the End terminal vehicle, There is only a small amount of upstream traffic, and the communication quality that causes the bottleneck does not deteriorate.

  On the contrary, in the case of FIG. 9B, when switching to another route to the parent station, a large amount of buffers of each End terminal vehicle is accumulated. Therefore, when the master station transmits to each route in S106 of FIG. 8 according to the first embodiment, it is necessary to compare uplink and downlink traffic and adjust the channel usage time of each route. Therefore, the processing operation of the vehicle radio apparatus according to the second embodiment will be described with reference to FIGS. 10 and 11. FIG.

  FIG. 10 is a flowchart showing a processing operation when the master station transmits a packet to each route in the centrally managed communication according to the second embodiment.

  The traffic for each route of the parent station can be recognized by the buffer accumulation amount held in the data temporary buffer 114 held by the parent station itself. On the other hand, with regard to the traffic of the End terminal vehicle, the master station makes a determination based on the buffer accumulation amount in the overhead information of the packet transmitted from the End terminal vehicle.

  In FIG. 10, the master station compares uplink and downlink traffic volumes (S201). If the amount of uplink traffic is larger than the amount of downlink traffic, the processing proceeds to S202, and if not, the processing proceeds to S203.

  If the amount of uplink traffic is larger, the master station allocates a time according to the buffer storage amount of the End terminal vehicle to each route and switches the route (S202). On the other hand, if the downlink traffic volume is equal to or greater than the uplink traffic volume, the master station transmits to each route the amount of traffic to be transmitted (S203).

  A specific example will be described using FIG. FIG. 11 is an explanatory view illustrating a method in which the master station according to the second embodiment determines uplink and downlink asymmetric communication.

  In FIG. 11, the master station serves as a data temporary buffer 114 and a buffer in overhead information of data packets received from each vehicle as an information source 501 of uplink and downlink transmission data amounts corresponding to traffic volume at the time of communication. There is an accumulation amount.

  That is, the master station can recognize the buffer accumulation amount for each End terminal vehicle held in the data temporary buffer 114. On the other hand, the master station determines the traffic of the End terminal vehicle based on the buffer accumulation amount in the overhead information of the packet transmitted from the End terminal vehicle by multi-hop communication.

  Here, the buffer accumulation amount level value in FIG. 11 is a level value described in (b6) buffer accumulation amount of the switching information in FIG. 7. Although it is possible to write the numerical value of the buffer accumulation amount into the overhead as it is, in order to reduce the information amount as much as possible, the quantized level value is used here. In addition, although the case where a buffer accumulation level value sets it as the level value of 0-7 steps is illustrated, the range of the level value to quantize is not specifically limited.

  The parent station, as shown in 502 of FIG. 11, based on the buffer amount for each End terminal vehicle held in the data temporary buffer 114 of the parent station itself and the buffer accumulation amount received from each End terminal vehicle, The buffer accumulation level value and the upstream buffer accumulation level value are obtained for each path.

  The downstream buffer storage level value and the upstream buffer storage level value are tables at reference times t1, t2 and t3, where the reference time t1 is the latest and the reference time t3 is the oldest. Thus, by holding a plurality of tables, it is possible to grasp the level change of each route.

  In the simulation evaluation and desktop design, when the autonomous distributed type-centralized control type switching is not frequent, if it is not necessary to look at the history because the topology change is not frequent, etc., the latest reference time t1 You may hold only the table.

  In the example of FIG. 11, when looking at the downstream buffer accumulation level value of each reference time, it is shown that the buffer level level value of the downstream route 1 gradually increases from “3” → “4” → “5”. ing. Also, looking at the upstream buffer accumulation level value of each reference time, the respective buffer accumulation level values of the respective uplink paths are the same value, and it is shown that the state is always the same.

The master station, transmission timing control unit of the control unit 111 refers to the buffer fullness level value and upstream of the buffer fullness level value of the downlink of FIG. 11, and downlink buffer fullness level value of the uplink for each path The determination is made for each path by comparing the buffer accumulation amount level value of.

  For example, in the first embodiment, as an example of converting the buffer accumulation amount to the buffer accumulation amount level value, “for example, up to 10 levels 1 to 50 levels 2 to 100 levels 3 to 4 Is defined as up to 500. ” In the first embodiment, there is no relation of buffer accumulation level value = α × buffer accumulation. In the first embodiment, in order to increase the priority as the buffer accumulation level value is larger, assuming that it is a function of buffer accumulation level value = f (buffer accumulation amount), the parabola is set as the setting. There is.

  However, when the asymmetry is large between the upstream and the downstream, the buffer storage amount and the buffer storage amount level value may set the level value linearly. In this case, the level value is related to the buffer accumulation amount ÷ n. Therefore, for example, “level value 1 may be up to 100 buffer accumulations, level 2 may be up to 200 accumulations, level 3 may be up to 300 accumulations,.

(B-3) Effects of Second Embodiment As described above, according to the second embodiment, in addition to the effects of the first embodiment, in the multi-hop communication, the bottleneck points at which communication concentrates Distribute traffic and reduce communication quality degradation.

(C) Third Embodiment Next, a third embodiment of a wireless communication apparatus, a wireless communication method, and a wireless communication system according to the present invention will be described in detail with reference to the drawings.

(C-1) Configuration and Operation of the Third Embodiment In the third embodiment, when the vehicle at the branch point does not initially become the transmission source or the destination, and the vehicle at the branch point relays and transfers, The case where the vehicle of the turning point serves as a master station and changes the route is illustrated.

  The configurations and operations of the communication system and the vehicle radio of the third embodiment are basically the same as the configurations and operations of the communication system and the vehicle radio according to the first and second embodiments. Therefore, the third embodiment will be described also using FIGS. 1 to 8 according to the first embodiment.

  12 and 13 are diagrams showing a network topology of the communication system according to the third embodiment. 12 and 13 show the case where there is branching in a straight path (string path).

  In FIG. 12A, the route 1 of “transmission source is vehicle 1 and destination is vehicle 6” and route 2 of “transmission source is vehicle 1 and destination is vehicle 8”, and the route is branched by vehicle 4 Is the case. In other words, it shows a topology in which there are two routes having the same transmission source, and one route from the transmission source to the vehicle at the branch point is one.

  In FIG. 13A, the route 1 of "the transmission source is the vehicle 6 and the destination is the vehicle 1" and the route 2 of the "transmission source is the vehicle 8 and the destination is the vehicle 1" Is the case. In other words, it shows a topology in which there are two routes with the same destination, and two routes from the transmission source to the vehicle at the branch point.

  In the network topology of FIGS. 12A and 13A, when the autonomous distributed communication is performed, the traffic increases at the vehicle 4 located at the branch point of the route 1 and the route 2, and the packet congestion It may occur and degradation of communication quality may occur.

  FIG. 14 is a flowchart illustrating processing of the transmission source terminal and the reception side terminal in the autonomous distributed communication according to the fourth embodiment. The process flow shown in FIG. 8 according to the first embodiment can be applied to the switching process between the autonomous distributed communication and the centrally managed communication.

  First, the vehicle as the transmission source of the packet determines whether it is the packet transmission timing in the autonomous distributed communication (S301). If it is the packet transmission timing, the control unit 111 determines the buffer accumulation amount of the data temporary buffer 114. Then, it is checked whether or not packet transmission waiting has occurred (S302).

  If a packet transmission wait has occurred, the control unit 111 fetches packet information from the data temporary buffer 114 (S303, S307), and the control unit 111 refers to the routing table to determine whether it is uplink or downlink information. Protocol is selected (S305), and the packet is transmitted (S306).

  On the other hand, when the packet transmission waiting has not occurred, the control unit 111 receives packet information to be transmitted from the upper layer 130 (S304). Then, the control unit 111 refers to the routing table, determines whether it is uplink or downlink information, selects a protocol (S305), and transmits a packet (S306).

  A packet transmitted by a transmission source vehicle is received by a reception type vehicle. In the reception type vehicle, it is judged whether or not a packet is received (S310), and when a packet is received, it is judged by the control unit 111 whether it is addressed to its own station based on header information of the received packet (S311) .

  Then, if the received packet is addressed to the own station, the control unit 111 raises the received information included in the received packet to the upper layer 130 (S316). On the other hand, if it is not a received packet addressed to the own station, the control unit 111 refers to the routing table and determines whether it is necessary to relay the received packet (that is, multi-hop relay processing) (S312) ).

  When multi-hop communication is unnecessary, the control unit 111 discards the received packet (S317). On the other hand, when the relay process of the received packet is necessary, the control unit 111 determines whether the own station is located at a branch point of a plurality of routes or is a central terminal (S313). When it is determined that the own station is located at a branch point of a plurality of routes, the control unit 111 changes the protocol if it is necessary to change the uplink and downlink protocols depending on whether or not it is the center terminal of the route. After (S314), transmission processing is performed (S318). Note that if there is no need to change the protocol, the control unit 111 performs transmission processing using the same protocol as the reception processing (S315) (S318).

Thus, as shown in FIG. 12 (B) and FIG. 13 (B), the vehicle of the branch point or center position of a plurality of routes changes the upstream and downstream protocols, and the upstream and downstream routes are obtained. Can be changed. That is, as shown to FIG. 12 (B) and FIG. 13 (B), it can change into the star-type topology centering on the vehicle 4. FIG.

  As described above, when the own station exists at a plurality of route positions, the process of determining whether to switch the communication method to centralized management communication is the process flow of FIG. 8 according to the first embodiment. It can be switched.

(C-2) Effects of Third Embodiment As described above, according to the third embodiment, in addition to the effects of the first and second embodiments, the initial topology is the relay terminal vehicle. Even in this case, a vehicle located at a branch point of a plurality of routes can be made to have a star topology in which its own station is a master station by changing the upstream and downstream protocols.

(D) Other Embodiments Although various modified embodiments have been described also in the first to third embodiments described above, the present invention can be widely applied to the following modified embodiments.

  (D-1) In the above-described first to third embodiments, the present invention is applied to a wireless communication apparatus mounted with a vehicle, but it is other than a wireless communication apparatus mounted in a vehicle and constitutes an ad hoc network. The present invention can be widely applied to wireless communication apparatuses that perform multi-hop communication.

  (D-2) In the first to third embodiments described above, the wireless communication device performing inter-vehicle communication is exemplified, but the present invention is not limited to inter-vehicle communication, and is widely applied to wireless communication devices that realize M2M. be able to.

  (D-3) In the first embodiment, the master station determines the amount of buffer storage of transmission data (for example, the amount of transmission data, the number of transmission packets, etc.) included in the overhead information of the header information of the packet received from the slave station. Based on the above, the transmission timing of the route may be determined in descending order of the buffer accumulation amount of the slave station. In addition, when the transmission time to be allocated to one path is determined, a plurality of continuous transmission times may be allocated to a specific path for a slave station with a large amount of buffer storage.

  (D-4) In addition, in the first to third embodiments, the master station inserts dummy data of a length corresponding to the buffer storage amount of the slave station and transmits it to the slave station. At this time, the master station determines in advance the dummy data length corresponding to the buffer storage amount (or level value), and inserts dummy data having a data length corresponding to the buffer storage amount received from the slave station. It is good.

  100 and 200: radio (vehicle radio) 101A: protocol 1 nondirectional antenna unit 101B: protocol nondirectional antenna unit 102A: protocol 1 radio unit 102B: protocol 2 radio unit 103: L3 Switch 104 ... Network control unit, 111 ... Control unit, 112 ... Reception information IF unit, 113 ... Own terminal information unit, 114 ... Data temporary buffer unit, 115 ... Transmission information IF unit, 105 ... GPS device, 130 ... Upper layer.

Claims (9)

In a wireless communication apparatus that configures an ad hoc network and performs multi-hop communication with another wireless communication apparatus,
Route search processing means for performing route search processing in the ad hoc network;
Based on the route search processing unit route search results throughput decreased cause of determination results determined using by centralized to the autonomous distributed communication, the master station wireless communication apparatus located in branch points of the plurality of paths Control means for switching to management type communication and performing transmission processing;
In the case of the master station to which the control unit is the source or destination of the own device,
An accumulated amount holding unit for holding an accumulated amount of data to be transmitted, which is acquired from a slave station serving as a destination or a transmission source of each of the above routes;
A transmission timing control unit for increasing the priority of transmission timing to the slave station with a large amount of storage with reference to the storage amount holding unit, and transmitting a downlink signal to each path according to the priority; A wireless communication device characterized by   The transmission timing control unit refers to the storage amount holding unit, and transmits to the slave station a downlink signal including dummy data of a data length according to the storage amount of the slave station. The wireless communication device according to.   When the transmission timing control unit satisfies a predetermined condition based on the route search result, a signal including a request for switching from the autonomous distributed communication to the centrally managed communication is a child of each of the routes. The wireless communication apparatus according to claim 1 or 2, which transmits to a station.   4. The transmission timing control unit according to claim 3, wherein the transmission timing control unit transmits the transmission start timing of the slave station of each path to the signal including the switching request, and transmits the signal to the slave station of each path. Wireless communication device.   The control unit is configured to, based on the storage amount of the slave station of the route stored in the storage amount retaining unit and the storage amount acquired from the slave station corresponding to the control unit, the slave station of the route. The uplink accumulation level value and the downlink accumulation level value are calculated for each route, and allocation of each path is performed based on the comparison result of the uplink accumulation level value and the downlink accumulation level value of the slave station of each path. The wireless communication device according to any one of claims 1 to 4, wherein the time is adjusted.   When the own device is not a transmission source or a destination and is located at a branch point of a plurality of routes according to the route search result, the control means centers each of the plurality of routes on the own device. The wireless communication apparatus according to any one of claims 1 to 5, wherein the route is changed.   The radio communication apparatus according to any one of claims 1 to 6, wherein the control means transmits and receives signals using different protocols for the upstream and downstream of the route. In a wireless communication method of configuring an ad hoc network to perform multi-hop communication with another wireless communication device,
Route search processing means performs route search processing in the ad hoc network;
Based on the determination result of the throughput reduction occurrence factor determined by the control means using the route search result by the route search processing means, from the autonomous distributed communication, the wireless communication device located at the branch point of a plurality of routes is a master station Switch to centralized management type communication to perform transmission processing,
In the case of the master station to which the control unit is the source or destination of the own device,
The accumulated amount holding unit holds the accumulated amount of data to be transmitted, which is acquired from the slave station serving as the destination or transmission source of each path.
The priority of transmission timing to the slave station with a large amount of storage is increased with reference to the storage amount holding unit, and a downlink signal is transmitted to each path according to the priority. . In a wireless communication system that configures an ad hoc network and performs multi-hop communication with a plurality of wireless communication devices,
The plurality of wireless communication devices are
Route search processing means for performing route search processing in the ad hoc network;
Centralized management with a wireless communication device located at a branch point of a plurality of routes as a master station from autonomous distributed communication based on the determination result of the throughput reduction occurrence factor determined using the route search result by the above route search processing means Control means for switching to communication type communication and performing transmission processing;
The wireless communication device that has determined that the own device is the source station or the above-mentioned parent station as the destination device,
The accumulated amount holding unit holds the accumulated amount of data to be transmitted, which is acquired from the slave station serving as the destination or transmission source of each path.
A wireless communication system characterized in that the priority of transmission timing to the slave station with a large amount of storage is increased with reference to the storage amount holding unit, and a downlink signal is transmitted to each path according to the priority. .

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