JP2005341171A - Inter-vehicle communications device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reactive routing communications device for configuring a stable communication path with little change in path, in inter-vehicle communication. <P>SOLUTION: In addition to information elements of a conventional reactive routing pathfinding packet, a packet-relaying vehicle address column, an east/west direction speed column, a south/north direction speed column and an evaluation value column are provided. When the received pathfinding packet is relayed, a relative speed value is added with an immediately front vehicle, calculated by a setting means 6 in the evaluation value column of the packet received for a predetermined standby time, since the packet was first received. A relay means 5 updates the packet whose value in the evaluation value column is the smallest among the packets stored in a queue 3 to the packet-relaying vehicle address column to an address of the own vehicle, the east/west direction speed column to the east/west direction speed of the own vehicle, and the south/north direction speed column to the south/north direction speed of own vehicle. They are broadcast via a transmitting means 9 and an antenna 10. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention belongs to the technical field of communication path construction in a vehicle-to-vehicle communication system that enhances the safety and comfort of drivers and passengers by connecting vehicles via an ad hoc network and exchanging information between vehicles.

Research on an inter-vehicle communication system that enhances the safety and comfort of drivers and passengers by connecting vehicles via an ad hoc network and exchanging information between vehicles has been actively conducted (for example, non-patented). References 1 and 2).
In this system, no special communication infrastructure is required, and each vehicle can communicate with a vehicle traveling outside the effective radio wave range by performing routing processing independently. Therefore, applications such as communication between vehicles and image transmission are possible. Can also be used at low cost. However, in an ad hoc network in which vehicles traveling at high speed are connected, the dynamic change in topology is large, and there is a concern that a control packet generated in association with a route maintenance change may press the wireless communication band. For this reason, in a vehicle-to-vehicle communication system using an ad hoc network, it is necessary to sufficiently study the routing method.

  A study on ad hoc networks is underway at the IETF MANET WG (see, for example, Non-Patent Document 3), and various routing methods have been proposed. Routing methods can be broadly divided into two types: proactive routing and reactive routing. Proactive routing is a method of updating its routing table by periodically exchanging messages with neighboring stations (see, for example, Non-Patent Documents 4 and 5).

  Reactive routing, on the other hand, floods a route search packet from the sender station to the destination station when communication is necessary, and the destination station that receives the packet unicasts the route response packet to the sender. This is a method for generating a route (for example, see Patent Documents 6 and 7).

  When the station moving speed is fast, there is a report that the reactive arrival rate is higher than the proactive routing (see, for example, Patent Document 8), and therefore, a routing method in an ad hoc network connecting traveling vehicles. For example, reactive routing is more appropriate.

  Reactive routing is an algorithm for establishing a communication path between any two stations in a network composed of a plurality of stations. The reactive routing process is classified into three procedures: route search, route response, and route change.

  In route search, a packet transmission station (hereinafter referred to as a “sender station”) searches a routing table when transmitting a packet to a communication partner station (hereinafter referred to as a “destination station”). In the routing table, when sending a packet to the destination station, it is written to which station the packet should be sent, and all the stations constituting the network have their own routing table. The routing table is searched, and if there is a route to the destination station, the information is used to unicast the packet.

Unicast is a communication means that allows a certain station to receive the packet only when a certain station wirelessly transmits the packet, and sets the address information of the receiving station in the transmission packet. This is realized.
When the route does not exist, the route search packet (hereinafter, RREQ: Route Request Packet) is flooded to the destination station.

  In the flooding, a station broadcasts a packet, and a broadcast packet receiving station broadcasts the packet again. By repeating this, the communication means for allowing all the stations constituting the network to receive the packet discards the packet without broadcasting if it has already been received.

  Broadcast is a means of communication that causes all stations that are within the reach of radio waves to receive the packet when a station wirelessly transmits the packet. The bit indicating broadcast is set in the transmission packet. This is realized.

The station that has received the RREQ registers the route to the sender station in the routing table.
In the route response, the destination station receives RREQs from a plurality of routes. A route reply packet (hereinafter referred to as RREP: Route Reply Packet) is unicasted to the sender station using the route received first among them. In the routing table, the route information that the RREQ arrives earliest is registered. The sending station that has received the RREP registers the route to the destination station in the routing table, and becomes communicable.

  In the route change, when it becomes impossible to communicate with the destination station using the route registered in the routing table, a route change process is required. The station that has detected the need for route change unicasts a route error packet (hereinafter referred to as RERR) to the sender station. The source station that has received the packet transmits an RREQ to the destination station. A valid route is acquired by receiving RREP from the destination station and registered in the routing table.

  As described above, reactive routing uses RREQ flooding for route establishment. When the route changes frequently, the wireless bandwidth consumption due to flooding increases, which hinders the original data packet communication. When the density of the stations constituting the network is high, the influence of radio band consumption due to flooding becomes stronger, and there arises a problem that data packet communication cannot be maintained.

As one of the methods for solving this problem, an improvement measure for reducing the probability of occurrence of RREQ flooding due to a subsequent route change by selecting a stable route at the time of route establishment has been taken. Specifically, there are the following two methods.
In the first method, each station periodically transmits a beacon. When a flooding packet is received, if the number of continuous beacon receptions from the station that sent the packet is equal to or greater than a threshold, a stable route is constructed by relaying the packet.

In the second method, each station periodically transmits a beacon. When a flooding packet is received, when the number of consecutive beacon receptions from the station that sent the packet is equal to or greater than a threshold value and the signal strength of the beacon is equal to or greater than a certain value, the flooding packet is relayed.
Ari Widodo, Takaaki Hasegawa: “Effect of inter-vehicle communication network on traffic flow”, IEICE B, Vol.J82-B, No.11, pp2010-2017, Nov 1999 Tomoyuki Yashiro, Atsushi Matsushita: “Proposal for building a vehicle network using inter-vehicle communication”, IEICE B, Vol.J82-B, No.1, pp9-18, Jan 1999 Mobile Ad-hoc Networks (manet) Chartr, http: //www.ietf.org/html.charters/manet-charter.html CEPerkins and P. Bhagwat, “Highly dynamic destination-sequenced distance-vector routing (DSDV) for mobile computers,” ACM SIGCOMM '94 Conerence on Communications Architectures, Protocols and Applications, pp.234-244,1994 RFC 3626 “Optimized Link State Routing Protocol (OLSR)” The Dynamic Source Routing Protocol for Mobile Ad Hoc Networks (DSR) http://www.ietf.org/internet-drafts/draft-ietf-manet-dsr-09.txt RFC 3561 “Ad hoc On-Demand Distance Vector (AODV) Routing” Josh Broch, David A. Maltz, David B. Johnson, Yih-Chun Hu, Jorjeta Jetcheva, “A Performance Comparison of Multi-Hop Wireless Ad Hoc Network Routing Protocols” Proceedings of the Fourth Annual International Conference on Mobile Computing and Networking (MobiCom '98), ACM, Dallas, TX, October 1998

Since the above countermeasure method suppresses the frequency of occurrence of flooding itself, it is possible to significantly reduce the consumption of the radio band. On the other hand, the stability is measured using a beacon. The accuracy of stability improves as the beacon transmission interval is shortened.
However, if the beacon transmission interval is shortened, a problem arises that when the station density is high, radio band consumption by the beacon increases.
In addition, there arises a problem of generation of the CPU beacon reception processing cost and occurrence of collision between the beacon and the data packet.

  The problem to be solved by the present invention is to change the route based on the relative speed between vehicles (between stations) and the distance fluctuation per unit time between vehicles without using such problematic beacons. An object of the present invention is to provide a vehicle-to-vehicle communication device that can construct a small number of stable communication paths.

In order to solve the above-described problems, the present invention has the following means configurations.
A first configuration of the present invention is a vehicle-to-vehicle communication device characterized in that a vehicle-to-vehicle communication path is constructed by including the following means.
(B) Transmission means for wirelessly transmitting a route search packet, route response packet, data packet and control packet (b) Receiving means for wirelessly receiving a route search packet, route response packet, data packet and control packet (c) Packet relay vehicle Route search packet generating means for generating a route search packet having an address column, an east / west direction speed column, a north / south direction speed column, and an evaluation value column indicating a relative speed accumulated value (d) The vehicle searches for a route to a specific destination station. When starting, the vehicle address in the packet relay vehicle address field of the route search packet, the vehicle east-west speed and the vehicle north-south speed in the east-west speed field and the north-south speed field, respectively, and zero in the evaluation value field Set
When a route search packet originated by another vehicle is received, the relative speed calculated from the east-west speed, the north-south direction speed and the host vehicle speed indicated in the received route search packet with respect to the value in the evaluation value column Set means for adding and updating values (e) Route search packet information table (f) that registers this reception when a route search packet from a specific route search packet source station to a specific destination station is received for the first time Route Search Packet Waiting Timer (g) that sets a certain waiting time from the first reception of a route search packet from the source station to the specific destination station for the first time. Route search packet registered in the route search packet information table The queue (h) for storing the route search packet received during the waiting time of the waiting timer and updated in the evaluation value column When the destination station address of the route search packet stored in the queue is not the own vehicle address, the route search packet having the smallest evaluation value column is selected from the stored route search packets, and the relay vehicle address column is selected. The relay means for sending to the transmission means to update the own vehicle address, the east-west speed field and the north-south speed field to the own vehicle east-west speed and the north-south speed, respectively, and broadcast to the transmission means (re) Store in the queue If the destination station address of the route search packet is the own vehicle address, the route response packet is selected by selecting the route of the packet having the smallest value in the evaluation value column from the stored route search packets. Route response packet sending means for sending to sending means to send to sending station

A second configuration of the present invention is a vehicle-to-vehicle communication device characterized in that a vehicle-to-vehicle communication path is constructed by including the following means.
(B) Transmission means for wirelessly transmitting a route search packet, route response packet, data packet and control packet (b) Receiving means for wirelessly receiving a route search packet, route response packet, data packet and control packet (c) Packet relay vehicle Route search having an address field, an east-west speed field, a north-south speed field, a longitude field, a latitude field, and an evaluation value field indicating a cumulative value of a relative speed value between two vehicles and a relative position fluctuation amount per unit time. Route search packet generation means for generating a packet (d) When the vehicle starts a route search to a specific destination station, the vehicle address in the packet relay vehicle address field of the route search packet, the east-west speed field and the north-south direction The speed column displays the vehicle's east-west speed and the vehicle's north-south speed, respectively. The longitude and latitude columns indicate the vehicle's longitude and Set latitude and zero in the evaluation value field,
When a route search packet issued by another vehicle is received, the relative speed calculated from the east-west speed and the north-south direction speed and the vehicle speed indicated in the received route search packet with respect to the value in the evaluation value column Set means for adding and updating the value and the sum of the longitude and latitude indicated in the packet and the relative position fluctuation amount per unit time calculated from the longitude and latitude of the own vehicle (e) Specific route search packet When a route search packet from a source station to a specific destination station is received for the first time, a route search packet information table that registers this reception (f) Route search from a specific route search packet source station to a specific destination station Route search packet wait timer that sets a fixed waiting time from the first packet reception (g) Route search registered in the route search packet information table A queue for storing a route search packet received during the waiting time of the waiting timer and updated in the evaluation value column (h) The destination station address of the route search packet stored in the queue is the vehicle address If not, the route search packet having the smallest value in the evaluation value column is selected from the stored route search packets, the relay vehicle address column is set as the own vehicle address, the east-west direction speed column and the north-south direction speed column are set. The relay means for sending to the transmission means to update the longitude and latitude fields to the own vehicle's east / west direction speed and the own vehicle's north / south direction speed, respectively, to the longitude and latitude of the own vehicle, and to send to the transmission means (re) stored in the queue When the destination station address of the route search packet is the host vehicle address, the packet with the smallest value in the evaluation value column among the stored route search packets is displayed. Route response packet sending means for sending a route response packet to the sending means to select the route of the packet and sending the route response packet to the route search packet transmitting station

  As described above, in the first configuration of the present invention, the packet searcher address field, the east / west direction speed field, the north / south direction speed field, and the route search packet are directly exchanged in the route search packet. A relative speed value between two vehicles is cumulatively added according to the chain of exchanges by relay, and an evaluation value column is provided to indicate the value, and a plurality of sender stations that have passed through different relay routes received within a certain period of time For each evaluation value column of the route search packet with the same destination station, calculate the relative speed value from the east-west speed, the north-south speed and the vehicle speed indicated in each packet and calculate the value In addition to updating the value in the evaluation value column of the received packet, the route search packet with the smallest value is selected, and the packet relay vehicle address column includes the east-west speed column and the north-south speed column in the own vehicle address. Each update to the east-west direction speed and the north-south direction speed of the vehicle, relays flooding.

  In this way, a destination station that has been searching for a route from a specific route search packet source station (sender station) will also receive a plurality of route search packets that have passed through different relay routes. The communication route is established by selecting the relay route followed by the route search packet with the smallest evaluation value and unicasting the route response packet to the sender station. The smaller the number of times and the smaller the relative speed value between the relay vehicles, the smaller the value.

The small number of relays is an indicator of route stability because the possibility of route change is low, and a small relative speed value indicates that there is little movement of the positional relationship. Therefore, it is predicted that the smaller the evaluation value, the higher the stability of the route, that is, the less frequent the route change.
The present invention has an effect that a stable communication route with little route change can be constructed by adopting an evaluation value in the route search packet in this way.

In the second configuration of the present invention, the route search packet in the first configuration is further provided with a longitude column and a latitude column, and the content of the evaluation value is not a cumulative value of the relative velocity value but a relative velocity value and a unit time per unit time. This is a cumulative value of the sum of the relative position fluctuation amounts.
The fact that there is a change in the relative positional relationship suggests the possibility of a situation where the route must be changed. The larger the amount of change per unit time, the more likely the route will be changed. Becomes big.

However, the relative velocity value may not change even if the relative position fluctuation value is different.
For example, with respect to a certain fixed position P on a straight line, when moving at a certain constant speed V so as to approach the position P on the straight line, and when moving away at the same speed V, the position P The relative position fluctuation with the moving body is different because the distance between the two becomes shorter in the former and longer in the latter, but the relative velocity value is the same in V.

Thus, even if the relative velocity value is the same, the possibility of route change differs if the relative position fluctuation amount is different.
Therefore, in the second configuration, the cumulative value of the sum of the relative speed value and the relative position fluctuation amount is used as the evaluation value.
Therefore, the second configuration has an effect that it is possible to select a communication route with higher accuracy than the first configuration and less possibility of route change.

  In the embodiment of the vehicle-to-vehicle communication device of the present invention, route packet generation means other than hardware means such as transmission means, reception means, route search packet information table, route search packet waiting timer, queue, etc., set means, relay means, route response The packet sending means and the like are best performed by software.

  In addition, the time to be registered in the route search packet information table and the wait time setting of the route search packet waiting timer are set based on values simulated by actual vehicle distribution, vehicle speed distribution, and travel route pattern. It is the best embodiment to do this while correcting it with the actual statistical results.

FIG. 1 is a functional block diagram of a first embodiment of the communication path construction means of the vehicle-to-vehicle communication device of the present invention.
In reactive routing, each station maintains a routing table (not shown) and communicates using the route (route) shown there. If there is no route to the destination station at the time of data transmission, or the route Exists but is invalid due to an expiration or the like, the route search is started, that is, the route search packet is broadcast.

FIG. 2 shows information elements of a route search packet used in the first configuration of the present invention. Among these information elements, the ninth packet relay address, the tenth east-west speed, the eleventh north-south speed, and the twelfth evaluation value are unique information of the present invention. The other information elements are used in general reactive routing.
The packet relay address is the address of the vehicle that relayed the packet immediately before, and an IP address, a MAC address, or the like is used. The east-west speed is the east-west travel speed of the vehicle indicated by the packet relay address, and the east direction is positive and the west direction is negative. The north-south direction speed is also the vehicle north-south direction traveling speed indicated by the packet relay address, and the north direction is positive and the south direction is negative.

The evaluation value is a value obtained by accumulatively adding the relative speed value between the two vehicles that directly exchanged the route search packet according to the relay chain.
When the evaluation value is M, the vehicle east-west speed is V _sx , the vehicle north-south speed is V _sy , the vehicle east-west speed is V _px , and the vehicle immediately preceding the vehicle north-south speed is V _py. It is represented by 1.

The vehicle that starts the route search has its own vehicle address in the packet relay vehicle address field of the route search packet generated by the route search packet generation means 7, and its own vehicle east-west speed in the east-west direction speed column and north-south direction speed column, and The own vehicle north-south direction speed is set by the setting means 6, and zero is set in the evaluation value column.
The set route search packet is broadcast via the transmission means 9 and the antenna 10.

  Conversely, a route search packet broadcasted by a specific route search packet source station (sender station) to search for a route to a specific destination station is received by the antenna 10 and the receiving means 8 directly or via a relay. When the reception of the route search packet is the first time, that is, when the route search packet information table 2 is not registered yet, the route search packet information table 2 is registered and the route search packet wait is received. A predetermined waiting time, for example, 10 ms is set in the timer 1. It is conceivable that a plurality of packets that have passed through different relay routes are received with a time lag, but the packets received within the waiting time of 10 ms are stored in the queue 3. Anything beyond this time is discarded.

  On the other hand, when a certain route search packet is received, if it is already registered by referring to the route search packet information table 2, if the reception is before the waiting time elapses, it is stored in the queue 3. If the waiting time has elapsed, it is discarded.

  Here, each packet stored in the queue 3 is stored by adding the relative speed value calculated from the east-west speed, the north-south speed and the own vehicle speed of the packet by the setting means 6 to the evaluation value. Next, when the destination station address of the route search packet stored in the queue 3 is not the own vehicle address, the route search packet having the smallest evaluation value is selected by the relay means 5, and the packet relay vehicle address of the packet is selected. The field is updated to the own vehicle address, the east / west direction speed field and the north / south direction speed field are updated to the own vehicle east / west direction speed and the own vehicle north / south direction speed, respectively, and transmitted to the transmission means 9 and broadcast from the antenna 10.

  In this way, the packet with the smallest evaluation value is selected from the packets received within a certain period of time (10 ms in the above example) from when the plurality of route search packets having different relay routes to the host vehicle are first received. By relaying, the route search packet that has passed through the communication route with the lowest possibility of route change out of at least the communication route to the host vehicle is relayed.

Next, when the destination station address of the packet stored in the queue 3 is the own vehicle address, the route response packet sending means 4 selects the relay route of the packet having the smallest evaluation value and routes it to the sender station. The response packet is sent to the transmission means 9 for unicast.
When the sender station receives this route response packet, a communication route is established and communication is possible.

In the second embodiment, a new information element is added to the information element of the route search packet compared to the case of the first embodiment.
FIG. 3 is a diagram illustrating information elements of a route search packet according to the second embodiment. The first to eighth elements are information elements used for general reactive routing, and are the same as in the first embodiment. The 12th longitude field and the 13th latitude field are added. This is the relay vehicle immediately before receiving the route search packet, that is, the packet transmission time of the vehicle having the address in the packet relay vehicle address field. The position is indicated by longitude and latitude.

The reason for adding the position information of the immediately preceding vehicle in this way is as follows.
In the configuration of the first embodiment, when a vehicle traveling on a straight road searches for a route to a vehicle traveling on the same road, the probability of selecting a vehicle traveling on the opposite lane as a relay vehicle is greatly reduced. The stability of is expected to increase. However, when only the relative speed is used as the evaluation value, it may be unclear whether a stable path can be constructed.

  For example, assume the situation shown in FIG. Assume that the vehicles A to D are traveling at a uniform speed and the vehicle A attempts to establish a route to the vehicle D. Since vehicle B is traveling in the same lane as vehicle A and vehicle D, a stable route can be established by selecting vehicle B as a relay vehicle. However, the relative speeds of the vehicle A viewed from the vehicle B or the vehicle C are different in direction but are equal in magnitude. Similarly, the relative speeds of the vehicle B or the vehicle C viewed from the vehicle D are also equal. Accordingly, in the first embodiment, whether to select the vehicle B or the vehicle C as the relay vehicle is determined by the first-come-first-served basis. Therefore, in the second embodiment, in order to correct the above problem, not only the relative speed but also the amount of change in the inter-vehicle distance is added to the evaluation value.

FIG. 5 is a functional block diagram of the second embodiment.
1 is basically the same as the functional block configuration of FIG. 1, but by providing a longitude field and a latitude field in the route search packet, the setting unit 6 and the relay unit 5 have longitude information and latitude indicating the position of the vehicle. Information is input, and the route search packet generation means 7 generates the route search packet of FIG. 3 in which the longitude column and the latitude column are added to the route search packet (FIG. 2) in the first embodiment.

  When updating the evaluation value of the received route search packet, the setting means 6 displays the position information of the immediately preceding vehicle indicated in the longitude field and the latitude field of the packet, the east-west speed field, and the north-south speed field. From the determined speed, the course on which the vehicle travels is made a linear function. Similarly, the traveling course of the own vehicle is made a linear function, and the intersection point is obtained.

In FIG. 4, when the vehicle B receives the route search packet transmitted by the vehicle A, the place indicated by W corresponds to this intersection. At this time, the inter-vehicle distance D when the route search packet is received and the inter-vehicle distance D ′ after a unit time are calculated by Equation 2 and Equation 3.
However, W _x ... East-west direction position of intersection W W _y ... North-west direction position of intersection W A _x ... East-west direction position of vehicle A A ' _x ... East-west direction position after unit time of vehicle A B _y ... North-north of vehicle B Direction position B ′ _y ... Position of vehicle B in the north-south direction after unit time. The position after unit time is obtained from the initial position and the velocity in that direction.

  The evaluation value M is calculated by Expression 4 using Expressions 1, 2, and 3.

  Note that when there is no intersection between the linear function describing the traveling direction of the host vehicle and the linear function describing the traveling direction of the immediately preceding vehicle, the simple inter-vehicle distance represented by Equation 5 and Equation 6 is used.

In this way, the sum of the relative speed value of the host vehicle and the immediately preceding vehicle and the amount of change in the inter-vehicle distance is added to the evaluation value of the received route search packet, and is stored in the queue 3.
The relay means 5 selects the route search packet having the smallest evaluation value M from the route search packets stored in the queue 3, and sets the packet relay vehicle address field of the packet as the own vehicle address, and the east-west speed field. And the north-south direction speed column are updated to the own vehicle east-west direction speed and the own vehicle north-south direction speed, respectively, and the longitude column and the latitude column are updated to the own vehicle longitude and the own vehicle latitude and transmitted to the transmission means 9 and broadcast from the antenna 10 To do.
Other operations are the same as those in FIG.

Next, the evaluation result by the simulation in the case of Example 1 and Example 2 will be described.
First, the case of the straight model will be described. The effectiveness of the present invention is evaluated by simulation for communication between vehicles traveling straight on the same road. A straight traveling model used in the simulation is shown in FIG. A two-lane road is arranged on a circumference with a radius of 600 m, and a straight road is simulated by running on the circumference. The road width is 5 m per lane, and a total of 120 vehicles are arranged uniformly, 60 units per lane. The wireless communication system conforms to IEEE802.11b, and the effective radio wave range is 80 m and the wireless bandwidth is 11 Mbps.

  As shown in FIG. 6, the packet arrival rate and the number of route changes are measured when 10000 packets of 512-byte UDP data are transmitted from a certain vehicle A to a vehicle B traveling on the same lane in a 50 ms cycle. The vehicle traveling speed is simulated for a case where the topology change amount is small as 40 km / h, and the topology change amount is large as 100 km / h. Ns-2 was used as a simulator, and AODV, which is a typical algorithm of reactive routing, was taken up as a comparison control of the present invention.

FIG. 7 and FIG. 8 show the measurement results of the number of times of changing the route (route) when the number of Hops from the vehicle A to the vehicle B is changed.
From FIG. 7, in the case of Example 1 and Example 2, the route (route) change count is kept low regardless of the number of Hops to the target station, and a stable route (route) can be constructed. On the other hand, in AODV, the route change frequency increases as the number of Hops to the target station increases. Further, from FIG. 8, in the case of Example 1 and Example 2, a stable route can be established regardless of the vehicle traveling speed, whereas AODV increases the frequency of route change as the vehicle traveling speed increases. ing.

  Since AODV does not consider the stability of the route, a vehicle traveling in the opposite lane can be selected as a relay station. The probability increases as the number of Hops to the destination vehicle increases, and when a vehicle traveling in the opposite lane is selected as a relay station, the faster the vehicle traveling speed, the faster the time until the route is cut. Since the flooding of the control (control) packet occurs when the route is changed, it can be understood that the overhead due to the flooding of the control (control) packet can be greatly reduced in the present invention.

  The measurement results of the packet arrival rate to the vehicle B are shown in FIGS. From the figure, almost 100% packets can be received in both the first, second, and AODV regardless of the vehicle traveling speed. This is because the packet retransmission control is performed by the routing protocol. When the route disconnection frequency is low, it is possible to reach the destination without omission by retransmission control, but when there are many connections and the vehicle density is high, packet collision occurs due to flooding of control packets, and retransmission control is performed. Even if it is incorporated, the packet arrival rate is lowered.

Next, the case of the meander model will be described.
When the vehicle speed is uniform, the absolute value of the relative speed is the same for vehicles traveling in a direction orthogonal to the traveling direction of the host vehicle regardless of the vehicle on the same lane and the vehicle on the opposite lane. For this reason, in the routing method using the relative speed as the evaluation value, there is a possibility that the vehicle traveling in the opposite lane is selected as the relay vehicle and the stability of the route is lowered. Therefore, the effectiveness of the present invention is evaluated by simulation for communication between vehicles traveling on meandering roads. FIG. 11 shows the meandering traveling model used in the simulation. The parameters used in the simulation are the same as those of the straight model shown in FIGS.

  FIGS. 12 and 13 show the measurement results of the number of route changes when a UDP packet is transmitted from the vehicle A to the vehicle B traveling in the same lane. From FIG. 12, the route change frequency is suppressed lower than that of AODV, and a stable route is constructed. The first embodiment may select a vehicle traveling in the opposite lane as a relay vehicle, whereas the second embodiment has a higher probability of selecting a vehicle traveling on the same lane as a relay vehicle. Build a stable route. From FIG. 13, it can be seen that even when the vehicle speed is high, the number of route changes is kept low in the present invention, whereas in AODV, the more stable the route, the more difficult it is to build.

The measurement results of the packet arrival rate in the vehicle B are shown in FIGS.
From the figure, it is understood that the packet arrival rate decreases as the number of H0Ps increases in AODV even though the packet is retransmitted when the route is reconfigured. This is because the route is changed so frequently that it cannot catch up even with packet retransmission control, and this tendency can be expected to become more prominent when the number of connections and the vehicle density are increased.

  As a result, the device of the present invention is superior in both the packet arrival rate and the route stability compared to AODV, and in particular, the route disconnection frequency is a low value regardless of the number of HOPs to the destination station and the vehicle traveling speed. It was found that The apparatus of the present invention is not only used for communication between vehicles traveling on a highway, but also because it does not use a beacon, it is effective even when used for communication between vehicles in an environment with high vehicle density such as an urban area or a parking lot. I think that the.

It is a functional block diagram of the 1st Example of the communication path construction means of the communication system between vehicles of the present invention. It is a figure which shows the information element of the route search packet in 1st Example of this invention apparatus. It is a figure which shows the information element of the route search packet in 2nd Example of this invention apparatus. It is explanatory drawing of inter-vehicle distance fluctuation | variation calculation. It is a functional block diagram of the 2nd Example of the communication path construction means of the communication apparatus between vehicles of this invention. It is a straight traveling model diagram in which a part of a large circle is simulated as a straight line. In the straight traveling model of FIG. 6, the number of route changes when the vehicle speed is 40 km / h and the Hop number from the vehicle A to the vehicle B is changed is defined as AODV, the first and second embodiments of the present invention. It is the graph which compared about the example. This is a case where the vehicle speed is 100 km / h in the graph of the number of Hops versus the number of route changes similar to FIG. In the straight traveling model of FIG. 6, the packet arrival rate when the vehicle speed is 40 km / h and the Hop number from the vehicle A to the vehicle B is changed is represented by AODV, the first embodiment of the present invention, and the second embodiment. It is the graph which compared about the example. This is a case where the vehicle speed is 100 km / h in the graph of Hop number versus packet arrival rate similar to FIG. It is a meandering travel model figure. In the meandering traveling model of FIG. 11, the number of route changes when the Hop number when the vehicle speed is 40 km / h and the UDP packet is transmitted from the vehicle A to the vehicle B traveling in the same lane is expressed as AODV. It is the graph which compared about the 1st Example of this invention and the 2nd Example. This is a case where the vehicle speed is 100 km / h in the graph of the number of Hops versus the number of route changes similar to FIG. In the straight traveling model of FIG. 11, the packet arrival rate when the vehicle speed is 40 km / h and the Hop number from the vehicle A to the vehicle B is changed is defined as AODV, the first embodiment of the present invention, and the second embodiment. It is the graph which compared about the example. This is a case where the vehicle speed is 100 km / h in the graph of Hop number versus packet arrival rate similar to FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Route search packet waiting timer 2 Route search packet information table 3 Queue 4 Path response packet transmission means 5 Relay means 6 Set means 7 Route search packet generation means 8 Reception means 9 Transmission means 10 Antenna

Claims (2)

A vehicle-to-vehicle communication device characterized by constructing a vehicle-to-vehicle communication path by including the following means.
(B) Transmission means for wirelessly transmitting a route search packet, route response packet, data packet and control packet (b) Receiver for wirelessly receiving a route search packet, route response packet, data packet and control packet (c) Packet relay vehicle Route search packet generating means for generating a route search packet having an address column, an east / west direction speed column, a north / south direction speed column, and an evaluation value column indicating a relative speed accumulated value (d) The vehicle searches for a route to a specific destination station. When starting, the vehicle address in the packet relay vehicle address field of the route search packet, the vehicle east-west speed and the vehicle north-south speed in the east-west speed field and the north-south speed field, respectively, and zero in the evaluation value field Set
When a route search packet originated by another vehicle is received, the relative speed calculated from the east-west speed, the north-south direction speed and the host vehicle speed indicated in the received route search packet with respect to the value in the evaluation value column Set means for adding and updating values (e) Route search packet information table (f) that registers this reception when a route search packet from a specific route search packet source station to a specific destination station is received for the first time Route Search Packet Waiting Timer (g) that sets a certain waiting time from the first reception of a route search packet from the source station to the specific destination station for the first time. Route search packet registered in the route search packet information table In the queue (h) for storing the route search packet received during the waiting time of the waiting timer and updated in the evaluation value column If the destination station address of the route search packet stored in the queue is not the own vehicle address, the route search packet having the smallest value in the evaluation value column is selected from the stored route search packets, and the relay vehicle address column The relay means for sending to the transmission means to update the own vehicle address, the east-west speed field and the north-south speed field to the own vehicle east-west speed and the north-south speed, respectively, and broadcast to the transmission means (re) Store in the queue If the destination station address of the route search packet is the own vehicle address, the route response packet is selected by selecting the route of the packet having the smallest value in the evaluation value column from the stored route search packets. Route response packet sending means for sending to sending means to send to sending station A vehicle-to-vehicle communication device characterized by constructing a vehicle-to-vehicle communication path by including the following means.
(B) Transmission means for wirelessly transmitting a route search packet, route response packet, data packet and control packet (b) Receiving means for wirelessly receiving a route search packet, route response packet, data packet and control packet (c) Packet relay vehicle Route search having an address field, an east-west speed field, a north-south speed field, a longitude field, a latitude field, and an evaluation value field indicating a cumulative value of a relative speed value between two vehicles and a relative position fluctuation amount per unit time. Route search packet generation means for generating a packet (d) When the vehicle starts a route search to a specific destination station, the vehicle address in the packet relay vehicle address field of the route search packet, the east-west speed field and the north-south direction The speed column displays the vehicle's east-west speed and the vehicle's north-south speed, respectively. The longitude and latitude columns indicate the vehicle's longitude and Set latitude and zero in the evaluation value field,
When a route search packet issued by another vehicle is received, the relative speed calculated from the east-west speed and the north-south direction speed and the vehicle speed indicated in the received route search packet with respect to the value in the evaluation value column Set means for adding and updating the value and the sum of the longitude and latitude indicated in the packet and the relative position fluctuation amount per unit time calculated from the longitude and latitude of the own vehicle (e) Specific route search packet When a route search packet from a source station to a specific destination station is received for the first time, a route search packet information table that registers this reception (f) Route search from a specific route search packet source station to a specific destination station Route search packet wait timer that sets a fixed waiting time from the first packet reception (g) Route search registered in the route search packet information table A queue for storing a route search packet received during the waiting time of the waiting timer and updated in the evaluation value column (h) The destination station address of the route search packet stored in the queue is the vehicle address If not, the route search packet having the smallest value in the evaluation value column is selected from the stored route search packets, the relay vehicle address column is set as the own vehicle address, the east-west direction speed column and the north-south direction speed column are set. Relay means for sending to the sending means for updating and broadcasting the longitude and latitude fields to the own vehicle's east / west direction speed and own car's north / south direction speed respectively to the longitude and latitude of the own vehicle (re) stored in the queue When the destination station address of the route search packet is the host vehicle address, the packet with the smallest value in the evaluation value column among the stored route search packets is displayed. Route response packet sending means for sending a route response packet to the sending means to select the route of the packet and sending the route response packet to the route search packet transmitting station

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