KR101119437B1 - A Method of message-transmitting in VANET - Google Patents

Abstract

The present invention relates to a message transmission method of a vehicle ad hoc network and a message transmission method of a receiving node of a vehicle ad hoc network, wherein the message transmission method of the vehicle ad hoc network is a message transmission method of a vehicular ad hoc network (VANET). A vehicle characterized in that the message receiving node calculates a distance from the message transmitting node and retransmits the message only if the receiving node belongs to a preset retransmission activation area of the vehicle communication area based on the calculated distance. This is a method of sending a message on an ad hoc network.

In addition, the above-described message transmission method of the receiving node of the vehicle ad hoc network, the message transmission method of the message receiving node of the vehicle ad hoc network, the method comprising the steps of: (a) receiving a message transmitted from the message transmission node; (b) determining a current position of a receiving node using GPS, and calculating a distance from the transmitting node; (c) determining whether the receiving node belongs to the message retransmission activation region based on the calculated distance; And (d) retransmitting the received message if the receiving node belongs to the message retransmission activation region.

According to the present invention, regardless of the density of the vehicle, the end-to-end message transmission delay time can be shortened, and packet collisions due to broadcasting can be minimized.

Vehicle ad hoc network, VANET, accident messages, emergency messages

Description

A method of message-transmitting in VANET}

The present invention relates to a method for determining an emergency message delivery range according to end-to-end message delivery delay time and collision distance of packets due to broadcasting regardless of vehicle density.

The vehicle ad hoc network is a type of mobile ad hoc network and is a key technology for Intelligent Transportation System (ITS). The vehicle ad hoc network is temporarily configured through wireless communication between vehicles without the aid of an infrastructure, and messages are propagated through vehicles selected as message relay nodes. However, vehicle ad hoc networks have more severe changes in network topology and node density than existing mobile ad hoc networks. Therefore, an effective relay node selection technique is required to rapidly propagate the message through multi-hop broadcast.

VANET (Vehicular Ad-hoc Network, VANET), which is emerging as a core technology of Intelligent Transportation System (ITS) for intelligent vehicles, is a kind of Mobile Adhoc Network (MANET) based on inter-vehicle wireless communication. . VANET forms a temporary network through autonomous wireless communication between vehicles without the help of infrastructure such as base stations around the road. This results in smooth traffic flow control, driver safety and convenience, and improved fuel economy and performance.

A vehicular ad-hoc network (VANET) is another type of network that combines a mobile ad-hoc network and a wireless sensor network as a technology for an intelligent transportation system (ITS). With the development of information and communication technology, automobiles are gradually becoming electronic systems beyond the function of the means of transportation. The smart car can recognize not only the abnormality inside the car but also the information of the road condition while driving through the sensor. The collected vehicle state information and driving situation information are used as information for improving the safety of the driver through wireless communication between the vehicles (in the present invention, the vehicle is described as a node). As such, in VANET, the car functions as a sensor node with intelligent and wireless communication capabilities. VANET can be used for warning service for driver's safe driving such as vehicle emergency warning, lane change assistance, intersection driving assistance, road condition warning and chain collision warning. VANET is a network that is temporarily configured through autonomous wireless communication between vehicles without using infrastructure such as base stations or access points. With VANET, drivers can not only broaden their vision of safety, but also receive various traffic information. Thus, VANET can significantly improve traffic flow as well as vehicle safety and efficiency.

Multi-hop broadcasts are required to propagate the alert message to all nodes in the danger zone. In ad hoc wireless networks, broadcasts are primarily a one-to-many communication technique for simultaneously delivering the same message to all nodes within a single hop distance of the source node. In VANET, however, the node's communication distance is not long enough to communicate with all nodes in the network. Therefore, in order to propagate an emergency message to all nodes involved in the danger zone, a multi-hop broadcast is required that carries the message through selected nodes among the nodes in the network. However, unlike MANET, VANET is characterized by fast node movement, frequent changes in network topology and node density, and frequent network disconnection. Moreover, since emergency messages in VANET are closely related to driver's safety, they must be spread quickly to nodes in the hazardous area, and the network load due to message propagation should be minimized.

The conventional vehicle safety message broadcasting protocol proposed for VANET includes flooding-based broadcast, table-based broadcast, cluster-based broadcast, and flooding distance-based broadcast schemes according to node role and transmission node selection method. have. Most of these techniques are configured to obtain location information via GPS mounted on the vehicle. The flooding-based broadcast scheme proposed a method to reduce the network load by limiting the number of times the nodes participating in vehicle safety message retransmission of vehicle safety messages. However, the overhead of network load and transmission delay due to the characteristics of flooding is greatly increased. The disadvantage is that it cannot be improved.

In order to reduce network load and transmission delay, the distance-based broadcast technique allows only one node of an emergency alert message receiving node in a communication area to deliver a message. At this time, the selection of the forwarding node is determined based on the distance from the message transmitting node. In other words, the waiting time for broadcasting the warning message varies depending on the distance for each forwarding node so that the edge node farthest away from the message transmitting node can deliver the emergency message first. The distance-based broadcast technique is suitable for mobile environments when the density of nodes is high, because of the high bandwidth and arrival required for emergency message transmission, and the low end-to-end message propagation delay. However, this conventional distance-based broadcast method has a problem of increasing the end-to-end message propagation time because it is difficult to select an efficient edge node when the node density is low.

In order to solve the problems of the prior art as described above, the present invention can reduce the end-to-end message delivery delay time regardless of the density of the vehicle, and minimize the collision of packets due to broadcasting. The purpose is to provide a method.

In addition, the present invention compares the position of the vehicle receiving the vehicle safety message with the location of the accident and determines whether to retransmit its own vehicle safety message by sending a message of the vehicle ad hoc network that can minimize the network load It is another object to provide a method.

In addition, the present invention is a vehicle ad hoc capable of generating a transmission structure having a real time to the rear of the current vehicle safety message generation vehicle based on the time when the vehicle safety message occurs without exchanging the position information of the vehicle and the neighboring vehicle Another object is to provide a method of transmitting a message on a network.

In order to achieve the above object, according to a preferred embodiment of the present invention, in the message transmission method of a vehicle ad hoc network (VANET, Vehicular Ad Hoc Networks), the message receiving node calculates the distance from the message transmission node In addition, a message transmission method of a vehicle ad hoc network is provided, wherein the message is retransmitted only when the receiving node belongs to a preset retransmission activation area in the vehicle communication area based on the calculated distance.

Here, the above-described vehicle communication area may be configured to include a retransmission deactivation area for retransmitting a message and a retransmission activation area for retransmitting a message according to a distance from a node transmitting a message.

In addition, the above-described vehicle communication area may be configured to further include a boundary area not retransmitting a message as an area from behind the retransmission activation area to a maximum vehicle communication radius.

In this case, the above-mentioned retransmission deactivation area is an area in which the distance from the message transmission node is less than 80% of the vehicle communication radius, and the retransmission activation area is in the range from 80% or more to 95% or less of the vehicle communication radius. The boundary area may be configured such that the distance from the message transmitting node is an area exceeding 95% of the vehicle communication radius.

Meanwhile, the message transmission method of the aforementioned vehicle ad hoc network may be configured to select a message retransmission node by applying a distance-based broadcast algorithm to at least one or more receiving nodes belonging to the message retransmission region.

In order to achieve the above object, according to another preferred embodiment of the present invention, a message transmission method of a message receiving node of a vehicle ad hoc network, comprising: (a) receiving a message transmitted from a message transmitting node; (b) determining a current position of a receiving node using GPS, and calculating a distance from the transmitting node; (c) determining whether the receiving node belongs to the message retransmission area based on the calculated distance; And (d) retransmitting the received message if the receiving node belongs to the message retransmission area.

Here, step (d) described above may include: (d1) calculating a transmission waiting time based on a distance from a transmitting node; (d2) discarding the received message and switching to the standby state when the same message as the received message is received during the transmission waiting time; And (d3) retransmitting the received message after the transmission waiting time has elapsed, if the same message as the received message is not received during the transmission waiting time.

On the other hand, the message retransmission waiting time (RWT _i ) in the above-described step (d1),

The message retransmission activation region may be divided into a plurality of regions according to the distance from the transmitting node, and may be defined as a message retransmission waiting time allocated in inverse proportion to the distance in each repartitioned region.

On the other hand, the message retransmission waiting time (RWT _i ) in the above-described step (d1),

식을 이용해 산출되며,

Is calculated using an equation,

Here, di may be defined as a distance from a transmitting node, RWTmax is a maximum transmission waiting time, and R is a transmission distance of a transmitting node.

As described above, according to the present invention, it is possible to provide a message transmission method of a vehicle ad hoc network capable of shortening end-to-end message delivery delay time and minimizing packet collision due to broadcasting regardless of vehicle density. There is an advantage.

Further, according to the present invention, the message of the vehicle ad hoc network which can minimize the network load by comparing the position of the vehicle receiving the vehicle safety message with the position of the accident and determining whether to retransmit its vehicle safety message. There is an advantage that the transmission method can be provided.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the message transmission method of the vehicle ad hoc network and the message transmission method of the receiving node of the vehicle ad hoc network according to the present invention.

1 is a conceptual diagram illustrating an algorithm for performing a message transmission method according to an embodiment of the present invention. Hereinafter, with reference to the accompanying drawings will be described in detail a message transmission method of a vehicle ad hoc network according to the present invention.

The transmission node 100 shown in FIG. 1 is a raw transmission node that generates and transmits an accident occurrence message when an accident occurs, or a relay node that receives and retransmits the transmitted accident occurrence message. In addition, the circle shown around the transmitting node 100 shows the communication radius of the transmitting node 100, and in the present invention, the communication radius of the transmitting node 100 is determined according to the distance from the transmitting node 100. The receiving node receiving the message transmitted from the transmitting node 100 may be configured to determine whether to retransmit by determining the area to which the current receiving node belongs.

In more detail, the message transmission method according to the present invention is the retransmission disable area 110, which is set to not retransmit the received message and the retransmission activation set to retransmit the received message in the communication radius of the transmitting node 100. Area 120 and a boundary area 130 that is set not to retransmit the received message. The division of such an area is determined by the distance from the transmission node 100. Various criteria may be applied as necessary. However, in one embodiment according to the present invention, the retransmission deactivation area 110, which is the first area, may be used as a transmission node. 80% of the communication radius of 100), the retransmission activation area 120, which is the second area, is set to 80% to 95% of the communication radius of the transmitting node 100, and the boundary area 130, which is the third area, is set. Set up to 95% to 100% of the communication radius of the transmission node 100.

According to one embodiment configured as described above, it is located in the retransmission activation area 120 that occupies 15% of the receiving nodes that receive the message transmitted from the transmitting node 100 located within the communication radius of the transmitting node 100. Since only the receiving node participates in the message retransmission, it is possible to reduce the network overload caused by the excessive message retransmission and to minimize the message transmission omission.

2 is a conceptual diagram illustrating a message retransmission process through an edge node in a distance-based emergency message broadcasting protocol. As shown in Figure 2, vehicle ad hoc networks (VANET, Vehicular Ad Hoc Networks) is a raw transmission node 200, a raw transmission node 200 or a relay node 210, 220, 230 to generate and transmit an accident occurrence message Retransmitting a message as a receiving node that receives an accident message transmitted from a network node but receives an accident message transmitted from a general receiving node, a raw transmitting node 200, or a relay node 210, 220, or 230 that does not retransmit. It may include a relay node (210, 220, 230).

As described above, in the case of the distance-based emergency message broadcasting protocol, the waiting time for broadcasting the warning message varies depending on the distance so that the edge node farthest from the message transmitting node can deliver the emergency message first. Technique.

Accordingly, the N1 210 located at the outermost position among the reception nodes in the communication radius of the original transmission node 200 has the shortest waiting time, so that the N1 210 performs the retransmission of the message as a relay node. Similarly, the N2 220 located at the outermost position among the receiving nodes in the communication radius of the relay node N1 210 has the shortest waiting time to function as a relay node, which is N3 230 and N4 240. ) Is also selected as a relay node according to the same algorithm.

In one embodiment according to the present invention, a message transmission method can be provided by applying the distance-based broadcast algorithm as described above can be a more efficient message transmission.

That is, as described above, the retransmission deactivation area 110 is set to 80% of the communication radius of the transmission node 100 according to the communication radius of the transmission node according to the present invention, and the retransmission activation area 120 is transmitted. When the boundary area 130 is set to 80% to 95% of the communication radius of the node 100, and the boundary area 130 is set to 95% to 100% of the communication radius of the transmitting node 100,

In the message transmission method according to the present invention, only receiving nodes located in the retransmission activation area 120 may be configured to participate in a relay node selection process as a relay node candidate. When the invention is configured in this manner, only receiving nodes located in an area corresponding to 15% of the total communication radius of the transmitting node 100 participate in the selection process as a relay node candidate according to the distance-based broadcast algorithm. Since the area itself is up to 80% to 95% of the communication radius of the transmission node 100, there is an advantage that it is possible to reduce the overload by retransmitting the message and minimize the omission of message transmission.

In the distance-based broadcast protocol, the waiting time for emergency message delivery of each node is determined by the distance from the transmitting node. For example, if the receiving nodes v1, v2, and v3 are located at a distance (D1 <D2 <D3) from D1, D2, and D3 away from the transmitting node for transmitting the emergency message, each node is sent from the message transmitting node. Have message delivery latency inversely proportional to distance. Therefore, the v1 node closest to the message transmission node has the longest t3 latency, and the farthest v3 has the shortest t1 latency.

According to one embodiment of the present invention, the message retransmission activation region as described above is subdivided into two or more regions according to the distance from the transmitting node, and inversely proportional to the distance to each of the divided regions. It can be configured to enable the distance-based broadcast by setting a constant latency.

In more detail, for example, when the retransmission activation region is 80% to 95% of the communication radius of the transmission node 100 as described above, again 80% to 85% (first retransmission activation region), Subdivided into 85% to 90% (second retransmission active area) and 90% to 95% (third retransmission active area) areas, and set the waiting time of the receiving node located in the first retransmission active area to 2 seconds. The distance-based broadcast may be configured by setting a waiting time of a reception node located in the second retransmission activation area to 1 second and setting a waiting time of a reception node located in the third retransmission active area to 0 seconds. Of course, the criteria for subdividing the retransmission activation region, the number of subdivided regions, and the wait time allocated to each subdivided region may be set in various ways according to the needs of those skilled in the art. It will be apparent to belong to the scope of the present invention.

Meanwhile, according to another embodiment of the present invention, each node has a wait time RWTi for emergency message delivery according to the distance from the message transmission node, and RWTi may be defined by Equation 1 below.

In Equation 1, di is defined as a distance from a transmitting node, RWTmax is a maximum transmission latency, and R is a transmission distance of a transmitting node.

Receiving node receiving urgent message sent from sending node calculates message delivery waiting time according to distance for retransmitting message, and only nude that expired first broadcasts message to nodes located in its sending area. Cast. Since the waiting time becomes shorter as the distance increases, the node farthest in the transmission area of the node broadcasting the emergency message retransmits the emergency message again. According to the present invention, the node located at the outermost position among the at least one or more receiving nodes located in the retransmission activation area will be determined as the retransmission node to perform message retransmission.

On the other hand, if a node that has already received an emergency message receives a duplicate message, the received emergency message is discarded and enters a standby state, thereby reducing the overload caused by retransmission of broadcasting and minimizing the omission of a message. do.

3 is a flowchart illustrating a message retransmission process in a receiving node according to an embodiment of the present invention. Hereinafter, referring to FIG. 3, a message retransmission process in a receiving node according to the present invention will be described in detail.

First, the receiving node receives an emergency message (vehicle safety message, etc.) transmitted from a transmitting node (a raw transmitting node or a relay node) (S300), and determines whether the received message is a new message (S302). As a result of the determination, if the received message is a message that has already been received, the received message is discarded and switched to the standby state (S318).

As a result, if the received message is a new message, the receiving node calculates the position of the current vehicle by using the GPS device installed in the vehicle (S304), and uses the calculated vehicle position and the transmission node information included in the received message. The distance between the transmitting node and the receiving node is calculated (S306).

After the distance calculation with the transmitting node is completed, the receiving node determines whether the current receiving node is located in the retransmission activation area among the entire communication areas of the transmitting node (S308). At this time, according to the configuration of the invention, a criterion for setting from which to which areas of the entire communication area as the retransmission activation area may be set in various ways. More preferably, 80% to 95% of the entire communication areas It may be set as a retransmission activation area. On the other hand, the total communication area of the transmission node is determined according to the communication radius of the corresponding transmission node, the communication radius of such a transmission node may be predetermined according to the wireless communication device standard mounted on the vehicle, or may be mounted on the vehicle It may be set to an average and effective communication radius of various kinds of wireless communication devices, or may be set to a minimum communication radius of various types of wireless communication devices that may be mounted in a vehicle, or transmitted from a transmitting node. The message may be configured to be interpreted by including information on the communication radius of the corresponding transmission node.

If it is determined that the receiving node is not located in the retransmission activation area, the receiving node outputs the message to the driver using the display device and / or the voice output device equipped with the message, and then discards the message and goes to the standby state. (S318).

On the contrary, when the reception node is located in the retransmission activation area, the reception node calculates a transmission waiting time for retransmission (S310). In this case, the waiting time may be calculated through Equation 1 as described above, and various known waiting time calculation formulas that may be calculated to be inversely proportional to distance according to the needs of those skilled in the art may be applied. Even if applied to the scope of the present invention will be apparent to those skilled in the art.

The receiving node determines whether to receive the same message again until the calculated transmission waiting time elapses (S312, S314), and when receiving the same message, determines that retransmission has been made by another receiving node in the retransmission activation area. After discarding the received message is switched to the standby mode (S318).

On the other hand, when the receiving node does not receive the same message until the calculated transmission waiting time elapses, since the corresponding receiving node is selected as the relay node, the receiving node retransmits the received message and ends the process (S316).

4 is an exemplary view illustrating inserting position data in a wireless communication module according to an embodiment of the present invention.

For the experiment of the message transmission method according to the present invention, the wireless communication device was developed and the experimental procedure was performed. The actual device used was a wireless communication device equipped with Koinonia, a wireless communication chip developed by KETI. The Koinonia wireless communication chip is used to construct a module using an embedded Linux system, and the program writes a program using C on the Linux system. 4 shows the device and the experimental environment.

1) RF Transceiver Development

 -Frequency: ISM Band (2.4GHz) / BW: 7.5 MHz

 -Transmission speed: Max. 6 Mbps

 Process: S3C2410

 Memory: Flash (32MB) SDRAM (32MB)

 Wireless communication module: Koinonia KWPAN1200 V2.0 based on Binary CDMA

 In fact, four devices equipped with an algorithm for executing the message transmission method according to the present invention were used, and the proposed two transmission methods (first transmission method: receiving a communication node in the retransmission activation area by dividing the communication area of the transmission node into three areas). A transmission method in which only nodes participate in retransmission (hereinafter, referred to as' 15P broadcasting algorithm ') and a second transmission method: a transmission method in which receiving nodes in a retransmission activation region select a relay node and perform retransmission based on a distance-based algorithm (hereinafter' In order to experiment with the Slotted 15P Broadcast Algorithm ')), we experimented with two experimental environments. First, the experiment is performed on the 15P broadcasting algorithm for efficient transmission of the vehicle safety message first proposed in the present invention, and the second is the experiment on the slotted 15P broadcast algorithm proposed by the present invention.

5A to 5D are diagrams showing execution results of receiving nodes for each region according to an embodiment of the present invention. As described above, the first algorithm proposed in the present invention divides the transmission range of the wireless communication device into three parts, and if there are vehicles in the first area (retransmission disabled area), the vehicles do not retransmit the message when the vehicle safety message is received. In this case, experiments were performed to ensure that vehicles in the second zone (retransmission active zone) retransmitted messages, while vehicles in the third zone (boundary zone) did not retransmit the message so that collisions on vehicle safety messages would not occur. .

The test equipment uses 4 units, and since the equipment is not equipped with GPS in actuality, the equipment is placed in close proximity to each other so that all the devices can communicate wirelessly and insert position data into each device in the program. 5 shows inserting position data in a wireless communication module using a Koinonia chip.

In order to perform the experiment, the actual communication radius was excluded, and the arbitrary communication radius was set to 500m and divided into three parts to apply the algorithm accordingly. Since the first area is 80% of the communication radius, the device within 400m is not to be retransmitted, and the device in the second area, 401m to 475m, is to be retransmitted. The device in the last 5% of the range 476m to 500m receives the message but does not retransmit it. In this way, practically all four devices receive the message, but it is determined whether or not to retransmit the data according to the location data inputted to them. 5A to 5D, the entire contents of the 15P broadcasting algorithm proposed by the present invention are shown.

FIG. 5A is a result of device execution for transmitting a vehicle safety message, FIG. 5B is a result of device execution without retransmission, FIG. 5C is a result of execution of a message retransmission device, and FIG. 5D shows a result of execution of a device out of a communication radius. .

As shown in FIG. 5, the current GPS value indicated by each device is a value indicating the distance between its own device and the device that first transmitted the message.

The execution result shown in FIG. 5A is a node that transmits a message for the first time, and sets the position data value to '0' so that a vehicle equipped with this device is set as an accident vehicle and transmits the point to another device.

Referring to the results of the experiment shown in FIG. 5B, his position is set to a point 210m away from the accident, and the safety message is transmitted but is not retransmitted because it exists in a section not retransmitted by the 15P broadcast algorithm.

As can be seen from the experimental result of FIG. 5C, since the vehicle safety message is received after the vehicle safety message, the safety message is retransmitted.

Lastly, in FIG. 5D, since the location data set in the device is 600m, the vehicle safety message sent from the first node is not received because it is outside the 500m section, the communication radius of the accident device. However, because the third device retransmitted the vehicle safety message at 460m, it can receive the vehicle safety message.

6A through 6D are diagrams illustrating execution results of a reception node applying a distance-based broadcast algorithm in a message retransmission area according to an embodiment of the present invention.

Referring to FIG. 6, an experiment for the Slotted 15P broadcasting algorithm is performed as the second algorithm proposed by the present invention. In the same way as the experiment for the 15P broadcasting algorithm above, the experiment is performed by having different actions according to the position data. Slotted 15P broadcasting algorithm is a algorithm that divides the retransmission section into slots in order to prevent the collision caused by the same data by transmitting vehicle safety messages to each other if there are many vehicles in the retransmission section. The device used in the experiment was divided into three parts by using 4 units to perform the experiment. Of the 500m of any communication radius, the retransmission section 401m to 475m is divided into three parts 401m to 425m, 426m to 450m, and 451m to 475m to determine whether each device transmits a safety message. 6A to 6D, the general content of the Slotted 15P broadcasting algorithm is disclosed.

FIG. 6A is a result of executing a device for transmitting a vehicle safety message, FIG. 6B is a result of executing a device not retransmitted in a retransmission section, FIG. 6C is a result of executing a device not retransmitted in a retransmission section, and FIG. 6D is a retransmission. Execution result of the device retransmitting in the interval.

As shown in FIGS. 6A to 6D, the retransmission activation region is further divided into three sections so that the location data is set so that one device exists in each section, and the device configured as the point of an accident transmits a vehicle safety message. do.

Referring to the result of FIG. 6B, the location of the device is set to 410m so as to be within the first section of the 15% retransmission activation area. So I received a car safety message, but I set it to wait 2 seconds because it is located closest to the point where the accident occurred. So if you get the same car safety message within two seconds, don't send it yourself. Since the device having its location set to 470m in FIG. 5D retransmits the message immediately after receiving the vehicle safety message, the vehicle at 410m receives the message so that the vehicle does not retransmit the vehicle safety message.

Referring to the experimental result of FIG. 5C, the location of the device is set to 440m so as to exist in the second section of the retransmission section. So the device receives a vehicle safety message sent by the first node, but waits for one second without retransmitting the message. Therefore, if the same vehicle safety message is sent within 1 second, the message is not transmitted and the duplicate message is not transmitted for the same reason as the device at 410m.

Preferred embodiments of the present invention described above are disclosed for purposes of illustration, and those skilled in the art will be able to make various modifications, changes and additions within the spirit and scope of the present invention. Additions should be considered to be within the scope of the following claims.

1 is a conceptual diagram showing an algorithm for performing a message transmission method according to an embodiment of the present invention.

2 is a conceptual diagram illustrating a message retransmission process through an edge node in a distance-based emergency message broadcasting protocol.

3 is a flowchart illustrating a message retransmission process in a receiving node according to an embodiment of the present invention.

4 is an exemplary view illustrating inserting position data in a wireless communication module according to an embodiment of the present invention.

5A to 5D are diagrams showing execution results of receiving nodes for each region according to an embodiment of the present invention.

6A to 6D are diagrams illustrating execution results of a reception node applying a distance-based broadcast algorithm in a message retransmission area according to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

100: transmission node 110: retransmission disabled area

120: retransmission active area 130: boundary area

200: raw transport node

210, 220, 230, 240: relay node

Claims (9)

In the message transmission method of vehicle ad hoc networks (VANET, Vehicular Ad Hoc Networks), The message receiving node calculates a distance from the message transmitting node, retransmits the message only when the receiving node belongs to a preset retransmission activation area of the vehicle communication area based on the calculated distance, The vehicle communication area, Retransmission disabled area in the area where the distance from the message transmission node that does not retransmit the message according to the distance from the node that sent the message is less than 80% of the vehicle communication radius and the distance from the message transmission node is 80% of the vehicle communication radius And a retransmission activation area for retransmitting a message to the area up to 95% or more from the above. delete The method of claim 1, The vehicle communication area, And a boundary area not retransmitting the message as an area from behind the retransmission activation area to a maximum vehicle communication radius. The method of claim 3, The retransmission deactivation area is an area where the distance from the message transmission node is less than 80% of the vehicle communication radius, The retransmission activation area is an area where the distance from the message transmission node is from 80% or more to 95% or less of the vehicle communication radius. And wherein the boundary area is an area where a distance from a message transmission node exceeds 95% of a vehicle communication radius. The method of claim 1, The message transmission method of the vehicle ad hoc network, A method for transmitting a message in a vehicle ad hoc network, comprising selecting a message retransmission node by applying a distance-based broadcast algorithm to at least one receiving node belonging to a message retransmission area. In the message transmission method of the message receiving node of the vehicle ad hoc network, (a) receiving a message transmitted from a message transmitting node; (b) determining a current position of a receiving node using GPS, and calculating a distance from the transmitting node; (c) determining, based on the calculated distance, whether or not the receiving node belongs to a message retransmission activation area in an area where a distance from the message transmission node is from 80% or more to 95% or less of the vehicle communication radius; And (d) if the receiving node belongs to the message retransmission activation area, retransmitting the received message; The step (d) (d1) calculating a transmission waiting time based on a distance from the transmitting node; (d2) discarding the received message and switching to the standby state when the same message as the received message is received during the transmission waiting time; And (d3) if the same message as the received message is not received during the transmission waiting time, retransmitting the received message after the transmission waiting time has elapsed, In step (d1), the message retransmission waiting time RWT _i is

Is calculated using an equation, Where di is a distance from a transmitting node, RWTmax is a maximum transmission waiting time, and R is a transmission distance of a transmitting node. delete The method of claim 6, In step (d1), the message retransmission waiting time RWT _i is The message retransmission activation area is subdivided into a plurality of areas according to the distance from the transmitting node, and a message retransmission waiting time allocated in inverse proportion to the distance in each subdivided area. Way. delete

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