CN101431468B - Greed data forwarding method based on direction in vehicle-mounted network - Google Patents

Abstract

A greedy data forwarding method based on direction in a vehicle network, including: the source node sends the location request information of the destination node: the source node sends the location information of the destination node in a blind flood broadcast mode; Periodically update the location information of the destination node on each node; each node periodically broadcasts and sends beacon messages within its own hop range, and the information is provided by GPS. After each node receives the beacon message sent by the neighbor node, according to The node position information and movement direction information establish and update the neighbor table; data packet forwarding: the data is forwarded according to the greedy forwarding algorithm in the general geographic location routing protocol. If no suitable next hop is found, the direction is enabled. Forward. The combination method of the present invention with the traditional standard routing protocol not only retains many advantages of the existing mature routing protocol, but also can be easily applied in the existing network without extensive changes.

Description

A Direction-Based Greedy Data Forwarding Method in Vehicle Networks

technical field

The invention relates to network communication. In particular, it relates to a direction-based greedy data forwarding method in a vehicle-mounted network based on greedy direction forwarding and reliable routing calculation of transmission data packets in a vehicle-mounted ad hoc network.

Background technique

Vehicles play a huge role in contemporary society. While the use of vehicles brings convenience to people's lives, it also brings some headaches, such as frequent traffic accidents and traffic jams. These problems directly threaten people's lives, bring great troubles to people's lives, and become problems that governments of all countries need to solve urgently. With the rapid development of wireless communication technology and the continuous improvement of automotive electronic technology, many governments and research institutions are trying to solve these problems by establishing an inter-vehicle communication (IVC) system. The demand for inter-vehicle communication and the huge value contained in it have promoted the emergence and development of Vehicle Ad hoc Network (VANET).

Inter-vehicle communication has great randomness in time and place, so VANET network is an inter-vehicle communication system established in ad hoc mode. Specifically, VANET is a multi-hop temporary ad hoc network composed of vehicles equipped with wireless communication transceivers. The purpose of the VANET network is to improve the safety and efficiency of driving. VANET has extremely high application prospects and research value.

At present, for the relatively mature routing protocols of Ad Hoc networks, the research on routing algorithms in VANET networks mainly focuses on two types, the first is topology-based routing protocols; the second is geographical location-based routing protocols. The general standards of the first protocol are mostly based on the consideration of hops or delays, looking for the route with the least hops or minimum delay between the source node and the destination node, without taking into account the rapid movement of nodes in the network, which caused some nodes A problem with path failure caused by leaving the original position. The second type of protocol is typically represented by a greedy peripheral state routing protocol, which independently and in real time determines each hop in the process of routing a data packet from a source node to a destination node. However, in the VANET network, due to the instability of the neighbor relationship between nodes caused by the rapid movement of nodes, the location information used in routing is outdated. That is, it cannot guarantee the accuracy of the information.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method that can obtain and maintain the location information of the destination node in time, and through a good combination of direction forwarding ideas, the routing algorithm is a reliable direction-based forwarding method that meets the requirements of the VANET network. The routing algorithm implements the direction-based greedy data forwarding method in the vehicular network for the reliable transmission of data packets.

The technical solution adopted in the present invention is: a greedy data forwarding method based on direction in a vehicle-mounted network, including sequentially completing the following components:

(1) The source node sends the location request information of the destination node: the source node sends the location information of the destination node in a blind flood broadcast mode, and the message ends when it reaches the requested destination node;

(2) The destination node responds to the destination node location request information: when the destination node location request information sent by the source node reaches the requested destination node, the destination node will start the propagation of the location information update message of the destination node, and start periodic Update the location information of the destination node on each node;

(3) Each node regularly broadcasts and sends beacon messages within its own one-hop range. The message contains its own location information and node movement direction information. These information are provided by GPS. After each node receives the beacon message sent by the neighbor node , establish and update the neighbor table according to the node position information and movement direction information;

(4) Forwarding of data packets: data forwards packets according to the greedy forwarding algorithm in the general geographic location routing protocol, if no suitable next hop can be found, then enable direction forwarding, including the following steps:

(4.1) When a node has data to send, it first traverses the neighbor table, searches the neighbor table to see if the destination node is within its own one-hop range, and forwards it directly if it is;

(4.2) If the destination node is not within its own one-hop range, forward according to the greedy forwarding strategy in the geographic location;

(4.3) If greedy forwarding does not find a suitable next hop, enable directional forwarding. Traversing the neighbor table, find out the node whose movement direction is closest to the direction of the destination node to forward the packet.

Described part (1) source node sends destination node position request information, comprises the following steps:

(1.1) When the source node has a data packet to send, if the source node has not obtained the location information of the destination node where the data packet is expected to arrive, the source node will send a destination node location request to the designated destination node;

(1.2) If the source node searches its destination node list and finds that the newer location information of the destination node already exists, it does not need to send the destination node location request information, and directly uses its existing destination location information for judgment.

Described part (2) comprises the following steps:

(2.1) When the destination node receives the location request message, it will periodically broadcast the location update message of the destination node to its direct neighbor nodes, and each neighbor node will create or update the corresponding location node by retrieving its destination node list according to this message. location information records;

(2.2) Each node except the destination node periodically broadcasts the destination node location interaction message to their direct neighbor nodes, through which each node communicates with each other about the location information of a destination node they save, so that each node can Can keep a "relatively up-to-date" record of the location information of the destination node;

(2.3) After any direct neighbor node of the destination node receives the node location update message, the action to be performed is: create or update the corresponding location information record for the specified destination node in their destination node list;

(2.4) After a node receives the node location interaction message, use the identifier ID of the destination node of the destination node carried in the received node location interaction message to retrieve the destination node list saved on the node and find the corresponding The record of the node; then, compare the timestamp ts1 in the node location interaction message with the timestamp ts2 in the destination node record just retrieved; if ts1>ts2, it means that the destination location information in the node location interaction message is relatively updated , then use the destination location information carried in the node location interaction message to update the corresponding location information in the destination node list of the node, otherwise do not make any processing.

The greedy data forwarding method based on direction in the vehicle-mounted network of the present invention considers various problems caused by the rapid change of network topology from various angles, and proposes a greedy direction forwarding routing protocol, which has the following advantages:

(1) It is a location-based routing algorithm, and the forwarding strategy adopted is "greedy forwarding", that is, when a data packet is transmitted, the next hop that the data packet should arrive at is determined in real time. There is no need to establish a complete path in advance, and the process of route establishment and route maintenance is not required.

(2) The routing algorithm uses the strategy of directional forwarding, and further searches for an available next hop after the greedy forwarding fails, so as to realize the reliability of data packet forwarding. The essence of direction forwarding is a retry mechanism.

(3) The routing algorithm uses two mutually independent message mechanisms to maintain and update the location information of the destination node. This way of updating information can cope with possible network segmentation. Even if there is a network split, it can ensure that each node maintains a relatively up-to-date destination node location information. Therefore, the routing algorithm ensures the accuracy and consistency of the destination node location information used in routing calculations to the greatest extent, and improves the quality of data transmission.

The present invention is developed from the typical location-based routing protocol in the current vehicle-mounted Ad Hoc network, improves its routing criteria on the basis of it, introduces the idea of direction forwarding, and then realizes reliability and accuracy of information. This combination with the traditional standard routing protocol makes the present invention retain many advantages of the existing mature routing protocol, and can be easily applied to the existing network without extensive changes, and the effect is ideal. The application prospect is promising.

Description of drawings

Fig. 1 is the schematic diagram of basic framework principle of the present invention;

Fig. 2 is a schematic diagram of the application of two message mechanisms of the present invention;

Fig. 3 is the message format of the request destination node position that the present invention uses;

Fig. 4 is the message format of updating destination node position that the present invention uses;

Fig. 5 is the message format of the interactive destination node position that the present invention uses;

Fig. 6 is a schematic diagram of the concept of directions used in the present invention;

Fig. 7 is an example diagram of the calculation and selection method of the direction used by the present invention;

Fig. 8 is a topological diagram of an example network used in the experimental stage of the present invention.

Detailed ways

The direction-based greedy data forwarding method in the vehicular network of the present invention will be described in detail below with reference to the embodiments and the accompanying drawings.

As shown in FIG. 1 , the basic framework principle of the direction-based greedy data forwarding method in the vehicular network of the present invention—the research on the greedy directional forwarding routing protocol of the vehicular ad hoc network. When the node has data to send, the location information of the destination node is updated according to the destination node location update message received periodically by the destination node, and the neighbor table is established and updated according to the periodic hello (beacon) message. Afterwards, the greedy forwarding strategy is adopted to forward the packets. If no suitable next hop is found, the forwarding mechanism will enter the direction and search for the next hop again. If forwarding in the other direction fails, the data packet is discarded, and other packets in the data packet queue continue to be processed.

As shown in Figure 2, the destination node interacts with its one-hop neighbor nodes using the destination node location update message q (query message). The destination node location interaction message d (destInfo message) is used to interact with other nodes except the destination node to update the location information of the destination node. And when the network is split, other nodes can also use the destInfo message to propagate the latest location information of the destination node. The location information is obtained by the GPS system on the car. This ensures that each node in the network maintains a relatively consistent piece of destination node information. Nodes H, I, and J in the figure are one-hop neighbor nodes of destination node D. Nodes K, L, and M are one-hop neighbor nodes of node A.

If the node has data to send, first use the greedy forwarding strategy to determine the next hop, if the greedy forwarding strategy does not find a suitable next hop, then turn to the direction forwarding mechanism and try again.

The direction-based greedy data forwarding method in the vehicle network of the present invention includes sequentially completing the following components:

(1) The source node sends the destination node location request information: the message format is shown in Figure 3, where the field id gives the number of the destination node requesting its location information. The source node sends the location information of the destination node in a blind flood broadcast mode, and the message ends when it reaches the requested destination node; it includes the following steps:

(1.1) When the source node has a data packet to send, if the source node has not obtained the location information of the destination node where the data packet is expected to arrive, the source node will send a destination node location request to the designated destination node;

(1.2) If the source node searches its destination node list and finds that the newer location information of the destination node already exists, it does not need to send the destination node location request information, and directly uses its existing destination location information for judgment.

(2) The destination node responds to the destination node location request information: when the destination node location request information sent by the source node reaches the requested destination node, the destination node will start the propagation of the location information update message (query message) of the destination node, Begin to periodically update the location information of the destination node on each node; including the following steps:

(2.1) When the destination node receives the location request message, it will periodically broadcast the location update message (query message) of the destination node to its direct neighbor nodes. The message format is shown in Figure 4, where the fields x and y indicate The coordinate value of the destination node that sends the location update message. According to this message, each neighbor node creates or updates the corresponding location information record by retrieving its destination node list; that is, it broadcasts a destination node location update message (query message) to its direct one-hop neighbors, and then its direct The neighbor establishes and updates the destination location information list according to this message.

(2.2) Each node except the destination node periodically broadcasts the destination node location interaction message (destInfo message) to their direct neighbor nodes. The message format is shown in Figure 5, where the field id points out the node in the interaction message number; the fields x and y indicate the coordinate value of the destination node in the interaction message; the field time stamp indicates the update time corresponding to the location information of the destination node in the interaction message. Through this message, each node communicates with each other about the location information of a certain destination node, so that each node can save a "relatively up-to-date" record about the location information of the destination node;

(2.3) After any direct neighbor node of the destination node receives the node location update message (query message), the action performed is: create or update the corresponding location information record for the specified destination node in their destination node list ;

(2.4) After a node receives the node location interaction message (destInfo message), use the identifier ID of the destination node of the destination node carried in the node location interaction message received to retrieve the destination node list stored on the node, Find the record of the corresponding node; then, compare the timestamp ts1 in the detInfo message with the timestamp ts2 in the destination node record just retrieved; if ts1>ts2, it means that the destination location information in the destInfo message is relatively updated If yes, use the destination location information carried in the destInfo message to update the corresponding location information in the destination node list of the node, otherwise do not do any processing.

(3) Each node regularly broadcasts and sends hello (beacon) messages within its own hop range. The message contains its own location information and node movement direction information. These information are provided by GPS. Each node receives the hello message sent by the neighbor node. After receiving the message, the neighbor table is established and updated according to the node position information and movement direction information in it.

(4) Forwarding of data packets: data forwards packets according to the greedy forwarding algorithm in the general geographic location routing protocol, if no suitable next hop can be found, then enable direction forwarding; including the following steps:

(4.1) When a node has data to send, it first traverses the neighbor table, searches the neighbor table to see if the destination node is within its own one-hop range, and forwards it directly if it is;

(4.2) If the destination node is not within its own one-hop range, it will be forwarded according to the greedy forwarding strategy in the general geographic location.

(4.3) If greedy forwarding does not find a suitable next hop, enable directional forwarding. Traversing the neighbor table, find out the node whose movement direction is closest to the direction of the destination node to forward the packet. That is, if greedy forwarding fails, retry with the directional forwarding mechanism. The concept of directional forwarding is shown in Figure 6, where A represents the neighbor node of the forwarding data packet node, D represents the destination node, A' represents the position A moves to after a short period of time, and a represents the distance between AD and AA' angle. Calculate the cosine value of the angle between the neighbor node of the forwarding node and the destination node by using the cosine law. Select the node with the largest positive median among them. This ensures that packets are forwarded in the correct direction towards the destination node.

The calculation process of the direction angle is shown in Figure 7, where A represents the neighbor node of the forwarding data packet node, D represents the destination node, and A' represents the position that A moves to after a short period of time. a represents the angle between AD and AA'. The position coordinate information of these nodes are in brackets respectively. Use the moving direction of the neighbor node in a short time to re-judge its position, and then use the cosine law to calculate the angle between it and the direction of the destination node. Among them, the position and movement direction information of forwarding node, neighbor node and destination node are used. This information is provided by the GPS system.

The direction-based greedy data forwarding method in the vehicle-mounted network of the present invention updates the location information of the destination node stored on each node by using two independent messages, thereby reducing the communication between nodes caused by the disconnected state of the VANET network The destination location information saved by the node caused by the lag is inaccurate. Direction-based forwarding enables data to quickly reach the destination according to a certain directionality. The algorithm of greedy direction forwarding routing protocol uses these two characteristics, the purpose is to ensure the accuracy of the location information of the destination node used in routing selection, and then improve the quality of data transmission. As an ideal, highly reliable, and practical technical solution, this method can obtain and maintain the location information of the destination node in time, and well combines the idea of direction forwarding, making this routing algorithm a satisfactory The reliable routing algorithm based on direction forwarding meets the requirements of VANET network, and realizes the reliable transmission of data packets.

The following takes the network scenario in Figure 8 as an example, and cooperates with the previously described mechanism to briefly introduce the workflow of the present invention:

(1) The vehicle node is driving on the road with a maximum speed of about 50m/s at a certain acceleration, and the road section uses two lanes.

(2) The service flow used is the CBR service flow, the size of the sent packet (packetSize) is 256 bytes, and 4 data packets are sent per second. The business flow defined here corresponds to the Internet multimedia application in the vehicular ad hoc network.

(3) Assuming that node 10 sends a data packet to node 15, it is judged that the location request message of the destination node is flooded and broadcasted. It can be seen from Fig. 10 that node 5 and node 24 are one-hop neighbors of node 10, they send hello messages regularly, and tell the source node their location information through GPS. After the destination node receives the destination node location request message, it sends its own location information regularly, and other nodes regularly send destination location interaction messages to update the location information of the destination node in time. These location information are obtained through GPS. Using d1 and d2 to represent the distances from node 5 and node 24 to the destination node 15 respectively, it can be seen that d1<d2 at this moment. According to the greedy forwarding strategy, the data packet is forwarded to node 4 first, and then the data packet is forwarded according to the same judgment in a later time, and finally transmitted to the destination node 15 .

(4) If a suitable next hop is not found in one of the hops, use the directional forwarding mechanism mentioned in stage (2) to search for the next hop again.

(5) As a mobile node, the vehicle is not limited by energy conditions, so the transmission power of wireless transmission can be applied to a larger power when the reality can be satisfied.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention within.

Claims (3)

1. In the In-vehicle networking based on the greedy data forwarding method of direction, it is characterized in that, comprise and finish following few component parts successively:

   (1) source node sends target node position request information: the broadcast mode that source node floods with blindness sends the positional information of destination node, and this message terminates when arriving the destination node of being asked;

   (2) destination node response target node position request information: when the target node position request information of being sent by source node arrives the destination node of being asked, this destination node will start the updating location information transmission of news of destination node, the periodic positional information of upgrading the destination node on each node of beginning;

   (3) the regular broadcast transmission beacon message in oneself jumping scope of each node, the positional information and the movement direction of nodes information that comprise oneself in the message, these information are provided by GPS, after each node is received the beacon message of neighbor node transmission, according to node location information and foundation of direction of motion information and renewal neighbor table wherein;

   (4) forwarding of packet: the forwarding that data are wrapped according to the greedy forwarding algorithm in the Routing Protocol of general geographical position, if can not find next suitable jumping, then enable direction and transmit, may further comprise the steps:

   (4.1) when node has data to send, first traversal neighbor table, whether the search destination node is in an oneself jumping scope, if in just directly forwarding from neighbor table;

   (4.2) if destination node not in the jumping scope of oneself, then transmit according to the greedy forwarding strategy in the geographical position;

   (4.3) if greedy the forwarding do not found next suitable jumping, then enable direction and transmit, the traversal neighbor table is found out the forwarding that the direction of motion is wrapped from that nearest node of destination node direction.
2. 2. based on the greedy data forwarding method of direction, it is characterized in that in the In-vehicle networking according to claim 1 that described part (1) source node sends target node position request information, may further comprise the steps:

   (1.1) when source node has packet to send, if source node does not also obtain the positional information that the destination node of arrival is estimated in packet, source node will send a target node position request to the destination node of appointment;

   (1.2) if source node is searched for the tabulation of its destination node, find to have existed destination node than new location information the time, then need not send target node position request information, directly judge with its existing destination locations information.
3. 3. based on the greedy data forwarding method of direction, it is characterized in that in the In-vehicle networking according to claim 1 that described part (2) may further comprise the steps:

   (2.1) after destination node is received location request message, it will be periodically to its immediate neighbor node broadcasting target node position updating message, each neighbor node is tabulated by the destination node of retrieving it according to this message and is created or upgrade corresponding positional information record;

   (2.2) node of each except destination node is periodically broadcasted the target node position interaction message to their immediate neighbor node, exchange the positional information that their are preserved mutually by each node of this message, make each node can both preserve the record about the positional information of this destination node of portion " up-to-date relatively " about certain destination node;

   (2.3) any one immediate neighbor node of destination node is after receiving the node location updating message, and performed action is: create for the destination node of appointment in their destination node tabulation or upgrade corresponding positional information record;

   (2.4) after a node is received the node location interaction message, use the identifier ID of the destination node of the destination node of carrying in the node location interaction message that receives, the destination node that retrieval is preserved on this node is tabulated, and seeks the record of corresponding node; Then, the timestamp ts2 in timestamp ts1 in the interaction message of comparison node position and the destination node that just the retrieved record; If ts1＞ts2, illustrate that then the destination locations information in the node location interaction message is to upgrade relatively, then upgrade relevant position information in the destination node tabulation of this node, otherwise do not make any reason that goes out with the destination locations information of carrying in the node location interaction message.

Images