CN106304237B - Terminal-Vehicle Communication Method Based on Wireless Protocol - Google Patents

Abstract

The invention provides a terminal-vehicle communication method based on a wireless protocol. The method includes: setting a cruising vehicle node, driving along a predefined route, sending messages continuously during the driving process, broadcasting the received message by the roadside node, and the vehicle node in the When passing through the network coverage of the cruising node, the corresponding message is received. The invention proposes a terminal-vehicle communication method based on a wireless protocol, which is suitable for the condition that the topology structure of the vehicle-mounted network changes frequently, improves the throughput of the network and reduces the network congestion.

Description

Terminal-Vehicle Communication Method Based on Wireless Protocol

technical field

The invention relates to a vehicle network, in particular to a terminal vehicle communication method based on a wireless protocol.

Background technique

In order to improve the efficiency of transportation and slow down the consumption of resources, intelligent transportation systems are inevitably used in vehicle research and development, and the inter-vehicle network has also become a hot topic in optimizing modern transportation. People can use the wireless communication equipment equipped on the vehicle to complete the direct or indirect communication between the vehicle nodes. In order to achieve the purpose of completing the transmission, processing and interaction process of various transmission information in the vehicle-to-vehicle network in the intelligent transportation system. From the perspective of improving service convenience, drivers can collect various information broadcasted by other vehicles, so that they can easily find some nearby service points. At the same time, the electronic non-stop toll collection system is adopted, which can greatly shorten the waiting time for vehicles to pay. After the equipment installed on both sides of the road and the information carried by the vehicle itself play a public role, relevant departments can make full use of this information to intelligently dispatch traffic.

However, the vehicle itself is moving at high speed, and due to the large restrictions on urban roads, the topology of the network is also changing rapidly, and the communication time between each node is short, and the existing inter-vehicle communication methods cannot be very real-time. It adapts to the dynamic characteristics of the frequent change of the topology structure of the vehicle network, so it does not play a relatively high-quality performance in terms of network characteristics such as improving the throughput of the network. Network congestion is often caused when there are too many on-board nodes.

SUMMARY OF THE INVENTION

In order to solve the problems existing in the above-mentioned prior art, the present invention proposes a terminal-vehicle communication method based on a wireless protocol, including:

The cruising vehicle node is set up to drive along a predefined route, and continuously send messages during the driving process. The roadside node broadcasts the received message, and the vehicle node receives the corresponding message when it passes through the network coverage of the cruising node.

Preferably, messages in the network have a unique message id number. After the target node R receives the message, if it is determined that the message has not been received before, the id number of the message is stored in the broadcast table; if the target node R Find the same id number of the received message in its broadcast table, indicating that the message has been received, it is determined to be a redundant message, and it is discarded directly, otherwise the target node R will process the data as follows;

According to the location information obtained by GPS, the vehicle node judges whether it is located in the dense area of vehicle nodes; if the target node R is located in the dense area of vehicle nodes or R belongs to the roadside node, then R forwards the received message after delaying WD ₁ ; The location of node R is not in the dense area of vehicle nodes but the source node S is located in the dense area of vehicle nodes, then R discards the message; if the source node S is not a node in the dense area of vehicle nodes, then _R connects its direction DR with the last hop source node S The direction D _S continues to compare, if their moving directions are the same, after a delay of WD ₂ , the message is sent, and if it is determined that their directions are opposite, the forwarding is abandoned;

where WD ₁ =(1-P _d )×T _p

WD ₂ =(1-P _d )×2T _p

T _p represents the minimum duration between one-hop broadcasts;

P _d =d _sr /d _max is the probability related to the distance, d _sr is the distance between the source node and the target node of the last forwarding, and d _max is the maximum value within the coverage area of the node.

Compared with the prior art, the present invention has the following advantages:

The invention proposes a terminal-vehicle communication method based on a wireless protocol, which is suitable for the condition that the topology structure of the vehicle-mounted network changes frequently, improves the throughput of the network and reduces the network congestion.

Description of drawings

FIG. 1 is a flowchart of a wireless protocol-based terminal vehicle communication method according to an embodiment of the present invention.

Detailed ways

A detailed description of one or more embodiments of the invention is provided below together with the accompanying drawings that illustrate the principles of the invention. The present invention is described in conjunction with such embodiments, but the present invention is not limited to any embodiment. The scope of the invention is limited only by the claims, and the invention encompasses numerous alternatives, modifications and equivalents. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. These details are provided for the purpose of example and the invention may be practiced according to the claims without some or all of these specific details.

An aspect of the present invention provides a wireless protocol-based terminal vehicle communication method. FIG. 1 is a flowchart of a wireless protocol-based terminal-vehicle communication method according to an embodiment of the present invention.

The application layer management module of the vehicle node collects data in the wireless network, analyzes the source and type of the data, and realizes the management of sending and receiving of upper-layer message information, and the setting and monitoring of encoding rules. The routing management module is responsible for the selection of routing mechanisms, routing requests, and monitoring responses and maintenance. The access management module exists between the routing layer and the MAC layer, and is responsible for obtaining data at the routing layer and assigning random target addresses to it, and then sending the address information to the MAC layer. The wireless transmission module is used for the management of the transmitting antenna and the receiving antenna. According to the coding result of the data, it is processed in an analog manner, and the data in the queue is transmitted in the corresponding transmission channel through the antenna, and the transmission performance is controlled by the antenna. and management.

For the message distribution of the application layer management module, the embodiment of the present invention expands the selection range of relay nodes, and simultaneously adopts location estimation to obtain the characteristics of low delay and low load of message broadcasting.

The vehicle sends a beacon message to adjacent nodes. When the difference between the estimated position and the actual position of the vehicle exceeds the set error threshold, periodic transmission and condition-driven transmission are simultaneously used. Through beacon messages, vehicles in the network can obtain the location information of adjacent nodes and continuously update the adjacency table.

The vehicle obtains its own position information through GPS, and calculates the current speed s and direction θ of the vehicle based on the historical record of vehicle movement and current position information.

Extract the vehicle node ID in the beacon message, and determine whether the vehicle sending the beacon is in the adjacency list of the current vehicle. If it is an adjacent node of the current vehicle, update the adjacency list; otherwise, add the vehicle sending the beacon message to the adjacency list.

Extract the vehicle position information, vehicle direction information, vehicle speed information and timestamp information in the beacon message. The position (X _p , Y _p ) of the adjacent node at the current time t ₂ is estimated.

X _p =X+s×(t ₂ -t ₁ )×cos(θ)

Y _p =Y+s×(t ₂ -t ₁ )×sin(θ)

where (X, Y) and t ₁ are the location information and timestamp carried by the last received beacon before the adjacent vehicle is estimated. And s and θ are the vehicle speed and direction information in the beacon last received by the vehicle before estimation.

The current vehicle calculates the effective time of the communication link between the current node and its adjacent nodes according to the estimated position of the adjacent vehicle.

The vehicle compares the estimated position of the adjacent point with its own position, and classifies the positional relationship into one of the following four categories: front co-directional, rear co-directional, front reverse, and rear reverse.

The current vehicle calculates the distance D between itself and its neighbors:

D=((X _v -X _p ) ² +((Y _v -Y _p )) ² ) ^1/2

Here (X _v , Y _v ) represents the coordinate position of the current vehicle, and (X _p and Y _p ) are the estimated coordinate values of the adjacent node positions.

The position estimation process stops and restarts until the current vehicle receives a new beacon message.

When a high-priority abnormal event occurs in a vehicle, the abnormal vehicle immediately generates an abnormal message and selects a forwarding node to broadcast. When other vehicle nodes receive the abnormal message, it is determined whether the abnormal message needs to be broadcast. The message needs to be forwarded if one of the other vehicle nodes is selected as the forwarding node.

If there is a vehicle node behind the abnormal vehicle in the same direction, the abnormal vehicle selects the farthest vehicle as the immediate successor node, and selects the next farthest vehicle as the second successor node. If there is a vehicle in the reverse direction behind the abnormal vehicle, the farthest vehicle is selected as the direct successor node, and the second farthest vehicle is selected as the second successor node. If there is a vehicle in the reverse direction of the abnormal vehicle, the nearest vehicle is selected as the immediate successor node, and the next closest vehicle is selected as the second successor node. If none of the above conditions are satisfied, the abnormal vehicle stores the abnormal message until the new vehicle enters its wireless information coverage area, and then selects forwarding again according to the above conditions.

After the abnormal vehicle selects the forwarding node, according to the positional relationship between the forwarding node and the abnormal vehicle node, the abnormal message is distributed from the forwarding node R to other nodes in two cases. Vehicle R with the same direction as the current vehicle is selected as the forwarding node. After receiving the abnormal message, R detects its own position. If its own position exceeds the boundary of the area where the abnormal vehicle is located, it broadcasts the copied abnormal message as confirmation information. If its own position is still within the boundary of the area where the abnormal vehicle is located, the forwarding node R selects the optimal successor node by judging.

(a) If there are vehicles traveling in the same direction behind the forwarding node's travel direction, the forwarding node R selects the farthest vehicle as the first choice for the next node, and selects the second farthest vehicle as the second choice for the forwarding node.

(b) If there is a vehicle node in the opposite driving direction, the current forwarding node selects the farthest vehicle as the immediate successor node, and the next farthest node as the second successor node.

(c) If the two conditions are not satisfied, the forwarding node broadcasts an exception message as confirmation, and then uses the store-and-forward mechanism to cache the exception message, and at the same time detects the current position of the forwarding node. If it is found that the forwarding node is passing by an abnormal vehicle, the forwarding node terminates the forwarding process; otherwise, when the forwarding node encounters other vehicles, the forwarding node selects the next forwarding node to forward the abnormal message.

When the reverse vehicle R is selected as the forwarding node, after receiving the abnormal message, the forwarding node detects its own position. If it exceeds the boundary of the area where the abnormal vehicle is located, the forwarding node R only needs to broadcast the repeated abnormal message for confirmation; otherwise , the forwarding node selects the next node according to the following process.

(a) If there is no vehicle node behind the forwarding node R in the reverse direction, it selects the farthest vehicle node and the second farthest vehicle node in the reverse direction as the first choice and the second choice of the subsequent relay.

(b) If there is a vehicle node in the same direction ahead of R, the farthest vehicle and the next farthest vehicle are selected as the immediate successor node and the second successor node, respectively.

(c) If both conditions are not satisfied, the forwarding node broadcasts the duplicated exception message as confirmation information, then switches to the store-and-forward mode, and performs location detection. If the relay vehicle exceeds the boundary of the area where the abnormal vehicle is located, the forwarding is terminated, otherwise, the forwarding node continues to select the next node. When the forwarding node or the subsequent forwarding node receives the abnormal message, a different vehicle is selected as the next forwarding node.

On the basis of the above forwarding method, the present invention further realizes data transmission with the help of cruising vehicle-mounted nodes with predetermined routes, which helps vehicle nodes to distribute data to one or more target nodes. The cruising vehicle node travels along a predefined route and continuously sends messages during the driving process. The roadside node broadcasts the received message, and the vehicle node receives the corresponding message when it passes the coverage of the cruising node. Messages in the network have a unique message id number. When the target node R receives the message, if it determines that the message has not been received before, the id number of the message is stored in the broadcast table. If the target node R looks up the same id number of the received information in its broadcast table, it means that the message has been received, it is determined to be a redundant message, and it is discarded directly, otherwise the target node R will process the data in the next step.

According to the location information obtained by GPS, the vehicle node determines whether it is located in a dense area of vehicle nodes. If the target node R is located in a dense area of vehicle nodes or R belongs to a roadside node, then R forwards the received message after a delay of WD ₁ . If the location of the receiving node R is not in the dense area of vehicle nodes but the source node S is located in the dense area of vehicle nodes, then R discards the message. If the source node S is not a node in the dense area of vehicle nodes, R will continue to compare its own direction DR with the direction D _S of the last hop source node _S , and if their moving directions are the same, after a delay of WD ₂ , send a message. If it is determined that they are in opposite directions, the forwarding is discarded.

where WD ₁ =(1-P _d )×T _p

WD ₂ =(1-P _d )×2T _p

T _p represents the minimum duration between one-hop broadcasts.

P _d =d _sr /d _max is the probability related to the distance, d _sr is the distance between the source node and the target node of the last forwarding, and d _max is the maximum value within the coverage area of the node.

The routing management module of the present invention divides the communication process between the source node and the target node into routing request, receiving response and encoding interception.

When a node receives a routing request message, it first creates or updates a routing table entry. Then check whether a routing request packet with the same source IP address and routing request ID message is received within a predefined interval, and if so, ignore the currently received routing request packet. When the received routing request is not ignored, first increase the number of hops in the routing request by 1, then search for the reverse path of the source node in the routing table, and use the longest matching principle to create a new reverse routing table entry. Or update the original routing table entry with the source node ID in the routing request. When a reverse path is created or updated, do the following:

(1) Compare the source node ID of the routing request message with the target node ID in the corresponding reverse route, and if the former is larger than the latter, replace the latter with the former.

(2) The effective ID value of the routing entry is set to true.

(3) The next item of the routing item is set as the node that transmits the routing request to the node.

When a node receives a routing response, it first searches for the predecessor routing entry in the routing table, and creates a new entry that does not contain a valid ID. The node then increments the hop count in the route response by 1. Compare the target node ID in the route response with the existing ID. If the current node is not the source node in the routing response, the routing table is consulted to determine the successor of the routing response. If the link of the route response sent by the node is faulty or unidirectional, the node causes the receiver of the route response to reply with an acknowledgement signal.

Any node that forwards the route response will add the successor of the route response to the predecessor table of the route entry to the target node, and at the same time, modify the lifetime of the source node path to the larger value of the existing lifetime. The routing response is to judge the listening through the broadcast packet of the routing response, and if there is, store the path of the current flow and the listening node information in the routing response. Whether the next step is performed is determined by the packet request in the routing layer and the judgment of the relevant judgment conditions in the control layer.

The judgment conditions for encoding interception are:

The k messages p ₁ , p ₂ , ..., p _k to be sent in the node queue, the corresponding successor nodes are v ₁ , v ₂ , ..., v _k , the encoded messages are obtained after encoding Broadcast the encoded message p to the above node sets v ₁ , v ₂ , . . . , v _k . _{If in v1} , _{v2 , .}

Node v _i is the precursor node of packet P _j , j≠i, or

Node v _i has detected the message P _j , j≠i;

Then the node v _i will buffer the message p _j for a certain period of time to obtain more codes.

During the encoding process, when the wireless channel is valid, the node takes out the header message from the output queue and checks whether the header message can be encoded with other initial messages in the queue. If the encoding can be performed, the initial packets will be ANDed and broadcast to each adjacent node. If it cannot be encoded, the node broadcasts the initial message directly without waiting for a matching initial message. If the forwarding node does not receive the reception report sent by the adjacent node, the node uses the routing protocol to calculate the arrival rate of the link between the successor nodes, and estimates the possibility of the successor node to store an initial message according to the arrival rate. This determines whether to do network coding.

If a forwarding node encodes n packets at a time, and the probability that the subsequent receiving node of the n-th packet hears another packet i is P _i , then the probability P that the receiving node can decode correctly is P i . _D is equal to the probability that this node can listen to the other n-1 initial packets participating in the encoding:

P _D =P ₁ ×P ₂ ×…×P _n-1

At this time, it is judged whether the probability _PD that the successor node set of the n initial messages can be decoded satisfies a threshold value P _G or not. If the threshold constraint is met, the node initiates a routing request process and broadcasts a routing request message to the network, which contains the target node ID, code ID, source node address and target node address. When the intermediate node receives the routing request message, the intermediate node first broadcasts the routing request message sent by the source node, then incrementally modifies the encoded ID in the packet, and broadcasts the message to the set of subsequent nodes with encoding, in the packet header List of addresses to join the node set. If different routing requests are received on a node, the size of the target node ID is first determined to update the route; if the target node ID is the same, the encoded path is determined according to the encoded ID. After the target node receives the routing request packet, it directly feeds back the route response to the source node according to the original path, and establishes a coded route from the source node to the target node.

In the in-vehicle network, due to the constant change of the network topology, the uncertainty and constant interruption of the communication link, there are two states: when the nodes u and v are within the communication range of each other, the link is connected and can be transmitted; if not in communication The link within the range fails.

(1) Each node u in the network initializes its own local group set C _u , frequent visit set _Fu , meeting duration W(u, v) of nodes u and v, and local group frequent visit set _Lu .

(2) When the nodes u and v meet, the nodes exchange local information with each other, including the group set, the frequent access set and the local group frequent access set. Determine whether node v belongs to C _u , if it belongs to jump 7, if not to jump 3.

(3) Count the number num of common nodes in the frequent access set F _v and u group set by node v. If the number of common nodes num>K-1, K is the preset threshold, add node v to the u group set, and v frequently visits The set F _v joins the _u local population to frequently visit the set Lu . If num<K-1 turn to 6.

(4) Take out the i-th node v _i in the node v cluster set, and count the node i frequently visits the common node I _num of the set F _vi and the u cluster set C _u , if I _num ≥ K-1, add the node v _i to the u cluster Set, vi frequently visited set F _vi joins _u local group frequently visited set _Lu . Turn 5 if I _num < K-1.

(5) Determine whether i is greater than the size of the node v group set, if so, turn to 7; if not, turn to 4.

(6) Calculate the cumulative meeting time W(u, v) of nodes u and v, determine whether W(u, v)>T, T is the preset threshold, if so, add node v to the u group set, and v frequently visits the set F _v joins the _u local group frequently visited set Lu . If not go to 7.

(7) The group update is over.

After the group is established, the intra-group and inter-group transmission modes are implemented with different data forwarding strategies.

When the message carried by node u encounters node v:

(1) If the target node D of the message, the u of the carried message, and the encountered node v, the three nodes belong to the same group, use the local activity to measure whether the data is forwarded; if the local activity of u is greater than that of v, then The packet is forwarded, otherwise the packet is forwarded to v.

(2) If the target node D and nodes u and v are not in the same group, use the global activity to measure whether the message is forwarded. If the current global activity of node u of the packet is greater than that of node v, it will not forward the packet; otherwise, the packet will be forwarded to v.

(3) If the target node D and node u are not in the same group, but belong to the same group as node v, then u forwards the message to v.

(4) If the target node and the u node carrying the message are in the same group, and the encountered node v is in a different group, u does not forward the message.

Forward the message according to the above conditions until the target node is encountered, and then submit the message.

In summary, the present invention proposes a terminal-vehicle communication method based on a wireless protocol, which is suitable for the condition that the topology structure of the vehicle network changes frequently, improves the throughput of the network, and reduces the network congestion.

Obviously, those skilled in the art should understand that the above-mentioned modules or steps of the present invention can be implemented by a general-purpose computing system, and they can be centralized on a single computing system or distributed in a network composed of multiple computing systems Alternatively, they may be implemented in program code executable by a computing system, whereby they may be stored in a storage system for execution by the computing system. As such, the present invention is not limited to any particular combination of hardware and software.

It should be understood that the above-mentioned specific embodiments of the present invention are only used to illustrate or explain the principle of the present invention, but not to limit the present invention. Therefore, any modifications, equivalent replacements, improvements, etc. made without departing from the spirit and scope of the present invention should be included within the protection scope of the present invention. Furthermore, the appended claims of this invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalents of such scope and boundaries.

Claims (2)

1. A method for wireless protocol-based end-vehicle communication, comprising:

arranging tour vehicle-mounted nodes, driving along a predefined route, continuously sending messages in the driving process, broadcasting the received messages by roadside nodes, and receiving corresponding messages when the vehicle nodes pass through the network coverage range of the tour nodes;

(1) each node u in the vehicle-mounted network initializes a respective local colony set C_uFrequent access set F_uTime duration W (u, v) of encounter of nodes u and v and local population frequent visit set L_u；

(2) When the nodes u and v meet, the nodes exchange local information mutually, wherein the local information comprises a group set, a frequent access set and a local group frequent access set; judging whether the node v belongs to C_uIf the jump (7) is performed, if the jump is not performed, the turn (3) is not performed;

(3) statistical node v frequent visit set F_vNumber of nodes num common to u group set, if common nodeNumber num>K-1, wherein K is a preset threshold value, adding a node v into a u group set, and v frequently accessing a set F_vJoining u local population frequent Access set L_u(ii) a If num<K-1 rotation (6);

(4) taking out the ith node v in the node v colony set_iStatistical node i frequent visit set F_viAnd u population set C_uCommon node I_numIf I is_numMore than or equal to K-1, node v_iAdd u population set, v_iFrequent access set F_viJoining u local population frequent Access set L_u(ii) a If I_num<K-1 is converted to (5);

(5) judging whether i is larger than the size of the group set of the node v, if so, turning to (7); if not, turning to (4);

(6) calculating the cumulative encounter duration W (u, v) of the nodes u and v, and judging whether W (u, v) exists or not>T and T are preset threshold values, if yes, the node v is added into the u group set, and v frequently visits the set F_vJoining u local population frequent Access set L_u(ii) a If not, turning to (7);

(7) the population update is finished.

2. The method of claim 1, further comprising:

the messages in the network all have unique message id numbers, and after the target node R receives the messages, if the target node R judges that the messages are not received before, the id numbers of the messages are stored in a broadcast table; if the target node R finds the id number which is the same as the received information in the broadcast table, the message is received, the message is determined to be a redundant message and is directly discarded, otherwise, the target node R processes the data as follows;

according to the position information acquired by the GPS, the vehicle node judges whether the vehicle node is located in a vehicle node dense area; if target node R is located in a dense area of vehicle nodes or R belongs to a roadside node, R is delayed WD₁Then, the received message is forwarded; if the location of the target node R is not in the vehicle node dense area but the source node S is in the vehicle node dense area, then R discards the message; if the source node S is not a vehicle node dense area node, then R will be its own direction D_RDirection D to last hop source node S_SContinuing the comparison, if their moving directions are the same, at delay WD₂Then, sending the message, and if the direction of the message is opposite, giving up forwarding;

wherein WD₁＝(1-P_d)×T_p

WD₂＝(1-P_d)×2T_p

T_pRepresents a minimum duration between one-hop broadcasts;

P_d＝d_s-r/d_maxas probability related to distance, d_s-rDistance between source node and target node for the last forwarding, d_maxIs the maximum value within the node coverage.

Images