CN107249203B - A Relay Agent Method for Long-distance Data Communication of Internet of Vehicles Based on Fountain Code - Google Patents

Abstract

The invention discloses a fountain code-based Internet of vehicles remote data communication relay agent method which comprises the steps of S1, coding data to be sent by a vehicle node at a sending end by using a fountain code, S2, forwarding a fountain code message by a relay node, decoding the fountain by using a roadside unit RSU as an agent, S3, re-coding the message after decoding is successful by the agent node, and S4, receiving end vehicle nodes receive the fountain code message and decode the fountain.

Description

A Relay Agent Method for Long-distance Data Communication of Internet of Vehicles Based on Fountain Code

technical field

The invention relates to the field of wireless communication, in particular to a method for relaying and proxying a long-distance data communication of the Internet of Vehicles based on a fountain code.

Background technique

Vehicle ad-hoc networks (VANETs), also known as the Internet of Vehicles, is an ad-hoc wireless communication network formed with vehicles and roadside facilities as nodes, mainly including vehicle-to-vehicle (V2V) and vehicle-to-vehicle (V2V). Communication with infrastructure (V2I) is an important part of intelligent transportation system. In the Internet of Vehicles, the movement of vehicles causes the instability of the network topology, and the connection establishment and disconnection between communication nodes frequently occur, making the network reliability of the Internet of Vehicles poor. In such an environment, existing reliable transmission protocols (such as TCP, etc.) based on Automatic Repeat-reQuest (ARQ) will constantly trigger retransmissions due to frequent timeouts and packet loss, resulting in the expected number of forwardings. high, resulting in a large delay and consumption of a large amount of communication resources, resulting in low transmission efficiency.

Fountain code is an encoding method for data recovery under deleted channel. Its sending method is similar to fountain. Original business data can be encoded into infinite encoded packets for transmission. The receiver only needs to receive enough encoded packets. The original data can be decoded and restored, regardless of which encoded messages are received. Only when the decoding is completed, a feedback is sent to the sender. In the long-distance data transmission of the Internet of Vehicles, its reliability and efficiency still need to be improved.

LT code (Luby Transform Codes) is a typical fountain code. Although it adopts a reasonable degree distribution function to achieve higher decoding efficiency, its decoding complexity increases nonlinearly. To obtain the last few pieces of original data, it is necessary to decode from the encoded message with the high number, and the encoding and decoding complexity is high, and the decoding success rate is low under the same decoding overhead.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the above-mentioned deficiencies of the prior art, and to provide a method for a long-distance data relay communication proxy for the Internet of Vehicles based on a fountain code.

To achieve the above object, the present invention adopts the following technical solutions:

A method of relaying proxy method for long-distance data communication of Internet of Vehicles based on fountain code, comprising the following steps:

S1. The sending end vehicle node encodes the data to be sent with the fountain code;

S2. The relay node forwards the fountain code message, and the roadside unit RSU acts as an agent to decode the fountain;

S3. The proxy node performs fountain encoding on the successfully decoded message again;

S4. The receiving end vehicle node receives the fountain encoded message and performs fountain decoding.

Further, the step S1 is specifically as follows: the sending end vehicle node divides the original data to be sent into m groups, each group contains K minimum data units, and sequentially performs Raptor fountain coding on the K data in each group to generate the fountain code. message.

Further, the fountain code adopts Raptor code.

Further, the step S2 includes the following specific steps:

S21. The sending-end vehicle node performs path planning according to a geographical location-based routing algorithm, and the relay node forwards the fountain code packet to the receiving-end vehicle;

S22. Select the RSU closest to the transmitting end as the relay entrance, denoted as RSU _in , and the RSU closest to the vehicle at the receiving end as the relay exit, denoted as RSU _out , within the communication range of the RSU, the vehicle node conducts V2I communication with it , V2V communication between vehicle relay nodes;

S23. Select RSU _out to be the relay agent, and cache the fountain code message while forwarding the fountain code message. When the proxy node receives slightly more than K fountain code messages, it attempts to decode the fountain code. If the relay node only contains an RSU, the RSU is selected as the agent;

S24. When the decoding is successful by the proxy node, it sends a confirmation signal of successful decoding to the vehicle node at the sending end, indicating that the group of data has been successfully decoded. After receiving the signal, the vehicle node at the sending end stops sending the group of fountain code messages and sends the message. Start sending the next group of messages; if the decoding is unsuccessful, continue to receive the encoded message and try to decode it;

S25. When the proxy node still receives the encoded message of the group of data after sending the confirmation signal to the sender, it will send another confirmation signal to the sender every time it receives an extra message until the group of data is no longer received. coded message.

Further, in step S21, the path planning preferentially selects an RSU as a relay node for forwarding, and the path includes at least one RSU.

Further, the step S3 is specifically as follows: the proxy node re-encodes the fountain according to a set of original data obtained by the fountain decoding, and sends it to the neighbor vehicle node according to the path planned by the routing algorithm.

Further, the step S4 specifically includes the following steps:

S41. The relay node continues to forward the fountain code message, and after the receiving end vehicle node collects slightly more than K fountain code messages, it performs fountain decoding to restore the original data;

S42, when the decoding of the receiving end node succeeds, a confirmation signal of successful decoding is sent to the proxy node, and the proxy node stops sending the group of fountain code messages; if unsuccessful, continues to receive fountain code packets and try to decode;

S43. If the receiving end still receives the encoded message of the group after sending the confirmation signal, it will send another confirmation signal to the proxy node every time it receives an extra message, until it no longer receives the coded message from the proxy node. group coded message;

S44. After the receiving end vehicle node successfully decodes the m groups of fountain code messages to obtain all the original data, the vehicle self-organizing network successfully completes a complete telematics long-distance data transmission.

After adopting the above-mentioned technical scheme, compared with the background technology, the present invention has the following advantages:

1. Simplify the encoding process and improve the decoding success rate. The present invention applies Raptor fountain coding to the coding process of data sent by the Internet of Vehicles, the coding and decoding complexity is lower than that of the transmission scheme based on LT code, the requirement for the quantity of transmitted coded messages is lower, and the decoding success rate is higher.

2. Improve the expected forwarding times of data transmission. By selecting the RSU as the relay agent node, the invention overcomes the problem of unreliable connection between nodes in the Internet of Vehicles, reduces the expected forwarding times of the data message, and saves the overhead of communication resources.

3. Improve the efficiency of data transmission. The relay agent of the present invention can transfer according to real-time conditions, adapt to the rapid movement of vehicle nodes and network topology changes, meet the requirements of long-distance, efficient and reliable data transmission for each node in the Internet of Vehicles, and improve the data transmission efficiency in the Internet of Vehicles. Delay and throughput and other key performance indicators, thereby improving the efficiency of data transmission.

Description of drawings

Fig. 1 is the realization flow chart of the present invention

Fig. 2 is the application scenario of Internet of Vehicles data transmission in the specific embodiment

Fig. 3 is a scenario in which the destination node of the vehicle moves and causes the data routing to change in the specific embodiment

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

Example

In this embodiment, the fountain code RaptorQ encoding (the latest version of Raptor encoding) is used to transmit data in the vehicle ad hoc network, and by selecting a reasonable RSU relay node as an agent in multiple transmissions, the data transmission efficiency is further improved, and the data transmission is improved. The expected number of forwardings.

A method of relaying proxy method for long-distance data communication of Internet of Vehicles based on fountain code, comprising the following steps:

S1. The sending end vehicle node encodes the data to be sent with the fountain code;

The sender vehicle node divides the raw data to be sent into m groups, each group contains K minimum data units, and sequentially performs Raptor fountain encoding on the K data in each group to generate a fountain encoded message.

S2. The relay node forwards the fountain code message, and the roadside unit RSU acts as an agent to decode the fountain;

S21. The sending-end vehicle node performs path planning according to a geographical location-based routing algorithm, and the relay node forwards the fountain code packet to the receiving-end vehicle;

S22. Select the RSU closest to the transmitting end as the RSU relay entrance, denoted as RSU _in , and the RSU closest to the receiving end vehicle as the RSU relay exit, denoted as RSU _out , within the communication range of the two RSUs, the other following vehicle nodes to communicate with them from vehicle to network;

S23. Select RSU _out to be the relay agent, and cache the fountain code message while forwarding the fountain code message. When the proxy node receives slightly more than K fountain code messages, it attempts to decode the fountain code. If the relay node only contains an RSU, the RSU is selected as the agent;

S24. When the decoding is successful by the proxy node, it sends a confirmation signal of successful decoding to the vehicle node at the sending end, indicating that the group of data has been successfully decoded. After receiving the signal, the vehicle node at the sending end stops sending the group of fountain code messages and sends the message. Start sending the next group of messages; if the decoding is unsuccessful, continue to receive the encoded message and try to decode it;

S25. When the proxy node still receives the encoded message of the group of data after sending the confirmation signal to the sender, it will send another confirmation signal to the sender every time it receives an extra message, until it no longer receives any data from the group. The encoded message of the data.

Wherein, the path planning in step S21 preferentially selects an RSU as a relay node for forwarding, and the path includes at least one RSU.

S3. The proxy node performs fountain encoding on the successfully decoded message again;

The proxy node re-encodes the fountain according to a set of original data obtained by the fountain decoding, and sends it to the neighbor vehicle node according to the path planned by the routing algorithm.

S4. The receiving-end vehicle node receives the fountain encoding message and performs fountain decoding;

S41. The relay node continues to forward the fountain code message, and after the receiving end vehicle node collects slightly more than K fountain code messages, it performs fountain decoding to restore the original data;

S42, when the decoding of the receiving end node succeeds, a confirmation signal of successful decoding is sent to the proxy node, and the proxy node stops sending the group of fountain code messages; if unsuccessful, continues to receive fountain code packets and try to decode;

S43. If the receiving end still receives the encoded message of the group after sending the confirmation signal, it will send another confirmation signal to the proxy node every time it receives an extra message, until it no longer receives the coded message from the proxy node. group coded message;

S44. After the receiving end vehicle node successfully decodes the m groups of fountain code messages to obtain all the original data, the vehicle self-organizing network successfully completes a complete telematics long-distance data transmission.

Fig. 1 shows the realization flow chart of the present invention, and its concrete coding and decoding process is as follows: at first the data content etc. to be sent are divided into m source blocks (Source Block), and different source block codes are independent of each other; The source block is further divided into K minimum data unit symbols.

After all symbols of the same source block are sent to the fountain code encoder, the encoded symbols for transmission can be obtained. In the encoded message, a source block number (SBN) is added to the header field to distinguish symbols from different source blocks. At the same time, in order to avoid receiving the same encoding symbols, different encoding symbols are also distinguished by different encoding message numbers (Encoding Symbol IDs).

预编码过程将原始输入符号通过LDPC码(即低密度奇偶校验码)将K个原始符号转换为

个中间编码校验单元，再将

个中间编码校验单元输入到弱化的LT编码器进行喷泉码编码。Next, use the RaptorQ code to pre-encode the K original symbols. Suppose the deletion rate of the channel is

The precoding process converts the K original symbols into

an intermediate coding check unit, and then

The intermediate code check unit is input to the weakened LT encoder for fountain code encoding.

After the receiving end receives the encoded message, it first uses the LT code technology to decode it, restores the fixed proportion of the intermediate code check unit, and then uses the decoding properties of the LDPC error correction code to restore all the original input symbols. Precoding reduces the decoding complexity of the RaptorQ code to O(K), and the probability of the receiver failing to decode after receiving K+2 encoded messages is lower than 10 ^-6 .

FIG. 2 shows an application scenario of Internet of Vehicles data transmission in this embodiment. Its vehicle networking consists of roadside units (RSU ₁ , RSU ₂ and RSU ₃ ), vehicle source node S at the data sending end, vehicle destination node D at the data receiving end, and 7 relay vehicle nodes (V ₁ , V ₂ , .. ., V ₇ ) composition.

The source node S plans the path to the destination node D according to the routing protocol based on geographic location information:

S, V ₁ , V ₂ , RSU ₁ , RSU ₂ , V ₆ , V ₇ , D

Let's first consider the data transmission situation of a source block, that is, the S node performs fountain coding on the K original symbols that need to be sent, and the header field of the RaptorQ coded message formed by it contains the following information: source node ID, destination node ID, source Block number, code symbol number, proxy node address (see Table 1 below for specific descriptions). After that, the S node sends the RaptorQ encoded message to its neighbor relay vehicle node, and the relay node forwards the RaptorQ encoded message according to the path planned by the routing algorithm after receiving the RaptorQ encoded message.

Table 1 Description of header fields of RaptorQ encoded packets

When the RaptorQ encoded message reaches the roadside unit RSU ₁ , the RSU ₁ forwards it to the RSU ₂ through the wired network, and the RSU ₂ becomes a proxy node at this time. RSU ₂ first establishes a cache according to the header fields (source node ID, destination node ID, source block number, code symbol number, proxy node address) of the message, and the quintuple uniquely determines a reliable transmission. After receiving the fountain-coded message, RSU ₂ forwards it to the neighbor relay vehicle node according to the path planned by the routing protocol, and stores the message in the corresponding cache at the same time.

Once RSU ₂ receives the RaptorQ encoded message of K+2, it starts to try fountain decoding. When its decoding is successful, it sends a signal to the source node S to stop sending the source block message. At this time, the RSU ₂ regenerates a new fountain coded message for the source block, and forwards it to the destination node D according to the path planned by the routing algorithm. The source node S starts to encode and send the message of the next source block.

When node D receives K+2 RaptorQ coded messages, it starts to try fountain decoding, and continues to receive fountain coded messages until the decoding is successful, and sends a message to the proxy node RSU ₂ to stop sending the source block. At this time, the transmission of one source block from node S to node D is completed. Then, node D starts to receive the encoded message of the next source block.

Since the nodes in the Internet of Vehicles are usually in constant motion, the route from the destination node D to the source node S may change during a data transmission process. Assuming that the data transmission path is changed due to the movement of the vehicle node or the route breakage, the relay node RSU ₂ becomes RSU ₃ in the new path, as shown in FIG. 3 . At this time, in the case that the current source block is not completely decoded successfully, the proxy node address in the RaptorQ encoded message sent by the S node still keeps the original RSU ₂ address unchanged. When the encoded packet is forwarded to RSU ₃ according to the routing path, RSU ₃ first forwards the fountain encoded packet to its neighbor relay node according to the path planned by the routing algorithm, and at the same time copies a copy of the encoded packet and forwards it to the proxy node RSU specified in the header field ₂ . The reason is to ensure that a proxy node RSU can receive enough encoded packets for successful decoding, and avoid the situation where the encoded packets are scattered on two different RSUs and cannot be successfully decoded, so as to ensure the success of the proxy. rate and overall transmission efficiency. RSU ₂ successfully decodes and transmits the source block data to RSU ₃ by wire. After the source node S receives the confirmation signal from RSU ₃ that the decoding of the current source block is successful, it changes the address of the proxy node to RSU ₃ and starts sending the next source block message.

Once the proxy node receives enough fountain coded messages and the decoding is successful, the proxy node will send a confirmation signal of successful decoding to node S, so that node S stops sending messages until it no longer receives messages from node S. arts. At the same time, the proxy node will regenerate a new fountain coded message, which will continue to play the role of the proxy node and send the fountain coded message to the destination node D. When the destination node D receives enough fountain-encoded messages and decodes them successfully, it will send a confirmation signal to the proxy node that the decoding of the source block is successful, so that it stops sending the message of the source block until no more The message of the source block is received. At this time, the transmission of one source block from node S to node D is completed.

When the source node or the proxy node receives the successful decoding confirmation signal of m source blocks, it stops the sending of all messages, and the long-distance data communication in the vehicle self-organizing network is completed at this time.

The fountain code encoding method in the above implementation process is implemented by RaptorQ code, and the node routing algorithm in the vehicle self-organizing network can use the vehicle networking routing protocol based on geographic location information such as Greedy Perimeter Stateless Routing (GPSR).

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. Substitutions should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims (5)

1. a kind of vehicle networking long-distance data communication relay agent method based on fountain code, is characterized in that: comprise the following steps: S1. The sending end vehicle node encodes the original data to be sent with the fountain code; Wherein, step S1 includes: The sending end vehicle node divides the original data to be sent into m groups, each group of original data contains K data units, and sequentially performs fountain coding on the K data units in each group to generate a fountain code message; S2. The relay node forwards the fountain code message, and the roadside unit RSU acts as an agent to decode the fountain; Wherein, the step S2 includes the following specific steps: S21. The sending-end vehicle node performs path planning according to a routing algorithm based on geographic location, and the relay node forwards the fountain code packet to the receiving-end vehicle node; S22. Select the RSU closest to the sender as the relay entrance, denoted as RSU _in , and the RSU closest to the vehicle node at the receiver as the relay outlet, denoted as RSU _out , within the RSU communication range, the vehicle node performs V2I with it (Vehicle and infrastructure) communication, V2V (vehicle-to-vehicle) communication between vehicle relay nodes; S23. Select RSU _out to be the relay agent, and cache the fountain code message while forwarding the fountain code message. When the proxy node receives more than K fountain code messages, it attempts to decode the fountain code. If the relay node only contains an RSU, the RSU is selected as the agent; S24. When the decoding is successful by the proxy node, a confirmation signal of successful decoding is sent to the vehicle node at the sending end, indicating that the group of original data has been successfully decoded, and the vehicle node at the sending end stops sending the fountain of the original data after receiving the signal. code message and start sending the next group of messages; if the decoding is unsuccessful, continue to receive the fountain code message and try to decode it; S25. When the proxy node still receives the fountain code message of the group of original data after sending the confirmation signal to the sending end, it will send another confirmation signal to the sending end every time it receives a redundant fountain code message until it no longer receives any more. to the fountain code message from the set of raw data; S3. The proxy node performs fountain encoding on the successfully decoded message again; S4. The receiving end vehicle node receives the fountain code message and performs fountain decoding. 2 . The method for relaying proxy data for Internet of Vehicles long-distance data communication based on a fountain code according to claim 1 , wherein the fountain code adopts a Raptor code. 3 . 3. a kind of vehicle networking long-distance data communication relay agent method based on fountain code according to claim 1, is characterized in that: described in step S21, the path planning preferentially selects to use RSU as a relay node to forward, and the path contains at least one RSU. 4. a kind of vehicle networking long-distance data communication relay proxy method based on fountain code according to claim 1, is characterized in that: described step S3 is specifically: a group of original data obtained by proxy node according to fountain decoding, Re-encode the fountain and send it to the neighbor vehicle node according to the path planned by the routing algorithm. 5. a kind of vehicle networking long-distance data communication relay agent method based on fountain code according to claim 1, is characterized in that: described step S4 specifically comprises the following steps: S41. The relay node continues to forward the fountain code message, and after the receiving end vehicle node collects more than K fountain code messages, it performs fountain decoding to restore the original data; S42, when the decoding of the receiving end node is successful, send a confirmation signal of successful decoding to the proxy node, and the proxy node stops sending the fountain code message of the group of original data; if unsuccessful, continue to receive the fountain code packet and try to decode; S43. If the receiving end still receives the fountain code message of the group of original data after sending the confirmation signal, it will send another confirmation signal to the proxy node every time it receives a redundant fountain code message until it no longer receives it. The fountain code message of the set of raw data from the proxy node; S44. After the receiving end vehicle node successfully decodes the fountain code messages of m groups of original data to obtain all the original data, the vehicle self-organizing network successfully completes a complete long-distance data transmission of the Internet of Vehicles.

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