CN106454756B

CN106454756B - Method, device and system for broadcasting message in vehicle-mounted self-organizing network

Info

Publication number: CN106454756B
Application number: CN201610680732.9A
Authority: CN
Inventors: 张珠华
Original assignee: Neusoft Corp
Current assignee: Neusoft Corp
Priority date: 2016-08-17
Filing date: 2016-08-17
Publication date: 2020-01-07
Anticipated expiration: 2036-08-17
Also published as: CN106454756A

Abstract

The invention discloses a method, a device and a system for broadcasting messages in a vehicle-mounted self-organizing network, relates to the technical field of communication, and aims to solve the problem of low success rate of receiving ESM messages in a VANET network. The method of the invention comprises the following steps: when an ESM message is generated in a CCH time interval, a source node adds a forwarding identifier for indicating a neighbor node to forward the ESM message in the ESM message; the source node broadcasts the ESM message added with the forwarding identifier to the neighbor node through a CCH (channel control channel); the neighbor node searches whether the ESM message carries a forwarding identifier; if the forwarding identifier is found, the neighbor node broadcasts the ESM message to the neighbor node through the SCH channel after switching to the SCH channel. The invention is mainly applied to the process of message broadcasting among vehicles in a road traffic environment.

Description

Method, device and system for broadcasting message in vehicle-mounted self-organizing network

Technical Field

The present invention relates to the field of communications technologies, and in particular, to a method, an apparatus, and a system for broadcasting a message in a vehicle-mounted ad hoc network.

Background

A Vehicular Ad-Hoc Network (VANET for short) is a Mobile Ad-Hoc Network (MANET for short) applied to a traffic road environment, and based on the VANET Network, real-time information such as driving assistance and accident avoidance is transmitted between nodes (including between vehicles and between a vehicle and a fixed Access Point (AP for short)) through a short-distance wireless communication mode, and services such as vehicle-mounted entertainment and road navigation are provided at the same time. The VANET network has the advantages of self-organization, convenient deployment, low cost, open structure and the like, and has become an important component of an Intelligent Transport System (ITS for short) in recent years.

Safety applications in VANET networks, which rely primarily on efficient transmission of messages between nodes, can provide drivers with information about the driving conditions of their surrounding vehicles and information about emergency situations, thereby improving the safety of vehicle operation. At present, in the mainstream technology, a broadcast mode is mainly adopted for message transmission between nodes. In a multi-channel network environment based on the WAVE protocol, the types of messages broadcast between nodes are mainly divided into two types: 1. safety type information, 2, service type information, wherein the safety type information is further divided into: a. a periodic broadcast Message, b, an Event-driven Safety Message (ESM). The periodic broadcast message is also called a Beacon (Beacon) message, and the message includes a status message of the vehicle, such as a position, a speed, a driving direction, and the like. The ESM message is an instant message generated based on an abnormal condition of the vehicle, and when the vehicle detects an abnormal condition such as an emergency brake, a large angle steering, etc., the vehicle transmits the ESM message to a neighbor node. Among all message types, the ESM message has the highest broadcast priority. The 1609.4 protocol specifies that a node performs broadcast communication using two channels, namely a Control Channel (CCH) and a Service Channel (SCH). The CCH channel is used for transmitting security messages and the SCH channel is used for transmitting service messages. For a single-antenna node, all nodes synchronously switch alternately on a CCH channel and an SCH channel, and the time interval of each channel is 50 ms. When an ESM message is generated by a node, there are different ways to handle it based on the following two cases: 1. when a node generates an ESM message in a time interval of a CCH (channel control channel), the node broadcasts the ESM message to a neighbor node in time through the CCH, and the neighbor node receives the ESM message through the CCH; 2. when the node generates the ESM message in the time interval of the SCH channel, the node caches the message, and broadcasts the ESM message through the CCH channel after switching to the next CCH channel, and meanwhile, the neighbor node receives the ESM message through the CCH channel.

In the above-described process of broadcasting the ESM message, the inventors found that: in an environment with high vehicle density, each node continuously broadcasts Beacon messages in the time interval of a CCH channel, and the wireless channel capacity of the VANET network is limited, so when Beacon messages are excessively sent and the node sending power is excessively high, congestion of the CCH channel is easily caused, and therefore neighbor nodes cannot receive ESM messages. Secondly, if the ESM message is generated when the time interval of the CCH channel is about to expire, the node generating the ESM message may have time to broadcast the message, but because there is a certain delay in the data transmission of the radio channel, when the ESM message is sent to the neighbor node, the neighbor node may have already switched to the SCH channel due to the existence of the delay, and cannot receive the ESM message sent on the CCH channel any more, so the problem of message reception failure also occurs, so that the success rate of receiving the ESM message is low. In the VANET network, the ESM message is used as important information for reflecting the vehicle emergency, and whether the ESM message can be normally transmitted is directly related to the personal and property safety of a driver.

Disclosure of Invention

The embodiment of the invention provides a method, a device and a system for broadcasting messages in a vehicle-mounted self-organizing network, which can solve the problem of low success rate of receiving ESM messages in a VANET network.

To solve the above problem, an embodiment of the present invention provides:

1. a method for broadcasting messages in a vehicle-mounted self-organizing network is applied to a source node side and comprises the following steps:

when an event-driven safety message ESM is generated in the time interval of a control channel CCH, adding a forwarding identifier for indicating a neighbor node to forward the ESM message in the ESM message;

the ESM message added with the forwarding identifier is broadcasted to the neighbor nodes through the CCH, so that the neighbor nodes receiving the ESM message added with the forwarding identifier broadcast the ESM message to the neighbor nodes of the neighbor nodes through the SCH after switching to the service channel SCH according to the forwarding identifier.

2. The method according to 1, before adding a forwarding identifier in the ESM message, which indicates the neighboring node to forward the ESM message, the method further comprises:

judging whether the current network condition of the source node side meets the message forwarding condition or not;

adding a forwarding identifier for indicating the neighbor node to forward the ESM message in the ESM message, wherein the forwarding identifier comprises:

and if the message forwarding condition is met, adding a forwarding identifier in the ESM message.

3. According to the method of 2, judging whether the current network condition of the source node side meets the message forwarding condition includes judging whether any one of the following conditions is met or the following two conditions are met simultaneously:

the number of neighbor nodes of the source node exceeds a preset node number threshold;

and the remaining time of the current CCH is less than a preset time length threshold.

4. According to the method of claim 1, wherein,

the forwarding identifier is a forwarding instruction, and the ESM message added with the forwarding identifier is broadcasted to the neighboring node through a CCH channel, including:

broadcasting the ESM message added with the forwarding instruction to all neighbor nodes through a CCH (shared channel), so that all neighbor nodes receiving the ESM message added with the forwarding instruction broadcast the ESM message according to the forwarding instruction;

or, the forwarding identifier is a node identifier of a neighboring node, and the ESM message with the forwarding identifier added is broadcast to the neighboring node through a CCH channel, including:

and broadcasting the ESM message added with the node identifier to all the neighbor nodes through a CCH (channel control channel), and broadcasting the ESM message by identifying the node identifier of the neighbor node corresponding to the node identifier.

5. According to the method of 4, before broadcasting the ESM message for adding the node identification to all neighboring nodes through the CCH channel, the method further comprises:

selecting a preferred node from the neighbor nodes based on a preset node selection algorithm;

the node identification of the preferred node is added as a forwarding identification to the ESM message.

6. According to the method of 5, based on a preset node selection algorithm, selecting a preferred node from neighbor nodes, including determining a neighbor node satisfying any one of the following conditions or both the following conditions as the preferred node:

the number of available SCH channels is not more than a preset first threshold value;

the number of the neighbor nodes is not less than a preset second threshold.

7. The method according to 6, before selecting a preferred node from the neighbor nodes based on a preset node selection algorithm, the method further comprises:

acquiring a channel identifier of an SCH channel used next by a neighbor node;

dividing neighbor nodes into different node sets according to the SCH channel identification, wherein the neighbor nodes in one node set correspond to the same SCH channel identification;

based on a preset node selection algorithm, selecting a preferred node from neighbor nodes, wherein the method comprises the following steps: and respectively selecting a preferred node from each node set based on a preset node selection algorithm.

8. The method of 1, after the source node switches from the CCH channel to the SCH channel, the method further comprising:

if the ESM message is generated within a time interval of the SCH channel, the ESM message is broadcast through the SCH channel to neighbor nodes using the same SCH channel as the source node.

9. According to the method of 8, after broadcasting the ESM message to the neighbor node using the same SCH channel as the source node through the SCH channel, or when there is no neighbor node using the same SCH channel as the source node, the method further comprises:

caching the ESM message;

after switching to the CCH channel again, the ESM message is broadcast to the neighboring nodes over the CCH channel.

10. The method according to any one of claims 1 to 9, further comprising:

receiving Beacon information periodically broadcast by a neighbor node on a CCH channel, wherein the Beacon information carries node information of the neighbor node, and the node information comprises:

node identification, number of neighbor nodes, channel identification of the next used SCH channel, and number of available SCH channels.

11. A method for broadcasting messages in a vehicle-mounted self-organizing network is applied to a neighbor node side of a source node and comprises the following steps:

receiving an event-driven safety message (ESM) broadcasted by a source node through a Control Channel (CCH);

searching whether the ESM message carries a forwarding identifier for indicating a neighbor node to forward the ESM message;

if the forwarding identifier is found, the ESM message is broadcasted to the neighbor node of the ESM through the SCH channel after the SCH is switched to the service channel SCH.

12. According to the method of 11, searching whether the ESM message carries a forwarding identifier indicating the neighboring node to forward the ESM message includes:

and searching the forwarding instruction or the node identification of the self in the ESM message, wherein the node identification of the self is the node identification of the preferred node selected by the source node based on a preset node selection algorithm.

13. The method according to 11, the method further comprising:

after switching to the SCH channel, the source node receives an ESM message broadcast on the same SCH channel.

14. The method according to any one of claims 11 to 13, further comprising:

receiving Beacon information periodically broadcast by a source node on a CCH channel, wherein the Beacon information carries node information of the source node, and the node information comprises:

15. An apparatus for broadcasting a message in a vehicular ad hoc network, the apparatus being located at a source node side, comprising:

an adding unit, configured to add, when an event-driven safety message ESM is generated within a time interval of a control channel CCH, a forwarding identifier indicating a neighboring node to forward the ESM message in the ESM message;

and the sending unit is used for broadcasting the ESM message added with the forwarding identifier to the neighbor nodes through the CCH, so that the neighbor nodes receiving the ESM message added with the forwarding identifier broadcast the ESM message to the own neighbor nodes through the SCH after switching to the service channel SCH according to the forwarding identifier.

16. The apparatus of claim 15, further comprising:

a judging unit, configured to judge whether a current network condition of a source node side meets a message forwarding condition before adding a forwarding identifier indicating a neighboring node to forward an ESM message in the ESM message;

and the adding unit is used for adding the forwarding identifier in the ESM message if the message forwarding condition is met.

17. The apparatus according to claim 16, wherein the judging unit is configured to judge whether any one of the following conditions is satisfied or both of the following conditions are satisfied:

18. According to the apparatus of 17, the forwarding identifier is a forwarding instruction, and the sending unit is configured to broadcast the ESM message to which the forwarding instruction is added to all neighboring nodes through a CCH channel, so that all neighboring nodes that receive the ESM message to which the forwarding instruction is added broadcast the ESM message according to the forwarding instruction;

or, the forwarding identifier is a node identifier of a neighboring node, and the sending unit is configured to broadcast the ESM message with the node identifier added to all neighboring nodes through a CCH channel, and the neighboring node corresponding to the node identifier broadcasts the ESM message by identifying its own node identifier.

19. The apparatus of 18, further comprising:

the selection unit is used for selecting a preferred node from the neighbor nodes based on a preset node selection algorithm before broadcasting the ESM message added with the node identification to the neighbor nodes through a CCH (channel control channel);

and the adding unit is used for adding the node identification of the preferred node as a forwarding identification into the ESM message.

20. The apparatus according to 19, the selecting unit is configured to determine, as the preferred node, a neighbor node that satisfies any one of the following conditions or both of the following conditions:

the number of the neighbor nodes is not less than a preset second threshold.

21. The apparatus of 20, further comprising:

the acquiring unit is used for acquiring the channel identifier of the SCH channel used by the neighbor node next before the neighbor node selects the preferred node based on the preset node selection algorithm;

and the selection unit is used for selecting the preferred nodes from each node set respectively based on a preset node selection algorithm.

22. According to the apparatus of claim 15, the transmitting unit is configured to broadcast the ESM message to the neighbor node using the same SCH channel as the source node through the SCH channel if the ESM message is generated within a time interval of the SCH channel after the source node is switched from the CCH channel to the SCH channel.

23. The apparatus of 22, further comprising:

a caching unit for caching the ESM message after broadcasting the ESM message to a neighbor node using the same SCH channel as the source node through the SCH channel or when there is no neighbor node using the same SCH channel as the source node;

and the sending unit is used for broadcasting the ESM message to the neighbor nodes through the CCH after the CCH is switched again.

24. The apparatus according to any one of claims 15 to 23, further comprising:

the receiving unit is used for receiving Beacon information periodically broadcast by a neighbor node on a CCH channel, the Beacon information carries node information of the neighbor node, and the node information comprises:

25. An apparatus for broadcasting a message in a vehicular ad hoc network, the apparatus being located at a neighboring node side of a source node, comprising:

the receiving unit is used for receiving an event-driven safety message ESM broadcast by a source node through a control channel CCH;

the searching unit is used for searching whether the ESM message carries a forwarding identifier for indicating the neighbor node to forward the ESM message;

and the sending unit is used for broadcasting the ESM message to the neighbor node of the sending unit through the SCH channel after the switching to the service channel SCH if the forwarding identifier is found.

26. The apparatus according to 25, the searching unit is configured to search for the forwarding instruction or the node identifier of the self in the ESM message, where the node identifier of the self is a node identifier of a preferred node selected by the source node based on a preset node selection algorithm.

27. According to the apparatus of 25, the receiving unit is configured to receive an ESM message broadcasted by the source node based on the SCH channel after the switching to the SCH channel.

28. According to the apparatus in any one of claims 25 to 27, the receiving unit is configured to receive Beacon information periodically broadcast on a CCH channel by a source node, where the Beacon information carries node information of the source node, and the node information includes:

29. A system for broadcasting messages in a vehicle-mounted self-organizing network comprises a source node and a neighbor node of the source node;

the source node comprises apparatus as claimed in any of claims 15 to 24 above;

the neighbour node comprises an apparatus as described in any of the above 25 to 28.

The method, the device and the system for broadcasting the message in the vehicle-mounted self-organizing network provided by the embodiment of the invention can add a forwarding identifier in the ESM message by the source node when the ESM message is generated in the time interval of the CCH, and broadcast the ESM message added with the forwarding identifier through the CCH. For the neighbor node which can receive the message on the CCH channel, the neighbor node broadcasts the ESM message to the neighbor node of the neighbor node through the SCH channel after switching to the SCH channel according to the forwarding identification carried in the ESM message. For other neighbor nodes with CCH channel congestion or switched to SCH channel when message arrives, although the ESM message broadcasted by the source node can not be directly received, in the actual road environment, nodes in a certain range are often mutually neighbor nodes, the node which can not receive the message is used as the neighbor node of the former node, and the ESM message forwarded by the former node can be received in the time interval of the next SCH channel, thereby achieving the purpose of indirectly receiving the message of the source node. In addition, in practical applications, the SCH channel has less possibility of channel congestion and more power consumption for transmitting ESM messages than the CCH channel, which are two reasons: firstly, the SCH channel does not need to broadcast periodic messages, and the idle channel capacity of the SCH channel is larger under the condition that the node load capacity is the same; secondly, the 1609.4 protocol specifies that a node can use 1 CCH channel and 6 different SCH channels, and after the time interval of the CCH channel expires, the node can select one SCH channel from at most 6 SCH channels according to its own capability to perform handover, so on average, under the condition of the same number of nodes, the node load of the SCH channel is much smaller than the node load of the CCH channel. In summary, the embodiment of the present invention provides a possibility of remedying a message reception failure through a secondary forwarding mechanism, and ensures the probability of successful reception of a node when an ESM message is retransmitted by using the characteristics of small SCH channel load and low probability of congestion.

The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:

fig. 1 is a flowchart illustrating a method for broadcasting a message in a first vehicle-mounted ad hoc network according to an embodiment of the present invention;

FIG. 2 is a schematic diagram illustrating a node relationship provided by an embodiment of the invention;

fig. 3 is a flowchart illustrating a method for broadcasting messages in a second vehicular ad hoc network according to an embodiment of the present invention;

fig. 4 is a flowchart illustrating a method for broadcasting messages in a third vehicular ad hoc network according to an embodiment of the present invention;

fig. 5 is a schematic diagram illustrating node information according to an embodiment of the present invention;

fig. 6 is a flowchart illustrating a method for broadcasting messages in a fourth vehicle ad hoc network according to an embodiment of the present invention;

fig. 7 is a flowchart illustrating a method for broadcasting a message in a fifth vehicle-mounted ad hoc network according to an embodiment of the present invention;

FIG. 8 illustrates a logic flow diagram for a source node provided by an embodiment of the present invention;

FIG. 9 is a logic flow diagram of a neighboring node provided by an embodiment of the present invention;

fig. 10 is a schematic structural diagram illustrating an apparatus for broadcasting a message in a first vehicular ad hoc network according to an embodiment of the present invention;

fig. 11 is a schematic structural diagram illustrating an apparatus for broadcasting a message in a second vehicular ad hoc network according to an embodiment of the present invention;

fig. 12 is a schematic structural diagram illustrating an apparatus for broadcasting a message in a third vehicular ad hoc network according to an embodiment of the present invention;

fig. 13 is a schematic diagram illustrating a system for broadcasting messages in a vehicle ad hoc network according to an embodiment of the present invention.

Detailed Description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

In order to solve the problem of low success rate of broadcasting the ESM message on the CCH, the embodiment of the invention provides a method for broadcasting the message in a vehicle-mounted self-organizing network, which is applied to a source node side. As shown in fig. 1, the method includes:

101. when an event-driven safety message ESM is generated within a time interval of a control channel CCH, the source node adds a forwarding identifier in the ESM message, which indicates the neighboring node to forward the ESM message.

When the ESM message is generated at a time within a time interval of the CCH channel, the source node should broadcast the ESM message to its neighbor nodes through the CCH channel in time. Different from the prior art, in this embodiment, the source node needs to add a forwarding identifier in the ESM message, where the forwarding identifier is used to indicate a neighboring node of the source node, and to broadcast the received ESM message to its neighboring node again.

In practical application, a field position with a preset length may be reserved in the ESM message for writing the forwarding identifier. The present embodiment does not specifically limit the content, data type, and data length of the forwarding identifier.

102. The source node broadcasts the ESM message with the forwarding identifier added to the neighboring node through the CCH channel.

In practical applications, although all nodes use the same CCH, the congestion level of CCH may vary from one node to another due to differences in geographic locations, so that the congestion level of CCH of each node may vary. For example, for a node with more neighboring nodes, the periodic messages received on the CCH channel are correspondingly more, and therefore, the CCH channel is occupied to a higher degree than for a node with less neighboring nodes. On the other hand, when the source node broadcasts the ESM message, some neighboring nodes may broadcast their Beacon messages or ESM messages to the outside at the same time, and in this case, there is a possibility that the ESM messages are not received by these neighboring nodes.

And for the neighbor node capable of receiving the CCH, the neighbor node analyzes the ESM message, and if the forwarding identifier is found in the preset field position, the ESM message is forwarded to the neighbor node of the neighbor node. In practical application, if multi-level forwarding is required, the neighboring node can keep the forwarding identifier in the message when forwarding the ESM message, so that the neighboring node can further forward the ESM message; if the forwarding is needed only once, the neighbor node clears the forwarding identifier in the preset field after receiving the ESM message, and then broadcasts the ESM message without the forwarding identifier to the neighbor node.

Generally, the time interval between the CCH channel and the SCH channel is in the millisecond level, and it is difficult for the channel congestion condition to be significantly improved in such a short time in practical application, so in order to ensure the receiving success rate of the neighbor node when broadcasting the ESM message again, in this embodiment, the neighbor node receiving the ESM message may select to forward the message through the SCH channel after switching to the SCH channel. As previously mentioned, the SCH channel is less likely to be congested relative to the CCH channel, and therefore the choice of forwarding the ESM message on the next SCH channel may enable the neighboring nodes to successfully receive the ESM message. The delay caused by waiting to switch to the SCH channel does not exceed a maximum of one channel interval (50ms), and the delay has little effect on the requirement of ESM message timeliness.

As shown in fig. 2, in an example of the present embodiment, there are A, B, C and D in a certain area, and these 4 nodes are neighboring nodes. When node a generates an ESM message n during the time interval of the CCH channel, it broadcasts the message n out through the CCH channel as the source node. Node B and node C may not receive the message n broadcast by node a because node D may receive the message n because there are other neighboring nodes as shown in fig. 2 and the CCH channel is more congested than node D. After waiting for switching to the next SCH channel, the node D broadcasts the message out through the SCH channel, and as a neighbor node of the node D, the node B and the node C can receive the message n broadcast by the node D on the SCH channel without congestion. Compared with the method for directly receiving the message n sent by the node a, the node B, C only delays the time for receiving the message n by tens of milliseconds, and compared with the message receiving failure in the prior art, the method and the device for receiving the message n ensure the success rate of message receiving with the minimum cost.

Of course, in practical applications, there are multiple SCH channels that can be used by a node (there are 6 SCH channels in the 1609.4 protocol), and in the above example, the node B, C needs to select the same SCH channel as the node D for use when switching the SCH channel, so that it can receive the message n broadcast by the node D.

Further, the embodiment of the invention also provides a method for broadcasting messages in the vehicle-mounted self-organizing network, and the method is applied to the neighbor node side of the source node. As shown in fig. 3, the method includes:

301. the neighbor node receives an event-driven safety message (ESM) broadcast by a source node through a Control Channel (CCH).

302. The neighbor node searches whether the ESM message carries a forwarding identifier for indicating the neighbor node to forward the ESM message.

In the flow shown in fig. 3, the neighbor node that performs message forwarding is a neighbor node that can receive the ESM message broadcast by the source node, and for this part of nodes, after receiving the ESM message, the node parses the message and searches for a forwarding identifier in a preset field position. If the forwarding identifier is found, step 303 is executed, the forwarding identifier is broadcasted to the neighbor node of the forwarding identifier, and the ESM message is responded according to the existing implementation mode; if the forwarding identifier is not found, the ESM message is only responded according to the existing mode, and the message forwarding is not carried out any more.

303. If the forwarding identifier is found, the neighbor node broadcasts the ESM message to the neighbor node through the SCH channel after switching to the service channel SCH.

In the foregoing example shown in fig. 2, although the node B, C cannot receive the ESM message sent by the node a through the CCH channel, the ESM message may be received on the SCH channel through forwarding of the node D, and compared with the prior art that the message cannot be obtained any more when the ESM message fails to be received, the embodiment of the present invention may ensure the success rate of message reception with a smaller delay cost.

The method for broadcasting the message in the vehicle-mounted self-organizing network provided by the embodiment of the invention can add a forwarding identifier in the ESM message by the source node when the ESM message is generated in the CCH time interval, and broadcast the ESM message added with the forwarding identifier through the CCH. For the neighbor node which can receive the message on the CCH channel, the neighbor node broadcasts the ESM message to the neighbor node of the neighbor node through the SCH channel after switching to the SCH channel according to the forwarding identification carried in the ESM message. For other neighbor nodes with CCH channel congestion or switched to SCH channel when message arrives, although the ESM message broadcasted by the source node can not be directly received, in the actual road environment, nodes in a certain range are often mutually neighbor nodes, the node which can not receive the message is used as the neighbor node of the former node, and the ESM message forwarded by the former node can be received in the time interval of the next SCH channel, thereby achieving the purpose of indirectly receiving the message of the source node. In addition, in practical applications, the SCH channel has less possibility of channel congestion and more power consumption for transmitting ESM messages than the CCH channel, which are two reasons: firstly, the SCH channel does not need to broadcast periodic messages, and the idle channel capacity of the SCH channel is larger under the condition that the node load capacity is the same; secondly, the 1609.4 protocol specifies that a node can use 1 CCH channel and 6 different SCH channels, and after the time interval of the CCH channel expires, the node can select one SCH channel from at most 6 SCH channels according to its own capability to perform handover, so on average, under the condition of the same number of nodes, the node load of the SCH channel is much smaller than the node load of the CCH channel. In summary, the embodiment of the present invention provides a possibility of remedying a message reception failure through a secondary forwarding mechanism, and ensures the probability of successful reception of a node when an ESM message is retransmitted by using the characteristics of small SCH channel load and low probability of congestion.

Further, as a supplement to the above embodiments, the embodiments of the present invention further provide a method for broadcasting a message in a vehicle-mounted ad hoc network, where the method relates to a source node and a neighbor node. As shown in fig. 4, the method includes:

401. when the ESM message is generated in the CCH time interval, the source node judges whether the current network condition of the source node side meets the message forwarding condition.

In this embodiment, the source node may first determine the network condition of the source node itself after generating the ESM message, and the purpose of determining the network condition is to evaluate the possibility that the neighboring node can successfully receive the ESM message. If the network conditions can ensure that all or almost all neighbor nodes receive the ESM message on the CCH, the source node cancels the process of forwarding the ESM message through the neighbor nodes and directly broadcasts the message on the CCH according to the existing implementation mode, thereby saving the processing resources of other neighbor nodes and the cost of network transmission resources and ensuring the overall operation efficiency of the network; if the network conditions can not ensure that most neighbor nodes receive the ESM message on the CCH, the source node executes the subsequent flow of the figure 4, and secondary forwarding is carried out on the ESM message through the neighbor nodes so as to ensure the success rate of message receiving.

In this embodiment, each node may maintain a node information list, where the list records each item of basic information of a neighboring node, and each node sends its latest node information to the neighboring node in a periodic broadcast manner, receives the node information sent by the neighboring node, and updates and maintains the node information list stored in itself based on the received node information. Since the update and maintenance of the node information are periodic, in order to reduce modifications to the existing protocol to the maximum extent, in an implementation manner of this embodiment, the node information may be transferred between nodes based on Beacon information periodically broadcast on a CCH channel.

Specifically, the node can add its own node information to the Beacon information, and the purpose of periodically updating the node information is achieved by sending the Beacon information. For a source node, the source node periodically receives Beacon information broadcast by a neighbor node, analyzes the node information of the neighbor node from the Beacon information, and updates a node information list maintained by the source node according to the information. Meanwhile, the source node also needs to add the latest node information of the source node to the Beacon information and periodically broadcast the Beacon information to the neighbor nodes, so that the neighbor nodes update the node information list of the source node.

As shown in fig. 5, the node information received by the source node may include, but is not limited to, the following information of the neighboring node: node identification, number of neighbor nodes, channel identification of the next used SCH channel, and number of available SCH channels. The number of neighbor nodes refers to the number of neighbor nodes of the neighbor node of the source node. In addition, the number and types of SCH channels that can be used by each node are different, and the SCH channels selected by each node are also different when switching to the SCH channels, and therefore, the node information also needs to include the channel identification of the SCH channel to be used next and the number of available SCH channels. When a certain node becomes a source node because of generation of an ESM message, the node can perform subsequent operations such as judgment of network conditions, selection of a preferred node, and the like, based on node information in the node information list.

When judging the network condition, the source node has two types of criteria based on: the number of neighbor nodes is excessive, the more the neighbor nodes are, the higher the congestion degree of a CCH channel is, and the lower the possibility that the neighbor nodes successfully receive the ESM message is; the second is that the remaining time of the current CCH channel is too short, and because the message is transmitted in the channel with a certain delay, when the remaining time of the CCH channel is too short, although the source node can send out the ESM message in time, when the message reaches the neighbor node, the neighbor node may already switch to the SCH channel, so that the ESM message cannot be received on the CCH channel.

Based on the above criteria, when step 401 is executed, the source node may determine whether the current network condition satisfies any one of the following conditions or both of the following conditions:

1. the number of neighbor nodes of the source node exceeds a preset node number threshold.

2. And the remaining time of the current CCH is less than a preset time length threshold.

Wherein, the remaining time refers to the time length from the generation of the ESM message to the end of the CCH time interval. When the condition 1 is judged, the source node extracts the node identifiers of the neighbor nodes from the node information list, and the counted number of the node identifiers is the number of the neighbor nodes. For the judgment of the time in the condition 2, the source node may calculate the remaining time by its own clock or a system clock on the network side. The node number threshold and the duration threshold may be set according to actual conditions, and the values of the node number threshold and the duration threshold are not specifically limited in this embodiment, but in general practical applications, the node number threshold should be greater than 1, and the duration threshold should be smaller than a time interval of one CCH channel.

In practical application, the source node may select different criteria based on different policies or requirements to perform network condition judgment, for example, only the condition 1 may be judged, and if the conditions are met, the subsequent flow of fig. 4 is executed; or only the condition 2 is judged, and if the condition is met, the subsequent flow of the figure 4 is executed; or both the condition 1 and the condition 2 may be determined, and when one of the two conditions meets the condition, the subsequent flow of fig. 4 is executed; or, both the condition 1 and the condition 2 may be determined, and the subsequent flow in fig. 4 may be executed only when both conditions are met. For the case that both the condition 1 and the condition 2 need to be determined, the embodiment does not limit the execution sequence of the condition.

It should be noted that, in this embodiment, the source node performs the network condition determination after generating the ESM message, and in practical applications, the source node may also perform the determination periodically at a preset time point, and after generating the ESM message, the source node may directly perform a subsequent corresponding process according to the previous determination result.

402. And if the message forwarding condition is met, the source node adds a forwarding instruction in the ESM message.

In this embodiment, the forwarding identifier is specifically a forwarding instruction, where the forwarding instruction may be a character string "transmit", and the source node adds the character string at a preset field position, that is, completes the addition of the forwarding instruction. Of course, in some implementations, the forwarding instruction may also be a flag bit, for example, a "0" indicates forwarding a "1" indicates not forwarding.

403. The source node broadcasts the ESM message with the forwarding identifier added to all the neighbor nodes through the CCH channel.

404. The neighbor node receives the ESM message broadcast by the source node over the CCH channel.

405. The neighbor node searches whether the ESM message carries a forwarding instruction for instructing the neighbor node to forward the ESM message.

406. If the forwarding instruction is found, the neighbor node broadcasts the ESM message to the neighbor node of the neighbor node through the SCH channel after switching to the SCH channel.

In this embodiment, the source node broadcasts the ESM message to all the neighboring nodes, and as long as the neighboring nodes receive the ESM message, the source node executes steps 404 to 406 to forward the message.

Besides forwarding the message, the neighboring node also needs to respond to the received ESM message according to the existing implementation manner, and perform corresponding early warning processing, for example, when the ESM message is "emergency brake of front vehicle", the neighboring node prompts the driver based on the message, or directly performs vehicle braking.

The method for broadcasting the message in the vehicle-mounted self-organizing network provided by the embodiment can judge the network condition of the source node by the source node before adding the forwarding identifier, and if the network condition cannot ensure that most nodes can successfully receive the ESM message, the neighboring nodes are instructed to forward the ESM message by adding the forwarding identifier; if the network conditions can ensure that all or almost all neighbor nodes can successfully receive the ESM, the processes of identification addition and message forwarding are not carried out any more, so that unnecessary node resources and network resource overhead can be reduced, and the overall operation efficiency of the network is ensured.

The foregoing embodiment is implemented by taking an example that a source node notifies all neighboring nodes to forward a message, and further, in another method according to the embodiment of the present invention, the source node may also select a part of nodes from the neighboring nodes as preferred nodes, and forward the message through the preferred nodes. Specifically, as shown in fig. 6:

601. when the ESM message is generated in the CCH time interval, the source node judges whether the current network condition of the source node side meets the message forwarding condition.

Similar to step 401 in fig. 4, in this embodiment, the source node also needs to periodically receive node information of the neighboring node, update the node information list maintained by the source node, and determine the network condition of the source node.

602. And the source node selects a preferred node from the neighbor nodes based on a preset node selection algorithm.

In this embodiment, all the neighboring nodes that receive the ESM message do not need to perform message forwarding, and the source node selects a part of nodes from the neighboring nodes as preferred nodes according to a preset node selection algorithm, and performs message forwarding through the preferred nodes. The criteria for selecting the preferred node are two: one of the two methods is that the number of available SCH channels is small, in practical applications, the number of SCH channels that different nodes are configured to use is different, and in the time interval of the SCH channels, although a node selects only one SCH channel to use, on the physical layer, no matter which SCH channel is used, the node receives messages sent on all available SCHs, on the network layer, only the messages on the currently used SCH channel are retained, and the messages received on other SCH channels are filtered. It can be seen that the larger the number of available SCH channels, the greater the load on the physical layer of the node. Since the neighbor node forwards the ESM message through the SCH channel, the lower the number of available SCH channels, the higher the success rate of the node broadcasting the ESM message on the SCH channel. The second is that the number of neighbor nodes is large, the neighbor nodes of the neighbor nodes themselves may include other neighbor nodes of the source node and may also include non-neighbor nodes of the source node, in order to ensure that the neighbor nodes of the neighbor nodes can cover all the neighbor nodes of the source node as much as possible, so that all the neighbor nodes which do not receive the ESM message can forward and receive the ESM message through the message, and therefore, the more the neighbor nodes of the neighbor nodes are, the better the ESM message is.

Based on the above criteria, in executing step 602, the source node may determine a neighbor node satisfying any one of the following conditions or both of the following conditions as a preferred node:

1. the number of available SCH channels is not greater than a preset first threshold.

2. The number of the neighbor nodes is not less than a preset second threshold.

When the condition 1 is judged, the source node extracts the number of the available SCH channels of each neighbor and the corresponding node identification from the node information list, compares the number of the available SCH channels with a first threshold value respectively, and eliminates the neighbor nodes of which the number of the available SCH channels is greater than the first threshold value. For the judgment in the condition 2, the source node extracts the number of neighbor nodes of each neighbor and corresponding node identifiers from the node information list, compares the number of neighbor nodes with the second threshold respectively, and rejects the neighbor nodes of which the number of neighbor nodes is less than the second threshold. The first threshold and the second threshold may be set according to practical situations, and the present embodiment does not specifically limit the values thereof, but in general practical applications, the first threshold should be less than 6 (for the limit on the number of SCH channels in the 1609.4 protocol), and the second threshold should be greater than 1.

Similar to the determination of the network condition, the source node may select a preferred node based on different criteria based on different policies or requirements, for example, based on only the above condition 1, or based on only the above condition 2, or based on both

conditions

1 and 2, and may select only when one of the two meets the condition, or may select in combination with both

conditions

1 and 2, and only when both meet the condition. For the case that both the condition 1 and the condition 2 need to be determined, the embodiment does not limit the execution sequence of the condition determination. In one implementation manner of this embodiment, a neighbor node with the least number of available SCH channels and the most number of neighbor nodes may be selected as the preferred node.

It should be noted that, in this embodiment, the source node performs node selection after determining the network condition, and in practical applications, the source node may also select a preferred node before or while determining the network condition, or select a preferred node before generating the ESM message, and the timing of executing the preferred node is not limited in this embodiment.

Further, in this embodiment, the neighbor node forwards the ESM message on the SCH channel, and since there are 6 SCH channels selectable under the 1609.4 protocol, and two nodes must perform messaging based on the same SCH channel, in order to enable the neighbor nodes using different SCH channels to receive the ESM message forwarded by the preferred node, in an implementation manner of this embodiment, the source node may select the preferred node for different SCH channels. Specifically, the method comprises the following steps:

s1, the source node acquires the channel identification of the SCH channel used by the neighbor node next.

And the source node acquires the channel identification of the SCH channel used next by all the neighbor nodes from the node information list, wherein the channel identification is the identification of the SCH channel selected by the neighbor nodes when the neighbor nodes switch the SCH channel next time.

And S2, the source node divides the neighbor nodes into different node sets according to the SCH channel identification.

And the source node groups the neighbor nodes according to the SCH channel identification to obtain a node set corresponding to different SCH channel identifications.

And S3, the source node selects a preferred node from each node set respectively based on a preset node selection algorithm.

The source node selects a preferred node from each node set based on the condition 1 and/or the condition 2, for example, in an implementation manner of this embodiment, the source node selects a node with the least number of available SCH channels and the most neighbor nodes from each node set as the preferred node.

Illustratively, the channel identifiers of SCH channels used by 7 neighboring nodes a to G next time are: 172. 172, 176, 174, 176, 172. The source node divides the 7 nodes into 3 groups of node sets according to the channel identification of the SCH channel:

node set 1 corresponding to channel identification 172, including neighbor nodes A, B and G;

node set 2, including neighbor node D, corresponding to channel identification 174;

node set 3, which corresponds to channel identification 176, includes neighbor nodes C, E and F.

Based on the above node selection algorithm, the source node selects node a as a preferred node in node set 1, node D as a preferred node in node set 2, and node F as a preferred node in node set 3, thereby determining three preferred nodes A, D and F.

It can be seen from the above example that, when the neighbor node of the source node switches the SCH channel, three channels 172, 174, and 176 are involved, and the source node selects a preferred node for each channel, thereby ensuring that when the neighbor node of the source node performs channel switching, the neighbor node of which SCH channel is used has a corresponding preferred node to forward the ESM message.

603. The source node adds the node identification of the preferred node as a forwarding identification to the ESM message.

In this embodiment, the source node adds the node identifier of the neighbor node as a forwarding identifier to the ESM message. After selecting the preferred node through the foregoing steps, the source node adds the node identification of the preferred node to the ESM message and broadcasts the ESM message through step 604.

604. The source node broadcasts the ESM message of adding the node identification to all the neighbor nodes through the CCH channel.

605. The neighbor node receives the ESM message broadcast by the source node over the CCH channel.

606. And the neighbor node searches whether the ESM message carries the node identification of the neighbor node.

607. If the node identification of the neighbor node is found, the neighbor node broadcasts the ESM message to the neighbor node of the neighbor node through the SCH channel after switching to the SCH channel.

When broadcasting the message, analyzing the ESM message by all the neighboring nodes capable of receiving the ESM message, identifying the node identification of the neighboring nodes, wherein the neighboring nodes which acquire the node identification belong to the preferred nodes selected by the source node, and after acquiring the node identification of the neighboring nodes, the neighboring nodes execute the step 607 to forward the ESM message and respond to the ESM message according to the existing mode; and if the node identification of the neighbor node is not identified, the neighbor node responds to the ESM message according to the existing mode.

The method provided by the embodiment of the invention can select the nodes with small SCH channel load and/or more neighbor nodes as the preferred nodes to forward the ESM message from all neighbor nodes, on one hand, the message forwarding of all neighbor nodes is not needed, the resource expenses of the nodes and the network can be saved, on the other hand, the forwarding information of the nodes with small SCH channel load can further improve the forwarding success rate of the ESM message on the SCH channel, and the forwarding information of the nodes with more neighbor nodes can make the neighbor nodes which do not receive the ESM message obtain the chance of receiving the message for the second time as much as possible. In summary, the method provided by the embodiment of the present invention can control the resource overhead to the minimum on the premise of ensuring the forwarding success rate and the forwarding coverage.

Further, in addition to the above embodiments, an embodiment of the present invention further provides a method for broadcasting a message in a vehicle-mounted ad hoc network, where the method provides an implementation manner different from the prior art for a case where a source node generates an ESM message after switching to an SCH channel. As shown in fig. 7, the method includes:

701. after the source node is switched from the CCH channel to the SCH channel, if the ESM message is generated in the time interval of the SCH channel, the source node broadcasts the ESM message to a neighbor node using the same SCH channel as the source node through the SCH channel.

In the prior art, when an ESM message is generated within a time interval of an SCH channel, a source node cannot broadcast the ESM message on the SCH channel, and can only cache the ESM message, and then broadcast the ESM message through a CCH channel after switching to the CCH channel. In practical application, if too many messages are cached by a node, more message collisions are easily generated after the CCH is switched to, so that the messages cannot be normally sent through the CCH, and therefore, a neighbor node cannot receive the ESM messages.

In this embodiment, the source node may broadcast the generated ESM message directly on the current SCH channel. Because the message is sent without waiting for switching to the CCH, the embodiment of the invention can prevent the problem of message sending failure caused by message collision and improve the success rate of message sending. Meanwhile, because the message is not required to be sent on the CCH, the embodiment of the invention can also reduce the time delay from the generation of the ESM message to the receiving of the neighbor node, and ensure the timeliness of the ESM message.

In practical application, because the SCH channel is not congested basically, and the probability that the ESM message is not received by the neighbor node is low, it is not considered that the ESM message is forwarded by the neighbor node for the second time. It should be clear that such considerations aim to make the scheme more optimal and do not act as an exclusion to the combination of the scheme shown in figure 7 with a "message forwarding" mechanism.

702. And after the neighbor node is switched to the SCH channel, the source node receives the ESM message broadcasted based on the same SCH channel.

After receiving the ESM message, the neighbor node responds to the ESM message according to the existing mode and makes corresponding early warning processing. When the neighbor node needs to forward the message, the source node may add a forwarding identifier in the ESM message before step 701, and after receiving the message, the neighbor node may forward the message on the current SCH channel, or forward the message through the CCH channel after switching to the CCH channel.

Further, as mentioned above, the SCH channels used by different nodes may be different, for example, node 1 uses 172 channel and node 2 uses 176 channel, so that when the SCH channel used by the neighbor node is different from the SCH channel used by the source node, the neighbor node cannot receive the ESM message broadcast by the source node on the SCH channel. In order to enable more neighboring nodes to receive the ESM message sent by the source node, in a modified manner of this embodiment, after the source node performs step 702, the source node may further cache the sent ESM message. After switching to the CCH channel again, the source node broadcasts the ESM message to neighboring nodes via the CCH channel in the manner shown in fig. 1, 4, or 6.

Furthermore, before broadcasting the ESM message through the SCH channel, the source node may also obtain a channel identifier of the SCH channel currently used by the neighbor node, and determine whether there is a neighbor node using the same SCH channel as the source node through statistics of the SCH channel identifier. If the message exists, the source node broadcasts the ESM message according to the flow shown in fig. 7, and if the message does not exist, the source node cancels sending the ESM message through the SCH channel, directly caches the message, and broadcasts the ESM message according to the manner shown in the foregoing fig. 1, fig. 4, or fig. 6 after waiting for switching to the CCH channel. Compared with the mode, the scheme can save the resource overhead on the SCH channel and further improve the overall operation efficiency of the network under the condition that the neighbor node using the same SCH channel does not exist.

The method provided by the embodiment of the invention can send the ESM message generated in the time interval of the SCH channel to the neighbor nodes in time, and for the neighbor nodes which can not receive the ESM message due to the use of other SCH channels, the ESM message broadcasted by the CCH channel by the source node can be received after the source node is switched to the CCH channel, so that each neighbor node can obtain the ESM message under the condition of short time delay.

For convenience of understanding, the logic flows of the source node and the neighbor node in the embodiments of the present invention are respectively given below.

A. The logic flow of the source node is shown in fig. 8:

1. an ESM message is generated and then goes to 2.

2. Whether the source node is on the CCH channel, if so go to 3, otherwise go to 8.

3. And whether the number of neighbor nodes of the source node is larger than a node number threshold value, if not, turning to 4, and if so, turning to 5.

4. And whether the remaining time of the CCH channel is less than a duration threshold, if so, turning to 5, and otherwise, turning to 7.

5. A preferred node is selected based on the node selection algorithm and a transition is made to 6.

6. The node identification of the preferred node is added to the ESM message and then goes to 7.

7. The ESM message is broadcast on the CCH channel.

8. If there is a neighbor node using the same SCH channel as the source node, go to 9 if there is, otherwise jump to 10.

9. The ESM message is broadcast on the SCH channel and then jumps to 3.

10. And after waiting for switching to the CCH channel, skipping to 3.

B. The logic flow of the neighbor node is shown in fig. 9:

1. the ESM message broadcast by the source node is received and then goes to 2.

2. If the neighbor node is in the SCH channel, otherwise go to 3, if yes, go to 5.

3. Whether the ESM message contains the node identification or not, if yes, turning to 4, and otherwise, turning to 5.

4. After switching to the SCH channel, the ESM message is broadcast to its own neighbor nodes through the SCH channel, and then goes to 5.

5. And responding to the ESM message and performing early warning processing.

Several application scenarios of the present embodiment are given below based on the above logic flow:

scenario 1, ESM messages are generated during the time interval of the CCH channel.

The node A generates ESM information in the CCH time interval, and obtains the identification of the neighbor node from the node information list: B. c, D and E, counting to obtain the number of neighbor nodes as 4, wherein the number is less than the threshold value 5 of the number of nodes, and the node A continues to judge whether the remaining time of the CCH is less than the time length threshold value. At this time, the remaining time is 4ms, and the time length threshold is 8ms, so that the condition is met, and the node A selects a preferred node from the nodes B, C, D, E according to the node selection algorithm. Specifically, the node a acquires the channel identifiers of the SCH channels used next by the 4 neighboring nodes from the node information list, which are 172, 174, 172, and 174 in order. The node A divides 4 neighbor nodes into 2 node sets according to the two channel identifiers 172 and 174, the node set 1 corresponding to the channel identifier 172 comprises a node B and a node D, and the node set 2 corresponding to the channel identifier 174 comprises a node C and a node E. Then the node A selects the preferred node from the two nodes respectively. Specifically, the node a obtains the number of available SCH channels of 4 neighbor nodes from the node information list, which is sequentially 2, 1, and 2, and the number of neighbor nodes, which is sequentially 5, 8, and 10. For node set 1, node a selects node D with 1 number of available SCH channels and 8 number of neighbor nodes as the preferred node. For node set 2, node a selects node E with a number of available SCH channels of 2 and a number of neighbor nodes of 10 as the preferred node.

Node a then adds the identities of node D and node E to the ESM message, which is broadcast over the CCH channel. The node B does not receive the ESM due to channel congestion, the node C does not find the own node identification after receiving the ESM, and only responds to the ESM; after receiving the ESM message, the node D and the node E find out the node identifiers of the node E, and after the node D and the node E are switched to the SCH channel, the node D and the node E broadcast the ESM message based on the SCH channels 172 and 174 respectively. Node B and node D use the same SCH channel 172 and successfully receive the ESM message generated at node a over the SCH channel 172.

Scenario 2, ESM message is generated during the time interval of the SCH channel.

The node A generates ESM information in the time interval of the SCH channel, and acquires the identification of the neighbor node from the node information list: B. c, D and E, the number of neighbor nodes is 4 by statistics. Then acquiring the current used SCH channel identifications of the 4 neighbor nodes as 172, 174, 172 and 176 in sequence. The currently used SCH channel of node a is 172, there are neighbor nodes using the same SCH channel, node a broadcasts ESM messages on SCH channel 172, and node B and node D receive the ESM messages through SCH channel 172. And then the node A caches the ESM message, the ESM message is broadcasted through the CCH after the CCH is switched to, and the node C and the node E receive the ESM message through the CCH.

As can be seen from the above application scenario, when the source node broadcasts the ESM message on the SCH channel and the neighbor node receives the ESM message on the same SCH channel, or when the source node broadcasts the ESM message on the CCH channel and the neighbor node receives the ESM message on the CCH channel, the message transmission occupies one channel time interval (i.e., SCH or CCH); when the source node broadcasts the ESM message on the CCH channel, the ESM message is forwarded by the preferred node on the next SCH channel, and the neighbor node receives the ESM message on the SCH channel through the preferred node, the message transmission occupies 2 channel time intervals (i.e., CCH + SCH); when a source node broadcasts an ESM message on an SCH channel and a neighbor node does not use the same SCH channel, the source node broadcasts the ESM message after switching to a CCH channel and the ESM message is received by the neighbor node on the CCH channel, and the message transmission occupies 2 channel time intervals (namely SCH + CCH); when the source node broadcasts the ESM message on the SCH channel, the neighbor node does not use the same SCH channel, the source node broadcasts the ESM message after switching to the CCH channel, and the neighbor node receives the ESM message on the next SCH channel through the preferred node, the message transmission occupies 3 channel time intervals (i.e., SCH + CCH + SCH). Therefore, the message broadcasting scheme provided by the embodiment of the invention can ensure that the neighbor node receives the ESM message broadcasted by the source node within at most 3 channel time intervals, and can ensure the success rate of message reception at the very low time delay cost.

Further, as an implementation of the foregoing method, an embodiment of the present invention further provides an apparatus for broadcasting a message in a vehicle-mounted ad hoc network, where the apparatus is located at a source node side, and as shown in fig. 10, the apparatus includes: adding section 1001 and transmitting section 1002. Wherein:

an adding unit 1001, configured to add, when an event-driven safety message ESM is generated in a time interval of a control channel CCH, a forwarding identifier indicating a neighboring node to forward the ESM message in the ESM message.

A sending unit 1002, configured to broadcast the ESM message with the forwarding identifier added to the neighboring node through the CCH channel, so that the neighboring node that receives the ESM message with the forwarding identifier added thereto broadcasts the ESM message to its own neighboring node through the SCH channel after switching to the SCH according to the forwarding identifier.

Further, as shown in fig. 11, the apparatus further includes:

a determining unit 1003, configured to determine whether a current network condition of the source node side meets a message forwarding condition before adding a forwarding identifier indicating a neighboring node to forward the ESM message in the ESM message.

An adding unit 1001, configured to add a forwarding identifier to the ESM message if the message forwarding condition is satisfied.

In this embodiment, the source node may first determine the network condition of the source node itself after generating the ESM message, and the purpose of determining the network condition is to evaluate the possibility that the neighboring node can successfully receive the ESM message. If the network conditions can ensure that all or almost all neighbor nodes receive the ESM message on the CCH, the source node cancels the process of forwarding the ESM message through the neighbor nodes and directly broadcasts the message on the CCH according to the existing implementation mode, thereby saving the processing resources of other neighbor nodes and the cost of network transmission resources and ensuring the overall operation efficiency of the network; if the network condition can not ensure most neighbor nodes to receive the ESM message on the CCH, the source node adds the forwarding identifier into the ESM message, and the ESM message is forwarded for the second time through the neighbor nodes so as to ensure the success rate of message receiving.

Further, the determining unit 1003 is configured to determine whether any one of the following conditions is satisfied or both of the following conditions are satisfied:

Further, the forwarding identifier is a forwarding instruction, and the sending unit 1002 is configured to broadcast the ESM message with the forwarding instruction added thereto to all neighboring nodes through a CCH channel, so that all neighboring nodes receiving the ESM message with the forwarding instruction added thereto broadcast the ESM message according to the forwarding instruction.

The forwarding identifier is specifically a forwarding instruction, the forwarding instruction may be a character string "transmit", and the source node adds the character string at a preset field position, that is, completes the addition of the forwarding instruction. Of course, in some implementations, the forwarding instruction may also be a flag bit, for example, a "0" indicates forwarding a "1" indicates not forwarding.

Or, the forwarding identifier is a node identifier of a neighboring node, and the sending unit 1002 is configured to broadcast the ESM message with the node identifier added to all neighboring nodes through a CCH channel, where the neighboring node corresponding to the node identifier broadcasts the ESM message by identifying its own node identifier.

When the message broadcasting is carried out, all the neighbor nodes capable of receiving the ESM message analyze the ESM message, identify the node identification of the neighbor nodes, for the neighbor nodes which acquire the node identification of the neighbor nodes, the neighbor nodes belong to the preferred nodes selected by the source node, forward the ESM message after acquiring the node identification of the neighbor nodes, and respond to the ESM message according to the existing mode; and if the node identification of the neighbor node is not identified, the neighbor node responds to the ESM message according to the existing mode.

Further, as shown in fig. 11, the apparatus further includes:

a selecting unit 1004, configured to select a preferred node from the neighboring nodes based on a preset node selection algorithm before broadcasting the ESM message with the node identifier added to the neighboring nodes through the CCH channel.

An adding unit 1001 configured to add the node identifier of the preferred node as a forwarding identifier to the ESM message.

And the source node selects a part of nodes from the neighbor nodes as preferred nodes according to a preset node selection algorithm, and the messages are forwarded through the preferred nodes. The criteria for selecting the preferred node are two: one of the two methods is that the number of available SCH channels is small, in practical applications, the number of SCH channels that different nodes are configured to use is different, and in the time interval of the SCH channels, although a node selects only one SCH channel to use, on the physical layer, no matter which SCH channel is used, the node receives messages sent on all available SCHs, on the network layer, only the messages on the currently used SCH channel are retained, and the messages received on other SCH channels are filtered. It can be seen that the larger the number of available SCH channels, the greater the load on the physical layer of the node. Since the neighbor node forwards the ESM message through the SCH channel, the lower the number of available SCH channels, the higher the success rate of the node broadcasting the ESM message on the SCH channel. The second is that the number of neighbor nodes is large, the neighbor nodes of the neighbor nodes themselves may include other neighbor nodes of the source node and may also include non-neighbor nodes of the source node, in order to ensure that the neighbor nodes of the neighbor nodes can cover all the neighbor nodes of the source node as much as possible, so that all the neighbor nodes which do not receive the ESM message can forward and receive the ESM message through the message, and therefore, the more the neighbor nodes of the neighbor nodes are, the better the ESM message is.

Further, the selecting unit 1004 is configured to determine, as a preferred node, a neighbor node that satisfies any one of the following conditions or both of the following conditions:

the number of the neighbor nodes is not less than a preset second threshold.

Further, as shown in fig. 11, the apparatus further includes:

an obtaining unit 1005, configured to obtain a channel identifier of an SCH channel used next by a neighbor node before selecting a preferred node from the neighbor node based on a preset node selection algorithm;

a selecting unit 1004, configured to select a preferred node from each node set based on a preset node selection algorithm, respectively.

Since 1609.4 protocols have 6 SCH channels to be selected, and two nodes must transmit and receive messages based on the same SCH channel, in order to enable neighboring nodes using different SCH channels to receive ESM messages forwarded by a preferred node, in an implementation manner of this embodiment, a source node may select a preferred node for different SCH channels.

Firstly, the source node acquires the channel identification of the SCH channel used next by all the neighbor nodes from the node information list, wherein the channel identification is the identification of the SCH channel selected by the neighbor nodes when the neighbor nodes switch the SCH channel next time. And then, the source node groups the neighbor nodes according to the SCH channel identification to obtain a node set corresponding to different SCH channel identifications. Finally, the source node selects a preferred node from each node set based on the condition 1 and/or the condition 2, for example, in an implementation manner of this embodiment, the source node selects a node with the least number of available SCH channels and the most neighbor nodes from each node set as the preferred node.

Further, the sending unit 1002 is configured to, after the source node switches from the CCH channel to the SCH channel, broadcast the ESM message to the neighboring nodes using the same SCH channel as the source node through the SCH channel if the ESM message is generated within a time interval of the SCH channel.

Further, as shown in fig. 11, the apparatus further includes:

a buffering unit 1006, configured to buffer the ESM message after broadcasting the ESM message to a neighbor node using the same SCH channel as the source node through the SCH channel or when there is no neighbor node using the same SCH channel as the source node.

A sending unit 1002, configured to broadcast the ESM message to the neighboring node through the CCH channel after switching to the CCH channel again.

As mentioned above, the SCH channels used by different nodes may be different, and when the SCH channels used by the neighbor nodes are different from the SCH channel used by the source node, the neighbor nodes cannot receive the ESM message broadcast by the source node on the SCH channel. In order to enable more neighboring nodes to receive the ESM message sent by the source node, the source node may also cache the sent ESM message after sending the ESM message on the SCH channel. When switching to the CCH channel again, the source node broadcasts the ESM message to the neighbor nodes through the CCH channel.

Further, as shown in fig. 11, the apparatus further includes:

a receiving unit 1007, configured to receive Beacon information periodically broadcast on a CCH channel by a neighbor node, where the Beacon information carries node information of the neighbor node, and the node information includes:

Further, as an implementation of the foregoing method, an embodiment of the present invention further provides a device for broadcasting a message in a vehicle-mounted ad hoc network, where the device is located on a neighboring node side of a source node, and as shown in fig. 12, the device includes: a receiving unit 1201, a searching unit 1202, and a sending unit 1203. Wherein:

a receiving unit 1201, configured to receive an event-driven safety message ESM broadcast by a source node through a control channel CCH;

a searching unit 1202, configured to search whether the ESM message carries a forwarding identifier indicating a neighboring node to forward the ESM message;

a sending unit 1203, configured to broadcast the ESM message to its own neighboring node through an SCH channel after switching to a serving channel SCH if the forwarding identifier is found.

The neighbor node for message forwarding is a neighbor node capable of receiving the ESM message broadcasted by the source node, and for the part of nodes, after receiving the ESM message, the nodes analyze the message and search the forwarding identifier in the preset field position. If the forwarding identifier is found, the forwarding identifier is broadcasted to the neighbor node of the forwarding identifier, and the ESM message is responded according to the existing implementation mode; if the forwarding identifier is not found, the ESM message is only responded according to the existing mode, and the message forwarding is not carried out any more.

Further, the searching unit 1202 is configured to search the forwarding instruction or the node identifier of the node in the ESM message, where the node identifier of the node is a node identifier of a preferred node selected by the source node based on a preset node selection algorithm.

When the forwarding identifier is the node identifier of the preferred node, all the neighbor nodes capable of receiving the ESM message analyze the ESM message, identify the node identifier of the neighbor nodes, for the neighbor nodes which acquire the node identifier of the neighbor nodes and belong to the preferred node selected by the source node, forward the ESM message by the neighbor nodes after acquiring the node identifier of the neighbor nodes, and respond to the ESM message according to the existing mode; and if the node identification of the neighbor node is not identified, the neighbor node responds to the ESM message according to the existing mode.

Further, the receiving unit 1201 is configured to receive, after the handover to the SCH channel, an ESM message broadcast by the source node based on the same SCH channel.

Further, the receiving unit 1201 is configured to receive Beacon information periodically broadcast by a source node on a CCH channel, where the Beacon information carries node information of the source node, and the node information includes:

Further, as an implementation of the foregoing method, an embodiment of the present invention further provides a system for broadcasting a message in a vehicle-mounted ad hoc network, where as shown in fig. 13, the system includes: a source node 1301 and a neighbor node 1302 of the source node 1301. Wherein:

source node 1301 comprises the apparatus shown in fig. 10 or fig. 11 described previously;

the neighboring node 1302 includes the aforementioned apparatus shown in fig. 12.

The device and the system for broadcasting the message in the vehicle-mounted self-organizing network provided by the embodiment of the invention can add a forwarding identifier in the ESM message by the source node when the ESM message is generated in the time interval of the CCH, and broadcast the ESM message added with the forwarding identifier through the CCH. For the neighbor node which can receive the message on the CCH channel, the neighbor node broadcasts the ESM message to the neighbor node of the neighbor node through the SCH channel after switching to the SCH channel according to the forwarding identification carried in the ESM message. For other neighbor nodes with CCH channel congestion or switched to SCH channel when message arrives, although the ESM message broadcasted by the source node can not be directly received, in the actual road environment, nodes in a certain range are often mutually neighbor nodes, the node which can not receive the message is used as the neighbor node of the former node, and the ESM message forwarded by the former node can be received in the time interval of the next SCH channel, thereby achieving the purpose of indirectly receiving the message of the source node. In addition, in practical applications, the SCH channel has less possibility of channel congestion and more power consumption for transmitting ESM messages than the CCH channel, which are two reasons: firstly, the SCH channel does not need to broadcast periodic messages, and the idle channel capacity of the SCH channel is larger under the condition that the node load capacity is the same; secondly, the 1609.4 protocol specifies that a node can use 1 CCH channel and 6 different SCH channels, and after the time interval of the CCH channel expires, the node can select one SCH channel from at most 6 SCH channels according to its own capability to perform handover, so on average, under the condition of the same number of nodes, the node load of the SCH channel is much smaller than the node load of the CCH channel. In summary, the embodiment of the present invention provides a possibility of remedying a message reception failure through a secondary forwarding mechanism, and ensures the probability of successful reception of a node when an ESM message is retransmitted by using the characteristics of small SCH channel load and low probability of congestion.

Secondly, the device and the system for broadcasting the message in the vehicle-mounted self-organizing network provided by the embodiment of the invention can judge the network condition of the active node before adding the forwarding identifier, and if the network condition can not ensure that most nodes can successfully receive the ESM message, the neighbor nodes are instructed to forward the ESM message by adding the forwarding identifier; if the network conditions can ensure that all or almost all neighbor nodes can successfully receive the ESM, the processes of identification addition and message forwarding are not carried out any more, so that unnecessary node resources and network resource overhead can be reduced, and the overall operation efficiency of the network is ensured.

Furthermore, the device and the system for broadcasting messages in the vehicle-mounted self-organizing network provided by the embodiment of the invention can select the nodes with small SCH channel load and/or more neighbor nodes from all neighbor nodes as the preferred nodes to forward the ESM messages, on one hand, all neighbor nodes are not required to forward messages, and the resource overhead of the nodes and the network can be saved, on the other hand, the node forwarding information with small SCH channel load can further improve the forwarding success rate of the ESM messages on the SCH channel, and the node forwarding information with more neighbor nodes can make the neighbor nodes which do not receive the ESM messages obtain the chance of receiving the messages for the second time. In summary, the method provided by the embodiment of the present invention can control the resource overhead to the minimum on the premise of ensuring the forwarding success rate and the forwarding coverage.

Finally, the device and the system for broadcasting messages in the vehicle-mounted self-organizing network provided by the embodiment of the invention can send the ESM messages generated in the time interval of the SCH channel to the neighbor nodes in time, and for the neighbor nodes which can not receive the ESM messages because of using other SCH channels, the ESM messages broadcasted by the CCH channel by the source node can be received after the source node is switched to the CCH channel, so that each neighbor node can obtain the ESM messages under a short time delay condition.

In the foregoing embodiments, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.

It will be appreciated that the relevant features of the method and apparatus described above are referred to one another. In addition, "first", "second", and the like in the above embodiments are for distinguishing the embodiments, and do not represent merits of the embodiments.

It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.

The algorithms and displays presented herein are not inherently related to any particular computer, virtual machine, or other apparatus. Various general purpose systems may also be used with the teachings herein. The required structure for constructing such a system will be apparent from the description above. Moreover, the present invention is not directed to any particular programming language. It is appreciated that a variety of programming languages may be used to implement the teachings of the present invention as described herein, and any descriptions of specific languages are provided above to disclose the best mode of the invention.

In the description provided herein, numerous specific details are set forth. It is understood, however, that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

Similarly, it should be appreciated that in the foregoing description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. However, the disclosed method should not be interpreted as reflecting an intention that: that the invention as claimed requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

Those skilled in the art will appreciate that the modules in the device in an embodiment may be adaptively changed and disposed in one or more devices different from the embodiment. The modules or units or components of the embodiments may be combined into one module or unit or component, and furthermore they may be divided into a plurality of sub-modules or sub-units or sub-components. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and all of the processes or elements of any method or apparatus so disclosed, may be combined in any combination, except combinations where at least some of such features and/or processes or elements are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise.

Furthermore, those skilled in the art will appreciate that while some embodiments described herein include some features included in other embodiments, rather than other features, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the following claims, any of the claimed embodiments may be used in any combination.

The various component embodiments of the invention may be implemented in hardware, or in software modules running on one or more processors, or in a combination thereof. Those skilled in the art will appreciate that a microprocessor or Digital Signal Processor (DSP) may be used in practice to implement some or all of the functionality of some or all of the components in the title of the invention (e.g., means for determining the level of links within a web site) in accordance with embodiments of the invention. The present invention may also be embodied as apparatus or device programs (e.g., computer programs and computer program products) for performing a portion or all of the methods described herein. Such programs implementing the present invention may be stored on computer-readable media or may be in the form of one or more signals. Such a signal may be downloaded from an internet website or provided on a carrier signal or in any other form.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by one and the same item of hardware. The usage of the words first, second and third, etcetera do not indicate any ordering. These words may be interpreted as names.

Claims

1. A method for broadcasting messages in a vehicle-mounted self-organizing network is applied to a source node side, and is characterized in that the method comprises the following steps:

when an event-driven safety message ESM is generated in a time interval of a control channel CCH, adding a forwarding identifier for indicating a neighbor node to forward the ESM message in the ESM message;

the ESM message added with the forwarding identifier is broadcasted to the neighbor nodes through a CCH (channel control channel), so that the neighbor nodes receiving the ESM message added with the forwarding identifier broadcast the ESM message to the neighbor nodes of the neighbor nodes through the SCH channel after switching to a Service Channel (SCH) according to the forwarding identifier.

2. The method according to claim 1, wherein before adding a forwarding identifier in the ESM message instructing the neighboring node to forward the ESM message, the method further comprises:

judging whether the current network condition of the source node side meets the message forwarding condition;

the adding a forwarding identifier indicating a neighbor node to forward the ESM message in the ESM message includes:

and if the message forwarding condition is met, adding the forwarding identifier in the ESM message.

3. The method according to claim 2, wherein said determining whether the current network condition at the source node side satisfies a message forwarding condition comprises determining whether any one or both of the following conditions are satisfied:

4. The method of claim 1,

the forwarding identifier is a forwarding instruction, and the broadcasting of the ESM message added with the forwarding identifier to the neighboring node through the CCH channel includes:

broadcasting the ESM message added with the forwarding instruction to all neighbor nodes through the CCH, so that all neighbor nodes receiving the ESM message added with the forwarding instruction broadcast the ESM message according to the forwarding instruction;

or, the forwarding identifier is a node identifier of a neighboring node, and the broadcasting of the ESM message added with the forwarding identifier to the neighboring node through the CCH channel includes:

5. The method of claim 4, wherein before the broadcasting the ESM message that adds the node identification to all neighboring nodes over the CCH channel, the method further comprises:

adding the node identification of the preferred node as the forwarding identification to the ESM message.

6. The method according to claim 5, wherein the selecting a preferred node from the neighbor nodes based on a preset node selection algorithm includes determining a neighbor node satisfying any one of the following conditions or both of the following conditions as the preferred node:

and the number of the neighbor nodes is not less than a preset second threshold value.

7. The method according to claim 6, wherein before the selecting a preferred node from the neighbor nodes based on the preset node selection algorithm, the method further comprises:

acquiring a channel identifier of an SCH channel used next by a neighbor node;

dividing the neighbor nodes into different node sets according to the SCH channel identification, wherein the neighbor nodes in one node set correspond to the same SCH channel identification;

the method for selecting the preferred node from the neighbor nodes based on the preset node selection algorithm comprises the following steps: and respectively selecting a preferred node from each node set based on a preset node selection algorithm.

8. The method of claim 1, wherein after the source node switches from a CCH channel to an SCH channel, the method further comprises:

if the ESM message is generated within a time interval of the SCH channel, the ESM message is broadcast to a neighbor node using the same SCH channel as the source node through the SCH channel.

9. The method of claim 8, wherein after the broadcasting the ESM message over the SCH channel to neighbor nodes using the same SCH channel as the source node, or when there are no neighbor nodes using the same SCH channel as the source node, the method further comprises:

caching the ESM message;

and after switching to the CCH channel again, broadcasting the ESM message to the neighbor nodes through the CCH channel.

10. The method according to any one of claims 1 to 9, characterized in that the method further comprises:

receiving Beacon information periodically broadcast by the neighbor node on a CCH channel, wherein the Beacon information carries node information of the neighbor node, and the node information comprises:

node identification, the number of neighbor nodes of the neighbor nodes, the channel identification of the next used SCH channel, and the number of available SCH channels.

11. A method for broadcasting messages in a vehicle-mounted self-organizing network is applied to a neighbor node side of a source node, and is characterized in that the method comprises the following steps:

receiving an event-driven safety message (ESM) broadcasted by the source node through a Control Channel (CCH);

and if the forwarding identifier is found, broadcasting the ESM message to own neighbor nodes through the SCH channel after switching to a Service Channel (SCH).

12. The method according to claim 11, wherein said searching whether the ESM message carries a forwarding identifier indicating a neighboring node to forward the ESM message comprises:

and searching a forwarding instruction or a node identifier of the ESM message, wherein the node identifier of the ESM message is the node identifier of the preferred node selected by the source node based on a preset node selection algorithm.

13. The method of claim 11, further comprising:

and after switching to the SCH channel, receiving the ESM message broadcast by the source node based on the same SCH channel.

14. The method according to any one of claims 11 to 13, characterized in that the method further comprises:

receiving Beacon information periodically broadcast by the source node on a CCH channel, wherein the Beacon information carries node information of the source node, and the node information comprises:

15. An apparatus for broadcasting a message in an ad hoc network in a vehicle, the apparatus being located at a source node side, the apparatus comprising:

16. The apparatus of claim 15, further comprising:

a judging unit, configured to judge whether a current network condition of the source node side meets a message forwarding condition before adding a forwarding identifier indicating a neighboring node to forward the ESM message in the ESM message;

17. The apparatus according to claim 16, wherein the determining unit is configured to determine whether any one of the following conditions is satisfied or both of the following conditions are satisfied:

18. The apparatus of claim 17, wherein the forwarding identifier is a forwarding instruction, and the sending unit is configured to broadcast an ESM message with the forwarding instruction added thereto to all neighboring nodes through the CCH channel, so that all neighboring nodes receiving the ESM message with the forwarding instruction added thereto broadcast the ESM message according to the forwarding instruction;

or, the forwarding identifier is a node identifier of a neighboring node, the sending unit is configured to broadcast the ESM message with the node identifier added to all neighboring nodes through a CCH channel, and the neighboring node corresponding to the node identifier broadcasts the ESM message by identifying its own node identifier.

19. The apparatus of claim 18, further comprising:

the adding unit is configured to add the node identifier of the preferred node as the forwarding identifier to the ESM message.

20. The apparatus according to claim 19, wherein the selecting unit is configured to determine, as the preferred node, a neighbor node that satisfies any one of the following conditions or both of the following conditions:

21. The apparatus of claim 20, further comprising:

an obtaining unit, configured to obtain a channel identifier of an SCH channel used next by a neighbor node before selecting a preferred node from the neighbor node based on a preset node selection algorithm;

and the selection unit is used for selecting the preferred node from each node set based on a preset node selection algorithm.

22. The apparatus of claim 15, wherein the transmitting unit is configured to broadcast the ESM message to the neighbor nodes using the same SCH channel as the source node through the SCH channel if the ESM message is generated within a time interval of the SCH channel after the source node switches from the CCH channel to the SCH channel.

23. The apparatus of claim 22, further comprising:

a caching unit, configured to cache the ESM message after broadcasting the ESM message to a neighbor node using the same SCH channel as the source node through an SCH channel or when there is no neighbor node using the same SCH channel as the source node;

24. The apparatus of any one of claims 15 to 23, further comprising:

a receiving unit, configured to receive Beacon information periodically broadcast by a neighbor node on a CCH channel, where the Beacon information carries node information of the neighbor node, and the node information includes:

25. An apparatus for broadcasting a message in an ad hoc network in a vehicle, the apparatus being located on a neighboring node side of a source node, the apparatus comprising:

a receiving unit, configured to receive an event-driven safety message ESM broadcast by a control channel CCH from the source node;

the searching unit is used for searching whether the ESM message carries a forwarding identifier for indicating a neighbor node to forward the ESM message;

and the sending unit is used for broadcasting the ESM message to the neighbor node of the sending unit through the SCH channel after switching to a service channel SCH if the forwarding identifier is found.

26. The apparatus according to claim 25, wherein the searching unit is configured to search, in the ESM message, a forwarding instruction or a node identifier of itself, where the node identifier of itself is a node identifier of a preferred node selected by the source node based on a preset node selection algorithm.

27. The apparatus of claim 25, wherein the receiving unit is configured to receive the ESM message broadcasted by the source node based on a same SCH channel after switching to the SCH channel.

28. The apparatus according to any one of claims 25 to 27, wherein the receiving unit is configured to receive Beacon information periodically broadcast by the source node on a CCH channel, where the Beacon information carries node information of the source node, and the node information includes:

29. A system for broadcasting messages in a vehicle-mounted self-organizing network is characterized by comprising a source node and a neighbor node of the source node;

the source node comprises the apparatus of any of claims 15 to 24;

the neighbour node comprises an apparatus according to any of claims 25 to 28.