CN111818465A - Internet of vehicles self-adaptive multi-hop broadcasting system and method - Google Patents
Internet of vehicles self-adaptive multi-hop broadcasting system and method Download PDFInfo
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Abstract
The invention belongs to the technical field of vehicle networking information interaction, and discloses a vehicle networking self-adaptive multi-hop broadcasting system and a method. And filtering the broadcasted neighbor nodes according to the information maintained in the management information base, then selecting proper next hop candidate forwarding nodes from the rest neighbor nodes, finally packaging the selected candidate node information and all the neighbor information of the neighbor nodes into a message and broadcasting the message, and receiving the message by the neighbor nodes and making corresponding forwarding judgment. In addition, the invention divides the application information of the Internet of vehicles into two categories of emergency information and non-emergency information, and designs two different multi-hop broadcast mechanisms aiming at the two different types of application information, namely a quick broadcast mechanism and a cooperative broadcast mechanism. The problems of high transmission delay, large network load and low reliability of the existing multi-hop broadcast strategy are solved.
Description
Technical Field
The invention belongs to the technical field of vehicle networking information interaction, and relates to an Adaptive Multi-hop Broadcast (AMHB) system and method based on a Wireless Access in Vehicular Environment (WAVE) protocol stack.
Background
With the continuous development of the automobile industry, the holding quantity of automobiles per capita is also rapidly increasing. Traffic jam in cities and highways, road safety in severe weather and traffic accidents gradually become common concerns of the whole society. By carrying out safe and effective multi-hop transmission on the Internet of vehicles information, the traffic information is quickly diffused into the possibly affected area, and the current traffic environment can be effectively improved. However, on one hand, due to the limitations of the WAVE protocol stack itself, the standard WAVE protocol stack does not forward information, and on the other hand, due to the complexity of the car networking environment, it has been a research hotspot and difficulty in this field to design a multi-hop broadcasting method that can well adapt to the current car networking environment.
The existing multi-hop broadcasting methods proposed for the internet of vehicles can be mainly divided into two categories, namely a multi-hop broadcasting method based on a sending end and a multi-hop broadcasting method based on a receiving end. The two methods are mainly different in the sender of the forwarding decision, wherein the basic idea of the method based on the sending end is to screen the relay node by the sending node and the receiving node is to transmit passively, while the method based on the receiving end means that the sending node does not select the relay node but the receiving node makes the forwarding decision. The two methods have advantages and disadvantages, and mainly show three aspects of high transmission delay, large network load and low reliability.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide a self-adaptive multi-hop broadcasting method suitable for an internet of vehicles environment, which can effectively reduce transmission delay and network load while ensuring reliability.
The AMHB method provided by the invention is structurally divided into five basic modules, namely a local information interaction module, a backoff waiting module, a relay screening module, a data forwarding module and an information maintenance module. The local information interaction module realizes information exchange among vehicles; a new back-off time calculation model is provided in the back-off module, so that information collision can be effectively reduced; a screening algorithm of the candidate nodes is provided in the relay screening module; the data forwarding module is responsible for data encapsulation and data forwarding; the information maintenance module realizes data support and data maintenance for other modules. The basic idea of the AMHB is to filter the broadcasted neighbor nodes according to the Information maintained in a Management Information Base (MIB), then select a suitable next hop candidate forwarding node from the remaining neighbor nodes, finally encapsulate the selected candidate node Information and all the neighbor Information of itself into a message and broadcast the message, and the neighbor nodes receive the message and make corresponding forwarding judgment. In addition, the invention divides the application information of the Internet of vehicles into two categories of emergency information and non-emergency information, and designs two different multi-hop broadcast mechanisms aiming at the two different types of application information, namely a quick broadcast mechanism and a cooperative broadcast mechanism.
The local information interaction module: the module is responsible for finishing data interaction work between each node and neighbor nodes in the Internet of vehicles. And the data interacted between the neighbor nodes is used as the theoretical basis of other modules and is dynamically maintained in the information maintenance module.
A back-off waiting module: the invention designs a segmented backoff waiting mechanism aiming at two conditions which can cause information conflict, wherein one condition is a plurality of Next-hop Candidate nodes (NCNs) screened by the same Node, the NCNs which are mutually neighbors can forward data at the same time, and the other condition is a plurality of NCNs screened by different nodes, the NCNs which are mutually neighbors can forward data at the same time. Aiming at the first situation, the invention provides a Back-off Wait based Priority Queue (BW-PQ) algorithm, wherein the BW-PQ algorithm is provided on the basis of research on the existing Back-off Wait algorithm, and the BW-PQ algorithm considers that the basic idea of most existing Back-off Wait algorithms is to randomly Wait for a time, on one hand, when the number of candidate nodes is large, the random waiting method still can cause a plurality of candidate nodes to simultaneously send messages, thereby causing unnecessary information collision. On the other hand, the random waiting method may also cause a node with a lower priority to forward preferentially, thereby causing problems of reduced broadcast efficiency and increased transmission delay. The BW-PQ algorithm has the advantages that a corresponding priority queue can be generated according to the selection condition of the candidate nodes, a specific back-off time is assigned to each candidate node in the queue, and the waiting time of the node with higher priority is shorter, so that each candidate node can share the channel resource in a specific time period, the node with higher priority can be preferentially forwarded, and the data transmission efficiency is improved. The BW-PQ algorithm includes two steps of generating a priority queue and calculating a back-off time.
The method comprises the following steps: a priority queue is generated. The transmitting node inserts the screened NCN information into a Priority Queue (PQ), and then encapsulates the PQ into an MH-WSA message. Each neighbor node can obtain complete PQ information after receiving the MH-WSA message, then sequentially dequeues the NCN information in the PQ, compares the NCN information with the information of the neighbor node to determine whether the neighbor node is the NCN or not, and calculates the backoff waiting time of the neighbor node if the neighbor node is the NCN.
Step two: the back-off time is calculated. The priority queue is composed of NCN information, and only the neighbor node selected as the NCN enters a backoff waiting stage to calculate the own backoff time. The back-off time is calculated as shown in equation (1).
T＝Tmax×(s-1) (1)
Where s denotes the dequeue order, TmaxRepresenting a standard one-hop maximum delay time.
For the second case, the present invention uses a default binary exponential backoff algorithm in IEEE 802.11p to perform backoff wait.
A relay node screening module: the selection of the relay node is the most core part in the invention, and an excellent relay node selection algorithm can effectively reduce the network load, avoid the broadcast storm problem and improve the data transmission efficiency. The module provides a Relay Node screening (RNS-RR) Algorithm based on request Response, and the Algorithm is divided into a request phase and a Response phase and is respectively responsible for NCN Selection and Relay Node (RN) Selection.
The method comprises the following steps: and selecting the NCN. Each node in the internet of vehicles maintains a respective neighbor list, and the neighbor list stores information such as position, speed, direction, signal strength and the like of neighbor nodes. Therefore, the transmitting node primarily calculates each neighbor first when selecting the NCNThe priority of the node, assuming that the priority of the neighbor node i is marked as pi，i∈[1，n]N is the number of neighbor nodes, then piCan be obtained from equation (2).
Wherein D isiThe distance between the neighbor node i and the sending node can be obtained by formula (3), wherein R is a one-hop communication range, ViThe relative speed of the neighbor node i and the sending node can be obtained by the formula (4), VmaxThe maximum relative velocity, RSSI, that can be theoretically achievediThe signal intensity of the neighbor node i, and alpha, beta and gamma are distances D respectivelyiRelative velocity ViWeighted RSSI of sum signal strengthiAnd α + β + γ ═ 1.
Di＝R′·arccos(cos(x)·cos(xi)·cos(yi-y)+sin(x)sin(xi)) (3)
Wherein R' is the radius of the earth, x and y are longitude and latitude information of the sending node respectively, and xi，yiRespectively longitude and latitude information of the neighbor node i.
Where v is the velocity of the transmitting node, viAnd theta is the speed of the neighbor node i, and theta is the included angle between the driving direction of the sending node and the neighbor node i.
After the priorities of all the neighbor nodes are obtained, the priority threshold value threshold is calculated according to the formula (5).
Priority satisfies condition p in neighbor nodeiNodes that are > threshold will be selected as NCN. Only the neighbor node selected as NCN is likely to become RN.
Step two: and selecting the RN. The neighbor node selected as the NCN enters a backoff waiting stage after receiving the message, the NCN counts repeated MH-WSA messages received in the backoff time, and stores neighbor node information of other NCNs carried in the message into a repeated MH-WSA data table of the NCN. After the back-off time is over, the NCN compares the own neighbor list with the repeated MH-WSA data table, and judges whether the neighbor node only belongs to the own neighbor list exists or not. If the area exists, the NCN considers that the area which is not broadcasted still exists in the communication range of the NCN, and at the moment, the NCN forwards the message to become the RN. If not, the NCN considers that all neighbor nodes in the current communication range of the NCN have received the broadcast message, and then the NCN gives up forwarding data.
A data forwarding module: the module is responsible for encapsulating and forwarding two messages, namely a Multi-hop WSA (MH-WSA) message and a Multi-hop WSM (MH-WSM) message. In order to ensure the compatibility with the standard WAVE protocol stack, the module encapsulates the fields related to the AMHB algorithm into the extension fields of the corresponding message.
An information maintenance module: the module is responsible for data maintenance work in the AMHB system and provides data support for other modules, and mainly comprises maintenance of a neighbor list, maintenance of a repeated MH-WSA data table and maintenance of a repeated MH-WSM data table.
Two message types: the invention divides the application messages into two categories of urgent messages and non-urgent messages according to the priority of the application messages. The priority of the application message is specified by an application layer, the value range of the priority is 1-8, and the smaller the value is, the higher the priority of the message is. Messages with priority < 4 are referred to as urgent messages, and such messages generally relate to personal safety, have high requirements on time efficiency and have small data volume; messages with priority >4 are called non-urgent messages, and are mainly used for improving the driving experience of users, and have relatively low requirements on timeliness and large data volume.
Two forwarding modes: corresponding to the two message types are two different forwarding modes, namely a fast forwarding mode and a cooperative forwarding mode. The fast forwarding mode is a forwarding mode designed for emergency messages, the mode only relates to the forwarding of MH-WSA messages, and broadcast data are carried by the MH-WSA messages; the cooperative forwarding mode is a forwarding mode designed for non-emergency messages, and relates to the forwarding of MH-WSA messages and MH-WSM messages, and broadcast data are carried by the MH-WSM messages.
Aiming at the problems of high transmission delay, large network load and low reliability of the existing multi-hop broadcasting strategy, the method of the invention designs a flexible and efficient relay node screening algorithm, provides a response backoff mechanism, improves the problems and has important reference value for the research of the multi-hop broadcasting technology in the internet of vehicles.
Drawings
Fig. 1 is a basic flow diagram of AMHB.
Fig. 2 is an overall architecture design diagram of the AMHB.
Fig. 3 is a schematic diagram of a Hello message sending flow.
Fig. 4 is a schematic diagram of a Hello packet receiving process.
Fig. 5 is a schematic diagram of MH-WSA message encapsulation flow.
Fig. 6 is a schematic diagram of MH-WSA message forwarding flow.
Fig. 7 is a schematic diagram of MH-WSM message encapsulation flow.
Fig. 8 is a schematic diagram of MH-WSM message forwarding flow.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings.
In the method of the embodiment, the software environment is Ubuntu 16.04, and the simulation environment is NS-3.
As shown in FIG. 1, the basic flow of the AMHB method designed by the invention, the normal operation of the AMHB algorithm is established on the basis of information interaction of each node in the Internet of vehicles. By maintaining the information of the neighbor nodes in the MIB, each node in the Internet of vehicles can clearly know the current network condition. Firstly, a certain number of neighbor nodes are selected as NCNs by a sending end node, and only the nodes selected as the NCNs have the permission to transmit MH-WSA messages and MH-WSM messages. Then the NCN node determines whether to execute the authority according to the forwarding condition of the current message, and finally only the NCN which finishes the action of forwarding the message is called as RN. The local information interaction runs through the whole operation period of the equipment and is not dependent on whether a multi-hop broadcast service request exists in the current Internet of vehicles or not. The non-broadcast area refers to the neighbor nodes which have not received the multi-hop broadcast message in the current NCN communication range.
An application method of an adaptive multi-hop broadcasting system of the Internet of vehicles comprises the following steps:
firstly, selecting candidate nodes according to information maintained in a management information base; each node in the Internet of vehicles maintains a respective neighbor list, and the neighbor list stores the position, speed, direction and signal strength information of neighbor nodes; when a sending node selects a candidate node, the priority of each neighbor node is mainly calculated at first, and the priority of a neighbor node i is set as pi，i∈[1，n]N is the number of neighbor nodes, then piThe result is obtained by formula (2);
wherein D isiThe distance between the neighbor node i and the sending node is obtained by formula (3), R is a one-hop communication range, ViThe relative speed of the neighbor node i and the sending node is obtained by the formula (4), VmaxThe maximum relative velocity, RSSI, that can be theoretically achievediThe signal intensity of the neighbor node i, and alpha, beta and gamma are distances D respectivelyiRelative velocity ViWeighted RSSI of sum signal strengthiAnd α + β + γ ═ 1;
Di＝R′·arccos(cos(x)·cos(xi)·cos(yi-y)+sin(x)sin(xi)) (3)
wherein R' is the radius of the earth, x and y are longitude and latitude information of the sending node respectively, and xi，yiRespectively longitude and latitude information of a neighbor node i;
where v is the velocity of the transmitting nodeiThe speed of the neighbor node i is shown, and theta is an included angle between the driving direction of the sending node and the driving direction of the neighbor node i;
after the priorities of all the neighbor nodes are obtained, calculating a priority threshold according to a formula (5);
priority satisfies condition p in neighbor nodeiNodes which are more than or equal to threshold are selected as candidate nodes; only the neighbor node selected as the candidate node is possible to become the relay node;
secondly, generating a priority queue; the sending node inserts the candidate node information screened in the first step into a priority queue, and then packages the priority queue into an MH-WSA message; each neighbor node obtains complete priority queue information after receiving the MH-WSA message, then sequentially dequeues candidate node information in the priority queue, compares the candidate node information with the self information, determines whether the neighbor node is a candidate node, calculates the backoff waiting time of the neighbor node if the neighbor node is the candidate node, and abandons forwarding if the neighbor node is not the candidate node;
thirdly, selecting a relay node; the candidate node counts repeated MH-WSA messages received in the back-off time, and stores neighbor node information of other candidate nodes carried in the messages into a repeated MH-WSA data table of the candidate node; after the back-off time is over, the candidate node compares the own neighbor list with the repeated MH-WSA data table, and judges whether the neighbor node only belongs to the own neighbor list exists in the own neighbor list or not; if the message exists, the candidate node considers that the area which is not broadcasted still exists in the communication range of the candidate node, and at the moment, the candidate node forwards the message to become a relay node; if the broadcast message does not exist, the candidate node considers that all neighbor nodes in the current own communication range have received the broadcast message, and at the moment, the candidate node gives up forwarding data.
Fig. 2 is an overall architecture design diagram of the AMHB algorithm, and in consideration of compatibility of the AMHB algorithm with a standard WAVE protocol stack, an information interaction module is designed in an application layer and used as a new car networking application to complete data interaction between neighboring nodes. And the information maintenance module is used as a part of the MIB and is responsible for completing maintenance work on the neighbor list, the repeated MH-WSA data table and the repeated MH-WSM data table. The BW-PQ backoff algorithm and the screening algorithm of the relay node are realized in the WSMP protocol flow. The data forwarding module and the BEB back-off algorithm are implemented in the LLC layer and the MAC layer, respectively.
Fig. 3 and fig. 4 are respectively a flow of sending and receiving a Hello message in a local information interaction process. When the sending node filters the NCN, the sending node needs to know the current position, speed, direction, signal strength and other information of all the neighbor nodes, and the purpose of local information interaction is to complete the information collection of the neighbor nodes, and store the collected neighbor node information into the neighbor list after performing corresponding processing. The Hello message adopts a periodic broadcast mode, and the broadcast period can be adjusted by applying parameters. In addition, since the information interaction is a spontaneous action, in order to avoid unnecessary interaction delay, the sending of the Hello message does not specify a specific channel, that is, the Hello message can be sent no matter in the SCH time slot or the CCH time slot, so that the condition of data failure caused by waiting for channel switching can be reduced.
Fig. 5 and 6 are respectively a flow of MH-WSA packet encapsulation and forwarding, where in forwarding control information carried by an MH-WSA packet, a value of an FCF field is specified by an application layer and is mainly used to identify a packet type and control a forwarding hop count, a Change count field in a source MAC and a packet is used to determine whether a current MH-WSA packet is a duplicate packet, a Hello _ Number and a Candidate _ Number are respectively used to indicate the Number of neighbor nodes of a sending node of the current MH-WSA packet and the Number of selected NCNs, the neighbor MAC sequence refers to a MAC sequence of a neighbor node of the sending node of the current MH-WSA packet, and the previous Candidate _ Number in the sequence is an NCN. These pieces of information are encapsulated in the header extension section of a standard WSA message. The MH-WSA message is responsible for informing all neighbor nodes of NCN information screened by the sending node in a fast forwarding mechanism or a cooperative forwarding mechanism, and the MH-WSA message is also responsible for carrying service data in the fast forwarding mechanism, so that the MH-WSA message is of great importance in the AMHB algorithm for forwarding.
Fig. 7 and 8 are respectively an encapsulation and forwarding flow of an MH-WSM message, where forwarding control information is encapsulated in a header extension field of a standard WSM message, and fields FCF and FEI are specified by an application layer. Besides carrying service data, the MH-WSM message carries an independent forwarding control field inside, and is used for forwarding judgment of response of candidate forwarding nodes. In addition, the MH-WSM message forwarding must comply with the interaction model of the standard WAVE protocol stack, and before forwarding the MH-WSM message, the corresponding MH-WSA message must be forwarded.
The neighbor list is a data table for storing information such as the position, speed, direction, and signal strength of the neighbor node. The data stored in the neighbor list will be used as screening basis and forwarding judgment basis for the NCN. Due to the high-speed mobility of the nodes, the network environments of the nodes at each moment are different, and the neighbor nodes in the communication range are different. Therefore, maintenance of the neighbor list is important. And the overdue data in the neighbor list is deleted in time through a dynamic maintenance means, so that the condition that the neighbor list is continuously enlarged and the efficiency of the AMHB algorithm is influenced is avoided. The maintenance of the neighbor list runs through the whole operation cycle of the node, and the maintenance process mainly comprises the following three aspects:
1) maintenance is performed when data is added or updated: when receiving the Hello message, the node firstly inquires whether a node identified by the Hello message exists in a neighbor list, and deletes outdated data in the inquiry process.
2) Maintenance is performed when calculating the neighbor priority: when a multi-hop broadcast service request is generated, the node traverses the neighbor list and calculates the priority, and the expired data is deleted in the traversing process.
3) Periodic maintenance: at intervals to traverse the neighbor list and delete stale data. Because the neighbor list may be huge, a certain time is required for the system to traverse the list, and the maintenance period is not set to be too short in order to avoid system deadlock. In addition, in order to avoid the excessively large neighbor list, the maintenance period is not set to be excessively large.
The repeated MH-WSA data table is used for storing neighbor MAC sequences carried in repeated MH-WSA messages received by the NCN node within the backoff time in a multi-hop broadcast service. In order to improve the stability of broadcast transmission, the AMHB algorithm proposed herein ensures that each node in an area can receive a broadcast packet by selecting multiple NCNs. This results in that an NCN may receive MH-WSA messages from other NCNs while waiting for forwarding, nodes corresponding to neighbor MAC sequences in the messages have received multi-hop broadcast data, and the NCN determines whether there is an area that has not been broadcast in the current communication range by recording these data and comparing with its own neighbor list at the end of the waiting time. The repeated MH-WSA data table stores the node information carried by the repeated MH-WSA message received by the forwarding node within the back-off time and sent by the neighbor node. The data is only effective in the multi-hop broadcasting process, and when the node finishes forwarding judgment, the data in the table is emptied.
The repeated MH-WSM data table is mainly used for identifying MH-WSM messages received in a multi-hop broadcasting process and avoiding the repeated reception of the same data. And the repeated MH-WSM data table only identifies the receiving condition of the message and does not store the data. The maintenance of the repeated MH-WSM data table relates to each node in the Internet of vehicles, a timer is adopted for maintenance, the timer is refreshed every time the node receives an MH-WSM message with the same MAC and psid, and if the timer is overtime, all bits of corresponding bitmap in the repeated MH-WSM data table are set to be 0.
Claims (4)
1. A self-adaptive multi-hop broadcasting system of the Internet of vehicles is characterized by comprising a local information interaction module, a backoff waiting module, a relay screening module, a data forwarding module and an information maintenance module;
the local information interaction module: the data interaction module is used for completing data interaction work between each node and neighbor nodes thereof in the Internet of vehicles, and the data interacted between the neighbor nodes is used as a theoretical basis of other modules to be dynamically maintained in the information maintenance module;
a back-off waiting module: the method comprises the steps of generating a corresponding priority queue according to the selection condition of candidate nodes, and assigning a specific back-off time to each candidate node in the queue, wherein the waiting time of the node with higher priority is shorter, so that each candidate node can share independent channel resources in a specific time period, and the node with higher priority can be preferentially forwarded;
a relay node screening module: the method is used for screening candidate nodes and relay nodes respectively according to two stages of request and response;
a data forwarding module: the method is used for packaging and forwarding two messages, namely a multi-hop WSA message and a multi-hop WSM message; in order to ensure the compatibility with a standard WAVE protocol stack, the module encapsulates fields related to a self-adaptive multi-hop broadcast algorithm into extension fields of corresponding messages;
an information maintenance module: the module is responsible for data maintenance work in the self-adaptive multi-hop broadcasting system, provides data support for other modules, and mainly comprises maintenance of a neighbor list, maintenance of a repeated MH-WSA data table and maintenance of a repeated MH-WSM data table.
2. The method for applying the adaptive multi-hop broadcasting system in the internet of vehicles according to claim 1, comprising the following steps:
firstly, selecting candidate nodes according to information maintained in a management information base; each node in the Internet of vehicles maintains a respective neighbor list, and the neighbor list stores the position, speed, direction and signal strength information of neighbor nodes; when a sending node selects a candidate node, the priority of each neighbor node is mainly calculated at first, and the priority of a neighbor node i is set as pi，i∈[1,n]N is the number of neighbor nodes, then piThe result is obtained by formula (2);
wherein D isiFor neighbor node i andthe distance before sending the node is obtained by formula (3), R is a one-hop communication range, ViThe relative speed of the neighbor node i and the sending node is obtained by the formula (4), VmaxThe maximum relative velocity, RSSI, that can be theoretically achievediThe signal intensity of the neighbor node i, and alpha, beta and gamma are distances D respectivelyiRelative velocity ViWeighted RSSI of sum signal strengthiAnd α + β + γ ═ 1;
Di＝R′·arccos(cos(x)·cos(xi)·cos(yi-y)+sin(x)sin(xi)) (3)
wherein R' is the radius of the earth, x and y are longitude and latitude information of the sending node respectively, and xi，yiRespectively longitude and latitude information of a neighbor node i;
where v is the velocity of the transmitting node, viThe speed of the neighbor node i is shown, and theta is an included angle between the driving direction of the sending node and the driving direction of the neighbor node i;
after the priorities of all the neighbor nodes are obtained, calculating a priority threshold according to a formula (5);
priority satisfies condition p in neighbor nodeiNodes which are more than or equal to threshold are selected as candidate nodes; only the neighbor node selected as the candidate node is possible to become the relay node;
secondly, generating a priority queue; the sending node inserts the candidate node information screened in the first step into a priority queue, and then packages the priority queue into an MH-WSA message; each neighbor node obtains complete priority queue information after receiving the MH-WSA message, then sequentially dequeues candidate node information in the priority queue, compares the candidate node information with the self information, determines whether the neighbor node is a candidate node, calculates the backoff waiting time of the neighbor node if the neighbor node is the candidate node, and abandons forwarding if the neighbor node is not the candidate node;
thirdly, selecting a relay node; the candidate node counts repeated MH-WSA messages received in the back-off time, and stores neighbor node information of other candidate nodes carried in the messages into a repeated MH-WSA data table of the candidate node; after the back-off time is over, the candidate node compares the own neighbor list with the repeated MH-WSA data table, and judges whether the neighbor node only belongs to the own neighbor list exists in the own neighbor list or not; if the message exists, the candidate node considers that the area which is not broadcasted still exists in the communication range of the candidate node, and at the moment, the candidate node forwards the message to become a relay node; if the broadcast message does not exist, the candidate node considers that all neighbor nodes in the current own communication range have received the broadcast message, and at the moment, the candidate node gives up forwarding data.
3. The method of claim 2, wherein the back-off time in the second step is calculated as follows:
T＝Tmax×(s-1) (1)
where s denotes the dequeue order, TmaxRepresenting a standard one-hop maximum delay time.
4. The method of claim 2, wherein after the third step of selecting the relay node, the application messages are classified into two categories, namely urgent messages and non-urgent messages according to the difference of the priority of the application messages; the priority of the application message is specified by an application layer, the value range of the priority is 1-8, and the smaller the value is, the higher the priority of the message is; messages with the priority less than or equal to 4 are called emergency messages, and the messages generally relate to personal safety, have higher requirements on time efficiency and have smaller data volume; messages with priority >4 are called non-urgent messages, and the messages are mainly used for improving the driving experience of a user, have relatively low requirements on timeliness and are generally large in data volume; two different forwarding modes, namely a fast forwarding mode and a cooperative forwarding mode, correspond to the two message types; the fast forwarding mode is a forwarding mode aiming at the emergency message, the mode only relates to the forwarding of MH-WSA message, and the broadcast data is carried by the MH-WSA message; the cooperative forwarding mode is a forwarding mode aiming at non-emergency messages, the mode relates to the forwarding of MH-WSA messages and MH-WSM messages, and broadcast data are carried by the MH-WSM messages.
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| CN113727459A (en) * | 2021-08-10 | 2021-11-30 | 哈尔滨工业大学 | Back-off algorithm based on multi-priority access protocol |
| CN114866960A (en) * | 2022-04-11 | 2022-08-05 | 华南理工大学 | Internet of vehicles multi-hop broadcasting method based on message type and network communication state |
| CN116846814A (en) * | 2023-09-01 | 2023-10-03 | 北京智芯微电子科技有限公司 | Networking method, networking device, computer equipment, chip and readable storage medium |
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