CN110881165B

CN110881165B - Clustering multichannel QoS access method, device and equipment for Internet of vehicles

Info

Publication number: CN110881165B
Application number: CN201910907123.6A
Authority: CN
Inventors: 刘凯; 张玥; 张涛; 曹先彬; 肖振宇; 谢晋东
Original assignee: Beihang University
Current assignee: Beihang University
Priority date: 2019-09-24
Filing date: 2019-09-24
Publication date: 2020-10-13
Anticipated expiration: 2039-09-24
Also published as: CN110881165A

Abstract

The application provides a clustering multichannel QoS access method, a clustering multichannel QoS access device and a clustering multichannel QoS access device for Internet of vehicles, wherein the method comprises the following steps: the cluster head vehicle acquires the current driving direction, the current position information and the midpoint position information of the current road; the cluster head vehicle determines the current cluster serial number of the cluster head vehicle according to the current driving direction, the current position information and the midpoint position information of the current road; and the cluster head vehicle distributes time slots for the cluster members according to the current cluster serial number and a preset rule, so that the cluster members and the cluster head vehicle send messages in the distributed time slots according to a preset message sending mechanism, the cluster members are communicated with other cluster members or the cluster head vehicle in the corresponding time slots through the channels corresponding to the current driving direction, the transmission collision is reduced, the communication efficiency in the cluster and between the clusters is improved, and the QoS support is provided.

Description

Clustering multichannel QoS access method, device and equipment for Internet of vehicles

Technical Field

The application relates to the technical field of vehicle communication, in particular to a clustering multichannel QoS access method, a clustering multichannel QoS access device and clustering multichannel QoS access equipment for an Internet of vehicles.

Background

The car networking is that on the basis of VANET (vehicle ad hoc networks), people, cars, things, roads and the internet form an interconnection system by means of an intelligent vehicle-mounted terminal, so that effective management and scheduling of a traffic network are realized. Currently, applications related to the internet of vehicles are mainly classified into three types according to functions, namely applications for road safety, applications for improving traffic management and trip efficiency, and applications for non-safety user information and entertainment.

The car networking is essentially one of Mobile Ad hoc networks, so that the Mobile Ad hoc network has the common characteristics of MANET (Mobile Ad hoc network), such as dynamic change of network topology, coexistence of single hop and multi hop, weak channel in a wireless environment, limited transmission bandwidth and the like, and has many unique characteristics, such as strong node mobility, frequent network topology change, large network scale, uneven node distribution, no energy restriction of nodes, rich external auxiliary information and the like.

Due to the different requirements of the internet of vehicles, in order to achieve the goals of guaranteeing road safety, efficient travel and information and entertainment described in the design of the internet of vehicles, the design of MAC (Multiple access control) protocols of the internet of vehicles with different applications also has a targeted requirement. For secure messages, message transmission latency, channel availability, and reliable transmission need to be guaranteed.

More research efforts are currently being made to utilize TDMA mechanisms to meet the requirements of different applications. In the central MAC protocol, the RSU is usually used as a central coordinator to collect communication link information in the area, and in the distributed MAC protocol, the topology is assumed to be as flat as possible. To effectively reduce interference between overlapping regions, some protocols use CDMA or FDMA access techniques, adding complexity and cost to the design of MAC protocols. The clustered MAC protocol is between a central MAC protocol and a distributed MAC protocol, and the advantages of the two protocols are combined. Inter-cluster interference problems can occur when time slots are scheduled and managed using a cluster-based TDMA scheme. The broadcast nature of VANETs presents the problem of hidden and exposed terminals within the network because it is not appropriate for broadcast messages to use RTS/CTS short handshake messages to prevent collisions. The hidden terminal problem occurs when two vehicles that are not within range of each other simultaneously transmit data packets to one vehicle that is within their transmission range. On the other hand, an exposed terminal problem occurs when a vehicle is prevented from transmitting data packets to other vehicles due to transmission by a neighbor node.

Disclosure of Invention

The application provides a cluster multi-channel QoS access method, a device and equipment for Internet of vehicles, which aim to solve the problem that cluster members in a cluster can not receive correct data packets due to collision in the data transmission process in a channel in the prior art.

The application provides a cluster multi-channel QoS access method for the Internet of vehicles in a first aspect, which comprises the following steps:

the cluster head vehicle acquires the current driving direction, the current position information and the midpoint position information of the current road;

the cluster head vehicle determines the current cluster serial number of the cluster head vehicle according to the current driving direction, the current position information and the midpoint position information of the current road;

the cluster head vehicle acquires the time slot of the cluster head vehicle according to the current cluster serial number and distributes the time slot for the cluster members according to a preset rule so that the cluster members can communicate with other cluster members or the cluster head vehicle through a channel corresponding to the current driving direction in the corresponding time slot;

and the cluster head vehicle and the cluster members send messages in respective corresponding time slots according to a preset message sending mechanism.

The second aspect of the present application provides a clustered multi-channel QoS access apparatus for internet of vehicles, comprising:

the acquisition module is used for acquiring the current driving direction, the current position information and the midpoint position information of the current road by the cluster head vehicle;

the determining module is used for determining the current cluster serial number of the cluster head vehicle according to the current driving direction, the current position information and the midpoint position information of the current road;

the distribution module is used for the cluster head vehicle to acquire the time slot of the cluster head vehicle according to the current cluster serial number and distribute the time slot for the cluster members according to a preset rule so that the cluster members can communicate with other cluster members or the cluster head vehicle in the corresponding time slot through a channel corresponding to the current driving direction;

A third aspect of the present application provides an electronic device, comprising: at least one processor and memory;

the memory stores a computer program; the at least one processor executes the computer program stored by the memory to implement the method provided by the first aspect.

A fourth aspect of the present application provides a computer-readable storage medium having stored thereon a computer program which, when executed, implements the method provided by the first aspect.

The application provides a cluster multichannel QoS access method, device and equipment for car networking, through confirming the current cluster serial number of cluster head vehicle distributes the time slot for the cluster member according to predetermineeing the rule, makes cluster member and cluster head vehicle send the message according to predetermined message sending mechanism in the time slot that is distributed to make the cluster member pass through at corresponding time slot the channel that current driving direction corresponds with other cluster members or cluster head vehicle communication reduces the transmission collision, improves the communication efficiency in the cluster and between the cluster and provides QoS support.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive exercise.

Fig. 1 is a schematic flowchart of a clustered multi-channel QoS access method for the internet of vehicles according to an embodiment of the present application;

fig. 2 is a schematic view illustrating a corresponding relationship between a driving angle and a driving direction of a vehicle according to an embodiment of the present application;

fig. 3 is a schematic diagram of a hierarchical network topology based on clustering according to an embodiment of the present application;

fig. 4 is a schematic diagram of a frame structure of the first three frames according to an embodiment of the present application;

fig. 5 is a schematic diagram of a slot structure in a clustering control period according to an embodiment of the present application;

fig. 6 is a schematic flowchart of clustering control according to an embodiment of the present application;

fig. 7 is a schematic flowchart of a clustered multi-channel QoS access method for the internet of vehicles according to another embodiment of the present application;

fig. 8A is a schematic diagram of a distance between cluster head vehicles according to an embodiment of the present application;

fig. 8B is a schematic diagram of another distance between cluster head vehicles according to an embodiment of the present application;

fig. 8C is a schematic view of another distance between the cluster head vehicles according to an embodiment of the present application;

fig. 8D is a schematic diagram illustrating another distance between cluster head vehicles according to an embodiment of the present application;

fig. 9 is a schematic distribution diagram of cluster numbers on a road according to an embodiment of the present application;

fig. 10A is a schematic diagram of a CH distribution within a communication radius 2R of a cluster head vehicle according to an embodiment of the present application;

fig. 10B is a diagram illustrating another CH distribution within a communication radius 2R of a cluster head vehicle according to an embodiment of the present application;

fig. 10C is a schematic diagram of another CH distribution within a communication radius 2R of a cluster head vehicle according to an embodiment of the present application;

FIG. 11 is a diagram illustrating a communication protocol provided by an embodiment of the present application;

FIG. 12A is a schematic diagram illustrating communication radii of cluster head distance vehicles according to an embodiment of the present disclosure;

FIG. 12B is a schematic diagram of communication radii of vehicles in another cluster head distance, according to an embodiment of the present disclosure

Fig. 13 is a schematic diagram of intra-cluster time slot allocation according to an embodiment of the present application;

fig. 14 is a schematic diagram of a timeslot structure for intra-cluster security/control message transmission according to an embodiment of the present application;

fig. 15 is a schematic diagram illustrating an allocation strategy of CM broadcast timeslots according to an embodiment of the present application;

fig. 16 is a schematic diagram of a broadcasting process of intra-cluster safety messages according to an embodiment of the present application;

fig. 17 is a flowchart illustrating a message sending mechanism according to an embodiment of the present application;

FIG. 18 is a flowchart illustrating another message sending mechanism according to an embodiment of the present application;

fig. 19 is a diagram illustrating an example of CH distribution on a road according to an embodiment of the present application;

FIG. 20 is a diagram illustrating an example of a clustering structure provided in an embodiment of the present application;

fig. 21 is a diagram illustrating a timeslot allocation result according to an embodiment of the present application;

fig. 22 is a diagram illustrating another timeslot allocation result according to an embodiment of the present application;

fig. 23 is a schematic structural diagram of inter-cluster communication according to an embodiment of the present application;

fig. 24A is a schematic structural diagram of inter-cluster communication according to another embodiment of the present application;

fig. 24B is a schematic structural diagram of another inter-cluster communication according to another embodiment of the present application;

fig. 24C is a schematic structural diagram of another inter-cluster communication according to another embodiment of the present application;

fig. 24D is a schematic structural diagram of another inter-cluster communication according to another embodiment of the present application;

fig. 24E is a schematic structural diagram of another inter-cluster communication according to another embodiment of the present application;

fig. 24F is a schematic structural diagram of another inter-cluster communication according to another embodiment of the present application;

fig. 24G is a schematic structural diagram of another inter-cluster communication according to another embodiment of the present application;

fig. 25A is a schematic diagram illustrating timeslot allocation between adjacent clusters according to an embodiment of the present application;

fig. 25B is a schematic diagram of timeslot allocation between adjacent clusters according to an embodiment of the present application;

fig. 25C is a schematic diagram illustrating timeslot allocation between adjacent clusters according to an embodiment of the present application;

fig. 26 is a schematic structural diagram of a clustered multi-channel QoS access apparatus for internet of vehicles according to an embodiment of the present application;

fig. 27 is a schematic structural diagram of an electronic device according to an embodiment of the present application.

With the above figures, there are shown specific embodiments of the present application, which will be described in more detail below. These drawings and written description are not intended to limit the scope of the disclosed concepts in any way, but rather to illustrate the concepts of the disclosure to those skilled in the art by reference to specific embodiments.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The terms referred to in this application are explained first:

QoS: quality of Service.

The functions of 7 channels in DSRC (Dedicated Short Range Communications), each channel having its specific special purpose, are specifically as shown in table 1 below, which is a new definition of a DSRC channel:

TABLE 1

Channel number	Description of the invention
		ch178	Inter-cluster communication between CHs is accomplished as a common control channel
ch172	Intra-cluster communication for east-bound vehicles
		ch182	Intra-cluster communication for westward vehicles
ch176	Retention
		ch174	Intra-cluster communication for southbound vehicles
ch184	Intra-cluster communication for northbound vehicles
		ch180	Retention

In order to simplify the representation of the channels, the present application re-identifies the seven channels, as shown in table 2 below, and a channel comparison table for simplifying the identification:

TABLE 2

DSRC

CH172

CH174

CH176

CH178

CH180

CH182

CH184

This application

ch1

ch4

ch3

ch0

ch6

ch2

ch5

Furthermore, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. In the description of the following examples, "plurality" means two or more unless specifically limited otherwise.

The following several specific embodiments may be combined with each other, and details of the same or similar concepts or processes may not be repeated in some embodiments. Embodiments of the present application will be described below with reference to the accompanying drawings.

The method and the device can be applied to the following target scenes, and under the use of multiple channels, the four-way intersection of the target scenes can be regarded as simple superposition of two-way roads, so that the two target scenes are unified and simplified into a one-way road scene. After clusters with different driving directions are regulated to use different channels, the target problem can be converted into a transmission collision problem between adjacent clusters in the same direction.

An embodiment of the application provides a cluster multi-channel QoS access method for an Internet of vehicles, which is used for allocating time slots to cluster head vehicles and cluster members. The implementation subject of this embodiment is a clustering multi-channel QoS access device for the internet of vehicles, which may be referred to as a vehicle-to-vehicle communication device for short, and the device is disposed on a vehicle-mounted electronic device, where the electronic device is a device dedicated for performing vehicle-to-vehicle communication and is disposed on each mobile vehicle node.

As shown in fig. 1, a schematic flow chart of a clustered multi-channel QoS access method for the internet of vehicles provided in this embodiment includes:

s101, acquiring a current driving direction, current position information and midpoint position information of a current road by a cluster head vehicle;

specifically, different areas are defined in advance by the road on which the vehicles travel, and different cluster serial numbers are set, for example, C1, C2 and C3 … …, and the vehicles traveling on the road section may be cluster head vehicles and cluster member vehicles which are clustered in advance or non-clustered vehicles. The cluster head vehicle can periodically acquire the current driving direction, the current position information and the midpoint position information of the current road;

s102, determining a current cluster serial number of a cluster head vehicle according to the current driving direction, the current position information and the midpoint position information of the current road;

for example, the cluster head vehicle is represented by CH, the current driving direction acquired by the cluster head vehicle is eastward, the current position information is acquired by GPS, the midpoint position information of the current road is acquired by an electronic map, and the cluster head vehicle calculates the cluster number of the current road of the cluster head vehicle according to the acquired information.

S103, the cluster head vehicle acquires the time slot of the cluster head vehicle according to the current cluster serial number and distributes the time slot for the cluster members according to a preset rule, so that the cluster members can communicate with other cluster members or the cluster head vehicle in the corresponding time slot through a channel corresponding to the current driving direction.

Illustratively, the cluster head vehicle CH acquires its own time slot according to the current cluster serial number C1 and the current cluster serial number C1, and allocates time slots to the cluster members CM according to a preset rule, and the cluster members CM communicate with other cluster members or the cluster head vehicle through the channel CH1 corresponding to the east in the current driving direction at the corresponding time slots.

The cluster members and the cluster head vehicle, and the cluster members can adopt a preset message sending mechanism to send messages to realize communication. Such as using a priority-based messaging mechanism.

The cluster head vehicle and the cluster members may include a transmission module for broadcasting beacons, safety messages or cluster control messages by the cluster head vehicle and the cluster member vehicles, and transmitting unicast messages of different priorities in the allocated non-safety message transmission time slots according to a preset message transmission mechanism. The preset messaging mechanism may include a priority-based messaging mechanism.

Illustratively, one priority-based messaging mechanism is to transmit high-priority messages preferentially in each frame; another priority-based message sending mechanism is that messages with various priorities are sent in sequence according to a certain order in the life cycle of the whole cluster. The setting of the specific priority may be set according to actual requirements, and this embodiment is not limited.

According to the cluster multi-channel QoS access method for the Internet of vehicles, the current cluster serial number of the cluster head vehicle is determined, the time slot is allocated to the cluster member according to the preset rule, the cluster member and the cluster head vehicle are enabled to send messages in the allocated time slot according to the preset message sending mechanism, so that the cluster member is enabled to communicate with other cluster members or the cluster head vehicle through the channel corresponding to the current driving direction in the corresponding time slot, transmission collision is reduced, communication efficiency in the cluster and among the clusters is improved, and QoS support is provided.

The method provided by the above embodiment is further described in an additional embodiment of the present application.

Optionally, the acquiring, by the cluster head vehicle, the current driving direction, the current position information, and the midpoint position information of the road where the cluster head vehicle is located includes:

acquiring the current position coordinates of the cluster head vehicle through GPS equipment;

and acquiring the current driving direction of the cluster head vehicle and the position coordinates of the midpoint of the road where the cluster head vehicle is located through the electronic map.

As shown in fig. 2, a schematic diagram of the corresponding relationship between the driving angle and the driving direction of the vehicle provided in this embodiment is that, in the embodiment of the present application, the east direction of 0 ° is taken as a reference, four directions in which the vehicle runs are defined at intervals of pi/2, and the angle range corresponding to each direction is as shown in fig. 2.

As shown in fig. 3, for the hierarchical network topology based on clustering provided in this embodiment, nodes in the network are divided into a plurality of clusters through some clustering algorithm. Each cluster has a Cluster Head (CH) and a plurality of Cluster Members (CM), and the cluster head can be generated by an algorithm or can be specified in advance.

If the communication radius of the node is R, the CM is in a circular coverage area with the radius of R as the center of the CH. The CMs may communicate directly with their own CH, and may communicate directly between two CMs or indirectly through a CH. Any two nodes in such a cluster can communicate through at most 2-Hop. The CH and the CM can perform intra-cluster communication on one frequency band or channel (chx), and the CH can also form a higher-level network with an adjacent CH on another frequency band or channel (CH0) by taking twice intra-cluster communication radius R as an inter-cluster communication radius to realize level communication.

Each intra-cluster CH selects a channel chx for intra-cluster message transmission and an inter-cluster message transmission between the CHs on channel CH 0. To ensure inter-cluster communication between adjacent CHs, the transmission radius on the common channel is 2 times the transmission radius R on the intra-cluster channel. As shown in fig. 3, the CM1 and its cluster head CH1 perform message transmission on the chx channel, and the cluster heads CH1 and CH2 perform message transmission on the channel CH 0. In fig. 3, the area covered by the solid line is the intra-cluster communication range, and the area covered by the dotted line is the inter-cluster communication range.

As shown in fig. 4, a schematic diagram of a frame structure of the first three frames is provided for the embodiment, and generally, at the time of network initialization, all vehicles are in an un (un clustered node) state. The process of initial cluster formation is done on a local channel, i.e., a default assigned channel. As shown in fig. 4, all UN nodes randomly select a time slot (1 to n) in the first frame and the second frame_max) Sending its own HELLO message. In addition to the sending time slot selected by the node, the UN listens for the HELLO message of the one-hop neighbor at other times, and in this way, the information of the surrounding neighbor nodes is obtained. After two frames of time, the UN node can determine whether the UN node is qualified to become the CH based on the known information, so that a cluster can be formed and message transmission can be performed from the third frame.

As shown in fig. 5, which is a schematic diagram of a slot structure in a clustering control period provided in this embodiment, in this application, the operation of a node in the clustering control period is also completed on a local channel. The frame structure of the clustering control period part is shown in fig. 5. The clustering control period mainly comprises three parts:

the first part is the UN broadcast slots, which are used for the UN nodes to broadcast their own HELLO messages.

The second part is CH broadcast slots that are used for CH nodes to broadcast their own HELLO messages as well as clustering control messages such as cluster establishment (CH _ ANNOUNCE) or cluster de-establishment (CH _ resolution), etc. If the UN node satisfies the condition to become CH, the node transmits a CH _ ANNOUNCE message announcing to be CH during the CH broadcast.

The third part is the time slots in which the UN JOINs the cluster, and if the UN node senses that a cluster can be joined, the UN randomly selects a JOIN request (JOIN) message to send to the cluster in these time slots. If the target CH receives the request information of the UN and agrees that the UN JOINs the cluster, it sends a JOIN agreement (JOIN _ ACK) message, and if the UN node does not satisfy the conditions of joining the cluster, the CH sends a JOIN rejection (JOIN _ NACK) message to the UN.

As shown in fig. 6, a schematic flow chart of the clustering control provided in this embodiment is described, taking a one-way full TDMA method as an example, when a vehicle node is ready to join a network after being started.

The vehicles are in the UN state when not joining a cluster. First, the vehicle can obtain the current speed direction by using a self-configured GPS device to determine the driving direction.

If the current speed of the vehicle node is 0, the driving direction of the lane can be obtained according to the current position information. After determining the driving direction of the vehicle, the vehicle node switches to the corresponding local channel to listen for a frame, and one frame is usually set to be 100 ms. After the duration of one frame is monitored, the UN node can acquire the node information in the driving direction and judge whether an addable cluster exists.

The vehicle node randomly selects one time slot from the UN broadcast time slots in the next frame to send its HELLO message. If the vehicle senses an accessible cluster, a time slot is selected from the time slots of the UN joining the cluster to send a request message of the vehicle, and the vehicle tries to join the cluster.

If the vehicle receives the JOIN _ ACK message for the target cluster CH within the validity period, it indicates that the node successfully joined the cluster. If the vehicle fails to receive a JOIN _ ACK message within the validity period or receives a JOIN _ NACK message for the target CH within the validity period, it indicates that the node has not successfully joined the cluster.

If there is no cluster that can be added around the UN, then the UN will determine whether it satisfies the condition of becoming a new cluster declared by the CH.

If the condition of establishing a new cluster is met, the vehicle can calculate the cluster serial number Ci of the vehicle according to the current position and road information, determine the communication channel chx in the cluster, send a CH _ ANNOUNCE message in the CH broadcast time slot corresponding to the Ci to ANNOUNCE that the channel is a CH, and wait for other UN nodes to apply for joining the cluster.

As shown in fig. 7, a flowchart of the clustered multi-channel QoS access method for the internet of vehicles provided in this embodiment is shown.

Fig. 8A to 8D are schematic diagrams illustrating different distances between cluster head vehicles, wherein, as shown in fig. 8A, a distance between cluster head vehicles according to the present embodiment is provided; as shown in fig. 8B, another schematic diagram of the distance between the cluster head vehicles provided in the present embodiment; as shown in fig. 8C, a schematic diagram of another distance between the cluster head vehicles according to the present embodiment is provided; as shown in fig. 8D, a schematic diagram of another distance between the cluster head vehicles is provided for the embodiment. Specifically, as shown in fig. 8A, assuming that the intra-node cluster communication radius is R, when the distance between two adjacent CHs is greater than 2R, the communication ranges of the two clusters do not overlap. As shown in fig. 8B, when the distance between two adjacent CHs is less than 2R, the coverage areas of the two clusters may overlap. In a clustering algorithm, when two cluster coverage areas overlap to a certain extent, cluster fusion usually occurs, and then two clusters are merged into one cluster. As shown in fig. 8C and 8D, when the distance between two CHs is smaller than R, the two nodes are within the communication range of each other, and the degree of overlap between the two clusters is large, and the two CHs are adjacent nodes to each other in one hop. It is assumed in the present application that cluster fusion occurs when the distance between adjacent CH is less than 4/5R and close to each other, that is, the distance between adjacent CH must be equal to or greater than 4/5R.

Specifically, as shown in fig. 9, the distribution diagram of cluster numbers on the road provided for this embodiment includes 12 clusters, CH of each cluster is represented by its cluster number Ci, the road SE can be divided into many small segments at intervals of R, and CH located on a small segment of the road obtains a specific cluster number. If there is one CH in each segment, the cluster numbers of the CH should be C1, C2, C3, C4, C5, and C6 in sequence in the direction of vehicle advance. It is provided in the present application that cluster fusion occurs when the distance between adjacent two CHs is less than 4/5R, so the distance between adjacent CHs is at least 4/5R. Since the radius of the inter-cluster communication is 2R, there are 5 CHs (including itself) at most within the inter-cluster communication range of a certain CH.

Fig. 10A to 10C are schematic diagrams illustrating several CH distributions within the communication radius 2R of the cluster head vehicle, wherein, as shown in fig. 10A, a CH distribution within the communication radius 2R of the cluster head vehicle provided in this embodiment is a schematic diagram; as shown in fig. 10B, another CH distribution within the communication radius 2R of the cluster head vehicle is provided in this embodiment; as shown in fig. 10C, a schematic diagram of another CH distribution within the communication radius 2R of the cluster head vehicle provided in this embodiment is shown. The area covered by the solid line is an intra-cluster communication area with a radius of R, and the area covered by the dotted line is an inter-cluster communication area with a radius of 2R. As shown in fig. 10A, when the distance between adjacent CHs is greater than 2R, there is no other CH node within the inter-cluster communication coverage of the CH node B. As shown in fig. 10B, when the distance between adjacent CHs is equal to 2R, the inter-cluster communication coverage of the CH node B includes 3 CH nodes (including the B itself) at the maximum. As shown in fig. 10C, when the distance between adjacent CHs is equal to R, the inter-cluster communication coverage of the CH node C contains 5 CH nodes (including C itself) at the maximum.

In the present application, it is specified that the distance between adjacent CHs is at least 4/5R, so that there are at most 5 CHs (including itself) within the inter-cluster communication range of a certain CH. Only when the time slots occupied by the five CH are different, the node C does not become a hidden terminal, and transmission collision does not occur.

As shown in fig. 11, a schematic diagram of a communication protocol provided for this embodiment includes a previous frame, a current frame, and a next frame, and each frame includes clustering control and message transmission, where the clustering control includes UN broadcast, CH broadcast, and UN join cluster, and the message transmission includes contention cluster sequence number, intra-cluster security/control message transmission, and intra-cluster inter-cluster parallel transmission.

Specifically, each vehicle node has a half-duplex transceiver, equipped with a GPS device. The vehicle node can acquire the current position and the information of the road to which the vehicle node belongs, so that collision-free message transmission is realized on the basis, and efficient intra-cluster and inter-cluster communication is performed.

Specifically, the current position coordinates of the cluster head vehicle are acquired through GPS equipment;

and acquiring the current driving direction of the cluster head vehicle and the position coordinates of the midpoint of the road where the cluster head vehicle is located through the electronic map. And acquiring a starting point coordinate and an end point coordinate of the current road from the electronic map, wherein the starting point coordinate and the end point coordinate are preset.

On the basis of the foregoing embodiment, optionally, determining, by the cluster head vehicle, the current cluster serial number of the cluster head vehicle according to the current driving direction, the current position information, and the midpoint position information of the road where the cluster head vehicle is currently located includes:

and determining the current cluster serial number of the cluster head vehicle according to the relative distance between the position coordinate of the cluster head vehicle and the position coordinate of the middle point of the road and the communication radius of the cluster where the cluster head vehicle is located.

Specifically, if two CHs within the 2R range of a CH use the same time slot to transmit messages, the CH becomes a hidden terminal and cannot correctly receive messages from the two CHs. In order to avoid the hidden terminal problem when CH performs inter-cluster communication, 6 cluster serial numbers C1, C2, C3, C4, C5, and C6 are set in the present application, and each cluster has its own corresponding cluster serial number.

Each CH cluster head selects a corresponding broadcast time slot according to the cluster serial number of the CH cluster head, and the CH in the 2R range is ensured to use different broadcast time slots. The cluster number based CH broadcast slot selection strategy avoids transmission collisions of CH broadcasts.

After the cluster head vehicle acquires the current position coordinate and the coordinate of the road midpoint, the current cluster serial number of the cluster head vehicle is determined according to the relative distance between the position coordinate of the cluster head vehicle and the position coordinate of the road midpoint and the communication radius of the cluster where the cluster head vehicle is located.

Optionally, determining a current cluster serial number of the cluster head vehicle according to a relative distance between the position coordinate of the cluster head vehicle and the position coordinate of the road midpoint and a communication radius of a cluster where the cluster head vehicle is located, specifically:

wherein, the delta D is the relative distance between the position coordinate of the cluster head vehicle and the position coordinate of the road midpoint;

r is the communication radius of the cluster where the cluster head vehicle is located; m is the number of cluster serial numbers;

C_ithe cluster number of the cluster head vehicle.

Where m is set to 6 in this application.

Specifically, the CH can calculate its own cluster number according to the current position coordinate and the road midpoint coordinate on the premise that the vehicle can obtain the current road information. Thereby CH_iCan calculate the cluster serial number C of the user according to the relative distance between the user and the middle point of the road_iThe calculation formula is as follows:

wherein Δ D is CH_iAnd M, R is the communication radius of the vehicle node, C_iIs CH_iM is the midpoint coordinate.

In the present application, roads are segmented such that clusters on the roads are arranged in a fixed order. Efficient intra-cluster and inter-cluster communication is provided for clusters traveling in the same direction, subject to the limitation of using a single channel for intra-cluster communication.

For example, in the present application, a road is divided into many small segments at intervals of a communication radius R, there is at most one CH cluster head on a small segment of the road, and the CH gets a specific cluster number. Along the advancing direction of the vehicle, the cluster serial numbers on each section of road are sequentially C1, C2, C3, C4, C5 and C6.

On the basis of the foregoing embodiment, optionally, allocating, by the cluster head vehicle, a time slot to a cluster member according to a preset rule according to the current cluster serial number includes:

if the cluster member vehicles in the cluster are positioned in front of the traveling direction of the cluster head vehicle, carrying out cluster broadcasting time slot allocation from far to near from the first time slot of the time slot block according to the distance from the cluster member vehicles to the cluster head vehicle;

and if the cluster member vehicles in the cluster are positioned behind the traveling direction of the cluster head vehicle, carrying out in-cluster broadcasting time slot allocation from far to near according to the distance from the cluster member vehicles to the cluster head vehicle from the last time slot of the time slot block.

On the basis of the above embodiment, the CH vehicle may calculate its own cluster number according to its current location information and road information, and select a corresponding time slot to transmit the broadcast message of the CH according to the cluster number. If the cluster number of the CH is 1, the CH will send a message in the time slot of C1, and keep the receiving status in the time slots corresponding to the other 5 cluster numbers. Since there are 5 CHs at most in the 2R communication range, consecutive 6 CHs do not use the same broadcast slot, thereby avoiding transmission collisions of CH broadcasts. During intra-cluster safety/control message transmission, each CH is allocated two broadcast slots for transmitting intra-cluster control messages and safety messages, respectively.

In the embodiment of the present application, the CH of each cluster allocates a unique broadcast slot for the CM in the cluster to send its own safety message and beacon message (HELLO packet).

As shown in fig. 12A, a schematic diagram of communication radius of a cluster head distance vehicle is provided in the present embodiment; as shown in fig. 12B, a schematic diagram of communication radius of another cluster head distance vehicle is provided for the present embodiment; assume that a1 and a2 are in different clusters, but are assigned the same time slot by the CH of the cluster to which they belong, i.e., a1 and a2 would send HELLO messages in the same time slot. If the distance between a1 and a2 is greater than 2 times the communication radius, as shown in fig. 12B, then the communication coverage of a1 and a2 have no overlap and the hidden terminal problem does not occur. However, in the case shown in fig. 12A, the distance between a1 and a2 is less than 2 times the communication radius, and the communication coverage areas of a1 and a2 overlap. If there is a vehicle M in the overlap area, then M becomes a hidden terminal.

It is obvious that the longer the distance of vehicles occupying the same time slot, the smaller the range of overlap and the smaller the probability of transmission collisions caused by hidden terminals. The present application thus provides two slot allocation schemes to avoid the presence of hidden terminals.

As shown in fig. 13, a schematic diagram of allocating time slots in clusters provided in this embodiment is shown, taking two clusters as an example, the cluster head vehicles are CH1 and CH2, respectively, and the cluster members are a1-E1 and a2-E2, respectively. In each cluster, the CH will allocate different time slots to each CM according to its front-to-back relative distance from itself. Fig. 13 shows two allocation schemes (a) and (b), and in the scheme (a) in fig. 13, CH allocates unique time slots to CM vehicles located in front of and behind itself according to the distance from itself, starting from the first and last time slot blocks, respectively. Whereas in scheme (b) in 13, the CH would continuously allocate unique slots to CMs from front to back without using this information relative to the front and back of the CH. The most significant difference between the two schemes is that (a) the scheme can alleviate the hidden terminal problem caused by the fact that CMs located in adjacent clusters occupy the same time slot to some extent. When the distance between adjacent CH is greater than 3R, the hidden terminal problem can be avoided to a large extent, which only occurs when the CM number distribution before and after CH is extremely uneven. The (a) scheme is preferably adopted in the CM broadcast slot allocation of the embodiment of the present application.

As shown in fig. 14, for the time slot structure diagram of intra-cluster security/control message transmission provided in this embodiment, the entire CM broadcast time slot is divided into three parts, i.e., S1, S2, and S3, on average. Wherein clusters with cluster numbers C1 and C4 use the slot block of the S1 section, C2 and C5 use the slot block of the S2 section, and C3 and C6 use the slot block of the S3 section. When the distance between adjacent CH is more than or equal to R, the distance between adjacent CH using the same time slot block cluster is more than or equal to 3R, thereby ensuring the conflict-free transmission of CM broadcast and avoiding the occurrence of hidden terminal problem. When the distance between adjacent CHs is the minimum distance 4/5R, the distance between two vehicles that may use the same slot is the minimum 7/5R in the case where the vehicles are evenly distributed around the CH. Although the minimum distance is less than 2R, the hidden terminal problem may occur, but only the distance 4/5R between adjacent CHs when cluster fusion occurs in the present application. In addition, the distance between two vehicles using the same time slot is maximized as much as possible when the time slot is allocated, so that transmission collision caused by hidden terminal problems can be relieved to a certain extent.

In the present application, 6 broadcast slots corresponding to cluster numbers one to one are set for CH in different directions during a contention cluster number period, and 12 CH broadcast slots corresponding to cluster numbers are also set during a CH broadcast period. If the cluster number of the CH is 1, the CH broadcasts using the time slot corresponding to C1. Since the CH with the same cluster number is at least 5R apart and is greater than the inter-cluster communication range 4R of the cluster head, the arrangement can ensure that no collision occurs when the CH transmits the broadcast message.

As shown in fig. 15, for the scheme of the CM broadcast time slot allocation strategy provided in this embodiment, the CH of each cluster allocates a unique broadcast time slot for the CM in the cluster to send its own beacon message and security message. In each cluster, the CH allocates different time slots to the CM according to the front-to-back relative distance of the CM from the CH. Within the intra-cluster communication range of a CH, there are A, B, C, D, E, F for nodes located in front of the CH and G, H, I, J, K for nodes located behind the CH. Node a is assigned the first CM broadcast slot since it is in front of and farthest from CH, while node K is behind and farthest from CH and assigned the last slot. Node B is located in front of CH and second farthest from CH in CM located in front of CH, so B is assigned the second broadcast slot from left to right, and so on for other nodes. In this time slot allocation scheme, the CH allocates time slots to the preceding CM node in order of the distance of the preceding CM from itself from the left side (first time slot) of the time slot block, and allocates time slots to the following CM node in the same manner from the right side (last time slot) of the time slot block. The order of the CMs in the broadcast slot is approximately the same as the order of the CMs before and after in the communication range within the CH cluster.

As shown in fig. 16, which is a schematic diagram of the intra-cluster security message broadcasting flow provided in this embodiment, after the clustering control period is finished, intra-cluster security/control message transmission may be started. Since the UN node has not yet successfully joined the cluster, the UN node does not participate in message transmission after the clustering control period. That is, the UN node only needs to listen and send messages on the local channel. After the clustering control period is over, the CH and CM nodes switch to the common channel CH 0.

At this time, CH increases its transmission power from Pr to 2Pr, and increases the communication radius to 2R, which is 2 times the original value. The CH broadcasts a CLUSTER _ ANNOUNCE message in a corresponding time slot in a competition CLUSTER sequence number period according to the current driving direction and the CLUSTER sequence number, publishes the information related to the CLUSTER, including a CLUSTER head ID, a CLUSTER sequence number, a local channel used for intra-CLUSTER communication, the ID of a CM, the broadcast time slot distributed by the CM, the current CLUSTER scale and the like, and carries the confirmation of the message received in the previous frame in the information. Unlike the CH, the CM node only listens to the channel during this period, and receives a message from the CH node to learn the scheduled CM broadcast slot.

After the contention cluster sequence number period ends, both the CH and the CM switch to the local channel chx again to enter the intra-cluster security/control message transmission period. During the broadcast of the CM, the CM broadcasts the beacon message or the security message in the allocated time slots in turn according to the time slot allocation sequence published in the CLUSTER _ ANNOUNCE message, and piggybacks the beacon message or the security message in the broadcast message to acknowledge the message received in the previous frame. The broadcast period of the CH starts after the CM has finished sending its own broadcast message. The CH broadcasts its own beacon message or security message in the broadcast time slot corresponding to its own cluster number.

If in TDMA mode, the CH and CM also complete the reservation of the non-secure message transmission slots during the broadcast. At this time, the CM needs to carry its own slot reservation information when broadcasting its own message. In the transmission mode of the parallel channel, the CM needs to inform the CH of the number of time slots required by the message of which the destination next hop in the message queue to be sent is the CH or the CM, respectively, in the broadcast message. And the CH counts the number of time slots required for all packets sent by the CM to the CH and sent by the CM to the CM after receiving the broadcast messages of all CMs.

The CH allocates proper time SLOTs for the CM according to the proportion of the time SLOT required number of each CM to the total time SLOT required number, and sends a SLOT _ ASSIGNMENT message in the CH broadcast time SLOT to inform the CM of the time SLOT allocation result. If a serial channel transmission mode is used, the CM only needs to inform the CH of the number of time slots it needs to reserve. Similar to the channel parallel transmission mode, the CH counts the total number of slots required by all CMs after receiving the broadcast message of all CMs. The CH allocates an appropriate number of SLOTs to each CM according to the ratio of the number of SLOTs required by the CM to the total number of SLOTs required, and sends a SLOT _ ASSIGNMENT message in the CH broadcast SLOT to inform the CM of the SLOT allocation result. In this application, each slot can be occupied by a CM member, that is, only one node in the cluster is in a transmitting state in each slot.

The above time slot allocation scheme is suitable for both the secure message and the non-secure message of a single priority and the message transmission of multiple priorities. In order to be compatible with the message priority in 802.11p and realize QoS support, the method also sets four priorities for safe messages and non-safe service messages in a TDMA mode. In the TDMA scheme, the priority may be set to one of four, High (High), Medium to High (Medium to High), Medium to Low (Medium to Low), and Low (Low). The four priority messages are transmitted in the present application with a time ratio p: q: r: s. Assuming that a CM node has infinite transmission time slots for transmitting non-safety messages and infinite messages are in a message queue of each priority, the CM node transmits high-priority messages on p continuous time slots, transmits high-priority messages on q continuous time slots, transmits low-priority messages on r continuous time slots, transmits low-priority messages on s continuous time slots, and repeats the transmission according to the sequence.

The following describes a message sending mechanism supported by QoS in the present application, taking non-secure message transmission in the serial channel mode as an example. In the present application, after the CM node senses the time slot allocated to the CH, it starts to transmit the secure or non-secure message on the corresponding time slot, and at this time, the node may select one of the two priority message-based transmission mechanisms. In the first transmission scheme, the node transmits high priority messages preferentially in each frame, and in the second transmission scheme, the node sequentially transmits messages with corresponding priorities in a fixed order in the lifetime of the whole cluster.

As shown in fig. 17, for a flow diagram of a message sending mechanism provided in this embodiment, it is assumed that a CM node i obtains Ni non-secure message transmission time slots in a frame, at this time, a time slot required for sending a high-priority message is Np, a time slot required for sending a high-priority message is Nq, a time slot required for sending a low-priority message is Nr, and a time slot required for sending a low-priority message is Ns.

When transmitting a certain priority message, if the remaining transmission time slot is greater than or equal to x (x is p or q or r or s), and Nx is greater than or equal to x, the node will send the priority message on x consecutive time slots.

If the remaining transmission slots are greater than or equal to x (x is p or q or r or s) and Nx is less than x, the node will send the priority message on Nx consecutive slots before attempting to send the next priority message.

If the number of remaining transmission slots is less than x (x is p or q or r or s) and the number of remaining slots is less than or equal to Nx, the node will send the priority message on all remaining slots. If the number of remaining transmission slots is less than x (x is p or q or r or s) and the number of remaining slots is greater than Nx, the node will send the priority message on Nx consecutive slots before attempting to send the next priority message.

As shown in fig. 18, a schematic flow chart of another message sending mechanism provided in this embodiment is provided, in which the sending of messages with different priorities is independent of the currently allocated number of time slots, and is only related to the sending order set in this application and the time slots required by messages with different priorities of nodes. In each time slot, the node will firstly judge the priority of the message which should be transmitted in the time slot, if the time slot required by the message of the priority is not 0, the message of the priority is transmitted in the time slot, if the time slot required by the message of the priority is 0, the message of the next priority is tried to be transmitted in the time slot. The two message transmission mechanisms are different in that when there are many messages to be transmitted in each priority message queue and the time slot allocated to a node is small, the first mechanism always transmits a message with higher priority first, and the second mechanism can also ensure the transmission of other messages with lower priority.

Secure and non-secure transmissions of different priorities in parallel channels are similar to non-secure messaging in serial channels. When the non-safety message is sent, the nodes in the parallel channel mode need to respectively maintain non-safety message queues with different priorities, the target next hops of which are CH and CM, and the serial channel does not need to distinguish the target next hops of the message. For the secure messaging, the parallel channel and the serial channel are identical because the secure message broadcasts the message and the destination node address is the broadcast address. In the application, the CM node usually only occupies one CM broadcast time slot, and when the safety message is sent, only the safety message queues with different priorities need to be maintained. Under the first transmission mechanism, in each CM broadcast slot, if the node has a high-priority message queue that is not empty, the high-priority message is transmitted preferentially. Under the second sending mechanism, the node records the sending sequence of messages with different priorities, judges which priority message should be sent in a certain time slot, sends the priority message if the current priority message is not empty, and sends the message with the next priority if the current priority message is empty.

In the present application, if the secure and non-secure messages between the CHs are transmitted in a TDMA scheme, each CH is assigned at least one time slot during the secure or non-secure message transmission period. If the CH does not sense any CH message of the driving direction deviation pi/2 during the competition cluster number (i.e. the eastern CH does not sense any north-south CH message or the north-south CH does not sense any east-west CH message), and knows that the current CH is more than 4R away from the road of the driving direction deviation pi/2 according to the acquired road information, the CH can use the broadcast time slot corresponding to the CH with the deviation of pi/2 but the same cluster number as the current CH. Assuming that a cluster number of a CH is C1 and the CH travels eastward, if the CH does not sense any CH information for north-south travel and is more than 4R away from the north-south road, the CH may use broadcast slots corresponding to N1 and S1 in addition to the slot corresponding to E1.

As shown in fig. 19, an exemplary diagram of CH distribution on a road is provided in the present embodiment. In addition, the CH can determine whether some free slot blocks can be utilized according to the sensed information of the co-directional CH. Assuming that the CH distribution on the road is as shown in fig. 19, the listening situation of CH during the competition cluster number is analyzed as shown in table 3:

TABLE 3

Cluster number of CH	Cluster number sensed in 2R range	Analysis of
			C1	C6、C1、C3	No C2 exists at the front, and no C5 exists at the back
C3	C1、C6	There must be no C4 at the front and no C2 at the back
			C6	C5、C6、C1	The front part does not know whether there is C2 or not, and the rear part does not know whether there is C4 or not

Based on the CH information detected during the cluster competition, the cluster C1 can conclude that there is no cluster corresponding to C2 in front, the cluster C3 can conclude that there is no cluster corresponding to C4 in front, and there is no cluster corresponding to C2 in back. Since there is no cluster corresponding to a cluster number, the time slot allocated to this cluster becomes a free time slot. It is specified in this application that if a CH concludes that there is no cluster corresponding to a certain cluster number in front, the CH can use all the time slots allocated to the cluster corresponding to this cluster number. In the case of cluster distribution as shown in fig. 19, the CH corresponding to C1 may use the CH broadcast slot corresponding to C2, and may also use the cluster corresponding to C2 for the time slot for intra-cluster communication. Also, the CH corresponding to C3 may use the CH broadcast slot corresponding to C4 and the intra-cluster communication slot.

Optionally, the allocating, by the cluster head vehicle according to the current cluster serial number and according to the preset rule, a time slot for the cluster member further includes:

the cluster head vehicle receives broadcast information sent by cluster members, wherein the broadcast information comprises a reservation time slot request of the cluster members;

the cluster head vehicle determines the total time slot demand number according to the reserved time slot request;

and the cluster head vehicle carries out time slot distribution of non-safety information broadcast for each cluster member vehicle according to the proportion of the reserved time slot request and the total time slot demand number.

Based on the above embodiment, the CH allocates an appropriate number of slots to the CMs according to the ratio of the number of slot demands of each CM to the total number of slot demands. In time slot allocation, the CH firstly judges whether the sum of the requested time slots is more than the total time slot number, and if the requested time slots are less than or equal to the total time slot number, the required time slot number is directly allocated to the CM;

and if the requested time slot is larger than the total time slot number, determining the time slot number allocated for each CM for the first time and the total number allocated for the first time according to the proportion of the request time slot number of each CM to the total request time slot. If there are unallocated timeslots and unsatisfied CM nodes, CH will make multiple rounds of reallocation, each round of reallocation only allocates one timeslot, and allocate this timeslot to the node with the most demanded timeslots in the current round. And finally, the CH allocates continuous time slots for the CM in sequence according to the front and back order of the CM in the cluster.

If the vehicle node accesses the channel in full TDMA, the node needs to first subscribe to the CH when it sends a traffic message (here, an unsafe message). During CM broadcast, the CM broadcasts beacon messages or security messages on the assigned slots, and carries its own slot reservation information.

That is, the CM will inform the CH of the number of CH or CM of the next hop of the message in the message queue to be sent in a carrying transmission manner. The CH, upon receiving the broadcast messages of all CMs, counts the number of time slots required for all packets sent by the CM to the CH, and sent by the CM to the CM. The CH allocates proper time SLOTs for the CM according to the proportion of the time SLOT demand number of each CM to the total time SLOT demand number, and sends a SLOT _ ASSIGNMENT message in the CH broadcast time SLOT to inform the CM of the time SLOT allocation result.

In this application, assuming that the non-safety message is transmitted in a TDMA manner, the CM may reserve a non-safety message transmission slot in the frame in a broadcast message transmitted in a broadcast slot, so that the CH may obtain the number of slots requested by each CM node. The step of the CH allocating TDMA slots to the CM is as follows:

the CH firstly judges whether the sum of the requested time slots is greater than the total time slot number, if the sum of the requested time slots is less than or equal to the total time slot number, the required time slot number is directly allocated to the CM, otherwise, the number of the time slots allocated for each CM for the first time and the total number allocated for the first time are determined according to the proportion of the number of the requested time slots of each CM to the total requested time slots;

if the time slot which is not allocated and the CM node which is not met exist, the CH carries out multi-round reallocation, each round of reallocation only allocates one time slot, and the one time slot is allocated to the node which requires the most time slots in the current round;

the CH allocates consecutive time slots to the CMs in sequence, according to their order in the cluster.

The formula for calculating the number of the time slots allocated to the CM according to the reservation proportion is as follows:

assuming that the CH has m CM nodes, the total time slot number to be allocated is N_sThe number of slots of the ith CM request is N_i，S_iThe number of time slots allocated for the ith CM.

The idea of slot reservation in this application is described below by taking the allocation of slots in a parallel channel full TDMA scheme as an example. In this mode, the node is required to know the next hop node for message transmission (in the TDMA mode of the serial channel, the node is not required to know the next hop node for message transmission, and the CM only needs to inform the CH of the number of slots required by itself at the time of reservation). In the method, the total number of the uplink time slots and the downlink time slots is fixed, the number of the uplink time slots and the number of the downlink time slots are initially set to be half of the total number, but the proportion of the uplink time slots and the downlink time slots can be coordinated according to the reservation condition in the cluster.

When the downlink time slot in the cluster is not allocated completely, the CH can allocate a part of the downlink time slot to the CM to be used as the uplink time slot; when the uplink timeslot in the cluster is not allocated completely, the CH may also use a part of the uplink timeslot as a downlink timeslot. During the uplink and downlink in the cluster, the CM will only be in transmission state in the time slot allocated by CH, and other time slots are all sensed on the local channel. The CH is in a receiving state in the uplink time slot and is adjusted to a transmitting state in the downlink time slot.

As shown in fig. 20, in an exemplary diagram of a cluster structure provided in this embodiment, it is assumed that the numbers of uplink and downlink timeslots and inter-CM transmission timeslots in each cluster are set to be 8, and 16, respectively. As shown in table 4, the reservation of the CM node in the parallel channel full TDMA scheme is performed:

TABLE 4

In this example, the total number of reservations of the uplink slots is 11, the total number of reservations of the downlink slots is 4, and the total number of reservations of the slots between CMs is 8. Although the number of time slots required for uplink reservation is greater than 10, since the number of time slots required for downlink is less than 10, the time slots actually allocated for uplink are 20-4-16 and 16>11, so all the time slot requests for uplink transmission of the CM can be satisfied.

Fig. 21 is a schematic diagram of a timeslot allocation result provided in this embodiment.

As shown in table 5, the reservation of the CM node in the parallel channel full TDMA scheme is performed:

TABLE 5

From the table, it is found that the total number of reservations of the uplink slots is 15, the total number of reservations of the downlink slots is 10, and the total number of reservations of the slots between CMs is 10. At this time, both uplink and downlink time slots will be fully used. As shown in table 6 below, a total of 3 rounds of time slot allocation are performed for each round of time slot allocation. In round 2, since both a and C request 2 slots in this round, one of the two nodes is randomly selected to obtain 1 slot allocated in this round.

TABLE 6

Fig. 22 shows another schematic diagram of the slot allocation result provided in this embodiment, and the final slot allocation result is shown in fig. 22. In the case of single-hop clustering, if a source CM in a cluster has a message to send to a destination CM in the cluster, but the source CM and the destination CM are not one-hop neighbors, then either such source CM may forward the packet to send to the destination CM in the cluster via the CH. In order to avoid the overload of the CH forwarding, the method supports the CM node as a relay node to forward the data packet. As shown in fig. 22, assuming that a has a service message to send to E, there are two paths that can be selected: a- > CH 1- > E or A- > C- > E, if there is a CM that can act as a forwarding node, the CM will reserve the transmission time slot among the CM preferentially.

Optionally, the method further comprises: the cluster head vehicle determines a pre-configured time slot corresponding to the current cluster serial number and the current running direction according to the current cluster serial number and the current running direction;

the cluster head vehicle communicates with other cluster head vehicles through a common channel in a pre-configured time slot.

As shown in fig. 23, which is a schematic structural diagram of inter-cluster communication provided in this embodiment of the present application, inter-cluster safety messages and non-safety messages can be completed through inter-CH communication, and a CH with a different cluster number in each direction is allocated at least one timeslot exclusively for transmission of safety or non-safety messages. If the CH is traveling eastward and the cluster number is C1, the CH will send a safe or non-safe message using the time slot identified as E1.

In addition to CH-specific slots, the CH may use other idle transmission slots to get more transmission opportunities if certain conditions are met. If the CH does not sense any CH message of pi/2 deviation of the driving direction during competition cluster number (i.e. the east-west driving CH does not sense any CH message of north-south driving or the north-south driving CH does not sense any CH message of east-west driving), and it can be known from the acquired road information that the current CH is more than 4R away from the road of pi/2 deviation of the driving direction, the CH can use the broadcast time slot corresponding to the CH with pi/2 deviation but the same cluster number as the cluster number. For example, if the distance of the CH driving to the east is greater than 4R from the north-south direction, the CH may use the time slots corresponding to S1 and N1.

If the CH infers that there is no cluster corresponding to a certain cluster number ahead of the traveling direction, the CH can use all the time slots (including the CH broadcast time slot and the time slot used for intra-cluster communication) allocated for the cluster using this cluster number.

The transmission of inter-cluster non-safety messages may also be accomplished through inter-CM communication. In this application the CM may send non-safety messages to one-hop CM neighbors belonging to neighboring clusters on allocated time slots. Since clusters with different cluster numbers use different and disjoint slot blocks and adjacent clusters must have different cluster numbers, collision-free transmission of non-safety messages between CMs can be guaranteed.

Inter-cluster communication or intra-cluster communication mainly transmits three types of messages: clustering control messages, safety messages and non-safety messages. The transmission of the clustering control message, the intra-cluster safety message and the inter-cluster safety message adopts a TDMA mode.

Exemplarily, as shown in fig. 24A, a schematic structural diagram of inter-cluster communication provided for this embodiment; as shown in fig. 24B, another schematic structure diagram of inter-cluster communication provided in this embodiment is shown; fig. 24C is a schematic structural diagram of another inter-cluster communication provided in this embodiment; as shown in fig. 24D, a schematic structural diagram of another inter-cluster communication provided in this embodiment is shown; fig. 24E is a schematic structural diagram of another inter-cluster communication provided in this embodiment; as shown in fig. 24F, a schematic structural diagram of another inter-cluster communication provided in this embodiment is shown; fig. 24G is a schematic structural diagram of another inter-cluster communication provided in this embodiment; however, as shown in fig. 24A, the access scheme using full TDMA is used, and fig. 24B is a scheme of transmitting an inter-CH non-secure message only by CSMA/CA based on contention, in addition to fig. 24A. Fig. 24C is a view comparing only the transmission of the non-safety message between CMs with the CSMA/CA based contention, in which a CM of a different cluster contends for transmission of the non-safety message in the CSMA/CA manner for a different period of time, with fig. 24B. Unlike fig. 24C, the CMs of all clusters in fig. 24D contend for transmission of non-safety messages in the CSMA/CA manner during the same time period. The number of competing nodes increases in this scheme, but the length of time that the CM can send messages also increases. In comparison with fig. 24E and 24D, the time of use of intra-cluster and inter-cluster channels no longer overlaps, and the two channels are no longer used in parallel. In fig. 24E, each cluster first communicates on the intra-cluster channel and then switches to the inter-cluster common channel in unison. In fig. 24F, the access scheme for intra-cluster communication is changed from CSMA/CA to TDMA, as compared with fig. 24E. In fig. 24F, to avoid transmission collisions, different clusters use different blocks of slots. In comparison with fig. 24F, fig. 24G changes the transmission scheme of non-safety message transmission between CHs from the contention-based CSMA/CA to TDMA.

As shown in table 7, the table is a comparison table of characteristics of seven transmission modes, i.e. intra-cluster and inter-cluster communication message transmission schemes under the same-direction single channel.

TABLE 7

In the present application, intra-cluster communication can be divided into CH to CM (downlink), CM to CH (uplink), and CM to CM according to node states of both intra-cluster communication parties. In the four schemes of a, b, c and d, the message transmission between CH and the non-safety message transmission between CM are parallel and are respectively carried out on the common channel and the cluster channel. When channels are used in parallel, the time slots for intra-cluster communication are divided according to the communication link. When the non-safety message is transmitted, the node transmits in different time slots according to whether the destination node of the next hop of the message is CH or CM. In the three schemes of e, f and g, the state of the next hop destination node of the message is not distinguished.

Non-secure message transmission between CMs can be divided into TDMA and CSMA/CA. Under the limitation of a single channel in the same direction, in order to avoid transmission collision between adjacent clusters, a time slot must be divided according to cluster serial numbers by adopting a TDMA mode, and the time slot can be divided according to the cluster serial numbers or not by adopting a CSMA/CA mode. The throughput of CSMA/CA within a certain range is increased along with the increase of the number of nodes, but the probability of collision is increased when the number of competing nodes is large, and the throughput is reduced. The mode of dividing the used time slot area according to the cluster sequence number can reduce the number of competitive nodes and reduce the probability of collision. Further, since no inter-cluster transmission slot of CM to CH is set, even if the CM of one cluster and the CH of another cluster are one-hop neighbor nodes, one-hop communication cannot be performed. However, the CSMA/CA method does not have such a limitation.

The non-safety message transmission between the CHs is similar to that between the CMs, and can be divided into two modes, TDMA and CSMA/CA. In the TDMA mode, each CH may occupy at least one timeslot to transmit non-safety messages, but when the node traffic is low or uneven, the TDMA timeslot utilization rate is not high, which may cause a certain timeslot to be idle and waste channel resources.

Exemplarily, as shown in fig. 25A, a schematic diagram of time slot allocation between adjacent clusters provided for this embodiment is provided; as shown in fig. 25B, another schematic diagram of time slot allocation between adjacent clusters provided for this embodiment; fig. 25C is a schematic diagram of timeslot allocation between adjacent clusters according to the present embodiment. It is assumed that two adjacent clusters C1 and C2 use the same CM broadcast slot block and that the broadcast slots of CMs are randomly allocated by CH. As shown in fig. 25A, two nodes a and B closest to each other in C1 and C2 may use the same time slot, and the transmission collision due to hidden terminal problem is not generated by CM using randomly allocated time slot broadcasting only when the distance between a and B is greater than 2R, i.e., the distance between two adjacent CH is greater than 4R.

It is assumed that two adjacent clusters do not use the same slot block and the CM broadcast slot allocation strategy is the scheme in this application. As shown in fig. 25B, the distance between adjacent CH is equal to R, C1 and C3 use the same slot block, and C2 uses a different slot block from C1 and C3. Assuming that a in C1 and C in C3 are the rearmost nodes in both clusters, then a and C use the same time slot according to the time slot allocation strategy in this application. At this time, the distance between a and C is less than 2R, and if node B exists in the overlapping area of the communication ranges of a and C, B becomes a hidden terminal. At this time, the broadcast messages of a and C may collide at B, resulting in that B cannot correctly receive the broadcast messages of a and C.

As shown in fig. 25C, the distance between adjacent CHs is equal to R, C1, C2, and C3 use different and disjoint slot blocks, respectively. Assuming that a and B are the last nodes in C1, a and B use the same time slot. At this time, the distance between a and B is larger than 2R, so that the hidden terminal problem occurred in fig. 25B does not occur. Therefore, in the CM slot allocation scheme adopted in the present application, the entire CM broadcast slot is equally divided into three parts, C1 and C4 use the slot block of the S1 part, C2 and C5 use the slot block of the S2 part, and C3 and C6 use the slot block of the S3 part, thereby ensuring collision-free transmission of the CM broadcast and avoiding the occurrence of hidden terminal problems.

It should be noted that the respective implementable modes in the present embodiment may be implemented individually, or may be implemented in combination in any combination without conflict, and the present application is not limited thereto.

According to the cluster multi-channel QoS access method for the Internet of vehicles, the current cluster serial number of a cluster head vehicle is determined, time slots are distributed to cluster members according to preset rules, the cluster members and the cluster head vehicle send messages in the distributed time slots according to a preset message sending mechanism, so that the cluster members communicate with other cluster members or the cluster head vehicle through channels corresponding to the current driving direction in the corresponding time slots, transmission collision is reduced, communication efficiency in clusters and among clusters is improved, and QoS support is provided.

Another embodiment of the present application provides a clustered multi-channel QoS access apparatus for internet of vehicles, configured to perform the method provided by the foregoing embodiment.

As shown in fig. 26, a schematic structural diagram of a clustered multi-channel QoS access apparatus for an internet of vehicles according to an embodiment of the present application is provided, where the clustered multi-channel QoS access apparatus for an internet of vehicles includes an obtaining module 10, a determining module 20, and an allocating module 30;

the acquiring module 10 is used for acquiring the current driving direction, the current position information and the midpoint position information of the current road by the cluster head vehicle;

the determining module 20 is configured to determine a current cluster serial number of the cluster head vehicle according to the current driving direction, the current position information, and the midpoint position information of the current road;

the distribution module 30 is configured to enable a cluster head vehicle to obtain a time slot of the cluster head vehicle according to a current cluster serial number and distribute the time slot to cluster members according to a preset rule, so that the cluster members communicate with other cluster members or the cluster head vehicle through a channel corresponding to a current driving direction in the corresponding time slot;

The specific manner in which the respective modules perform operations has been described in detail in relation to the apparatus in this embodiment, and will not be elaborated upon here.

According to the cluster multi-channel QoS access device for the Internet of vehicles, the cluster members are allocated with time slots according to the preset rules through the current cluster serial numbers of the cluster head vehicles, the cluster members and the cluster head vehicles are enabled to send messages in the allocated time slots according to the preset message sending mechanism, so that the cluster members are enabled to communicate with other cluster members or the cluster head vehicles through the channels corresponding to the current driving direction in the corresponding time slots, transmission collision is reduced, communication efficiency in the clusters and among the clusters is improved, and QoS support is provided.

The present application further provides a supplementary description of the apparatus provided in the above embodiments.

On the basis of the foregoing embodiment, optionally, the determining module is configured to:

On the basis of the foregoing embodiment, optionally, the current cluster serial number of the cluster head vehicle is determined according to the relative distance between the position coordinate of the cluster head vehicle and the position coordinate of the road midpoint and the communication radius of the cluster where the cluster head vehicle is located, specifically:

C_ithe cluster number of the cluster head vehicle.

On the basis of the foregoing embodiment, optionally, the allocation module is configured to:

On the basis of the foregoing embodiment, optionally, the allocation module is further configured to:

the inter-cluster communication module is used for determining a pre-configured time slot corresponding to the current cluster serial number and the current running direction by the cluster head vehicle according to the current cluster serial number and the current running direction;

On the basis of the foregoing embodiment, optionally, the obtaining module is configured to:

According to the cluster multi-channel QoS access device for the Internet of vehicles, the current cluster serial number of the cluster head vehicle is determined, the time slot is allocated to the cluster member according to the preset rule, the cluster member and the cluster head vehicle are enabled to send messages in the allocated time slot according to the preset message sending mechanism, so that the cluster member is enabled to communicate with other cluster members or the cluster head vehicle through the channel corresponding to the current driving direction in the corresponding time slot, transmission collision is reduced, communication efficiency in the cluster and among the clusters is improved, and QoS support is provided.

Yet another embodiment of the present application provides an electronic device for performing the method provided by the foregoing embodiment.

As shown in fig. 27, a schematic structural diagram of an electronic device provided in an embodiment of the present application is shown, where the electronic device includes: at least one processor 51 and memory 52;

the memory stores a computer program; at least one processor executes the computer program stored in the memory to implement the methods provided by the above-described embodiments.

According to the electronic device of the embodiment, the current cluster serial number of the cluster head vehicle is determined, and the time slot is allocated to the cluster member according to the preset rule, so that the cluster member can communicate with other cluster members or the cluster head vehicle through the channel corresponding to the current driving direction in the corresponding time slot, and the communication efficiency of intra-cluster and inter-cluster communication of clusters driving in the same direction is improved.

Yet another embodiment of the present application provides a computer-readable storage medium, in which a computer program is stored, and when the computer program is executed, the method provided in any one of the above embodiments is implemented.

According to the computer-readable storage medium of this embodiment, by determining the current cluster serial number of the cluster head vehicle, and allocating a time slot to the cluster member according to the preset rule, the cluster member and the cluster head vehicle transmit messages in the allocated time slot according to the preset message transmission mechanism, so that the cluster member communicates with other cluster members or the cluster head vehicle through a channel corresponding to the current driving direction in the corresponding time slot, transmission collision is reduced, communication efficiency in and between clusters is improved, and QoS support is provided.

Finally, it should be noted that: the above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A clustering multi-channel QoS access method for Internet of vehicles is characterized by comprising the following steps:

2. The method of claim 1, wherein the determining, by the cluster head vehicle, the current cluster serial number of the cluster head vehicle according to the current driving direction, the current position information, and the midpoint position information of the road where the cluster head vehicle is currently located comprises:

and determining the current cluster serial number of the cluster head vehicle according to the relative distance between the position coordinate of the cluster head vehicle and the position coordinate of the road midpoint and the communication radius of the cluster where the cluster head vehicle is located.

3. The method according to claim 2, wherein the determining a current cluster serial number of the cluster head vehicle according to a relative distance between the position coordinate of the cluster head vehicle and the position coordinate of the road midpoint and a communication radius of a cluster in which the cluster head vehicle is located specifically includes:

r is the communication radius of the cluster where the cluster head vehicle is located; m is the number of cluster numbers, CH_iThe position coordinate of a cluster head vehicle of the ith cluster, and M is the position coordinate of the road midpoint;

C_iand the cluster serial number of the cluster head vehicle.

4. The method of claim 1, wherein the cluster head vehicle allocating time slots to cluster members according to a preset rule based on the current cluster serial number comprises:

if the cluster member vehicles in the cluster are positioned in front of the traveling direction of the cluster head vehicle, carrying out in-cluster broadcasting time slot allocation from far to near according to the distance between the cluster member vehicles and the cluster head vehicle from the first time slot of the time slot block;

and if the cluster member vehicles in the cluster are positioned behind the traveling direction of the cluster head vehicle, carrying out in-cluster broadcasting time slot allocation from far to near according to the distance between the cluster member vehicles and the cluster head vehicle from the last time slot of the time slot block.

5. The method of claim 1, wherein the cluster head vehicle allocating time slots to cluster members according to a preset rule based on the current cluster serial number further comprises:

the cluster head vehicle receives broadcast information sent by a cluster member, wherein the broadcast information comprises a reservation time slot request of the cluster member;

and the cluster head vehicle carries out time slot distribution of non-safety information broadcasting for each cluster member vehicle according to the proportion of the reserved time slot request and the total time slot demand number.

6. The method of claim 1, further comprising:

the cluster head vehicle determines a pre-configured time slot corresponding to the current cluster serial number and the current running direction according to the current cluster serial number and the current running direction;

and the cluster head vehicle communicates with other cluster head vehicles through a public channel in the pre-configured time slot.

7. The method of claim 1, wherein the obtaining of the current driving direction, the current position information, and the midpoint position information of the current road by the clusterhead vehicle comprises:

and acquiring the current driving direction of the cluster head vehicle and the position coordinates of the midpoint of the road where the cluster head vehicle is located through an electronic map.

8. A clustering multichannel QoS access device for Internet of vehicles is characterized by comprising:

9. An electronic device, comprising: at least one processor and memory;

the memory stores a computer program;

the at least one processor executes the memory-stored computer program to implement the method of any of claims 1-7.

10. A computer-readable storage medium, characterized in that a computer program is stored in the computer-readable storage medium, which computer program, when executed, implements the method of any one of claims 1-7.