Internet of vehicles communication method and system

Abstract

The invention discloses an Internet of Vehicles communication method and system, and relates to the technical field of Internet of Vehicles communication, a set of fine layering mechanism is constructed on a channel resource allocation level, when the system does not detect a high-key message transmission demand, channel resources are preferentially allocated to general messages, and the channel resources are allocated to the general messages. Normal operation of basic communication functions of the Internet of Vehicles is guaranteed, idle waste of resources is avoided, once high-priority messages are monitored, a dynamic preemption mode is started immediately, channel resources are accurately allocated according to safety key levels of the messages, rapid and reliable transmission of the high-priority messages is guaranteed, transmission of general messages is reasonably avoided, and the service life of the Internet of Vehicles is prolonged. According to the layered resource allocation strategy, the overall utilization efficiency of channel resources is remarkably improved, the transmission requirements of different levels of messages in the Internet of Vehicles system are considered, and efficient and stable operation of the Internet of Vehicles communication system is promoted.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of Internet of Vehicles communication, in particular to an Internet of Vehicles communication method and system. BACKGROUND

[0002] As a key technology for realizing efficient information interaction between vehicles, infrastructure, people and network, the importance of Internet of Vehicles is increasingly prominent. In urban traffic scenarios, Internet of Vehicles can collect traffic flow data in real time, guide vehicles to plan driving routes intelligently, and relieve congestion. On highways, vehicles interact with each other through Internet of Vehicles to exchange driving states, realize adaptive cruise and other advanced driving assistance functions, and improve driving safety. However, with the exponential growth of Internet of Vehicles devices, the contradiction between limited communication channel resources and explosive growth of data transmission demand is increasingly prominent. Especially in high-density traffic scenarios, message collision, channel congestion, security threats and other problems have become the core bottleneck restricting the performance improvement of Internet of Vehicles. However, under the current Internet of Vehicles communication technology system, there are still significant shortcomings in the core link of channel resource management. Existing solutions mostly rely on static or semi-static channel allocation strategies, and do not fully consider the complex and changeable factors such as dynamic driving of vehicles and real-time fluctuations of traffic flow in Internet of Vehicles environment. Traditional static allocation method is easy to cause rapid saturation of channel resources, and high-priority messages are difficult to transmit. It cannot cope with large-scale channel congestion caused by traffic peak periods and emergencies, so that high-priority messages are blocked in the transmission process and the delivery time of critical information is delayed. In summary, the existing Internet of Vehicles communication technology in channel resource management cannot meet the increasingly complex traffic scenarios and stringent communication requirements. An innovative solution is urgently needed to accurately understand the spatio-temporal evolution law of channel state and flexibly and efficiently implement dynamic channel resource preemption to ensure reliable and timely transmission of high-priority messages in Internet of Vehicles and lay a solid foundation for the stable operation of intelligent transportation. SUMMARY

[0003] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a vehicle-to-everything (V2X) communication method and system. This system constructs a sophisticated hierarchical mechanism at the channel resource allocation level. When the system does not detect a high-priority message transmission requirement, it prioritizes allocating channel resources to general messages, ensuring the normal operation of basic V2X communication functions and avoiding resource idleness and waste. Once a high-priority message is detected, a preemption mode is immediately activated. Based on the message's security criticality level, channel resources are precisely allocated. While ensuring the fast and reliable transmission of high-priority messages, the transmission of general messages is reasonably avoided. This hierarchical resource allocation strategy significantly improves the overall utilization efficiency of channel resources, takes into account the transmission needs of different levels of messages in the V2X system, and promotes the efficient and stable operation of the V2X communication system.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution: On one hand, a vehicle-to-everything (V2X) communication method, the specific steps of which are as follows: S100 and on-board unit (OBU) collect vehicle motion status data and traffic flow information broadcast by roadside unit (RSU) in real time. S200: Calculate the Channel Busyness Index (CBI) and Key Message Collision Probability (MCP) for vehicles entering the area within 300-500ms based on the collected data; S300: When CBI and MCP meet the preemption judgment conditions, the preemption mode is triggered, and the resource reservation parameters are calculated according to the security criticality level SL, CBI and MCP of the message. The S400 and OBU broadcast a preemption request signaling PRS to nearby RSUs and vehicles in the target area, and determine the information priority and sending order according to the response mechanism; S500, the initiator OBU in During the period, with The transmit power is used to send high-priority messages and the automatic retransmission request mechanism is enabled.

[0005] Furthermore, the vehicle motion state data collected by the on-board unit (OBU) in S100 includes: self-positioning, speed, and heading angle data; The traffic flow information broadcast by the Roadside Unit (RSU) includes vehicle density, average speed, and event markers. The event markers include the latitude and longitude coordinates of the accident and construction events, and the event type code. In the event type code, A represents an accident and B represents construction.

[0006] Furthermore, in S200, the Channel Busyness Index (CBI) is used to quantify the channel resource scarcity in the target area, with a value range of [0, 1], where 0 indicates the channel is completely idle and 1 indicates the channel is completely occupied. ,in, , , is a weight coefficient and is used to adjust the contribution of each factor to CBI, is the number of messages registered in the target area in the current period, is the maximum number of messages that the target area can accommodate in the same period in historical data statistics, used to normalize the current number of messages, through the message quantity influence term reflects the activity level of current message sending, is the average duration of historical channel occupation in the target area, is the total duration of the statistical period, used to normalize the channel occupation duration, through the historical occupation influence term reflects the historical busy degree of the channel, is the current vehicle density of the area broadcast by the Roadside Unit RSU; The critical message collision probability MCP is used to evaluate the probability of collision between the new message and the registered high-priority message in the current area, with a value range of [0, 1], 0 indicating no collision risk, and 1 indicating certain collision, and the wherein, is the number of registered high-priority messages in the current area, and the safety level SL of the high-priority message is ≥3, is the transmission power of the th registered high-priority message, the greater the transmission power, the wider the signal coverage, and the higher the possibility of collision with the new message, is the transmission frequency of the th registered high-priority message, the higher the transmission frequency, the greater the probability of time overlap with the new message, T is the transmission period of the th registered high-priority message and the time overlap coefficient of the planned transmission period of the new message , with a value range of [0, 1], 0 if there is no overlap at all, and 1 if there is complete overlap, obtained by calculating the ratio of the intersection duration to the union duration of the two periods.

[0007] Further, the preemption decision condition in S300 is: When CBI> , MCP> , the event marker broadcast by the RSU shows that there are types A and B within 500 meters in front of the vehicle, satisfying any one of the conditions, wherein and are preset channel busy threshold and message collision probability threshold, and initially , ; The safety critical level SL is determined by predefined rules and real-time calculation rules, wherein: Predefined rule: the predefined safety critical level is set to three levels, SL=5 is applicable to the pre-warning message of emergency braking, SL=3 is applicable to the message of lane change intention notification, and SL=1 is applicable to the message of state reporting; Real-time calculation rule: when the message event type code broadcast by the road side unit RSU is A and B, the distance between the message sending vehicle and the event point is calculated by the vehicle-mounted unit OBU based on the positioning data obtained by the vehicle-mounted unit OBU as the center When the distance is less than 50 meters, it indicates that the vehicle is in the core influence area of the accident, at this time SL is determined to be 5, to ensure that the messages in this area can occupy the channel resources in priority and quickly deliver the key information When the distance is less than 100 meters, SL is determined to be 4 When the distance is less than 150 meters, SL is determined to be less than or equal to 3

[0008] Further, the reserved parameters in the S300 include a reserved time length and a minimum transmission power, wherein: The reserved time length is Tres , wherein, Tres is the message transmission time length and Tres , is the message length, is the transmission rate, is the protection interval, and the value is 50 ms, is the safety coefficient, and the value range is 1.2-1.5; The minimum transmission power is Pmin , wherein, Pmin is the reference power, Pmin is the power compensation step, and CBI and MCP are the channel busy index and the critical message collision probability respectively.

[0009] Further, the PRS in the S400 includes a message ID, an initiator ID, a safety level SL, a reserved period and a minimum transmission power , the reserved period is and , is the information transmission start time, is the information transmission end time; The response mechanism is: when the RSU and the vehicle receiving the PRS have the messages initiated by the initiator SL, the communication scheduling thereof is actively avoided for the reserved time length, and the transmission power is reduced in the reserved time length, when there is a conflict, the SL priority is compared, the message reservation request of the high SL is reserved, and the low SL message returns a reservation rejection signaling.

[0010] ​Further, the automatic repeat request mechanism in the S500 is that: after the receiver successfully decodes the message, the acknowledgement information is returned to the sender within 20ms, and when the sender does not receive the acknowledgement information within 50ms, the retransmission is triggered, and the upper limit of the retransmission number is 3 times.

[0011] In another aspect, a vehicle networking communication system, the components of the system include: a data acquisition module, a channel state module, a dynamic decision module, a resource reservation module, a message transmission and feedback module; The data acquisition module includes an on-board unit (OBU) and a roadside unit (RSU), and is used for continuously acquiring OBU self-positioning, speed, heading angle data and traffic flow information. The channel state module calculates the channel busy index (CBI) and the message collision probability (MCP) of the entering area based on the data collected and received by the data acquisition module. The dynamic decision module includes a preemption decision engine, which is used to trigger the preemption mode when the calculated CBI and MCP exceed the preset threshold, and calculate the required channel reservation duration and minimum transmission power according to the safety criticality level of the message itself and the CBI and MCP. The resource reservation module is used to control the OBU to broadcast a preemption request signaling (PRS) to the RSU and target area vehicles, and judge the information priority and sending order according to the response mechanism. The message transmission and feedback module is used to make the OBU initiating preemption preferentially use the reserved channel resources to send its high criticality message within the reservation period, and monitor the actual transmission success rate and delay in real time.

[0012] Compared with the prior art, the vehicle networking communication method and system have the following beneficial effects: Firstly, the present application constructs a set of fine hierarchical mechanism at the channel resource allocation level, when the system does not detect the high criticality message transmission demand, the channel resources are preferentially allocated to general messages, to ensure the normal operation of the vehicle networking basic communication function, avoid resource idle waste, once the high priority message is monitored, the dynamic preemption mode is started, and the channel resources are accurately allocated according to the safety criticality level of the message, which ensures the fast and reliable transmission of high criticality messages and reasonably avoids the transmission of general messages, this hierarchical resource allocation strategy significantly improves the overall utilization efficiency of channel resources, and meets the transmission demands of messages of different levels in the vehicle networking system, and promotes the efficient and stable operation of the vehicle networking communication system.

[0013] Other advantages, objects, and features of the present application will be in part apparent and in part pointed out hereinafter in the specification, and in part will be observed by persons skilled in the art upon examination of the following specification, or can be learned by practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0015] Figure 1 An operation flowchart of a vehicle networking communication method; Figure 2 A step diagram of a vehicle networking communication method; Figure 3 A module composition diagram of a vehicle networking communication system. DETAILED DESCRIPTION

[0016] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined application purposes, the specific embodiments, structures, features and effects according to the present application will be described in detail below in combination with the drawings and preferred embodiments.

[0017] Embodiment one: the present embodiment provides a vehicle networking communication method, as shown in the figure, through the cooperative work of the on-board unit OBU and the road side unit RSU, the real-time collection of the vehicle motion state data and the traffic flow information is realized, the channel busy degree index and the key message collision probability are calculated, the dynamic resource preemption mechanism is triggered when the preemption condition is met, the resource reservation parameter calculation, the preemption request signaling broadcast and the high priority message transmission are completed, the channel congestion and message collision problems in the high density traffic scene are effectively solved, and the reliable transmission of the high criticality message is guaranteed. Figure 2

[0018] ​First, enter the data real-time collection phase (S100), which is the basis of the entire vehicle networking communication method, and is used to provide accurate and comprehensive data support for subsequent channel state evaluation and resource preemption decision-making. The on-board unit OBU continuously collects the motion state data of the vehicle itself at a set high-frequency sampling frequency, which includes the self-positioning information for determining the position coordinates of the vehicle in the geographical space, the speed data measured by the vehicle sensor in real time, reflecting the speed of the vehicle, and the heading angle data obtained by the inertial navigation device, representing the driving direction of the vehicle. At the same time, the road side unit RSU sends traffic flow information to the surrounding area according to a fixed broadcast period. These information covers the vehicle density, which is calculated by detecting and counting the vehicles in the covered area by the RSU, and can intuitively reflect the traffic congestion degree of the area. The average speed is the statistical average of the speed of all vehicles in the area, which can be used to judge the running state of the traffic flow. The event marker contains the latitude and longitude coordinates of the accident and construction events, which are obtained by the event detection device and reported to the RSU, as well as the event type code, where A represents accident and B represents construction, which is used to quickly identify the nature of the event. The OBU receives and parses these information broadcast by the RSU while collecting its own data, and stores them in the local cache for subsequent processing.

[0019] Next, enter the channel state evaluation phase (S200). Based on the collected data, the channel busy index CBI and the key message collision probability MCP of the vehicle entering the area after 300-500 ms are calculated. The channel busy index CBI is used to quantify the degree of channel resource shortage in the target area, and its value range is defined in the interval [0, 1], where 0 represents a completely idle channel and 1 represents a completely occupied channel. The calculation formula of CBI is where , β, γ are weight coefficients, and α + β + γ = 1. These three weight coefficients are used to adjust the contribution of each influencing factor to CBI, is the number of messages registered in the target area in the current period, is the maximum number of messages that the target area can accommodate in the same period in historical data statistics, which reflects the activity level of current message sending through If this ratio is larger, it means that more messages are sent in the current period, and the channel is more likely to be congested, is the average length of time the target area's historical channel is occupied, is the total length of the statistical period, which is used to reflect the average length of time the target area's historical channel is occupied through The historical occupation impact term reflects the historical busy degree of the channel. The larger the ratio is, the longer the channel is occupied in the historical statistical period, and the higher the past busy degree is. D is the vehicle density of the current area broadcast by the road side unit RSU. The larger the vehicle density is, the more vehicles in the area are likely to send messages, thereby increasing the burden of the channel. The key message collision probability MCP is used to evaluate the probability of collision between the new message and the registered high priority message in the current area. The value range is also [0, 1]. 0 represents no collision risk, and 1 represents inevitable collision. The calculation formula is Where n is the number of registered high priority messages in the current area. The high priority message here refers to the message with a safety level SL≥3, is the transmission power of the ith registered high priority message. The larger the transmission power is, the wider the signal coverage range is, and the higher the possibility of spatial overlap between the new message and the message is, thereby increasing the collision probability, is the transmission frequency of the ith registered high priority message. The higher the transmission frequency is, the greater the probability of temporal overlap between the message and the new message is, is the transmission period of the ith registered high priority message is the time overlap coefficient of the planned transmission period of the new message The value range is [0, 1]. The time overlap coefficient is obtained by calculating the ratio of the intersection length to the union length of the two periods. If there is no overlap, it is 0. If there is complete overlap, it is 1. The coefficient directly reflects the degree of conflict between the two messages in time. According to the collected data and historical statistical information, the channel state in the future 300-500 ms is predicted, the values of CBI and MCP are calculated, and they are passed to the subsequent decision module.

[0020] Then, enter the preemption decision and resource parameter calculation phase (S300). According to the values of CBI and MCP and the event marker broadcast by the RSU, it is judged whether to trigger the preemption mode, and the resource reservation parameters are calculated after triggering. The preemption condition is: when CBI> , MCP> , and the event marker broadcast by the RSU shows that there are three types of coding A and B within 500 meters in front of the vehicle, any one of the three conditions is met, the preemption mode is triggered, wherein, and preset channel busy threshold and message collision probability threshold; the safety critical level SL is determined by a predefined rule and a real-time calculation rule, in the predefined rule, the safety critical level is set to three levels of 1, 3 and 5, SL=5 is applicable to the pre-warning message of emergency braking, such a message is related to driving safety, and is set to the highest priority, SL=3 is applicable to the message of lane change intention notification, and SL=1 is applicable to the message of state reporting, which is a general message, and the real-time calculation rule dynamically adjusts SL according to the distance between the vehicle and the event point, when the message event type code broadcast by the road side unit RSU is A and B, the distance d between the message sending vehicle and the event point is calculated by the positioning data obtained by the on-board unit OBU taking the event point as the center, when 0<d m, it indicates that the vehicle is in the core influence area of the accident, at this time, SL is determined as 5 to ensure that the messages in the area can preempt the channel resources and quickly deliver the key information, when 500<d m, SL is determined as 3, and when 1000<d After the SL is determined, the reservation parameters including the reservation time length and the minimum transmission power are calculated, the calculation formula of the reservation time length T is , wherein is the message transmission time length, and L is the message length, R is the transmission rate, is the protection interval, the value is 50ms, k is the safety coefficient, the value range is 1.2-1.5, the safety coefficient is used to cope with possible transmission delay and other uncertain factors to ensure that the message has enough transmission time, and the calculation formula of the minimum transmission power is , wherein is the reference power, is the power compensation step, CBI and MCP are respectively the calculated channel busy index and critical message collision probability, through the formula, the minimum transmission power is increased correspondingly in the case that the channel busy degree is higher and the message collision probability is larger, so that the message can overcome the channel interference and be successfully transmitted.

[0021] Then, the preemption request signaling broadcast and response processing stage (S400) is entered, the OBU broadcasts the preemption request signaling PRS to the adjacent RSU and target area vehicle, and judges the information priority and sending order according to the response mechanism, the PRS includes the message ID, the initiator ID, the safety level SL, the reservation period and the minimum transmission power , wherein the reservation period is , and , is the information transmission start time, is the reserved time length calculated above, and the specific content of the response mechanism is: when receiving the PRS, the RSU and the vehicle will actively avoid the reserved time length in their communication scheduling and reduce the transmission power within the reserved time length to reduce the interference to the initiator message transmission; when there is a conflict, i.e., the reserved requests of different messages overlap in time or resources, the SL priorities are compared, the reserved request of the high SL message is retained, and the reserved rejection signaling is returned to the low SL message to ensure that the transmission demand of the high priority message is met; after broadcasting the PRS, the OBU receives the response information from the RSU and other vehicles, and analyzes and processes the information to determine the final resource allocation and message transmission sequence.

[0022] Finally, enter the high priority message transmission and automatic retransmission phase (S500), and the initiator OBU transmits the high priority message in the reserved period with the transmission power of 411, and enables the automatic retransmission request mechanism; the specific process of the automatic retransmission request mechanism is: after the receiver successfully decodes the message, it needs to return the confirmation information to the sender within 20 ms; when the sender does not receive the confirmation information within 50 ms, the retransmission operation is triggered, and the upper limit of the retransmission number is 3 times; the purpose of this mechanism is to deal with the message transmission failure problem caused by noise, interference and other factors in the channel, and to improve the reliability of message transmission through automatic retransmission; during the transmission process, the OBU monitors the transmission state of the message in real time, including whether it is successfully sent and whether it receives the confirmation information, etc., and processes accordingly according to the monitoring result; if the confirmation information is not received after the retransmission number reaches the upper limit, it is considered that the message transmission fails, and corresponding error handling measures are taken.

[0023] In summary, through the cooperative work of real-time data collection, channel state evaluation, preemption decision and resource parameter calculation, preemption request signaling broadcast and response processing, high priority message transmission and automatic retransmission, this embodiment can accurately understand the spatio-temporal evolution law of the channel state, flexibly and efficiently implement dynamic channel resource preemption according to the channel busy degree index and the collision probability of the key message, and combine the safety critical level of the message, effectively solve the channel congestion and message collision problem in high-density traffic scene, and comprehensively guarantee the reliable and timely transmission of high criticality messages in the Internet of Vehicles, significantly improve the overall utilization efficiency of channel resources, and take into account the transmission demand of different levels of messages in the Internet of Vehicles system, and promote the efficient and stable operation of the Internet of Vehicles communication system.

[0024] Embodiment two: as Figure 1As shown, the embodiment provides a vehicle networking communication method for the specific process of vehicle information transmission, and the steps of the specific process are as follows: (1) Data acquisition The OBU collects the motion state data of the vehicle itself, such as positioning, speed, and heading angle, in real time; The OBU receives the traffic flow information broadcast by the RSU, including vehicle density, average speed, and event markers; (2) Channel state evaluation Based on the collected data, the channel state of the vehicle entering the area after 300-500 ms is predicted; The channel busy index CBI is calculated to quantify the degree of tightness of the channel resources in the target area; The message collision probability MCP is calculated to evaluate the probability of collision between the new message and the registered high-priority message in the current area; (3) Preemption decision and resource parameter calculation Determine whether the preemption decision condition is met (CBI is greater than a preset threshold, MCP is greater than a preset threshold, and the event marker broadcast by the RSU shows that there is any one of type codes A and B within 500 meters in front of the vehicle); If the preemption mode is triggered, determine the safety level SL of the message (determined by predefined rules and real-time calculation rules); According to SL, CBI, and MCP, calculate the resource reservation parameters, including reservation duration and minimum transmission power; (4) Preemption request signaling broadcast The OBU broadcasts the preemption request signaling PRS containing the message ID, initiator ID, safety level SL, reservation period, and minimum transmission power to the adjacent RSU and target area vehicles; (5) Response processing The RSU and vehicle receiving PRS respond according to the comparison result of the safety level SL of their own message and the SL of the initiator; If the SL of the currently and planned to be sent message of the receiver is less than the SL of the initiator, actively avoid the reservation duration in the communication scheduling, and reduce the transmission power within the reservation duration; When there is a conflict, compare the SL priority, reserve the message reservation request of high SL, and return a reservation rejection signaling to the low SL message; The initiator OBU determines the information priority and transmission order according to the response information; (6) High-priority message transmission The initiator OBU transmits the high-priority message within the reservation period with the minimum transmission power calculated; (7) Automatic retransmission request The receiver returns the confirmation information to the sender within 20 ms after successfully decoding the message; If the sender does not receive the confirmation information within 50 ms, retransmission is triggered, and the upper limit of the retransmission number is 3 times; The information whose retransmission number exceeds the upper limit is recorded and is subjected to regular transmission.

[0025] The above is only the preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with the preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content to obtain equivalent embodiments with equivalent changes, without departing from the technical solution of the present application. Any modification, change, and modification of the above embodiments, which are made according to the technical essence of the present application, still belong to the scope of the technical solution of the present application.

Claims

1. A vehicle-to-everything (V2X) communication method, characterized in that, The specific steps of the method are: S100, the vehicle-mounted unit OBU collects vehicle motion state data and the roadside unit RSU broadcasts traffic flow information in real time; S200, based on the collected data, the channel busy index CBI and the key message collision probability MCP of the vehicle entering the area within 300-500 ms are calculated; S300, when the CBI and MCP meet the preemption decision condition, the preemption mode is triggered, and the resource reservation parameters are calculated according to the safety criticality level SL of the message, CBI and MCP; S400, the OBU broadcasts the preemption request signaling PRS to the adjacent RSU and the target area vehicle, and judges the information priority and sending order according to the response mechanism; S500、the initiator OBU transmits a high priority message at a transmission power and enables an automatic repeat request mechanism within a time period. S500、the initiator OBU transmits a high priority message at a transmission power and enables an automatic repeat request mechanism within a time period. S500、the initiator OBU transmits a high priority message at a transmission power and enables an automatic repeat request mechanism 2.The Internet of Vehicles communication method according to claim 1, characterized in that, The vehicle motion state data collected by the vehicle-mounted unit OBU in S100 includes: self-positioning, speed, and heading angle data; The traffic flow information broadcast by the roadside unit RSU includes: vehicle density, average speed, and event marker, the event marker includes the latitude and longitude coordinates of the accident and construction event, and the event type code, in which A represents an accident and B represents construction. 3.The Internet of Vehicles communication method of claim 1, wherein, The channel busy index CBI in S200 is used to quantify the tightness of channel resources of the target area, with a value range of [0, 1], 0 representing a completely idle channel, and 1 representing a completely occupied channel, and the wherein, , , is a weight coefficient and is used to adjust the contribution degree of each influencing factor to CBI, is the number of registered messages of the target area in the current period, is the maximum number of messages that the target area can accommodate in the same period in historical data statistics, used for normalizing the current number of messages, and the message quantity influencing term reflects the activity level of the current message sending, is the average duration of historical channel occupation of the target area, is the total duration of the statistical period, used for normalizing the channel occupation duration, and the historical occupation influencing term reflects the historical busy degree of the channel, is the current vehicle density of the area broadcast by the road side unit RSU; The Key Message Collision Probability (MCP) is used to assess the probability of a new message colliding with a registered high-priority message in the current region. Its value range is [0, 1], where 0 indicates no collision risk and 1 indicates a collision is certain. ,in, This represents the number of high-priority messages registered in the current region, where the security level of these high-priority messages is SL≥3. For the first The transmission power of the registered high-priority messages, For the first The transmission frequency of the registered high-priority messages, T For the first Transmission period for registered high-priority messages With new message planned transmission period The time overlap coefficient, which ranges from [0, 1], is obtained by calculating the ratio of the intersection duration to the union duration of the two time periods.

4. The Internet of Vehicles communication method according to claim 1, wherein, The preemption decision condition in S300 is: When CBI , MCP> , the event flag broadcast by RSU shows that there are types A and B within 500 meters in front of the vehicle, which meets any one condition, the preemption mode is triggered, wherein, and are preset channel busy threshold and message collision probability threshold, and initially , ; The safety criticality level SL is determined by pre-defined rules and real-time calculation rules, wherein: Pre-defined rules: the pre-defined safety criticality level is set to 1, 3, and 5, SL=5 is applicable to pre-warning messages of emergency braking, SL=3 is applicable to messages of lane change intention notification, and SL=1 is applicable to state reporting messages; Real-time calculation rule: when the message event type code broadcast by the roadside unit RSU is A and B, the distance between the message sending vehicle and the event point is calculated by acquiring positioning data through the on-board unit OBU with the event point as the center When meters, the SL is determined to be 5, when meters, the SL is determined to be 4, and when meters, the SL is determined to be less than or equal to 3.

5. The Internet of Vehicles communication method according to claim 1, wherein, The reservation parameters in S300 include the reservation duration and the minimum transmission power, wherein: The reserved time length Wherein, The message transmission time length and , The message length, The transmission rate, The protection interval is 50 ms, The safety factor is in the range of 1.2-1.5; the minimum transmit power wherein, is a reference power, is a power compensation step size, CBI and MCP are Channel Busy Index and Message Collision Probability, respectively.

6. The Internet of Vehicles communication method according to claim 1, wherein, The S400 includes a message ID, an initiator ID, a security level SL, a reservation period and a minimum transmission power The reservation period is and , is an information transmission start time, is an information transmission end time; The response mechanism is: when the RSU and vehicle receiving PRS and its current and planned to send the message When the initiator SL time, then actively avoid the reservation duration in its communication scheduling, and reduce the transmission power within the reservation duration, when there is a conflict, then compare the SL priority, reserve the high SL message reservation request, return the reservation rejection signaling to the low SL message.

7. The Internet of Vehicles communication method according to claim 1, wherein, The automatic repeat request mechanism in S500 is: after the receiver successfully decodes the message, the acknowledgement information is returned to the sender within 20 ms, and when the sender does not receive the acknowledgement information within 50 ms, the retransmission is triggered, and the upper limit of the retransmission times is 3 times.

8. A V2X communication system, adapted to a V2X communication method according to any one of claims 1-7, characterized in that, The components of the system include: a data acquisition module, a channel state module, a dynamic decision module, a resource reservation module, and a message transmission and feedback module; The data acquisition module: includes the vehicle-mounted unit OBU and the roadside unit RSU, and is used for continuously collecting OBU self-positioning, speed, and heading angle data and traffic flow information; The channel state module: based on the data collected and received by the data acquisition module, the channel busy index CBI and the key message collision probability MCP of the entering area are calculated; The dynamic decision module: includes a preemption decision engine, which is used for triggering the preemption mode when the calculated CBI and MCP exceed the preset threshold, and calculating the required channel reservation duration and minimum transmission power according to the safety criticality level of the message itself and CBI and MCP; The resource reservation module: is used for controlling the OBU to broadcast the preemption request signaling PRS to the RSU and the target area vehicle, and judging the information priority and sending order according to the response mechanism; The message transmission and feedback module: is used for making the OBU initiating preemption to use the reserved channel resources to send its high criticality message within the reservation period, and monitoring the actual transmission success rate and delay in real time.

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