CN117119522A - Message transmission method for LTE-V2X packet priority - Google Patents

Message transmission method for LTE-V2X packet priority Download PDF

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Publication number
CN117119522A
CN117119522A CN202311086199.XA CN202311086199A CN117119522A CN 117119522 A CN117119522 A CN 117119522A CN 202311086199 A CN202311086199 A CN 202311086199A CN 117119522 A CN117119522 A CN 117119522A
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priority
packet
channel resource
message
lte
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朴昌浩
何彦琪
高俊
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Chongqing University of Post and Telecommunications
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Chongqing University of Post and Telecommunications
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W28/00—Network traffic management; Network resource management
    • H04W28/02—Traffic management, e.g. flow control or congestion control
    • H04W28/0231—Traffic management, e.g. flow control or congestion control based on communication conditions
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W28/00—Network traffic management; Network resource management
    • H04W28/02—Traffic management, e.g. flow control or congestion control
    • H04W28/10—Flow control between communication endpoints
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/30—Services specially adapted for particular environments, situations or purposes
    • H04W4/40—Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P]

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

The invention relates to the field of communication, in particular to a message transmission method facing LTE-V2X packet priority, which comprises the steps of setting message classification and packet priority, and setting a threshold value of a channel resource duty ratio CRB according to the packet priority; judging that the node buffer area is full, and discarding the subsequent data packet if the node buffer area is full; calculating the channel resource utilization rate threshold value according to the threshold value of the channel resource duty ratio CRB of the current node and the users in the current user communication range; acquiring the channel resource utilization rate of the node, and if the channel resource utilization rate of the current node is smaller than the channel resource utilization rate threshold value, continuing to transmit according to the current state; if the channel resource utilization rate of the current node is greater than or equal to the channel resource utilization rate threshold value of the current node, sorting the data packets according to the priority, preferentially transmitting the data packets with high priority and discarding the data packets with low priority; the invention can carry out differentiation processing according to the importance and the urgency of the communication message, thereby realizing more efficient communication transmission.

Description

Message transmission method for LTE-V2X packet priority
Technical Field
The invention relates to the field of communication, in particular to a message transmission method facing LTE-V2X packet priority.
Background
With the development of intelligent transportation systems and the rise of vehicle autopilot technology, communication between vehicles is becoming increasingly important. LTE-V2X, as a powerful communication technology, can support direct communication between vehicles and communication with infrastructure, providing great potential for vehicle safety, traffic efficiency and driving experience. Compared with a dedicated short-range communication standard (DSRC) based on an IEEE 802.11p communication standard, the LTE-V2X based on a 3GPP long-term evolution (LTE) standard has a remarkable improvement in communication performance, application range and communication service quality (Quality of Service, qoS) requirements.
However, in practical applications, LTE-V2X networks may face problems of transmission delay, capacity limitation, and message loss due to high vehicle density and limited communication resources. Particularly in emergency situations, such as emergency braking or traffic accident pre-warning, it is important to transmit critical information in time.
The existing LTE-V2X message transmission strategy is mainly based on a fixed scheduling algorithm, and cannot meet the priority requirements of different messages. The existing strategy can not fully utilize LTE-V2X network resources and can not conduct differentiated processing and preferential transmission on different types of messages. Therefore, a new message transmission strategy is needed, which can dynamically allocate resources according to the importance and the emergency degree of the message, and improve the transmission reliability and the real-time performance of the key information.
First, since communication demands between vehicles are various, different types of communication messages have different demands for communication delay and reliability. For example, emergency notification messages need to be transmitted quickly and ensure timely arrival, whereas ordinary traffic information is less critical. The existing LTE-V2X protocol stack has unified processing modes for different types of messages, and cannot meet the packet priority requirements of different messages, so that the communication efficiency is low.
Secondly, there are certain channel contention and collision problems in LTE-V2X communications. When a plurality of vehicles simultaneously transmit messages, the message transmission collision and collision can be caused due to the limited channel resources, thereby affecting the reliability and throughput of communication. The current LTE-V2X protocol stack has limited capability of scheduling and conflict processing of messages, and cannot effectively solve the problem of channel competition.
In a word, the LTE-V2X message transmission strategy based on the packet priority can solve the bottleneck problem in LTE-V2X network transmission, and improve the transmission efficiency and reliability of key information. This will bring important driving forces for the development of intelligent transportation systems and the implementation of vehicle autopilot technology.
Disclosure of Invention
Aiming at the defects of the packet priority and the channel competition of the communication message, the invention provides a message transmission method facing to the LTE-V2X packet priority, as shown in figure 5, which specifically comprises the following steps:
setting message classification and packet priority, and setting a threshold value of a channel resource duty ratio CRB according to the packet priority;
judging that the node buffer area is full, and discarding the subsequent data packet if the node buffer area is full;
calculating the channel resource utilization rate threshold value according to the threshold value of the channel resource duty ratio CRB of the current node and the users in the current user communication range;
acquiring the channel resource utilization rate of the node, and if the channel resource utilization rate of the current node is smaller than the channel resource utilization rate threshold value, continuing to transmit according to the current state;
and if the channel resource utilization rate of the current node is greater than or equal to the channel resource utilization rate threshold value, sorting the data packets according to the priority, preferentially transmitting the data packets with high priority and discarding the data packets with low priority.
Further, message classification and packet priority are set, that is, a class and priority are set for each type of message, and the messages are subdivided into a plurality of groups according to the emergency degree of the messages, and the priorities of the groups have the same priority weight.
Further, for the priority weight of each packet priority, the priority weight varies with the channel resource ratio of the current node, wherein the packet with high priority increases with the channel resource ratio of the current node, and the packet with low priority decreases with the channel resource ratio of the current node.
Further, setting the weight of the priority packet of each packet includes the steps of:
if the message is divided into three priority packets according to priority, i.e., p= { P 0 ,P 1 ,P 2 Setting two channel resource occupation ratio thresholds X1% and X2% for the current node;
if the channel resource ratio of the current node is greater than X1%, setting the priority weight of the priority packet as follows: { omega 0 ,ω 1 ,ω 2 }＝{0.9,0.09,0.01}；
If the channel resource ratio of the current node is less than or equal to X1% and greater than X2%, setting the priority weight of the priority packet as: { omega 0 ,ω 1 ,ω 2 }＝{0.6,0.39,0.01}；
If the channel resource duty ratio of the current node is less than or equal to X2%, setting the priority weight of the priority packet as follows: { omega 0 ,ω 1 ,ω 2 }＝{0.5,0.33,0.17}；
Where P represents the priority grouping of user messages, P i Representing the ith user priority packet, i e {1,2,3}; omega i Representing the priority weight of the ith user priority packet.
Further, each priority packet includes a plurality of priorities, each priority packet is provided with a channel resource utilization threshold, and when the channel resource utilization corresponding to the current priority packet is greater than or equal to the channel resource utilization condition of the packet, the data packet with high priority in the packet is preferentially sent.
Further, if there are m priority packets in total, the channel resource utilization condition of each priority packet is:
wherein,representing the m-1 th priority packet P m-1 Channel resource utilization threshold of (c).
Further, the ith bestFirst order packet P i The channel resource utilization threshold of (2) is expressed as:
wherein,for the ith priority packet P i A channel resource duty cycle threshold of (2); n represents the number of vehicles communicable within the current vehicle communication range.
Further, whether the current node is congested is judged according to the channel resource utilization rate, namely, a channel resource utilization rate threshold is set, and when the channel resource utilization rate of the current node exceeds the threshold, congestion is judged.
Further, the process of judging whether the current node is congested includes: acquiring time interval deltat of packet arrival in And packet service time delta T out When DeltaT out /ΔT in Congestion occurs when the traffic is more than or equal to 1.
Compared with the prior art, the invention has the following advantages and positive effects:
1. communication efficiency is improved: by introducing a packet priority message transmission mechanism and protocol stack optimization, the invention can carry out differentiation processing according to the importance and the urgency of the communication message, thereby realizing more efficient communication transmission. The key message can be transmitted quickly and responded in time, so that the communication efficiency and the instantaneity are improved.
2. And the communication reliability is improved: the protocol stack communication method and the device reasonably allocate channel resources and reduce message collision and collision through an intelligent scheduling algorithm and a collision processing mechanism, thereby improving the reliability of communication, effectively solving the problem of channel competition in the existing LTE-V2X communication and providing a more stable and reliable communication environment.
3. Support packet priority: the invention introduces a packet priority message transmission mechanism, and can set different packet priorities according to different types of communication messages, so that a communication system can flexibly schedule according to urgency and importance of different messages, ensure the priority transmission of key messages and improve the priority management capability of communication.
4. System adaptability is enhanced: the communication device provided by the invention is optimized by hardware, and is better suitable for special requirements of LTE-V2X communication. The optimized hardware design enables the communication device to provide higher performance and reliability, adapting to complex communication environments and diversified communication requirements.
5. Promote the development of the internet of vehicles: as an improved LTE-V2X communication method and device, the invention is helpful to promote the development of the Internet of vehicles technology and the construction of an intelligent traffic system. By improving communication efficiency, reliability and priority management capability, the invention provides a more reliable basis for efficient communication between vehicles and intelligent traffic applications.
In conclusion, compared with the prior art, the method has obvious advantages and positive effects, can improve the efficiency, reliability and adaptability of LTE-V2X communication, and makes positive contribution to the development of the field of Internet of vehicles.
Drawings
Fig. 1 is a schematic diagram of a protocol stack with LTE-V2X packet priority message transmission according to the present invention;
fig. 2 is a flow chart of a congestion control and flow control transmission strategy based on packet priority in accordance with the present invention;
fig. 3 is a schematic flow chart of a congestion control policy based on priority in the present invention;
FIG. 4 is a schematic diagram of node traffic transmission according to the present invention;
fig. 5 is a flowchart of a message transmission method for LTE-V2X packet priority according to the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention provides a message transmission method facing LTE-V2X packet priority, as shown in figure 3, which specifically comprises the following steps:
setting message classification and packet priority, and setting a threshold value of a channel resource duty ratio CRB according to the packet priority;
judging that the node buffer area is full, and discarding the subsequent data packet if the node buffer area is full; if the node buffer area is not full, the input packet rate and the output packet rate are monitored;
calculating the channel resource utilization rate threshold value according to the threshold value of the channel resource duty ratio CRB of the current node and the users in the current user communication range;
calculating the channel resource utilization rate of the node according to the input packet rate and the output packet rate of the current node, and if the channel resource utilization rate of the current node is smaller than the channel resource utilization rate threshold value, continuing to transmit according to the current state;
and if the channel resource utilization rate of the current node is greater than or equal to the channel resource utilization rate threshold value, sorting the data packets according to the priority, preferentially transmitting the data packets with high priority and discarding the data packets with low priority.
In this embodiment, an LTE-V2X packet priority-oriented message transmission method is implemented based on an LTE-V2X communication protocol stack, as shown in fig. 1, where the protocol stack uses the idea of software layering, so as to achieve the purposes of being able to be transplanted and used on different V2X devices, and the LTE-V2X protocol stack is divided into an application layer, a network layer, and an LTE-V2X access layer according to the technical requirements of network layers of LTE-based internet of vehicles wireless communication technology.
The application layer in the LTE-V2X protocol stack is the uppermost layer of the protocol stack and mainly comprises a data encoding and decoding module and a message filling module, and in order to realize efficient data transmission and analysis, the application layer adopts an ASN.1 encoding and decoding technology, has better flexibility and higher standardization, can effectively encode and decode LTE-V2X messages, reserves an interface and can send a filled message set to a network layer.
The application layer in the LTE-V2X protocol stack comprises a user application part and a message layer part, wherein the message layer performs data interaction with the network layer through an API reserved by the network layer, and is mainly responsible for creating, filling and encoding the Internet of vehicles message set at a transmitting end; at the receiving end, the message layer decodes the received Internet of vehicles message set sent by other devices and analyzes the data, and the user application can finish the Internet of vehicles application operation of the user layer by acquiring the Internet of vehicles message set analyzed by the message layer.
The network layer in the LTE-V2X protocol stack includes a data sublayer and a management sublayer, specifically:
the data sub-layer of the network layer mainly comprises a DSMP data transmission module and a DSA data transmission module, wherein the DSMP data transmission module processes a filled message set sent by the received application layer, adds corresponding DSMP header information and sends the DSMP header information to the adaptation layer; the DSA data transmission module adds corresponding DSA header information and sends the DSA header information to the adaptation layer for processing, wherein the DSMP data flow is mainly at a sending end, the application layer initiates a DSM service request to the network layer, and the DSMP module processes the data and transmits the data to the access layer. At the receiving end, the access layer receives the DSM message, initiates a DME request, processes the DSM message at the network layer and then sends the DSM message to the application layer;
specifically, at the transmitting end, the application layer firstly initiates a DSM request to the network layer, the prepared internet of vehicles message set is transmitted to the network layer through the network layer interface, after the data transmission part of the network layer receives the request, the message set is further processed, and a corresponding message header is attached, wherein the specific content of the message header accords with the specification of the internet of vehicles DSMP protocol and mainly comprises information such as version, extension domain, application identifier, data length and the like. After encapsulation is completed, DSMP initiates an adaptation layer request to an adaptation layer, the adaptation layer adds a frame header containing classification information to the DSM frame, and finally, the adaptation layer sends an access layer request to an access layer, and the DSM frame is sent to the access layer through an interface exposed by the access layer. The data sublayer part determines a transmission specification for a protocol stack by packaging the data treasures, and under the specification, the equipment of different manufacturers can realize cross-equipment and cross-platform data intercommunication as long as the equipment can meet the unified data packaging standard;
the management sub-layer comprises an application registration module, a service management module, an MIB information maintenance module and a service announcement module, wherein:
the application registration module is used for providing an application registration function and is provided with a corresponding data management table MIB, any application needing to use a management sub-layer DME management entity is registered at the DME, and corresponding registration information is stored in the MIB table, so that the DME can send the received DSM to the corresponding application;
the service management module is mainly used for managing service requests of a provider, service requests of a user and service requests of a short message, and when the DME receives the service requests of different types, different action types are adopted, namely three action types of adding, updating and deleting, in particular:
a) When a service request with the action type of 'increasing' is received, corresponding service information is increased in the MIB;
b) When a service request with the action type of update is received, updating corresponding service information in the MIB;
c) When a service request with the action type of 'delete' is received, deleting the corresponding service information in the MIB;
the MIB information maintenance module is mainly used for maintaining protocol stack application configuration and state information, and DME can set or inquire MIB information through specified signaling; the DME sets and inquires MIB information through a designated signaling, and when the DME receives a service request message, an MIB information table corresponding to the service is established in the MIB, wherein the information table comprises application configuration and state information, and the transmission environment configuration of service data is based on the state information; in the MIB table, four types of data items are divided, respectively: the local information table, the short message service request table, the provider service request table and the user service request table respectively correspond to the management and maintenance of protocol stack local information, short message service information and business announcement service information, and the table records necessary information in service requests supported by DME (digital media to be used) on upper layer applications;
the service announcement module is mainly used for processing special service announcement (Dedicated Service Advertisement, DSA) messages, and is mainly implemented by setting a corresponding identification code AID as a value corresponding to the DSA, and carrying out data stream transmission, namely broadcasting optional service information to a vehicle user by the special service announcement DSA of the Internet of vehicles based on LTE, judging whether the broadcast announcement has interesting contents or not after the vehicle user receives the DSA, and if so, accessing a service channel SCH and a service provider to carry out information downloading of a large amount of data according to channel parameter information carried by the DSA;
specifically, in service announcement service management, there are two roles, namely a Provider (Provider) and a User (User), the Provider is generally acted by an RSU or other roadside facilities and is responsible for broadcasting optional service information to road participants (such as vehicles and the like), vehicle equipment wants to receive the optional service information, registering the optional service information to the DME as a User, informing the DME of own interested content types, screening the received DSA by the DME according to the content types, and after finding out matched DSA, completing operations of analyzing DSA carried data, informing upper-layer applications, accessing corresponding service channels to complete data exchange and the like by the DME; the frame may contain a plurality of application information, the number of application information in the frame being represented by an application information count field, the application information carrying information of the optional application service, the optional application service being distinguished by an application identification field.
As an alternative embodiment, the network layer may generally further include a setting module and a connection request module, where:
the setting module is used for setting an intermediate layer at the joint between the network layer and the application layer as a service end and setting the network layer as a client;
and the service primitive module is used for initiating a connection request to the middle layer through the application layer so as to realize internal data transmission.
The LTE-V2X access layer is a physical bottom layer, in this embodiment, an emerging V2X communication module ZM8350 and an enzhi core board IMX6Q are used as hardware components, and the communication module provides an interface function for CBR acquisition, and can acquire the CBR value at this time by directly calling an interface. The protocol stack is built according to a protocol stack architecture given in T/ITS 0108-2019 technical requirement of network layer of wireless communication technology of Internet of vehicles based on LTE, and consists of an application layer, a network layer and an access layer, wherein the layers are independently packaged and necessary interfaces are exposed.
The data flow of the LTE-V2X protocol stack can be analyzed from a transmitting end and a receiving end, at the transmitting end, a vehicle sensor acquisition system sends acquired information into an application layer, processes the data at the application layer, creates a vehicle networking message set through operations such as creating a message frame, filling the message frame, coding and the like, sends the message set into a network layer through a network layer reserved interface to package the message frame, sends the message frame into an access layer through an access layer interface after the package is completed, packages the data frame, and sends the message set through an air interface; at the receiving end, the access layer needs to strip the MAC layer frame head of the data frame after receiving the data frame through the air interface, then sends the data frame into the network layer through the access layer interface, carries out screening treatment on the network layer, sends the data frame into the application layer through the network layer interface, and sends the data frame to the upper application entity after decoding and treatment on the data. In the protocol stack, the layers are all in modularized design, each layer is independently packaged after development, and only necessary interfaces (APIs) are exposed to interact information with other layers or other modules.
Based on the protocol stack, the invention provides a message transmission method oriented to LTE-V2X packet priority, which optimizes the communication quality of vehicle-to-vehicle communication by combining congestion control based on the packet priority and flow control based on a vehicle transmission node.
The invention classifies the packet priority according to the specific application scene of the Internet of vehicles message, and provides a congestion control algorithm based on the packet priority, and the congestion control process is described in the embodiment.
In the resource pool, the Priority of the data Packet is mapped into a PPPP (ProSe Per-Packet Priority) value, one data Packet corresponds to one PPPP, the PPPP is set to be a value of 0-7, the PPPP is used as a Priority level for transmission in advance, a grouping Priority classification method based on the emergency degree and the importance of the message is introduced, and the message is classified into different Priority groups according to the attribute and the associated information of the message, so that the key information can be processed and transmitted preferentially.
Firstly, the message used for emergency and major safety accidents in the internet of vehicles is set as a PPP0-PPP2 level message, and the message transmission has the shortest acceptable time delay, and is generally sent by an emergency vehicle (medical care vehicle, police car, etc.) or generated by an emergency situation (such as emergency brake, overtaking warning, etc.) of the vehicle, specifically including:
PPP0 level message, the highest priority of the message is generally the time-limited periodic message time in the emergency message in the Internet of vehicles, such as collision risk warning, intersection collision warning and the like;
PPP level 1 message: setting the broadcast event of the overrun state as a PPP1 level message, such as overtaking warning, head collision warning and the like;
PPP level 2 message: the messages mainly comprise messages for ensuring road safety through cooperation among vehicles, such as lane changing assistance, cooperation merging assistance and the like;
secondly, the safety information broadcast by vehicles related to traffic safety in the Internet of vehicles is defined as PPP3-PPP4 level information, the safety information is used for improving the traffic condition of roads, and timely verification of the safety information can predict and plan safety traffic in advance, and the safety information comprises the following specific steps:
PPP3 level message, namely, a periodic permanent broadcast message which assists a driver to manage the speed of the vehicle through periodic broadcast and helps smooth running is defined as PPP3, such as supervision speed limit notification, green team optimal speed consultation and the like;
PPP4 level messages locating collaboration awareness messages that can manage vehicle navigation through V2V/V2I collaboration as PPP4 level messages, e.g., collaborative adaptive cruise control class messages, collaborative vehicle highway automation system classes;
finally, messages of entertainment and service type in the Internet of vehicles are defined as PPP6-7 level messages, the messages are related to the user's entertainment experience, the delay tolerance of the messages is long, and the traffic safety of the Internet of vehicles is not affected by a small amount of lost message packets, so that serious safety accidents are caused. Entertainment and service type information in the Internet of vehicles is also randomly generated, and specifically comprises the following steps:
PPP6, namely setting related contents such as vehicle software/data supply and update related to the vehicle, related media downloading and the like as PPP6;
PPP7, according to the user's network connection demand, setting some interest point notification messages with advertisement demand and ITS local e-business messages as PPP 7-level messages;
the above is only one scheme for dividing the priority of the message according to the present invention, and those skilled in the art may also divide the priority of the message according to actual needs.
After the LTE-V2X message is set according to the above classification, only the classification of the service layer is performed, and in order to schedule radio resources, the channel quality on each resource block needs to be considered to facilitate the description of such classification, in this embodiment, the priority is further classified into three classes (those skilled in the art may also divide PPP0-PPP7 into multiple packets according to actual needs), the PPP0-PPP3 class message is divided into more urgent P0 class message, the periodic new road auxiliary message is divided into P1 class message, and the entertainment message is divided into P2 class message. And describes the channel quality according to two indexes of the channel resource duty ratio CBR and the channel resource utilization ratio CR given by 3GPP Release14 for congestion control.
CBR is defined in 3gpp release14 as the ratio of the number of subframes with RSSI values exceeding a preset threshold to the total number of subframes in the past 100 subframes of the transmitting vehicle, typically using-107 dBm/RB as this preset threshold; CR is defined as the ratio of the number of sub-channels occupied by a transmitting vehicle during 1000 sub-frames, where CBR can be used for control and data transmission, which can be obtained in real time by the aforementioned protocol stack. In the transmission process of the embodiment, different CBR threshold CBR values are set for the packets with different priorities limit And corresponds to different channel resource utilization thresholds CR limit Congestion control can be performed by adjusting transmission parameters or VUE transmitting power, and CR < CR is ensured limit 。
Vehicle User Equipment (VUE) can pass a threshold CBR of CBR limit Dividing by the number of stations or users present in the communication range to calculate CR limit The method specifically comprises the following steps:
wherein N is sta F (CBR) is an association function representing the number of users within communication range.
The specific user packet priority is configured by the above-mentioned F (CBR). VUE controls packet transmission by priority, i.e. for p= { P as described above 0 ,P 1 ,P 2 The internet of vehicles message priority grouping of }, the following CBR threshold may be givenIs->And is configured as F 0 (CBR)、F 1 (CBR) and F 2 (CBR)。
For priority-based transmission procedures, using a single threshold for CBR independent of transmission priority may not allow higher priority transmissions to be preferred over lower priority transmissions. For example, when the channel resource utilization CR exceeds some set threshold of 50%, then the VUE may not transmit data of lower priority packets first. In the above process, we will P 0 Set to the highest priority, P 1 Next, P 2 For the lowest priority, there is the following expression:
and according to the relation between CBR and CR, there are:
when P= { P is sent 0 ,P 1 ,P 2 When packet data packets are packet data packets, VUE should ensure that packets with p=2 are addressed toVUE should ensure +_ for packets with p=1>VUE should ensure +_ for packets with p=0>
As described above, the VUE can assign different weights to different priority packets, with the weight of each priorityMay define a packet P with priority to be sent i Is a part of the same. If the set of priorities that VUE can send is p= { P 0 ,P 1 ,…P p-1 Normalized weights based on this are:
the normalized weight sum is equal to 1 in the set P; the weight for a priority is also based on CBR values, e.g., the weight portion assigned to a higher priority may increase as CBR increases, and similarly the weight portion assigned to a lower priority may increase as CBR decreases. In particular, the three priority packets for LTE-V2X messages described above, for CBR>At X1 { ω } 0 ,ω 1 ,ω 2 = } {0.9,0; and for x2%<CBR<At X1%, the weight may be { ω } 0 ,ω 1 ,ω 2 } = {0.6,0.39,0.01}; for CBR>At X2%, the weight may be { ω } 0 ,ω 1 ,ω 2 The lower priority queues may be made to clear more slowly = {0.5,0.33,0.17}Null, avoiding not sending packets with lower priority at all.
In summary, the flow of the congestion control algorithm based on priority is as follows:
firstly, classifying and grouping priority according to the information of the Internet of vehicles;
secondly, setting corresponding CBR thresholds for different priority groups according to the priority groups;
then, according to CR and CR limit Is determined whether congestion control is required, if CR < CR at this time limit I.e. the transmission state is good, the current weight is kept for transmission, if CR > CR limit That is, when congestion occurs, it is necessary to process a message with a high priority first, and modify the transmission authority of the priority packet according to the real-time CBR value for transmission.
Because the transmission amount of the internet of vehicles information is larger, the buffer area of the transmission node overflows along with the accumulation of time, so that the data packet is lost, and the queuing delay is increased. Therefore, the present embodiment considers that congestion control is not only performed based on packet priority, but also node control based on vehicle communication is added according to the initial priority and the congestion condition at that time, and further optimizes the communication quality of LTE-V2X. First, it is considered to determine when the transmission node overflows the buffer and congestion occurs, and monitor the transmission quality of the transmission node at all times. And judging whether flow control and congestion control of message transmission are needed according to the condition of the transmission node at the moment.
In this embodiment, it may be assumed that the total buffer size of the transmitting node is Q, and the number of packets in the current buffer is Q, where there are two cases, i.e., q=q, where the node is already fully congested and the subsequent incoming packets will be discarded.
When Q is not equal to Q, the transmission node is not congested by monitoring the incoming packet rate R in And output packet rate R out To determine the transmission quality at that time. If the node is judged to still have the congestion condition, adopting a priority algorithm to transmit, judging the priority of message transmission again, and discarding the data packet with low priority according to the judging result. If it isThe transmission quality is good at this time, i.e. sequential transmission at this time is maintained. The present embodiment uses end-to-end control to perform accurate rate adjustment for each transmission node, simplifying the design of intermediate nodes, which requires a high degree of Round Trip Time (RTT). According to the internet of vehicles network layer transmission layer protocol, packet scheduling rate and service rate can be put in the packet header, the sending end and the receiving end of the transmission node can obtain congestion notification messages, and when C (t) =1 of the receiving end of the transmission node, a message transmission strategy based on priority is triggered. The transmission path is subjected to rate adjustment, the output rate of the node is controlled by adjusting the scheduling rate, and according to fig. 2, it can be seen that the transmission traffic received by the transmission node and the source transmission traffic thereof are aggregated by the network layer, and the total traffic is transmitted into the LTE-V2X access layer, and at this time, how to perform traffic control on the transmission process can be determined by the relation between the total transmission traffic and the forwarding rate of the LTE-V2X access layer. Due to the transmission of trafficApproximately equal to->When total input flow->Is greater than the forwarding rate of the data packet>When the transmission is blocked, the transmission node can be internally provided with a transmission blocking state, and the data packet can be queued in an LTE-V2X access layer, so that the flow control is required; when total input flow->Less than the forwarding rate of the data packet->Output packet rate +.>Approximately equal to the total input flowAt this time, no flow control is needed, and the source rate can be changed by changing the sampling frequency, so that the transmission rate is adjusted to achieve the effect of relieving congestion. Wherein the total input flow->Expressed as:
wherein,calling through the bottom communication module>Locally generated. But->Mainly influenced by the number of sensor nodes and the traffic density thereof. After the output flow and the input flow are obtained, the output packet rate and the input packet rate can be calculated according to the output flow and the input flow, so as to obtain the congestion determination parameter C (t). As in fig. 4, by inputting packet rate R in And output packet rate R out To monitor the quality of the transmission at that time. R is R in Can be described as DeltaT in The inverse of the output packet rate R out Can be described as DeltaT out Is the inverse of (c).
R in ＝1/ΔT in
R out ＝1/T out
Wherein DeltaT in Indicating the time interval between packet arrivals, i.e., the time interval during which two consecutive packets are received by the MAC layer of the node. Delta T out Indicating the packet service time. The packet service time refers to the time interval between the arrival time of a packet at the MAC layer and the last successful transmission, at this time, we can also define a congestion metric parameter C (t) to represent the congestion at the present moment, and send congestion information along with the sending rate back to the sender according to the channel condition, where the sender selects the rate to send a limited number of data packets according to the feedback information.
C(t)＝ΔT out /ΔT in
C (t) is defined as the ratio between the average packet service time and the average packet arrival time interval of the transmitting node. When C (t) > 1, the node is congested, otherwise, when C (t) < 1, no congestion occurs. Every time there is N P When 50 data packets arrive, the input flow and output flow are updated periodically to update delta T in 、ΔT out 。
Thus, the real-time data packet service time DeltaT can be used out And packet arrival time interval delta T in Judging whether the congestion condition exists at present, if the congestion condition exists, performing congestion control based on the packet priority, and if the transmission condition is good, continuing to perform the current service priority order transmission.
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims (9)

1. The message transmission method for the LTE-V2X packet priority is characterized by comprising the following steps of:
setting message classification and packet priority, and setting a threshold value of a channel resource duty ratio CRB according to the packet priority;
judging that the node buffer area is full, and discarding the subsequent data packet if the node buffer area is full;
judging whether the current node is congested, if so, judging the transmission weight of the data of each priority according to the channel resource occupation ratio CRB of the current node;
if not, forwarding the messages in turn according to the priority of the messages.
2. The message transmission method for LTE-V2X packet priority according to claim 1, wherein the message classification and packet priority are set, i.e. a class and priority are set for each type of message, and the messages are subdivided into a plurality of groups according to the urgency of the message, and the priorities of each group have the same priority weight.
3. The message transmission method for LTE-V2X packet priority according to claim 2, wherein for each packet priority, the priority weight varies with the channel resource ratio of the current node, wherein the packet with higher priority increases with the channel resource ratio of the current node, and the packet with lower priority decreases with the channel resource ratio of the current node.
4. The message transmission method for LTE-V2X packet priority according to claim 2, wherein setting the weight of the priority packet of each packet comprises the steps of:
if the message is divided into three priority packets according to priority, i.e., p= { P 0 ,P 1 ,P 2 Setting two channel resource occupation ratio thresholds X1% and X2% for the current node;
if the channel resource ratio of the current node is greater than X1%, setting the priority weight of the priority packet as follows: { omega 0 ,ω 1 ,ω 2 }＝{0.9,0.09,0.01}；
If the channel resource ratio of the current node is less than or equal to X1% and greater than X2%, setting the priority weight of the priority packet as: { omega 0 ,ω 1 ,ω 2 }＝{0.6,0.39,0.01}；
If the channel resource duty ratio of the current node is less than or equal to X2%, setting the priority weight of the priority packet as follows: { omega 0 ,ω 1 ,ω 2 }＝{0.5,0.33,0.17}；
Where P represents the priority grouping of user messages, P i Representing the ith user priority packet, i e {1,2,3}; omega i Representing the priority weight of the ith user priority packet.
5. The message transmission method for LTE-V2X packet priority according to claim 2, wherein each priority packet includes a plurality of priorities, each priority packet is provided with a channel resource utilization threshold, and when the channel resource utilization corresponding to the current priority packet is greater than or equal to the channel resource utilization condition of the packet, the packet with the higher priority is preferentially transmitted.
6. The message transmission method for LTE-V2X packet priority according to claim 5, wherein if there are m priority packets in total, the channel resource utilization condition of each priority packet is:
wherein,representing the m-1 th priority packet P m-1 Channel resource utilization threshold of (c).
7. The message transmission method for LTE-V2X packet priority as claimed in claim 5, which isCharacterized in that the ith priority packet P i The channel resource utilization threshold of (2) is expressed as:
wherein,for the ith priority packet P i A channel resource duty cycle threshold of (2); n represents the number of vehicles communicable within the current vehicle communication range.
8. The message transmission method for LTE-V2X packet priority according to claim 1, wherein whether the current node is congested is determined according to a channel resource utilization, i.e. a channel resource utilization threshold is set, and congestion is determined when the channel resource utilization of the current node exceeds the threshold.
9. The message transmission method for LTE-V2X packet priority according to claim 1, wherein the process of determining whether congestion occurs in the current node comprises: acquiring time interval deltat of packet arrival in And packet service time delta T out When DeltaT out /ΔT in Congestion occurs when the traffic is more than or equal to 1.
CN202311086199.XA 2023-08-25 2023-08-25 Message transmission method for LTE-V2X packet priority Pending CN117119522A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117962835A (en) * 2024-03-29 2024-05-03 长春深蓝智造电子产品有限公司 Automobile electronic stability control system and method

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117962835A (en) * 2024-03-29 2024-05-03 长春深蓝智造电子产品有限公司 Automobile electronic stability control system and method

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