新空口车联网（New Radio-Vehicle to Everything, NR-V2X）已经成为实现未来智慧交通系统的关键技术。《国家车联网联产业标准体系建设指南（智能网联汽车）》提到从信息通信、交通运输、交通领域创新等多个角度将车联网纳入新基建、智慧交通、智慧城市的重要范畴，加快建设汽车强国。NR-V2X构建了“人-车-路-云”智能交通领域数据的互联互通系统，将在增强驾驶安全、降低事故发生率、节能减排、提高交通效率等方面发挥重要作用。然而，这也对可靠性、端到端时延等方面提出了更严苛的要求，是未来车联网业务所关注的通信痛点。

未来NR-V2X系统存在挑战包括：（1）由于复杂的交通环境与车辆移动性，车辆网络状态在时间与空间上具有动态性，致使系统机动性强，数据通信稳定性差；（2）随着车载通信设备指数性增长，日益稀缺的频谱资源极易造成车辆间复杂的通信干扰问题和网络拥塞，影响车辆关键信息的即时交付；（3）车联网存在广泛的数据业务，如车载多媒体娱乐、视频会议、安全信息传递、高精度地图下载，不同车辆通信类型服务质量（Quality of Service, QoS）需求差异化大，很难同时满足可靠性、时延、吞吐量等方面不同的需求。因此，对NR-V2X系统中低时延高可靠的资源分配方案的研究具有非常重要的理论意义和广泛的应用前景。本论文的主要内容为：

首先，研究了车辆对车辆（vehicle to vehicle, V2V）多播通信最小-最大译码错误率资源分配方案，旨在最小化多播组最大译码错误率，确保车辆安全信息准确及时的传输。本方案通过坐标下降法将复杂混合整数非凸优化问题解耦为连续码长优化和功率优化子问题，进而利用最优化方法将子问题转化为凸优化问题，交替求解。最后，将连续码长转换为整数，得到最优多播译码错误率。仿真结果展现了数据量、码长、最大发射功率、能耗、多播接收端数量及车辆速度对V2V多播译码错误率的影响。与对比方案相比，本方案更加接近全局最优解且多播可靠性总高于99.9%，对NR-V2X多播技术增强的实现具有一定意义。

其次，研究了NR-V2X系统长期稳定资源分配，设计了一种长期双尺度资源分配方案，旨在保障车联网中V2V和V2I车辆用户QoS，提高车联网频谱利用率和网络稳定性。本方案通过多播分组策略，减少因车辆高速移动性造成的通信开销。通过信息年龄与信干噪比概率约束确保低时延高可靠通信，且对系统资源块、各车辆用户发射功率进行资源分配，降低各用户间信息干扰，提高频谱资源利用率。通过仿真实验验证了该方案理论分析的正确性，与对比方案相比，本方案在系统V2I平均总吞吐量与V2V时延上有一定的优越性，可通过调控控制参数V权衡V2I最优平均总吞吐量和队列稳定，且同时满足V2V组内端到端毫秒级通信与高达99.99%的链路可靠性，在一定程度上有助于未来NR-V2X网络长期稳定。

New radio-vehicle to everything (NR-V2X) has become a key technology to achieve future intelligent transportation systems. The National Connected Vehicle Industry Standard System Construction Guidelines (Intelligent Connected Vehicles) mentioned that the Internet of vehicles has been included into the important category of new infrastructure, smart transportation and smart city from the perspectives of transportation, information communication and innovation in the field of transportation, accelerating the construction of an automobile power. NR-V2X supports the interconnection of data in the transportation field of "person-vehicle-road-cloud". It will play an important role in enhancing driving safety, reducing accident rates, saving energy and reducing emissions, and improving transportation efficiency. However, this also poses more stringent requirements on reliability, end-to-end latency, and other aspects, which is a communication pain point that future connected vehicle services are concerned about.

 

Challenges for future NR-V2X systems include: (1) Complex traffic environment and vehicle mobility. The state of vehicle network is dynamic in time and space, which may result in strong system maneuverability and poor data communication stability. (2) Exponential growth of vehicle-mounted communication equipment. The scarce spectrum resources easily cause complex interference problems and network congestion. This affects the immediate delivery of critical vehicle information. (3) Extensive data services in the Internet of Vehicles, such as vehicle multimedia entertainment, video conferencing, security information transmission, high-precision map download. The demand for quality of service (QoS) varies greatly among different vehicle communication types. It is difficult to meet the different requirements in terms of reliability, delay, throughput, etc. Therefore, it is of great theoretical significance and application prospect to study the resource allocation scheme with low delay and high reliability in NR-V2X system. The main content of this paper is as follows.

 

Firstly, the minimum-maximum decoding error resource allocation scheme of vehicle-to-vehicle (V2V) multicast communication is studied, in order to minimize the maximum decoding error rate of multicast groups and ensure the accurate and timely transmission of vehicle safety information. In this scheme, the complex mixed-integer non-convex optimization problem is decoupled into continuous block length optimization and power allocation subproblems by using the coordinate descent method. Then the optimization method is used to transform the subproblems into convex optimization problems solved alternately. Finally, the block length is converted to the integer variable, and the corresponding optimal solution is derived. The simulation results show the effects of data size, block length, maximum transmitting power, energy consumption, number of receivers, and vehicle speed on the error rate of V2V multicast decoding. Compared with the comparison schemes, this scheme is closer to the global optimal solution and the multicast reliability is generally higher than 99.9%，that has the advantages and certain significance for the enhancement of NR-V2X multicast technology.

 

Secondly, the long-term stable resource allocation scheme of NR-V2X system is studied. It is a long-term dual-scale resource allocation scheme. It guarantees the QoS of different communication types of vehicles in the Internet of vehicles and improves the spectrum utilization rate and network stability. This scheme uses a multicast clustering strategy to reduce communication overhead caused by high-speed vehicle mobility. It realizes high reliability and low delay communications by age of information and signal to interference plus noise ratio probability constraints. Then allocated block length, transmission power, and information interference can be reduced with the enhanced spectrum resource utilization. The correctness of the theoretical analysis of the scheme is verified by the simulation experiment. Compared with the existing scheme, the proposal has great advantages in the average total throughput and delay of the system. The trade-off between optimal average total throughput and queue stability is realized by adjusting parameter V, which can achieve 99.99% reliability and millisecond level end-to-end latency within V2V groups. To a certain extent, this will contribute to long-term stability of future NR-V2X network deployment.

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