The emerging road safety and autonomous vehicle applications require timely and reliable data delivery between vehicles and between vehicles and infrastructure. To satisfy this demand, 3GPP develops a 5G Vehicle-to-Everything (V2X) technology. Depending on the served traffic type, 5G V2X specifications propose two channel access methods: (i) Mode 1, according to which a base station allocates resources to users, and (ii) Mode 2, according to which users autonomously select resources for their transmissions. In the paper, we consider a scenario with sporadic traffic, e.g., a vehicle generates a packet at a random time moment when it detects a dangerous situation, which imposes strict requirements on delay and reliability. To satisfy strict delay requirements, vehicles use Mode 2. We analyze the performance of Mode 2 for sporadic traffic and propose several approaches to improve it. Simulation results show that the proposed approaches can increase the system capacity by up to 40% with a low impact on complexity.

翻译：新兴的道路安全与自动驾驶应用要求车辆之间以及车辆与基础设施之间实现及时可靠的数据传输。为满足这一需求，3GPP开发了5G车联网（V2X）技术。根据所服务的交通类型，5G V2X规范提出了两种信道接入方法：（i）模式1：基站为用户分配资源；（ii）模式2：用户自主选择传输资源。本文研究偶发交通场景（例如车辆在检测到危险状况时随机生成数据包），该场景对时延和可靠性提出严苛要求。为满足严格的时延要求，车辆采用模式2。我们分析了模式2在偶发交通场景下的性能，并提出多种改进方案。仿真结果表明，所提方案能在对复杂度影响较低的情况下，将系统容量提升最高达40%。