为探究信息包大小对无人配送车通信性能的影响，确保其在复杂城市交通环境中的可靠通信与安全运行，构建基于OMNeT++、SUMO 和 Veins 框架并集成 SimuLTE 协议的联合仿真环境。设定无人配送车与机动车平均速度分别为10 km/h和40 km/h，以模拟真实城市交通条件；在高网络渗透率（100%）与低网络渗透率（20%）且仅包含无人配送车与网联车辆的理想化实验环境下，采用25字节与50字节两种信息包大小，利用基础场景及对照实验系统评估无人配送车通信性能。研究结果表明，在低网络渗透率条件下，减小路侧单元（RSU）信息包大小会显著提升丢包率，其中最大丢包率从0.840%提升至14.747%，平均丢包率从0.013%升至0.055%，导致通信稳定性明显下降；而在高网络渗透率下，该调整对通信性能影响较小，最大丢包率仅略降至0.784%。相比之下，减小车载单元（OBU）信息包大小在高网络渗透率下导致的平均通信时延与平均丢包率变化均不足0.05%，说明影响有限；但在低网络渗透率下，最大丢包率增至7.231%，显示出对信道资源紧张情境较弱的适应性。总体而言，信息包大小对无人配送车通信性能的影响受网络渗透率调节显著，其中RSU配置对丢包率的影响更为明显，特别是在链路拥塞与调度压力较大时，RSU参数设计应作为通信优化的优先考虑因素。

To investigate the impact of packet size on the communication performance of unmanned delivery vehicles, and ensure their reliable communication and safe operation in complex urban traffic environments, a joint simulation environment was constructed based on the OMNeT++, SUMO, and Veins frameworks, integrated with the SimuLTE protocol. By setting the average speeds of unmanned delivery vehicles and motor vehicles to 10 km/h and 40 km/h respectively, real-world urban traffic conditions were simulated. In an idealized experimental environment with high network penetration rate (100%) and low network penetration rate (20%), which only includes unmanned delivery vehicles and connected vehicles, two packet sizes of 25 bytes and 50 bytes were used to evaluate the communication performance of unmanned delivery vehicles using basic scenarios and control experimental systems. The research results indicate that under low network penetration conditions, reducing the RSU packet size significantly increases the packet loss rate, with the maximum packet loss rate increasing from 0.840% to 14.747% and the average packet loss rate increasing from 0.013% to 0.055%, resulting in a noticeable decline in communication stability; under high network penetration, this adjustment has a relatively small impact on communication performance, with the maximum packet loss rate only slightly reducing to 0.784%. In contrast, the average communication delay and average packet loss rate change of reducing the OBU packet size under high network penetration rate are both less than 0.05%, indicating limited impact. However, at low network penetration rate, the maximum packet loss rate increases to 7.231%, indicating weak adaptability to channel resource constraints. Overall, the impact of packet size on the communication performance of unmanned delivery vehicles is significantly modulated by network penetration rate, with RSU configuration having a more pronounced effect on packet loss rate, especially under conditions of high link congestion and scheduling pressure. Therefore, RSU parameter design should be prioritized as a key consideration in communication optimization.