Internet of vehicles (IoV) has emerged as a key technology to realize real-time vehicular application. For IoV, vehicles adopt cellular vehicle-to-everything (C-V2X) standard to support direct communication among them. C-V2X mode 4 controls resource allocation without the assistance of cellular network, hence it is widely used for IoV. However, C-V2X mode 4 has two drawbacks. First is that vehicles cannot communicate with each other for a period in some case which will cause an increase in age of information (AoI); second is that vehicles may select resource already occupied by others which will deteriorate the reliability. To address the two drawbacks, we propose an enhanced C-V2X mode 4 to optimize AoI and reliability. In addition, we consider the fact that for most vehicular applications, each vehicle periodically requires fresh information of vehicles within a certain distance and propose a new performance metric to evaluate the system AoI for IoV. Furthermore, we construct a platform through integrating SUMO and NS3. We demonstrate the superiority of the enhanced C-V2X mode 4 base on this simulation platform.

翻译：车联网（IoV）已成为实现实时车载应用的关键技术。在车联网中，车辆采用蜂窝车联网（C-V2X）标准支持彼此间的直接通信。C-V2X模式4无需蜂窝网络辅助即可控制资源分配，因此被广泛应用于车联网。然而，C-V2X模式4存在两个缺陷：其一，某些情况下车辆之间会在一定时间内无法通信，导致信息时效性（AoI）增加；其二，车辆可能选择已被其他车辆占用的资源，从而降低可靠性。为解决这两个缺陷，我们提出一种增强型C-V2X模式4，以优化信息时效性与可靠性。此外，考虑到大多数车载应用中，每辆车周期性需要特定距离范围内其他车辆的新鲜信息，我们提出一种评估车联网系统信息时效性的新性能指标。进一步地，我们通过集成SUMO与NS3构建仿真平台，并基于该平台验证了增强型C-V2X模式4的优越性。