In our previous work, a request-transmission splitting slotted ALOHA-based (RTS-SA) scheme was proposed to improve access capacity of vehicles with a single infrastructure coordination. However, in a smart city with widely deployed micro base stations (mBSs) scenario, the implementation of the RTS-SA scheme suffers from some new inter-microcell interference problems. To address these problems, an enhanced RTS-SA (eRTS-SA) scheme is proposed, in which each vehicle reports both its request and location information to the mBS with the help of the global positioning system (GPS) and the mobile edge computing (MEC) in the contention access phase (CAP). To reduce the overhead, the road between two mBSs is divided into segments, and each vehicle utilizes the segment number (8 bits are good enough) to replace its location information. Aware of the locations of the detected vehicles, each mBS conducts the allocation by sorting these vehicles in ascending order in terms of the segment number and then allocates the time slots sequentially. This strategy ensures that the same time slot would be assigned to vehicles that are geographically far apart, thus minimizing the mutual interference between signals transmitted in the contention-free transmission phase (CTP). Finally, the duration of the broadcast feedback phase (BFP) is doubled and divided into two equal parts, which are assigned to two adjacent mBSs respectively to prevent interference. In the simulation, the throughput of eRTS-SA is verified to be only 4.8% lower than the theoretical maximum throughput. Compare to the RTS-SA and VeMAC schemes, eRTS-SA can also achieve about 44% and 154% throughput improvement.

在我们以前的工作中，提出了一种基于请求-传输拆分时隙的ALOHA（RTS-SA）方案，以通过单个基础结构协调来提高车辆的访问能力。但是，在具有广泛部署的微基站（mBS）场景的智能城市中，RTS-SA方案的实施会遇到一些新的微蜂窝间干扰问题。为了解决这些问题，提出了一种增强的RTS-SA（eRTS-SA）方案，其中，每辆车都借助全球定位系统（GPS）和移动边缘计算功能向mBS报告其请求和位置信息（ MEC）处于竞争访问阶段（CAP）。为了减少开销，将两个mBS之间的道路划分为多个路段，每辆车都利用路段号（8位足够好）替换其位置信息。意识到检测到的车辆的位置，每个mBS都会通过根据路段号以升序对这些车辆进行排序来进行分配，然后依次分配时隙。该策略确保将相同的时隙分配给地理上相距较远的车辆，从而最大程度地减少了在无竞争传输阶段（CTP）中传输的信号之间的相互干扰。最后，广播反馈阶段（BFP）的持续时间加倍并分为两个相等的部分，分别分配给两个相邻的mBS，以防止干扰。在仿真中，eRTS-SA的吞吐量仅比理论上的最大吞吐量低4.8％。与RTS-SA和VeMAC方案相比，eRTS-SA还可以实现大约44％和154％的吞吐量提高。