基于图着色理论的异构车联网时隙分配方案

A scheme based on graph coloring theory for time slot allocation in integrated VANET-cellular heterogeneous networks

针对异构车联网系统车辆较多导致时隙分配困难的问题,提出了一种基于图着色理论的时隙分配方案。该方案以考虑两跳内节点的图为模型,通过图着色的方法分配时隙,有效降低了隐藏终端带来的丢包;另外给出了一种高效实用的时隙重用分配算法。该算法根据度定义权值以确定车辆分配时隙数目,保证了公平性,提高了时隙重用,进而提高了消息发送的可靠性,同时也适用于网络拓扑多变的车联网场景。仿真结果表明,在车辆数为200、时隙数为100时,与传统时隙分配方法相比,该方案的车辆平均收包率获得大幅提升。此外,随着时隙重用的增加,车辆间干扰增强,从而导致平均收包率降低。研究还发现,增加车辆发射功率时,由于接收端信干噪比先增加后趋于不变,所以平均收包率也先增加后趋于不变。

To solve the problem that the time slots of integrated VANET-cellular heterogeneous networks are not easy to allocate when there are more vehicles on the road, a new time slot allocation scheme is proposed based on the graph coloring theory, and its time slot allocation algorithm is given.The scheme uses the nodes within two-hop to form the graph coloring model, and allocates time slots by using the graph coloring method to reduce the packet loss caused by hidden terminals.Through defining a weight coefficient based on the degree of node, the algorithm en-sures the fairness, and improves the reuse of time slots, thus improving the reliability of message delivery.Moreo-ver, it is efficiently and practically applicable to the vehicle networking scene whose topology changes rapidly.The simulation showed that, compared with the traditional method, the average packet reception increased greatly in the condition of 200 vehicles and 100 time slots.In addition, it showed a trade-off between the time slot reuse and the average packet reception rate.The study also found that the packet reception rate increased with the increasing of the transmit power until to a certain value when the SINR tends to a constant.