Abstract: For the backoff time problem of Ad Hoc network MAC protocol（SPMA protocol）, in order to reduce packet-to-packet collisions and improve channel utilization, a backoff algorithm based on channel occupancy and priority（A-COP algorithm） is proposed for the first time. Firstly, the impact of backoff time on system performance and the insufficient of existing backoff algorithm are analyzed. Then, the back-off algorithm model is established according to the characteristics of SPMA protocol and elementary function model. Finally, the system simulation based on OPNET is performed, and the protocol model is compared with the original algorithm model. The simulation result shows that the SPMA protocol based on this algorithm can make the system throughput more stable through the access control of low-priority services, and it can meet the requirement of high-priority services with high communication quality.

Key words: Ad Hoc network, Statistic Priority-based Multiple Access（SPMA） protocol, backoff algorithm, channel occupancy, priority

摘要： 针对Ad Hoc网络MAC协议（SPMA协议）的退避时间问题，为降低包与包之间的冲突并提高信道利用率，提出了一种基于信道占用及优先级的自适应退避算法（A-COP算法）。分析了退避时间对系统性能的影响以及现有退避算法的不足；根据SPMA协议的特点以及初等函数模型建立退避算法模型；基于OPNET对该模型进行系统仿真，并与原算法协议模型进行比较。仿真结果表明，基于该算法的SPMA协议通过对低优先级业务的接入控制，可使系统吞吐量更加稳定，并且可满足高优先级业务高通信质量的要求。

关键词: Ad Hoc网络, 基于优先级概率统计的多址接入（SPMA）协议, 退避算法, 信道占用, 优先级