中文摘要：

文章研究了在Ad hoc网络中存在暴露节点时双忙音多址接入（DBTMA）协议的工作机制.发现当暴露节点是发送节点时,DBTMA协议的忙音监听机制能够令暴露节点不受干扰地收发数据,从而获得较高的信道利用率.但当暴露节点是接收节点时,忙音传输范围的局限性令DBTMA协议出现了严重的不公平问题.针对该问题,文章提出了一种DBTMA协议改进方案,方案包括数据确认机制和利用忙音感知冲突的退避算法.仿真证明,在保证了原有网络吞吐量的情况下,该方案较DBTMA协议获得了更好的公平性.

英文摘要：

The working mechanism of the DBTMA protocol in Ad hoc network with exposed terminals is investigated in this paper.It is found when the exposed terminals are transmitters,the busytone sensing mechanism in DBTMA protocol can reach a high aggregate throughput by enabling the exposed terminals to transmit data without being interfered.However,the limitation of the busytone＇s transmission range may cause a great fairness problem to DBTMA protocol when the exposed terminals are receivers.To address this problem,an improved scheme that includes data acknowledge mechanism and a new backoff algorithm based on collision perception by making use of busytones is proposed.The simulation results show that this scheme can greatly improve the fairness of the DBTMA protocol without impairing aggregate throughput in Ad hoc networks.