Abstract: A new Dynamic Prediction Backoff Algorithm（DPBA） in MAC layer is presented.The basic idea of DPBA is that each node should compute the collision probability through sensing the channel to predict the contending condition around it，and then it will choose a corresponding strategy to compute the value of contention window in regard to different network condition.Analysis and simulation results show that，compares with the traditional backoff algorithm BEB，DPBA descends the packet collision probability effectively and increases the network throughput.It also makes an improvement to the channel fairness.

Key words: Ad Hoc, MAC, backoff algorithm, dynamic prediction, contention window

摘要： 提出了MAC层一种新的动态退避算法DPBA，它以报文的冲突概率来预测节点附近信道的争用状况，对不同的网络状况下竞争窗口的取值采用相应的退避策略，以达到改善网络性能的目的。分析与仿真结果表明，与传统的退避算法BEB算法相比，本算法有效地降低了数据包的碰撞概率，提高了网络的吞吐量，同时对信道的公平性也有所改善。

关键词: Ad Hoc, MAC, 退避算法, 动态预测, 竞争窗口