Abstract: The performance of a backoff algorithm is determined by its adjustment strategy of Contention Window（CW） to a great extent. Aiming at the deficiency of fixed methods for adjusting CW when node collisions occur, continuous collision times of nodes are regarded as the indication of measuring how severe channel contention is and introduced into the adjustment strategy of CW, and on the basis of GDCF an adaptive backoff algorithm with CW Fast Increasing（FI-GDCF） is proposed, where a node will adjust its CW according to the exponential law of its continuous collision times. Theoretical analysis and simulation results show that collision probability, normalized network throughput and average packet access delay of FI-GDCF algorithm can all obtain improvement with varying degrees under two access modes and especially basic access mode, by contrast with BEB and GDCF algorithms.

Key words: adjustment strategy of contention window, backoff algorithm, continuous collision times, （Contention Window）Fast Increasing Gentle Distributed Coordination Function（FI-GDCF）

摘要： 竞争窗口（Contention Window，CW）的调整策略在很大程度上决定了退避算法的性能。针对节点碰撞时CW固定调节方式存在的不足，将节点的连续碰撞次数作为衡量信道竞争激烈程度的标志并将其引入到CW的调整策略中，在GDCF基础上提出一种具有自适应特点的CW快速增加退避算法（Fast Increasing GDCF，FI-GDCF），节点碰撞时按照其连续碰撞次数的指数律调整CW大小。理论分析和仿真结果表明，与BEB和GDCF算法相比，FI-GDCF算法在两种接入模式尤其是基本接入模式下，其碰撞概率、归一化网络吞吐量以及分组平均接入时延等性能均可获得不同程度的提升。

关键词: 竞争窗口调整策略, 退避算法, 连续碰撞次数, （竞争窗口）快速增加的温和分布式协调功能（FI-GDCF）