Backoff mechanism is a key component of contention-based medium access control（MAC） layer protocol.It has been shown that the backoff mechanism of IEEE 802.11 standard may be very inefficient especially when the net...Backoff mechanism is a key component of contention-based medium access control（MAC） layer protocol.It has been shown that the backoff mechanism of IEEE 802.11 standard may be very inefficient especially when the network is congested.Numbers of methods have been proposed to tune the contention window（CW） with the aim to achieve the optimal throughput in IEEE 802.11 WLANs.However,the mechanisms do not specifically address proper settings for the variable packet length influence and CW diverging problem.This paper proposes a novel four-way handshaking full-feedback backoff algorithm named adoptive contention window backoff（ACWB） to overcome these drawbacks.The performance of the proposed algorithm is investigated through analysis and simulation.Simulation results demonstrate that the ACWB algorithm provides a remarkable performance improvement in terms of short-term fairness,packet delay and delay jitter,while maintaining an optimal throughput close to the theoretical throughput limit of the IEEE 802.11 distributed coordination function（DCF） access scheme.展开更多
文摘Backoff mechanism is a key component of contention-based medium access control（MAC） layer protocol.It has been shown that the backoff mechanism of IEEE 802.11 standard may be very inefficient especially when the network is congested.Numbers of methods have been proposed to tune the contention window（CW） with the aim to achieve the optimal throughput in IEEE 802.11 WLANs.However,the mechanisms do not specifically address proper settings for the variable packet length influence and CW diverging problem.This paper proposes a novel four-way handshaking full-feedback backoff algorithm named adoptive contention window backoff（ACWB） to overcome these drawbacks.The performance of the proposed algorithm is investigated through analysis and simulation.Simulation results demonstrate that the ACWB algorithm provides a remarkable performance improvement in terms of short-term fairness,packet delay and delay jitter,while maintaining an optimal throughput close to the theoretical throughput limit of the IEEE 802.11 distributed coordination function（DCF） access scheme.
文摘着眼于IEEE802.11MAC协议的改进与优化。根据马尔可夫理论分析了MAC层性能,首次提出利用平均冲突次数来代替以往算法中对竞争终端个数的精确测量,在此基础上将冲突权值引入DCF(distributed coordi-nation function)机制中,从而提出了基于冲突权值的动态优化方案(dynamic optimization algorithm based on theconflict weights,DOBCW)。经仿真对比测试,改进方案DOBCW在系统吞吐量和系统时延方面很具优势,最高可提高两倍的系统吞吐量和降低80%的系统时延。而在对系统稳定性的考察中,改进方案DOBCW的吞吐率和系统时延也表现得比原有机制更为稳定。通过仿真实验,有效地证明了改进方案高效性。
