摘要
IEEE 802.11网络中的传统退避算法利用竞争窗口机制进行冲突解析,冲突节点被重新分布在一个更大的窗口范围内以避免冲突.然而,只要这些分布窗口之间存在着交集,就仍有可能引发冲突.为了解决一个问题,提出了一种冲突分类模型,将网络中的分组冲突分成交叉冲突和同级冲突,并且提出针对这两种不同类型的冲突应该采取不同的策略进行解析.利用顺序离散窗口分布机制(sequential discrete window distribution,简称SDWD)解析交叉冲突,通过节点分布窗口的离散化避免交叉冲突;同时,通过设置合适的分布窗口大小在同级冲突概率和分组延迟之间取得折衷.在此基础上,实现了两种冲突解析算法:冲突分类解析算法(cross collision resolution,简称CR)和无冲突分类解析算法(collision-free CCR,简称CF-CCR).仿真结果表明,同IEEE 802.11DCF协议相比,CCR和CF-CCR在冲突率、吞吐量、分组延迟、公平性以及延迟抖动方面均有提高.并且,这两个算法在不同场合表现出不同的优越性.
Traditional backoff algorithms in IEEE 802.11 networks adopt contention window scheme for collision resolution. Collided nodes are redistributed in extended window ranges to avoid further collisions. However, as long as these distribution windows intersect with each other, collision may still occur. To solve this problem, this paper puts forward a collision classification model to classify collisions into cross collision and intra collision and proposes to solve them with different policies. It utilizes sequential discrete window distribution （SDWD） scheme to resolve cross collision by distributing the collided nodes in a series of discrete Elementary Windows and the intra collision is resolved with an appropriate elementary window size to achieve a tradeoff between intra collision probability and packet latency. Based on this proposal, two algorithms are developed featuring cross collision resolution （CCR） and collision-free CCR （CF-CCR）. The extensive simulations demonstrate that compared with IEEE 802.1t DCF protocol, the CCR and CF-CCR algorithms consistently excel, in terms of collision rate, throughput, delay, fairness and delay jitter. Moreover, CCR and CF-CCR exhibit their respective advantages in different scenarios.
出处
《软件学报》
EI
CSCD
北大核心
2010年第3期548-563,共16页
Journal of Software
基金
国家自然科学基金Nos.60602029
60772088
湖北省高等学校优秀中青年科技创新团队资助计划项目No.T200902
湖北省教育厅科研项目Nos.D20081904
Q20091903
B20091904
湖北经济学院校级青年项目No.XJ2009011~~
