Ad hoc网络中一种生命周期约束的自适应退避算法

doi:10.3969/j.issn.1000-436x.2012.11.008

摘要/Abstract

摘要：

在IEEE 802.11标准定义的BEB退避算法基础上，提出一种生命周期约束的自适应退避算法LCAB，以生命周期代替最大重传次数作为分组丢弃的依据，并根据网络忙闲程度自适应地调整节点执行退避过程的权限，以最大化系统归一化有效吞吐量，适合于ad hoc网络中有严格时延要求的VoIP等实时性业务。构建Markov链模型分析LCAB算法性能，得到系统归一化有效吞吐量表达式。仿真结果表明，理论分析与仿真结果一致，且LCAB算法的归一化有效吞吐量优于BEB算法。

关键词: adhoc网络, 退避算法, IEEE802.11, 时延, 吞吐量, 马尔可夫链

Abstract:

Based on researching binary exponential backoff algorithm which defined in IEEE 802.11 standard,a life cycle constrained adaptive backoff algorithm(LCAB) was proposed.LCAB used life cycle instead of maximum retransmission times as the reference of packet dropping,and controlled process of backoff adaptively according to degree of network congestion.It fitted for real-time traffic such as VoIP which used widely in ad hoc network.A Markov model was introduced to analyze the performance of LCAB,and the normalized effective throughput of LCAB was obtained.The results show that the theoretic analysis is in accordance with the simulation,and the throughput of LCAB is better than that of BEB.

Key words: ad hoc network, backoff algorithm, IEEE 802.11, delay, throughput, Markov chain

王叶群,黄国策,张衡阳,郑博,景渊. Ad hoc网络中一种生命周期约束的自适应退避算法[J]. 通信学报, 2012, 33(11): 57-66.

Ye-qun WANG,Guo-ce HUANG,Heng-yang ZHANG,Bo ZHENG,Yuan JING. Life cycle constrained backoff algorithm for ad hoc network[J]. Journal on Communications, 2012, 33(11): 57-66.

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参数	数值
信道速率(R)	1Mbit/s
时隙大小(s)	50μs
MAC层首部(H_MAC)	224bit
物理层首部(H_PHY)	128bit
分组长度(L)	8 192bit
分组生命周期(T_Life)	0.2s
初始退避窗口(CW_min)	16
退避窗口最大递增次数(m)	6
退避窗口递增因子(a)	2
DIFS	128μs
SIFS	28μs
ACK	112bit+H_{P HY}