非饱和情况下基于802.11 DCF的改进协议DIDD

DIDD(double increase double decrease)协议是一种无线局域网介质访问控制802.11DCF(distributed coordination function)协议的改进。为分析DIDD协议在非饱和情况下的性能,该文使用三维Markov链模型,分析DIDD协议的回退过程求解节点的稳态发包概率;使用一维Markov链模型,求解起始回退阶段数的稳态分布;使用排队理论,计算了网络的非饱和吞吐量和数据包延迟。结果表明:在各种数据速率下,理论分析结果与仿真结果一致。

Modeling a typical enhanced 802.11 DCF-based protocol DIDD in non-saturated conditions

DIDD(double increase double decrease) protocol is a typical enhanced 802.11 DCF protocol for WLANs(wireless local area networks).To analyze the performance of DIDD in non-saturated conditions,a 3-D discrete-time Markov chain model of the backoff procedure was presented to compute the steady state packet transmission probability;a 1-D discrete-time Markov chain model of the initial backoff stage transition was presented to compute the steady state distribution of initial backoff stage number.The non-saturated throughput and packet delay expressions were made by queuing theory.Given a certain offered load,the stable throughput and mean packet delay can be recursively computed.The throughput and packet delay of theoretical analysis are consistent with that of simulations under various load rates.This model provides a theoretical analysis framework for the similar enhanced DCF protocols and presents a criterion for the protocol parameters design.