饱和情况下基于非竞争带宽请求机制的IEEE 802.22 MAC层协议性能分析

Performance Analysis of IEEE 802.22 MAC Protocol Based on Noncontention Bandwidth Request Mechanism under Saturated Condition

为了分析IEEE 802.22MAC(Medium Access Control)协议性能以及各协议参数对性能的影响,针对饱和情况下基于非竞争BR(Bandwidth Request)机制的IEEE 802.22MAC协议提出了一种三维离散时间马尔科夫链分析模型.该模型同时考虑了协议的子信道预留机制和频谱感知的虚警概率,在帧节点处分析了离开事件以及到达事件,并在建模场景下准确得到了马尔科夫链的状态转移概率矩阵.通过马尔科夫链分析,得到了吞吐量、强迫中断率和切换队列的平均排队时延3种最主要性能指标的表达式.仿真结果表明:本文的分析模型可以准确评估协议性能,定量分析各项性能指标,为合理地选取协议参数提供理论依据.

In order to evaluate the performance of IEEE 802.22 MAC layer and study the influence of pro- tocol parameters, this paper proposed an analytical model using 3-dimention discrete-time Markov chain for IEEE 802.22 MAC layer based on non-contention bandwidth request （BR） mechanism under saturated condition. This model takes both sub-channel reservation mechanism and false alarm probability of spec- trum sensing into consideration, analyzes service event and arrival event at the frame node and derives the state transition probability matrix accurately. After Markov chain analysis, the formulas of throughput, forced termination probability and average delay of handoff queue were derived. The numerical results show that the model can be used to evaluate the protocol performance and analyze the trade-off of perform- ance metrics, and it can provide theoretical basis for choosing proper parameters.