一种区分优先级自适应抖动的媒质接入控制协议
An Adaptive Jitter Based Media Access Control Protocol with Priorities

针对军事航空通信系统中随机接入类协议不支持多优先级且在重负载时传输性能急剧恶化问题,提出一种区分优先级自适应抖动的多信道媒质接入控制(MAC)协议PAJ_MAC。协议基于随机接入机制,采用为各个优先级设置不同最大抖动阶段的方法来区分各优先级业务的QoS,通过估计信道忙闲程度并根据估计值调节抖动阶段转移概率自适应因子,使协议具备业务负载自适应能力。分别建立了分组等待阶段发送缓冲区的M/G/1/K排队模型、信道接入阶段抖动状态的二维马尔科夫链模型和传播阶段的突发包碰撞模型,得到了协议各项性能指标的理论表达式,并通过编程求出了自适应因子在保证最高优先级可靠性需求下随业务负载变化的最优解。仿真表明,该协议支持多优先级业务,并始终保证最高优先级业务的低时延(端到端时延<10 ms)、高可靠(成功传输概率≥95%)传输以及系统吞吐量的稳定。
A prioritized adaptive jitter media access control protocol (PAJ_MAC) based on multi？？channel random access mechanism is proposed to solve the issues of multi？？priority traffic differentiation and poor performance under heavy loads in military aeronautical communication. The protocol bases on the random access mechanism and classifies QoS for multiple priorities by setting different maximum jitter stages. It adaptively implements traffic loads by regulating the jitter stage transition probability based on continuous feedback of channel occupation statistic. All of the protocol performance expressions are deduced through building three models. These models are a queuing process model with M/G/1/K theory, an adaptive jitter mechanism model with 2？？D Markov chain and a propagation process model with burst collision. The optimal adaptive factor to guarantee the reliability of the highest priority traffic under different traffic loads is derived through programming. Simulation results show that the protocol provides correct traffic differentiation, guarantees the timeliness and reliability of the highest priority traffic (i.e. the time delay is less than 10 ms and the successful transmission probability is more than 95%), and maintains the stability of the system throughput all the time