基于流量自适应的S-MAC协议的优化

The optimization of S-MAC based on traffic adaptation

S-MAC(sensor-MAC)是经典的基于竞争的无线传感器网络MAC层协议.协议采用固定占空比的侦听、休眠机制,节点拥有相同的竞争窗口值,很符合无线传感器网络对MAC层协议节能、简单的要求;然而,固定的占空比和竞争窗口使S-MAC无法适应网络流量的变化.文中引入队列信息,依此判定网络流量的大小,对S-MAC协议进行优化.当流量大时,通过修改休眠时间来调整占空比.同时引入竞争窗口调节算法,以减小流量大时发生碰撞的概率,提高效率.通过NS2仿真证明在网络流量大时,优化的协议在性能上得到了提升.

sensor-MAC（S-MAC） is a classic MAC protocol based on competition for wireless sensor networks（WSN）.The protocol adopts interception and sleep mechanism with fixed duty cycle,and the nodes have the same competition window（CW）.So it agrees well with the requirements of WSN MAC protocol which should be energy-saving and simple.However,S-MAC can not adapt to the Internet traffic change due to the fixed duty cycle and CW.The queue information is introduced to judge the size of traffic and optimize S-MAC protocol.When the traffic is heavy,modify sleep time to adjust the duty cycle.And the CW adjustment algorithm is added to reduce probability of collision when the traffic is heavy,thereby increasing efficiency.The simulation results on NS2 show that when the traffic is heavy the proposed optimization protocol has better performance.