中文摘要：

介质访问控制（MAC）协议是保证网络高效通信的关键网络协议之一。传感器介质访问控制（SMAC）协议是以节能为目的的MAC协议。介绍了SMAC协议工作原理，针对SMAC协议退避机制的缺陷，借鉴二进制指数退避算法，在SMAC协议的基础上引入了一种具有公平性的退避机制。节点根据接入信道的次数动态调整竞争窗口，退避失败时冻结退避计时器，在下个竞争周期继续计时，增加了节点接入信道的公平性，减小了碰撞，增大了吞吐量和信道利用率。仿真结果表明：改进后的SMAC协议在吞吐量，能量消耗和能量利用率方面相对于SMAC协议有显著的提高，起到了节能的效果。

英文摘要：

Media access control （MAC） protocol is one of the key protocols to ensure efficient communication network. SMAC protocol, a kind of MAC protocol, is proposed for the purpose of energy saving. This paper describes the working princi-ple of SMAC protocol. For the defect of back-off mechanism in SMAC protocol, the paper takes binary exponential backoff algo- rithm as reference and introduces a fair backoff mechanism based on the SMAC protocol. Node adjusts the contention window dy- namically according to the number of accessing the channel. When backoff is failed, node freezes the backoff timer and continues to count at the next competitive cycle time. This algorithm increases the fairness of node accessing the channel, reduces the col- lision and increases the throughput and the channel utilization. Finally, the simulation results show that the new scheme signifi-cantly improves throughput, energy consumption and energy efficiency compared with the original protocol SMAC and reduces the energy cost.