An Adaptive Contention Window Mechanism for SMAC Protocol in Wireless Sensor Network

This paper proposes an adaptive contention window mechanism (ACWM) to improve the performance of SMAC protocol in wireless sensor network. This mechanism adjusts contention window by introducing two parameters to measure the state and the fairness of the network. In order to reflect the congestion of the network, ACWM introduces a parameter which represents the occupancy of the channel. This parameter is the ratio between conflict time and free time of each node. We use another parameter to measure the fairness among nodes and balance the time when nodes occupy channel. According to the dynamic changes of the network, the competition window is adaptively adjusted to improve the throughput, reduce the network delay and minimize the additional energy consumption caused by conflicts. ACWM protocol was compared with SMAC via the simulation software NS2 in a scenario of dense node topology. Simulation results show that ACWM protocol achieved better performance with higher throughput, lower average delay and higher energy utilization efficiency.