Abstract: This paper analyzes the working process of S-MAC protocol and the principle of backoff algorithm. An improvement is proposed aiming at the deficiencies of BEB backoff algorithm. The state of the wireless channel is informed by current backoff window and a counter that accumulates the times of busy state of the communication channel. The nodes can adaptively adjust the value of backoff window to reduce collision. The simulation results show that the performance of improved S-MAC protocol is better in both throughput and energy efficiency in the case of high-load networks.

Key words: wireless sensor network, S-MAC protocol, backoff algorithm, BEB