S-MAC protocol is a typical competition-based random access MAC protocol.S-MAC protocol has good expansibility

and doesn’t need strict synchronization

but the problem of latency caused by the activity time of nodes can’t change with the communication load and nodes sleeping.A MAC protocol based on task activity awareness is proposed.This protocol improves energy efficiency and throughput by the channel access schedule according to the network load

i.e.the channel access probability of nodes.And the traffic load of WSNs is estimated by the task activity of nodes and its neighbor’s.The results show that the proposed protocol can reduce the energy consumption

and improve the network throughput by eliminating unnecessary collisions.