Energy efficiency sleep scheduling in wireless sensor networks is one of the most crucial technologies.In this paper,we propose a simple and feasible synchronous node sleeping and waking mechanisms for small scale wireless sensor networks.Sensor nodes are divided into forwarding nodes and listening nodes.Beacon frame containing sleep command from the coordinator can be forwarded to listening nodes via forwarding nodes.All the nodes in the network can enter sleep at about the same time.Through such network synchronization mechanisms,we can realize synchronous sleep and wake of the entire network.Furthermore,a new power control scheme based on routing protocol(PCBRP) in the medium access control(MAC) layer is proposed.It operates with the help of routing protocol and calculates optimal transmission power according to the distance between neighbor nodes.A mapping table including optimal transmission power and node address is established during the route building procedure.The transmission power can be obtained by searching the table with the address of next-hop neighbor in subsequent data transmissions.The proposed mechanisms are implemented in sensor nodes and are evaluated in a test-bed.The analysis and evaluation based on the experimental results confirm that the proposed energy-saving mechanisms are feasible and effective.
