Research On Contention-based MAC Protocol In Wireless Sensor Networks

In recent ten years, wireless sensor networks have emerged as one of the dominant technology trends in Electrical & Information field. Wireless sensor networks (WSN) consists of a large number of distributed nodes with sensing, data processing, and communication capabilities. These nodes are self-organized into a multi-hop wireless network and collaborate to accomplish a common task. As sensor nodes are usually battery-powered, and they should be able to operate without attendance for a relatively long period of time, energy efficiency is critical in design of wireless sensor networks.The research of medium access control, which is critical on energy efficiency, becomes the focus. This paper analyse the problems which need to be considered in the design of MAC protocol and research into the MAC protocol. Finally, two new MAC protocols are presented.The first one is: An Energy-efficient and Low-latency MAC Protocol in Wireless Sensor Networks. In this protocol, nodes periodically sleep to conserve energy. When the source node has data packets to send, it uses a wakeup message to awake the sleeping nodes. The protocol needn't take the synchronization which must be achieved in S-MAC. Forwarding delay mechanism is adopted to mitigate the problem on hidden node interference. It especially suits to the wireless sensor networks with narrow bandwidth.The second one is: A MAC Protocol with Little Idle Listening for Wireless Sensor Networks. The node only periodically turns on its radio in polling period and checks for a wake-up signal by sampling the energy on the channel, it can determine whether there is wake-up signal. After polling period, the node enters the long sleep period, so energy is conserved. A spot of control messages are adopted to decrease the data latency through reserving the channel in polling period.To validate that the new MAC protocols are correct and powerful, this paper reason mathematically and run simulation in OPNET software. The result proves that new protocols have better performance in energy conservation, delay, through put.