Research On MAC Protocols For Wireless Sensor Networks

As the improvement of the sensor technology, networks and the technology of wireless communication, the technology of wireless sensor networks appears. The technology of Wireless Sensor Networks (WSN) is an important technology which can affect people's life. People in military, business and science areas begin to research it. At present, energy problem becomes the most important one in all the problems, In ordor to saving energy, this paper introduces the idea of time schedule of DMD protocol and promotes S-MAC protocol in MAC layer. This method decrease the nodes' idle time which greatly saving their energy. And this paper does the mainly research as follow:Firstly, the function of the MAC protocol and the signifigant of the research of MAC protocols are showed in the paper. A good MAC protocol can share the wireless channel properly for the nodes and avoid the collision between nodes. This can greatly save the node's energy.Sencondly, the MAC protocols in Wireless Sensor Networks are analyzed in the paper. The MAC protocols can be classified as contention-based MAC protocols, schedule-based protocols and other kind of protocols which have both of the above two kind. The contention-based protocols, such as MD and S-MAC protocols, are mainly discussed in the paper.Thirdly, the DMD and S-MAC protocols are analyzed and a new protocol named DMDS-MAC protocol is promoted. DMD protocol has a time schedule strategy which makes the nodes in network listen and sleep periodically. And the node can be on duty as low as 1% in the cycle and sleep in the rest time, which can save the energy greatly. Nevertheless it lacks good strategies as collision and overhearing avoidance. S-MAC protocol also has strategy of periodic listen and sleep which is different from DMD protocol. The duty cycle of S-MAC protocol can not be too small. As the virtual clusters in S-MAC protocol need to allocate the channel for the nodes in them. The more nodes in a cluster the more it needs time. But S-MAC protocol has good collision and overhearing avoidance, message passing and adaptive listening. They can avoid the data collision which can save the energy greatly. So this paper replaces the the strategy of listen and sleep in S-MAC by the strategy of DMD's which makes the new protocol appear. Then it analyses the new Protocol's performance in theory, and compares it with other protocols simply. And there is a conclusion that the DMDS-MAC protocol performs better than S-MAC protocol in saving energy, but more time dealy than S-MAC.Finally, the network simulator-NS is presented in the paper. And the new protocol is simulated with the NS2 simulator. The results of the new protocol are compared with S-MAC protocol's. And there is a conclusion that the DMDS-MAC protocol proforms better than S-MAC protocol in saving energy, but it will bring more time delay and lower thoughput than S-MAC protocol when the density of nodes in network is small.