The Improvement Of Energy-effect Based On S-MAC Protocol

Wireless sensor network (WSN:Wireless Sensor Networks) is a multi-hop and self-organized communication network, which is composed of a lot of cheap and small sensor nodes. It can be used for sensing, collecting and processing the information of the monitored objects, and send to the observer, it can be widely used in military, commercial, medical care, environmental monitoring, etc. It lives usually depending on the battery power, which is hard to be changed because of the environment and the numbers of the nodes. So saving energy is the most important goal of designing in WSN.In WSN, the MAC(MAC:Medium Access Control) determines the way of the wireless channel, distributes Limited wireless communication resources among the sensor nodes for the construction of the underlying sensor network system. As the characteristic such as limited source and dynamic topology in WSN, more requests are referred to while designing the MAC protocol. That is ensuring the system performance and saving energy at the same time.The MAC protocol can be classed for many ways, and the study of this paper depends on contention-based MAC protocol. Many existing contention-based MAC protocol to save energy by sacrificing the network performance, following the bad network performance, there may be other problems occur, and it takes disadvantage of the dynamic topology and the lifetime of the WSN.The thesis firstly introduces the total thing of the WSN, which including the concept, construction, characteristic and the application of the WSN. Then the thesis introduces the existing MAC protocol and the focus of the MAC protocol design, Discuss the major energy consumption and performance in WSN. Next step is expatiating the S-MAC (S-MAC:Sensor-Medium Access Control) protocol working principle, summarizing its limitation and the improved S-MAC protocols, based on the S-MAC, a new energy-efficient MAC protocol-EE-MAC (EE-MAC:Energy Effective-Medium Access Control) is designed. S-MAC protocol is raised for the demand of the energy-saving sensor and self-organized, primarily through the availability of low-duty cycle. But the S-MAC protocol uses the active/sleep scheduling mechanism with fixed cycle, the event time is usually fixed, while the information rate usually changes, the time of the node in active can not Adjust when the traffic in WSN changes, so it can not save energy effective. Against this problem in WSN, the thesis proposes the design of EE-MAC protocol:use the utilization of the sending queues to measure the size of the network load, then the nodes adjust the active/sleep cycle under the size of the net work load. When the utilization of the sending queues is high, the nodes increase their duty-cycle, reduce the sleep time; otherwise, the nodes reduce their duty-cycle, increase the sleep time. it ensures that the nodes can adjust their active/sleep cycles when the traffic change. Through the OPNET simulation, the result shows that the EE-MAC protocol not only save most energy but also has more throughput than S-MAC protocol.