S-MAC Protocol For Wireless Sensor Networks Based On Energy Efficiency

Wireless Sensor Network is a typical communication Network without infrastruc-ture. It monitors environment real-time and collects information of the monitoring object. These data information will be processed and sent to the manage users. Wireless sensor network with low economic cost and flexible network topology, is widely used for environmental detection, military defense, intelligent household, biomedical and so on. In the application, some nodes will be placed in the place that is harsh environment, remote, and hard to reach. So for sensor nodes to get energy from batteries, battery replacement or supplement energy is not easy. How to reduce the node energy consumption, extend the life of the node and the network life cycle become the research hot spot of the wireless sensor network.Wireless transmitting module of the sensor node consumes the most of the battery energy. Media access control (MAC) protocol is responsible for managing the use of wireless way. Through the reasonable design of MAC protocol, consumption of wireless transmitting module can be reduced a lot. S-MAC protocol is one of the MAC protocols, which is used for wireless sensor network usually. Energy-saving is special design of the S-MAC. Periodically listen/sleep mechanism of S-MAC protocol makes sensor node sleep when no data is to transmission. It gets the low duty cycle to reduce energy consumption which is caused by the idle listening. But the fixed duty cycle of S-MAC protocol does not adapt to the changes of network traffic. When the network traffic is high, time delay will become long and network utilization is not high. If the channel competition is very fierce, there may be waste of energy with data retransmission. In this paper, we design dynamic duty cycle for S-MAC. And the modified S-MAC protocol can adjust the changes of the network traffic and save more energy for sensor nodes.In this paper, we study deeply the energy-saving mechanism of the S-MAC protocol. The contradiction between time delay and energy consumption is deduced by means of mathematics. Basic on S-MAC protocol, we get the A-SMAC protocol, which adjusts the changes of the network traffic. In the A-SMAC protocol, the network traffic is forecasted by the throughput capacity. The duty cycle is adjusted automatically according to the size of the network traffic. At the beginning of the network, the wireless sensor network with A-SMAC protocol, adjust duty cycle according to the size of the network. Until the network traffic is stable, the duty cycle is the best for network condition. If the nodes move usually, the duty cycle is adjusted to adapt to the changes of network traffic. Time delay is reduced and network utilization is enhanced. More energy is saved. Finally A-SMAC protocol is simulated by the NS2simulation. The results show that A-SMAC protocol reduces energy consumption, network delay and improve the network throughput. The Energy saving effect is better than S-MAC protocol.