The Research Of The MAC Protocols In Wireless Sensor Network

Wireless Sensor Network (WSN) is composed of a larger number of sensors which have functions of data sensing, gathering, handling and communicating. The characteristic of WSN includes low price, small size, powerful data-gathering capacity, which makes it can be widely used in many areas. In WSN, MAC (medium access control) protocol provides the way of wireless channel use and reasonable distribution of communication resources for nodes. The design of traditional MAC protocols usually focuses on throughput maximizing, latency minimizing and guarantee the fairness of channel access at the same time. As a result of the power limitation in sensor nodes, the MAC design in WSN always put minimizing energy-consumption into the top goal.First of all, we introduced the classic MAC protocols in WSN. Then we have given a detailed introduction to SMAC (Sensor-MAC), which is mainly designed for WSN. We analyzed its energy-saving mechanism, and pointed out the latency affection brought by periodic sleeping.We put forward two schemes that based on SMAC: DC-SMAC and TPC-SMAC. DC-SMAC aimed to improve the fixed duty cycle of SMAC, which have a high latency and couldn't adapt to the traffic change in the network. DC-SMAC can adjust the duty cycle dynamically according to the average packet delay, and can choose an appropriate delay tolerance according to the specific application. The results of our simulation show that in contrast to SMAC, DC-SMAC have a remarkable improvement on end-to-end latency, energy consumption and throughput. TPC-SMAC uses transmission power control to optimize network topology and reduce collision. The optimal power table is built in synchronization process of SMAC, and the appropriate transmission power level is selected for every neighbor. In addition, neighbor optimal scheme is used in TPC-SMAC, which can select neighbor node by transmission power adjusting. The result of the simulation shows that TPC-SMAC has a certain extent of improvement on energy consumption and throughput.