Research On Energy-Saving Mechanism Of MAC Protocol In Wireless Sensor Network

Wireless Sensor Network is a multi-hop ad-hoc network which is composed of a large number of low-power sensor nodes hat are randomly deployed in monitoring area. And the main aim of a wireless sensor network is to real-time monitor and collect interest information in the deployment area, and to deal with this information, then send to the observer through the wireless network.This paper describes an overview of the wireless sensor networks, focuses on wireless sensor network MAC protocol, and makes detail analysis of the working principle and energy-saving mechanisms of the classic S-MAC (Sensor-MAC) protocol. In S-MAC protocol, fixed duty cycle can’t adapt to the dramatically changing traffic in WSN. In order to achieve a balance between energy consumption and delay, we propose PR-SMAC (PageRank-SMAC) protocol base on PageRank algorithm that dynamically adjusts the node’s duty cycle to the changing traffic. In this protocol nodes are divided into two categories:ordinary nodes and key nodes (sink nodes and boundary nodes). For ordinary node, based on the PageRank algorithm, the duty cycle of receiving node is calculated by the packet size and duty cycle of the sending node. The duty cycle calculated through self-learning algorithm can well reflect the current network load conditions, to achieve the purpose of saving energy and reducing delay. For more energy consumption of key nodes, we propose two necessary conditions for the communication of the key nodes. One of two conditions must be satisfied to be able to communicate. When the cache capacity radio of neighbor nodes around the key nodes reach a threshold, the key nodes can communicate. If no key nodes transmit data within the data update interval to,the key nodes need communicate to update the data in order to ensure real-time data. NS2simulation results show that in PR-SMAC protocol, the duty cycle of ordinary nodes can well adapt to load changes, having a very good improvement in terms of energy consumption and latency; the problem of excessive energy consumption of the key nodes had been improved, prolonging the lifetime of the network. Finally, the status of current research are concluded and saving mechanism in the direction of future research on the MAC protocol are pointed out.