Power Control And Traffic Adaptive MAC Protocol For Wireless Sensor Networks

Wireless sensor networks are getting more and more attention in the field of information technology. It is composed of a large number of cheap and small sensor nodes, which integrates sensing, computing and wireless communicating modules. By deploying numbers of sensor nodes in monitoring region, WSN can cooperatively sense, collect and process the information in its coverage area, and then send the information to the observer. With the advantages of small volume, low power consumption and operation in dangerous environment, WSN can be widely used in military applications, environment monitoring, healthy care, medical treatment and so on.The consumption energy of the sensor nodes come from the battery, so the energy is limited and often can not be replaced. The key question we care about is how to reduce the consumption energy and prolong the lifetime of WSN. Media Access Control (MAC) protocol is fundamental protocols in the research of WSN. Because it has deep and broad influence on energy consumption and transmission delay, in this thesis, the MAC protocol of the link layer is studied to find the optimization method which can improve the performance of networks.In this article, a protocol is proposed to make some improvements in the shortage of SMAC. Firstly, SMAC protocol does not choose different transmit power on different distance. All of the nodes send data with the same transmit power, resulting in a huge waste of energy. PCTA-MAC protocol uses the maximum value of optimal transmit power, which is calculated from a node to all its neighbor nodes, as its own transmit power. It has a good effect on saving energy. Secondly, because SMAC protocol use fixed contention window as backoff algorithm and fixed duty cycle as listen/sleep mode, it can not adapt to the dynamic change of network flux. In the proposed protocol, a new backoff algorithm is adopted, which can adjust the contention window based on the number of failed to seize the channel and handle the backoff time properly. It can decrease the collisions’ probability of the data packet and reduce the idle listening time effectively. At the same time, according to the number of data packet in the transmit queue, nodes adaptively adjust the duty cycle, so that increase the nodes’ transmitting time, decrease the data packets’ end-to-end delay on the high traffic network.The NS2simulation results show that PCTA-MAC protocol in this article has shown good performance in different network load. It is better than SMAC protocol in the field of energy consumption, throughout and data packets’ end-to-end delay.