Research On MAC Protocols Of WSN Based On Controlling Of Energy Consumption

Wireless sensor networks (WSN) is composed of a collection of mobile sensor nodes, which are connected together by their wireless links. One distinguishing feature is that users, when communicating to each other, may establish a multi-hop path among these wireless links, quite different current existing networks, another distinguishing feature is that the nework topology in wireless sensor networks may be frequently changed and dynamically adapted.It is known that medium access control (MAC) plays an important role on link utilization and fairness issue. Particularly in wireless sensor networs, MAC mechaims would become more complicated because of hidden-terminal and exposed-terminal occurrence and frequenct changes of network topology. These open problems motivated us to conduct a comprehensive study in this dissertation.Power control mechanisms can be applied in any layer of the networking protocol stack. Low power modes, where for example the devices are powered on periodically, can be used in physical layer. Power controlled data link layer protocols can be implemented in order to limit the amount of unnecessary retransmissions or reduce collisions. Network layer can make use of power-aware routing protocols. Among these the most suitable layer to apply a power control mechanism seems to be the MAC layer since it determines the state of the radio (transmit, receive or sleep modes) effecting the overall energy consumption more than other layers of protocol stack.We summarizes the research results on Ad Hoc wireless sensor networks MAC (Media Access Control) protocols, primary characteristics and typical applications of wireless sensor networks. The latest progresses on the routing protocols, security mechanism are reviewed. Lately, there are more and more investigations on wireless sensor networks MAC protocols. We analyzes some typical MAC protocols, such as S-MAC, T-MAC and D-MAC.Then, a new power controlled contention-based MAC protocol is introduced for wireless sensor networks where nodes can adjust their transmission power level on a per-frame basis.The main idea of PCSMAC is to send RTS, CTS, DATA and ACK frames with appropriate transmission power levels instead of maximum. While reducing the power consumption PCSMAC preserves the collision and overhearing avoidance properties of the original S-MAC protocol.Experimental results show that the power controlled sensor MAC protocol reduces the energy sonsumption by up 30-96% comparing to the conventional sensor MAC protocol.In the end, we gives some advice for future work according to the advantages of each protocol, concludes this dissertation and some future works are discussed.