Research On Energy Efficient Cross-Layer Protocol For Wireless Sensor Network

Wireless sensor networks(WSN) is a kind of special Ad Hoc network which is integration of advanced techniques including sensor, embedded computation, computer network, wireless communication and distributed computation. Usually, a large number of sensor nodes are deployed in a certain area. These small sensor nodes can sense, collect the real-time information of monitored objects in the surroundings,and process these information and transfer them to user via multi-hop wireless communication through mutual cooperation between nodes. Now WSN has a wide range of applications ,such as military, environment monitoring ,intelligent transportation and medical, etc.Because WSN is formed by a lot of cheap sensor nodes, each one of which is small in size and carries extremely limited energy, and once deployed, it is difficult to add energy to it, the problem that how to save energy and extend the network lifetime has been a key in wireless sensor network application. When the hardware is under the same conditions, the excellent wireless sensor network protocols will greatly save energy and prolong the life of the network. The main achievement in this paper is that a new cross-lay protocol (NCL) is proposed, by studying the existing MAC layer protocols and routing protocols. NCL protocol not only has a good performance in balancing and reducing the energy consumption, but also has both MAC and routing functions, which is very useful for wirelss sensor network used in applications,such as environmental monitoring, etc.The thesis firstly analyzes the reason causing energy consumption in each layer of the network protocol. Then summarize the idea and method how to design an energy efficient protocol. At last, by reference to the existing MAC protocols, such as S-MAC, routing protocols and cross-layer protocols, NCL protocol is proposed, which adopts the following three kinds of mechanisms:(1) Choosing routing based on the residual energy of node. This mechanism can fully balance the network load, and make the load evenly crossing the network. It not only can reduce the collision probability and the delay, but also make the nodes evenly consume energy and prolong the life of the network.(2) The maximum information flow according to the routing information in adaptive listening phase. The mechanism can guarantee as many as possible nodes in sleeping state in the adaptive listening phase to reduce unnecessary idle listening and save a large quantity of energy.(3) A low latency active relay mechanism. This mechanism can help the node who has already joined the net or have no lower level relaying node temporarily transmit data quickly with little delay and enhance the network response ability.Finally, analysis the energy consumption in NCL and S-MAC, and simulate both NCL and S-MAC in NS2. The result shows that NCL has a better performance than S-MAC in delay, energy consumption and throughput.