Improving The Energy Efficiency Of Wireless Sensor Networks, Clustering And Routing

Due to the energy constraint of the sensors, how to employ energy efficiently has become a primary challenge for wireless sensor networks. The network topology design and routing selection play important role in sensors' energy consumption for data gathering. Aiming at the inadequate energy utilization issue brought by the unbalanced traffic load and energy consumption over the network, this thesis focuses on improving energy efficiency by developing a clustering scheme and a layered routing protocol. The main works are as follows:Firstly, to solve the energy waste problem caused by the unbalanced energy employment, a distributed dynamic clustering scheme (DDCS) based on power proportion is proposed. Taking the power proportion among different clusters as a constraint, DDCS predefines an expected clustering distribution model, and the energy in different clusters is expected to be used up simultaneously. When clustering, sensors organize themselves into corresponding clusters by comparing their location with parameters of the proposed model by individual decision, and then compete for the cluster head role based on the assessments for their residual energy and locations. The sink periodically adjusts the model parameter and broadcasts it, then new clustering process begins and the cluster heads are rotated among sensors, thus the energy consumption among different sensors and clusters can be well balanced.Secondly, according to the diversity of different types of sensors in the layered topology in terms of transmission ability, traffic load and energy consumption, an energy-efficiency oriented two-layered routing (EETLR) is proposed. In EETLR, the routing problem is divided into the backbone routing among the cluster heads and the low layer routing among the sensors in a cluster. For the backbone routing, a metric based on minimal transmission energy consumption and load balance is designed. This metric is used not only to reduce the cluster head energy consumption, but also to balance the traffic load and energy for different relay sensors by adopting the attraction factors. While for the low layer routing, a path metric of adaptive minimal path transmission energy consumption is suggested. According to it, in the premise of the relay sensors having adequate energy, the cluster members will select the path with minimal required transmission energy via single hop or multi-hop to the corresponding cluster head.Finally, performance evaluations of the proposed DDCS and EETLR are taken under NS2 simulation. The performances of energy consumption balancing, network lifetime and energy consumption for data transmission are analyzed, and the results show the reasonability of DDCS and EETLR on improving energy efficiency.