A distributed wireless sensor network is the network composed of sensor nodes, capable of sensing the environment, processing and storing the sensed data and transmitting the data through wireless channels. It can be deployed as a system with static sensors or a system with mobile nodes. As the energy capacity of the node hardware is limited, sensor networks suﬀer greatly from a severe energy constraint. Furthermore, as many of the environments or objects that need to be monitored, such as volcanoes, bushland, battle ﬁelds or animals, are normally diﬃcult to reach, it is very costly or even impossible to renew the energy supply of the sensors or redeploy the nodes. Hence the energy conservation and network lifetime prolongation problem becomes one of the key issues for the deployment of the sensor network.In this thesis the energy conservation and network lifetime prolongation problem of the sensor network is rigorously examined. Through the investigation of existing works, the design of a non-uniform node deployment scheme for tackling the energy hole problem of the static sensor network is identiﬁed to be a vital issue for the prolongation of the network lifetime. Since the non-uniform node deployment mechanism requires a region-by-region routing style, a spatially energy balanced routing strategy for this kind of mechanism is also crucial for the longevity of the network and needs to be studied. For a mobile wireless sensor network, the design of an energy eﬃcient duty cycle scheduling scheme for the node detection is recognised as very important for the energy conservation of the node and thus should be carefully investigated.Aimed at making progress on these issues, three novel schemes are provided in this thesis. Taking the energy consumptions of nodes, in active mode, without transmitting or receiving data into consideration, the non-uniform node deployment scheme for the event detection sensor network is proposed. This scheme is designed using the analytical results of the impacts of spatial and temporal distribution of events on the node deployment strategy according to the network lifetime requirement of the application.Although spatially balanced energy consumption in routing for a network with non-uniform node deployment can be achieved through selecting the neighbour node with maximum residual energy, special equipment is required for obtaining accurate information and the transmission of real-time energy information is costly. Hence it is necessary to design an energy balanced routing strategy without the energy information and the region constraint routing scheme, in accordance with the analytical result of the spatially unbalanced energy consumption for random node selection method, is presented in this thesis for this purpose. By combining the region constraint scheme and maximum residual energy strategy, a hybrid mechanism is also proposed to improve the performance of the maximum residual energy scheme.Since the sensor nodes in a mobile wireless sensor network must exchange information among each other to increase the probability for data collection, nodes need to detect the existence of each other through beaconing and listening. However the sensors also need to work in very low duty cycle to conserve energy. The low duty cycle of the sensor nodes makes the chance for the nodes to ﬁnd other neighbours become very low. Thus a duty cycle scheduling strategy that enables nodes to eﬀectively discover other nodes as well as saving the power necessary to fulﬁll the lifetime demand of applications is required. In this thesis the ﬂock based duty cycle scheduling scheme is presented through the neighbour node number estimation method based on an analytical model.For all the schemes proposed in this thesis, the experimental results are provided. The results show that the three mechanisms designed in this thesis are capable of improving the performance of the system signiﬁcantly.
|Date of Award||9 Jun 2012|
|Supervisor||Zheng Da Wu (Supervisor)|