Energy-saving Schemes And Mobility In Wireless Sensor Networks

Wireless Sensor Network (WSN) is a new type of network made up of sensors, microprocessors and wireless communication interfaces, with novel technology of information acquiring and information processing. Its broad potential applications make this technology develop rapidly in many fields. Nowadays both academia and industries are very interested in WSN. There are also many unresolved problems in the researches of WSN especially the energy efficiency problem, which means designing specific algorithms or protocols to reduce energy consumption as much as possible.The focuses of this thesis are energy-efficient algorithms and protocols, which include:1 Mobile Wireless Sensor Networks (mWSN).Traditional WSNs generally assume a homogeneous and static deployment of either sensor nodes or sink nodes, and the network protocols are not designated for the presence of mobility. There is a big challenge to combine the traditional wireless sensor network with some number of heterogeneous mobile-enabled nodes. We investigate the impacts of different features and behavior of mobile sinks on the hybrid wireless sensor networks. Analysis and simulation results show that, instead of deploying mobile sinks as much as possible, choosing appropriate number, transmission range, velocity and gathering mode of the sink nodes can significantly decrease the average end-to-end data delivery delay and improve the energy conservation. The comparisons of performance metrics between fixed sinks and mobile sinks are also made in sparse networks along with the results that mobile sinks can bring higher data success rate and energy balance.2 An Improved Directed Diffusion Algorithm in Wireless Sensor Networks.In directed diffusion routing, the diffusion of exploratory message can lead to heavy traffic load periodically. The performance of data transmission may severely deteriorate at that moment. This paper proposes a gradient-based constrained diffusion algorithm. By analyzing the gradients of node's neighbors, the breadth and depth for diffusion can be conducted firstly. Then diffusion is performed in the optimal set of chosen forwarding nodes. The simulation results indicate that this algorithm can decrease both duration of diffusion and data transmission delay significantly. In addition, it achieves greatly energy savings compared to prior method. Finally, it is compatible with original algorithm without additional control overhead.3 An Energy-conserving and Collision-free MAC Protocol Based on TDMA for Wireless Sensor Networks.