System design for wireless sensor networks

Pao Yue-kong Library Electronic Theses Database

System design for wireless sensor networks

 

Author: Cheng, Chi-tsun
Title: System design for wireless sensor networks
Degree: Ph.D.
Year: 2009
Subject: Hong Kong Polytechnic University -- Dissertations.
Wireless sensor networks.
Department: Dept. of Electronic and Information Engineering
Pages: xix, 151 p. : ill. ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2321244
URI: http://theses.lib.polyu.edu.hk/handle/200/5307
Abstract: The advent of wireless electronics and sensing technologies has made the production of versatile low-cost wireless sensor nodes possible. A wireless sensor network typically consists of a large number of wireless sensor nodes. The main use of wireless sensor networks is to collect data from sensing areas where human beings are not able to access. In contrast to conventional sensing systems, sensor networks utilize a huge volume of low-cost wireless sensor nodes to perform close-range sensing. The data collected will undergo in-network processes and then return to the user who is located in a remote site. This high redundancy of sensing power can greatly enhance the sensing resolution and make sensor networks robust to any adverse environmental conditions. However, these large number of wireless sensor nodes have also introduced a lot of challenging problems in system design. Some major problems are network lifetime, data collection efficiency, interference among wireless sensor nodes, and retransmissions due to noise and interference. Among all the problems mentioned above, the network lifetime problem and the data collection efficiency problem have been selected as the focus of this thesis. Since wireless sensor nodes are power-constrained devices, the number of distant transmissions should be minimized in order to reduce energy consumption in wireless sensor nodes and prolong the network lifetime. An effective approach to improve efficiency is to divide the network into several clusters. By raising the sensing power of a sensor network in excess of the necessary level, the overall target tracking capability can be increased. However, a high sensing power also implies a greater interference to the network in addition to higher energy consumption. Such disadvantages can be relieved by adopting appropriate scheduling schemes and putting unnecessary sensor nodes into a sleep state. As mentioned earlier, clustering can provide a significant improvement in energy saving. In practice, most nodes in a sensor network are only capable of handling a single connection at any one time. With such configurations, cluster heads may become the bottlenecks in the data collection process. This bottleneck problem can be alleviated by modifying the network structure. The contributions of this thesis are threefold. First of all, an energy-efficient clustering algorithm is proposed to tackle the network lifetime problem. Second, an energy-aware scheduling scheme is proposed to alleviate the surplus sensing power problem. Finally, a delay-aware network structure and its formation algorithms are proposed to tackle the data collection efficiency problem. Compared with other existing algorithms in wireless sensor networks, the proposed algorithms are shown to be more efficient in extending network lifetime and improving data collection efficiency.

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