Node reliance : an approach to extending the lifetime of wireless sensor networks

A Wireless Sensor Network (WSN) consists of a number of nodes, each typically having a small amount of non-replenishable energy. Some of the nodes have sensors, which may be used to gather environmental data. A common network abstraction used in WSNs is the (source, sink) architecture in which data is generated at one or more sources and sent to one or more sinks using wireless communication, possibly via intermediate nodes. In such systems, wireless communication is usually implemented using radio. Transmitting or receiving, even on a low power radio, is much more energy-expensive than other activities such as computation and consequently, the radio must be used judiciously to avoid unnecessary depletion of energy. Eventually, the loss of energy at each node will cause it to stop operating, resulting in the loss of data acquisition and data delivery. Whilst the loss of some nodes may be tolerable, albeit undesirable, the loss of certain critical nodes in a multi-hop routing environment may cause network partitions such that data may no longer be deliverable to sinks, reducing the usefulness of the network. This thesis presents a new heuristic known as node reliance and demonstrates its efficacy in prolonging the useful lifetime of WSNs. The node reliance heuristic attempts to keep as many sources and sinks connected for as long as possible. It achieves this using a reliance value that measures the degree to which a node is relied upon in routing data from sources to sinks. By forming routes that avoid high reliance nodes, the usefulness of the network may be extended. The hypothesis of this thesis is that the useful lifetime of a WSN may be improved by node reliance routing in which paths from sources to sinks avoid critical nodes where possible. I, Alan W. F. Boyd, hereby certify that this thesis, which is approximately 78,843 words in length, has been written by me, that it is the record of work carried out by me, and that it has not been submitted in any previous application for a higher degree. date signature of candidate I was admitted as a research student in October 2005 and as a candidate for the degree of Doctor of Philosophy in October 2005; the higher study for which this is a record was carried out in the University of St Andrews between October 2005 and June 2010. date signature of candidate I hereby certify that the candidate has fulfilled the conditions of the Resolution and Regulations appropriate for the degree of Doctor of Philosophy in the University of St Andrews and that the candidate is qualified to submit this thesis in application for that degree. date signature of supervisor In submitting this thesis to the University of St. Andrews I understand that I am giving permission for it to be made available for use in accordance with the regulations of the University Library for the time being in force, subject to any copyright vested in the work not being affected thereby. I also understand that the title and abstract will be published, and that a copy of the work may be made and supplied to any bona fide library or research worker, that my thesis will be electronically accessible for personal or research use unless exempt by award of an embargo as requested below, and that the library has the right to migrate my thesis into new electronic forms as required to ensure continued access to the thesis. I have obtained any third-party copyright permissions that may be required in order to allow such access and migration, or have requested the appropriate embargo below. The following is an agreed request by candidate and supervisor regarding the electronic publication of this thesis: Access to printed copy and electronic publication of thesis through the University of St Andrews. date signature of candidate signature of supervisor