A conditional multi-copy strategy with multiple central nodes for more reliable wireless sensor networks

Recent advances in micro-electronic mechanical systems (MEMS) led to the development of tiny, cost-efficient, independent and functional sensors with limited capabilities. Wireless Sensor Networks (WSNs) are information delivery systems and they consist of independent sensors generating data by sensing physical or environmental conditions such as temperature, humidity, sound, pressure etc., and transmit it to a special point or location within a cooperation. In this thesis, we consider the Wireless Sensor Network (WSN) Design Problem under an energy efficient conditional multi-copy and multi-path routing strategy so as to improve network reliability. Our strategy is an improvement over the simple restricted multi-copy strategies where every sensor duplicates its data since we provide comparable levels of network reliability and yet extend network lifetime significantly. Hereunder, instead of whole data only the data routed through the central nodes which are more critical in terms of network reliability would be duplicated at its source and sent to the BS (base station) on another node disjoint path. Hence, instead of the whole data in the network only the data visiting central nodes is protected while safeguarding against malicious attacks or failures on nodes. We offer two different mixed integer programming models for two variates of the our strategy. The novel conditional multi-copying with multiple central nodes strategy, CM (Conditional Multi-copying,) and other multi-copying strategies are compared with respect to the network lifetime and reliability metrics. According to the test results, CM improves network reliability by giving of a little reliability in contrast with other strategies. Afterwards, we present several valid inequalities significantly shortening solution times in commercial solvers for both models. Moreover, we present a multi step heuristic method especially for tests on larger networks. The algorithm provides good solutions in reasonable times when compared with the commercial solver. Finally, a series of sensitivity analyses are done on CM by changing the values of some parameters. Keywords: Wireless sensor networks, conditional multi-copying, multi-path routing, reliability, mathematical modelling.