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UBC Theses and Dissertations

Lifetime analysis and improvement of an amplify-and-forward wireless relay network Li, Shuotong


In a wireless relay network, the source and the destination are not able to communicate directly with each other because they are out of radio communication range. Instead, they communicate with the aid of intermediate node(s) which relay the signals. In the first part of the thesis, we analyze the lifetime distribution in a variable gain amplify-and-forward (VG-AF) opportunistic wireless relay network (OWRN) in the presence of Rayleigh fading. Two different methods are proposed to derive the probability density function (pdf) of the network lifetime. The first method is the Pearson method, which is useful in obtaining approximate expressions for probability distributions. Using a relatively short simulation for the network lifetime of interest, we obtain estimates of the first four moments of the network lifetime. Based on these moments, a fairly accurate approximation of the lifetime distribution is derived. The second method is based on the central limit theorem (CLT). Based on the fact that there are sufficient transmissions in one lifetime of a network, the lifetime distribution is close to normal distribution. To verify our methods, we use large Monte Carlo simulations to obtain good approximations for the network lifetime distribution. In the second part of the thesis, we analyze the lifetime distribution in the presence of Weibull fading as well as Nakagami fading. First, exact outage probability expressions for both cases with the opportunistic amplify-and-forward relaying strategy are derived. Simulations results verify our theoretical analysis. Using the techniques in the first part, we then obtain the lifetime distributions for both cases with the methods used in the first part of the thesis. In the third part of the thesis, an algorithm based on an energy saving adaptive transmit power threshold is proposed to improve the relay network lifetime. Calculated based on the residual energy information, QoS requirements and the number of relays, this transmit power threshold is adaptive to the residual energy value of each relay. Simulation results verify that this algorithm prolongs the lifetime of the relay network compared with a number of other existing relay selection strategies while satisfying the QoS requirements.

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Attribution-NonCommercial-NoDerivs 2.5 Canada