Lifetime analysis of wireless sensor nodes using queuing models
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Prolonging the lifetime of wireless sensor networks (WSN) is one of the key issues for wireless sensor network applications. For increasing the lifetime of network, each node should conserve its energy. Sensor nodes consume different power in different operating modes. It also consumes significant amount of power while switching from one mode to another mode. So it is important that how frequently a node is changing its mode. To address this question we have used queuing theory based control policy, which finds the optimal parameter for switching between modes. We have analysed two different control policies namely, N-policy and T-policy and their effect on the lifetime of a sensor node. In N-policy, a sensor node switches its mode only when total number of packets are N. We find an optimal value of N that minimizes the energy consumption per unit time. Similarly, in T-policy whenever system becomes empty it goes on vaccation for a fixed duration T. It changes its mode only again after T unit of time and stays in the same mode as long as there is a packet. In this case also we find the optimal value of T that minimizes the energy consumption per unit time. But this improvement in lifetime comes at the cost of longer delay and larger waiting time. We have given the expression for the latency delay. Depending on the application requirement one can tune the parameters to get the best result between the energy saving and latency delay.
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