This work studies the secrecy performance of wireless powered sensor networks (WPSNs) under eavesdropping attacks by proposing an energy-aware node selection algorithm. The non-identical N sensor nodes harvest the required energy from a dedicated power station and use it for data transmission to a certain destination. The nodes selection procedure takes place over two phases. In the first phase, K nodes out of the total number of N nodes are selected under the condition that they succeed to harvest sufficient energy for transmission from the power station. In the second phase, among the selected K nodes from the first phase, two nodes are chosen in each time slot. The node with best channel conditions is selected for data transmission to the base station, while the other node that has the worst channel state acts as a cooperative jammer for the eavesdropper. We derive exact and asymptotic closed-form expressions for the secrecy outage probability (SOP) over Nakagami-m fading channels. Moreover, a power allocation problem is formulated to get the optimal uplink power values by minimizing the exact SOP expression using particle swarm optimization (PSO). Numerical results are obtained to validate our proposed model, followed by the conclusion to show its effectiveness.
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