Charger and receiver deployment for trajectory coverage with delay constraint in mobile wireless rechargeable sensor networks.

Wireless Rechargeable Sensor Networks (WRSNs) powered by radio-frequency radiation attract a lot of attention for their sustainability and convenience, etc. One focus is how to rationally deploy the key devices, such as receiver and charger, to improve the network performance and deployment budget. This paper considers a novel deployment problem for WRSNs in a two-dimensional space with static trajectories, deploying the minimum number of wireless chargers and receivers for mobile nodes, subject to the non-overtime updating probability requirement for mobile node at any location of the trajectories. This timeliness communication problem is tricky and NP-hard when involving the influence of three practical delays (retransmission delay, charging delay and competition delay). Therefore, a performance controllable discretization strategy is proposed, based on which the Greedy Heuristic (GH) and Particle Swarm Optimization (PSO) based approximate solutions are introduced. The execution process and time complexity of these two solutions are analyzed, and then the numerical results of extensive simulations are introduced to verified the scalability, accuracy and efficiency of the two solutions. As a result, the GH solution has better deployment success rate and efficiency, and is the recommended solution for the novel problem. Finally, two real-life scenarios (indoor exhibition hall and hospital interior road) are introduced to further verify the robustness of the two solutions under the practical challenges of uneven density of mobile nodes, restricted deployment locations and occlusion of wireless links.