Cooperative wireless energy harvesting and information transfer in stochastic networks

In this paper, we consider a large-scale wireless ad hoc network with multiple source-destination communication pairs, where the sources operate with wireless energy harvesting. Before data transmission, each source should first harvest the radio frequency energy transferred from its corresponding destination. Since the source-destination distance is long, the efficiency of wireless energy transfer is very low. As a result, the transmission power of the source is weak, which is detrimental to the successful data transmissions. Instead, we introduce a relay in-between each source and destination for the wireless energy transfer and data transmission. The close distance between the relay and the source can improve the energy harvesting efficiency and the data relaying can improve the link robustness. With the assistance from the relay, the area spectrum efficiency is significantly enhanced compared with the non-cooperative system. A series of discrete power levels is defined for the sources and the probability of choosing each power level is analyzed by averaging over the random channel fading. We analyze the data success probabilities through averaging over the uncertain interference caused by the random locations of users, the channel fadings, and the various source transmission powers. The upper and lower approximations of data success probabilities are derived using the stochastic geometry theory for the cooperative energy and data transfer system. The optimal time allocation between the wireless energy transfer and the data transmission is investigated to maximize the system area throughput. Numerical and simulation results are provided to validate our theoretical analysis and show the dependence of system performance on various parameter settings. The results can provide the guidelines for the deployment of the energy harvesting cooperative communication system.