Performance of Wireless Powered Multi-user Multi-relay Communication Networks with Outdated CSI

In this paper, we investigate the wireless powered multi-user multi-relay communication network, in which only relay nodes need energy harvesting with power splitting-based simultaneous wireless information and power transfer architecture. A low-complexity practical scheme, in which the best user selection and partial Nth best relay selection are adopted, is proposed and analyzed under the impact of outdated channel state information (CSI). The exact and lower bound closed-form expressions for the outage probability are derived over independent but not necessarily identical distributed (i.n.i.d) Rayleigh fading channel, and its asymptotic analysis is also given. The asymptotic analysis reveals that the diversity gain can achieve 2, which is different from the system without outdated CSI. The correctness of analytical result is validated by Monte Carlo simulations, and simulation results provide insights into the effect of system parameters, i.e., the impact of outdated CSI, the number of relays and users, average channel fading power, energy harvesting coefficient and power-splitting ratio, on the outage performance. At last, simulation results show that the outdated CSI and the number of relays also affect the optimal value of the power-splitting ratio.