Energy Efficiency and Delay Tradeoff in Wireless Powered Communication Networks

초록

Energy efficiency (EE) and delay are two crucial metrics in WPCN. In general, the transmitter always transmits the information in a good channel state to improve EE while it may lead to delay due to waiting for a good channel state. Thus, there exists a tradeoff between EE and delay. In this paper, we investigate the EE and delay tradeoff with considering the timevarying channel and stochastic traffic arrivals. We formulate this problem as a stochastic optimization model, which optimizes the EE subject to both the data queue stability and the harvested energy availability. To solve the formulation, a general and effective algorithm, referred to as EE and delay tradeoff algorithm (EEDTA), is developed by employing the fractional programming method and Lyapunov optimization theory, which does not require any a prior distribution knowledge of channel states and data arrivals. Moreover, the theoretical analysis and simulation results show that the EEDTA achieves an EE-delay tradeoff, which mathematically depicted by [O(1/V),O(V)] with V as a control parameter, and can flexibly strike the tradeoff by simply tuning V. Simulation results verify the theoretical analysis.