Optimization of Rate Fairness in Multi-Pair Wireless-Powered Relaying Systems

Abstract

This letter considers a multi-pair decode-andforward relay network where a power-splitting (PS) protocol is adopted at the energy-constrained relay to provide simultaneous wireless information and energy harvesting (EH). To achieve higher efficiency of EH, we propose a new PS-based EH architecture at the relay by incorporating an alternating current (AC) computing logic, which is employed to directly use the wirelessly harvested AC energy for computational blocks. Under a nonlinear EH circuit, our goal is to maximize the fairness of end-to-end rate among user pairs subject to power constraints, resulting in a nonconvex problem. We propose an iterative algorithm to achieve a suboptimal and efficient solution to this challenging problem by leveraging the inner approximation framework. Numerical results demonstrate that the proposed algorithm outperforms the traditional direct current computing and other baseline schemes.Index Terms-Inner approximation, relay network, simultaneous wireless information and power transfer (SWIPT).

Resource Allocation for AF Relaying Wireless-Powered Networks With Nonlinear Energy Harvester

“…Moreover, relay-based wireless-powered communication networks (RWPCNs) have attracted significant research interest, as they help extend both the lifetime and communication coverage of wireless networks [6]- [9]. In [6], the sum throughput maximization problem of multi-user wireless-powered communication networks (WPCNs) adopting amplify-andforward (AF) and decode-and-forward (DF) relays was investigated, where the energy harvesting (EH) duration in the downlink (DL) wireless energy transfer (WET) and the energy expenditure at the relay for each time slot in the uplink (UL) wireless information transfer (WIT) were jointly optimized.…”

“…Aiming at maximizing the sum throughput for multiple DF relays in a WPCN, an effective algorithm for optimizing the time allocation and EH power coefficients was developed in [8]. Very recently, the work in [9] proposed an iterative algorithm to obtain a suboptimal solution for the optimization problem of max-min end-to-end (e2e) rate for a multi-pair SWIPT DF relaying network. However, the works cited above (i.e., [6]- [8]) mainly focused on UL WIT, and ignored the benefit of power allocation (PA) at the relay.…”

“…However, the works cited above (i.e., [6]- [8]) mainly focused on UL WIT, and ignored the benefit of power allocation (PA) at the relay. In addition, the iterative algorithm developed in [9] was heavily based on a large number of approximate functions, and the convex program at each iteration was solved using existing solvers, making it unimplementable in practice. Thus, we investigate a joint design of power and time fraction for EH so that the system performance is remarkably enhanced.…”

“…In contrast to [6]- [8], we study the PA at the relay for the DL WIT to serve multiple users under a practical EH model. Through time-division multiple access (TDMA) and the AF protocol, the PA in our problem becomes more complex than in [9] due to the strong coupling between the optimization variables and the presence of a fractional form in the e2e throughput function. Owing to the nonconvexity of the formulated problem, we first transform it into a more computationally tractable form and then propose a very efficient iterative algorithm for its solution.…”

“…Owing to the nonconvexity of the formulated problem, we first transform it into a more computationally tractable form and then propose a very efficient iterative algorithm for its solution. Unlike [9], the proposed algorithm does not rely on any existing convex solvers owing to closed-form solutions obtained in each iteration. Simulation results are provided to demonstrate the effectiveness of the proposed algorithm in terms of e2e sum throughput.…”