Power control and beamforming design for SWIPT in AF two-way relay networks

Abstract

Abstract-In this paper, we study the problem of joint power control and beamforming design for simultaneous wireless information and power transfer (SWIPT) in an amplify-and-forward (AF) based two-way relaying (TWR) network. The considered system model consists of two source nodes and a relay node. Two single-antenna source nodes receive information and energy simultaneously via power splitting (PS) from the signals sent by a multi-antenna relay node. Our objective is to maximize the weighted sum power at the two source nodes subject to quality of service (QoS) constraints and the transmit power constraints. However, the joint optimization of the relay beamforming matrix, the source transmit power and PS ratio is intractable. To find a closed-form solution of the formulated problem, we decouple the primal problem into two subproblems. In the first problem, we intend to optimize the beamforming vectors for given transmit powers and PS ratio. In the second subproblem, we optimize the remaining parameters with obtained beamformers. It is worth noting that although the corresponding subproblem are nonconvex, the optimal solution of each subproblem can be found by using certain techniques. The iterative optimization algorithm finally converges. Simulation results verify the effectiveness of the proposed joint design. I. INTRODUCTION Simultaneous wireless information and power transfer (SWIPT) is a promising energy harvesting (EH) techniqueto prolong the operational time of energy-constrained nodes in wireless networks [1], [2]. Recently, SWIPT has been investigated for various wireless channels, e.g., the point-topoint additive white Gaussian noise (AWGN) channel [3], the frequency selective channels [4], the fading AWGN channel [5], the multiple-input-multiple-output (MIMO) channel [6], and the multiple-input-single-output (MISO) broadcast channel [7].Besides the above studies related to one-hop transmission, the SWIPT technique has also been extended to wireless relay networks [8]- [14]. For the one-way single-antenna relay channel, two protocols, namely time switching (TS) and power splitting (PS), are proposed for amplify-and-forward (AF) relay networks in [8], [9]. Later on, SWIPT was extended to a full-duplex wireless-powered one-way relay channel in [10], [11], where the data and energy queues of the relay are updated simultaneously in every time slot. However, compared with the one-way relaying (OWR), two-way relaying (TWR) can further improve system spectral efficiency, the SWIPT protocols for TWR channel recently have attracted much attention. In [12], the authors provided a SWIPT protocol in two-way AF relaying channels, where two sources exchange

A Survey on Simultaneous Wireless Information and Power Transfer With Cooperative Relay and Future Challenges

“…An iterative algorithm based on constrained concave-convex procedure (CCCP) to secure relay beamforming in SWIPT based cooperative network was proposed in [113]. Other relevant works of beamforming in SWIPT-based CoR network were done in [184]- [186].…”