Linear Precoder Design for SWIPT-Enabled Relay Networks With Finite-Alphabet Inputs

Abstract

This paper considers the problem of mutual information maximization in a two-hop relay network with simultaneous wireless information and power transfer (SWIPT), where the relay nodes use the power splitting (PS) scheme to harvest the energy for information forwarding. Unlike previous research, this paper focuses on a more practical scenario, where the inputs to the network are assumed to be finite-alphabet signals. Although each node in the network is assumed to have single antenna, we show that the relay network can be regarded as an effective multiple-input multiple-output (MIMO) system. Our goal is to perform the joint optimization on the precoder at source and PS ratio at relays to maximize the mutual information. Although the formulated problem is nondeterministic polynomial-time (NP)-hard, we theoretically analyze the optimal PS ratio; then, by using the structure of optimization problem, a near optimal precoder design based on semidefinite relaxation (SDR) is proposed; further, to reduce the complexity of algorithm, another precoder design based on search technique, which exploiting the structure of precoder, is developed only with a slight performance degradation. Simulation results verify the efficacy of proposed precoder designs.INDEX TERMS Finite-alphabet inputs, precoder design, SWIPT, relay network.

Joint Precoder Design for SWIPT-Enabled MIMO Relay Networks With Finite-Alphabet Inputs

“…Refer to our previous work [33] for details. Note that, after the optimal solution to (32) is obtained, the Gaussian randomization technique [35], [36] needs to be used to extract an approximately optimal solution p opt to problem (30). The overall source precoder design based on SDR is presented in detail in Algorithm 2.…”

“…, step size µ := µ int , and minimum step size µ min ; 2: Set n := 1, calculate Γ(R (n) |P) according to (20); 3: If µ > µ min , go to 4. Otherwise, return R (n) and stop; 4: Calculate Θ as (35). If Θ is not satisfied (33b), project Θ into the feasible set; Otherwise, update µ := 1 2 µ and go to 3; 7: Set n := n + 1.…”

Rate-Energy Balanced Precoding Design for SWIPT Based Two-Way Relay Systems

“…In [2], for the multipleinput multiple-output (MIMO) SWIPT-based AF-TWR systems, hybridized power-time splitting ratios and precoders are obtained via the maximization of convexified bounds on the sum rate. In [24], [25], transceivers and splitters are designed via semi-definite relaxation (SDR) based convex problems for finite constellation symbols. For DF relaying in [23], power allocation and splitting ratios are computed via the formulated convex problem.…”

Rate-Energy Balanced Precoding Design for SWIPT based Two-Way Relay Systems

“…In [2], for the multipleinput multiple-output (MIMO) SWIPT-based AF-TWR systems with hybridized power-time splitting ratios and precoders are obtained via the maximization of convexified bounds on the sum rate. In [24], [25], transceivers and splitting ratios are designed via semi-definite relaxation (SDR) based convex optimization technique for finite constellation symbols. For DF relaying in [23], power allocation and splitting ratios are computed via the formulated convex problem.…”