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

TL;DR

This paper proposes a low-complexity, balanced precoding design for SWIPT-enabled two-way relay systems that improves energy harvesting while analyzing the trade-offs with data rate performance.

Contribution

It introduces a chordal distance decomposition-based precoder that balances energy harvesting and rate, offering a flexible and less complex alternative to existing convex relaxation methods.

Findings

Proposed precoder achieves higher harvested energy than interference alignment (IA) precoders.

Loss in sum rate is bounded and analyzed.

Simulation shows MSE-based IA schemes outperform subspace alignment methods for SWIPT.

Abstract

Simultaneous wireless information and power transfer (SWIPT) technique is a popular strategy to convey both information and RF energy for harvesting at receivers. In this regard, we consider a two-way relay system with multiple users and a multi-antenna relay employing SWIPT strategy, where splitting the received signal leads to a rate-energy trade-off. In literature, the works on transceiver design have been studied using computationally intensive and suboptimal convex relaxation based schemes. In this paper, we study the balanced precoder design using chordal distance (CD) decomposition, which incurs much lower complexity, and is flexible to dynamic energy requirements. It is analyzed that given a non-negative value of CD, the achieved harvested energy for the proposed balanced precoder is higher than that for the perfect interference alignment (IA) precoder. The corresponding loss in sum rates is also analyzed via an upper bound. Simulation results add that the IA schemes based on mean-squared error are better suited for the SWIPT maximization than the subspace alignment-based methods.