Relaying Strategies for Wireless-Powered MIMO Relay Networks

TL;DR

This paper explores relaying strategies in wireless-powered MIMO relay networks, proposing optimized schemes that enhance performance by leveraging energy flows and channel diagonalization, with proven convergence and improved results.

Contribution

It introduces novel optimization algorithms for energy-flow-assisted and non-assisted schemes, simplifying complex matrix problems to power optimizations with closed-form solutions.

Findings

EFA schemes outperform NEFA schemes in simulations.

More antennas at the relay improve signal space and EF leakage management.

The iterative optimization algorithm converges to a global optimum.

Abstract

This paper investigates relaying schemes in an amplify-and-forward multiple-input multiple-output relay network, where an energy-constrained relay harvests wireless power from the source information flow and can be further aided by an energy flow (EF) in the form of a wireless power transfer at the destination. However, the joint optimization of the relay matrix and the source precoder for the energy-flow-assisted (EFA) and the non-EFA (NEFA) schemes is intractable. The original rate maximization problem is transformed into an equivalent weighted mean square error minimization problem and optimized iteratively, where the global optimum of the nonconvex source precoder subproblem is achieved by semidefinite relaxation and rank reduction. The iterative algorithm finally converges. Then, the simplified EFA and NEFA schemes are proposed based on channel diagonalization, such that the matrices optimizations can be simplified to power optimizations. Closed-form solutions can be achieved. Simulation results reveal that the EFA schemes can outperform the NEFA schemes. Additionally, deploying more antennas at the relay increases the dimension of the signal space at the relay. Exploiting the additional dimension, the EF leakage in the information detecting block can be nearly separated from the information signal, such that the EF leakage can be amplified with a small coefficient.