Optimal Unitary Linear Processing for Amplify-and-Forward Cooperative OFDM systems

TL;DR

This paper develops an analytical framework to optimize relay processing in OFDM systems, revealing that permutation matrices for subcarrier pairing maximize achievable rates, leading to significant performance gains.

Contribution

It introduces a novel framework for optimal unitary linear processing in amplify-and-forward OFDM systems, identifying permutation matrices as optimal solutions.

Findings

Permutation matrices are optimal for relay processing.

Optimal subcarrier pairing improves achievable rate.

Simulation confirms performance gains over non-optimal methods.

Abstract

In this paper, we consider the amplified-and-forward relaying in an OFDM system with unitary linear processing at the relay. We proposed a general analytical framework to find the unitary linear processing matrix that maximizes the system achievable rate. We show that the optimal processing matrix is a permutation matrix, which implies that a subcarrier pairing strategy is optimal. We further derived the optimal subcarrier pairing schemes for scenarios with and without the direct source-destination path for diversity. Simulation results are presented to demonstrate the achievable gain of optimal subcarrier pairing compared with non-optimal linear processing and non-pairing.