Power Allocation in Multi-hop OFDM Transmission Systems with Amplify-and-Forward Relaying: A Unified Approach

TL;DR

This paper introduces a unified, low-complexity power allocation framework for multi-hop OFDM systems with amplify-and-forward relaying, improving transmission rates under various power constraints and channel conditions.

Contribution

It develops a set of near-optimal and suboptimal iterative algorithms for power allocation, addressing the complexity of multi-hop OFDM systems with Rayleigh fading.

Findings

Proposed algorithms outperform existing methods in simulations.

The two-stage power allocation approach effectively balances performance and complexity.

Algorithms adapt to short and long-term power constraints in multi-hop scenarios.

Abstract

In this paper a unified approach for power allocation (PA) problem in multi-hop orthogonal frequency division multiplexing (OFDM) amplify-and-forward (AF) relaying systems has been developed. In the proposed approach, we consider short and long-term individual and total power constraints at the source and relays, and devise decentralized low complexity PA algorithms when wireless links are subject to channel path-loss and small-scale Rayleigh fading. In particular, aiming at improving the instantaneous rate of multi-hop transmission systems with AF relaying, we develop (i) a near-optimal iterative PA algorithm based on the exact analysis of the received SNR at the destination; (ii) a low complexity-suboptimal iterative PA algorithm based on an approximate expression at high-SNR regime; and (iii) a low complexity-non iterative PA scheme with limited performance loss. Since the PA problem in multi-hop systems is too complex to solve with known optimization solvers, in the proposed formulations, we adopted a two-stage approach, including a power distribution phase among distinct subcarriers, and a power allocation phase among different relays. The individual PA phases are then appropriately linked through an iterative method which tries to compensate the performance loss caused by the distinct two-stage approach. Simulation results show the superior performance of the proposed power allocation algorithms.