End-to-End Outage Minimization in OFDM Based Linear Relay Networks

TL;DR

This paper develops an optimal power and time allocation strategy for OFDM-based linear relay networks to minimize end-to-end outage probability under power constraints, using a two-step approach with both optimal and sub-optimal algorithms.

Contribution

It introduces a novel two-step optimization framework for joint power and time adaptation in OFDM relay networks, including a low-complexity sub-optimal algorithm.

Findings

The optimal policy minimizes outage probability effectively.

The sub-optimal algorithm reduces computational complexity.

Numerical results demonstrate improved performance over existing schemes.

Abstract

Multi-hop relaying is an economically efficient architecture for coverage extension and throughput enhancement in future wireless networks. OFDM, on the other hand, is a spectrally efficient physical layer modulation technique for broadband transmission. As a natural consequence of combining OFDM with multi-hop relaying, the allocation of per-hop subcarrier power and per-hop transmission time is crucial in optimizing the network performance. This paper is concerned with the end-to-end information outage in an OFDM based linear relay network. Our goal is to find an optimal power and time adaptation policy to minimize the outage probability under a long-term total power constraint. We solve the problem in two steps. First, for any given channel realization, we derive the minimum short-term power required to meet a target transmission rate. We show that it can be obtained through two nested bisection loops. To reduce computational complexity and signalling overhead, we also propose a sub-optimal algorithm. In the second step, we determine a power threshold to control the transmission on-off so that the long-term total power constraint is satisfied. Numerical examples are provided to illustrate the performance of the proposed power and time adaptation schemes with respect to other resource adaptation schemes.