Impact of Propagation Environment on Energy-Efficient Relay Placement: Model and Performance Analysis

TL;DR

This paper investigates how the radio environment and relay coding schemes influence relay placement and system performance, proposing a geometrical model for energy efficiency and analyzing the trade-offs between coverage and energy consumption.

Contribution

It introduces a simple geometrical model for energy-efficient relay placement considering environmental factors and compares coding schemes' performance in relay networks.

Findings

Full decode-forward performs close to energy-optimized partial decode-forward at optimal relay locations.

Performance drops rapidly when relay is away from optimal position, requiring advanced coding schemes.

A trade-off exists between cell coverage and energy efficiency, with a relay location minimizing energy impact when increasing coverage.

Abstract

The performance of a relay-based cellular network is greatly affected by the relay location within a cell. Existing results for optimal relay placement do not reflect how the radio propagation environment and choice of the coding scheme can impact system performance. In this paper, we analyze the impact on relaying performance of node distances, relay height and line-of-sight conditions for both uplink and downlink transmissions, using several relay coding schemes. Our first objective is to propose a geometrical model for energy-efficient relay placement that requires only a small number of characteristic distances. Our second objective is to estimate the maximum cell coverage of a relay-aided cell given power constraints, and conversely, the averaged energy consumption given a cell radius. We show that the practical full decode-forward scheme performs close to the energy-optimized partial decode-forward scheme when the relay is ideally located. However, away from this optimum relay location, performance rapidly degrades and more advanced coding scheme, such as partial decode-forward, is needed to maintain good performance and allow more freedom in the relay placement. Finally, we define a trade-off between cell coverage and energy efficiency, and show that there exists a relay location for which increasing the cell coverage has a minimal impact on the average energy consumed per unit area.