Relay Selection and Performance Analysis in Multiple-User Networks

TL;DR

This paper analyzes relay selection strategies in multi-user networks, proposing optimal and suboptimal algorithms, deriving their diversity orders, and validating the results through simulations.

Contribution

It introduces an optimal relay selection algorithm for multi-user networks and a low-complexity suboptimal scheme, with theoretical diversity analysis and performance comparisons.

Findings

Optimal RS achieves full diversity.

Suboptimal RS's diversity decreases with more users.

SRS outperforms naive RS as relays increase.

Abstract

This paper investigates the relay selection (RS) problem in networks with multiple users and multiple common amplify-and-forward (AF) relays. Considering the overall quality-of-service of the network, we first specify our definition of optimal RS for multiple-user relay networks. Then an optimal RS (ORS) algorithm is provided, which is a straightforward extension of an RS scheme in the literature that maximizes the minimum end-to-end receive signal-to-noise ratio (SNR) of all users. The complexity of the ORS is quadratic in both the number of users and the number of relays. Then a suboptimal RS (SRS) scheme is proposed, which has linear complexity in the number of relays and quadratic complexity in the number of users. Furthermore, diversity orders of both the ORS and the proposed SRS are theoretically derived and compared with those of a naive RS scheme and the single-user RS network. It is shown that the ORS achieves full diversity; while the diversity order of the SRS decreases with the the number of users. For two-user networks, the outage probabilities and array gains corresponding to the minimum SNR of the RS schemes are derived in closed forms. It is proved that the advantage of the SRS over the naive RS scheme increases as the number of relays in the network increases. Simulation results are provided to corroborate the analytical results.