Splitting Algorithms for Fast Relay Selection: Generalizations, Analysis, and a Unified View

TL;DR

This paper introduces a unified analysis and new algorithms for relay selection in cooperative communications, improving efficiency and providing bounds for selecting multiple relays in distributed systems.

Contribution

It develops a novel asymptotic analysis for splitting algorithms, introduces a new algorithm for selecting multiple relays, and offers a unified framework for distributed relay selection.

Findings

The analysis yields simpler expressions for the average number of slots needed.

The new algorithm efficiently selects the top two or three relays within a few slots.

Bounds and schemes are provided for discrete metric cases.

Abstract

Relay selection for cooperative communications promises significant performance improvements, and is, therefore, attracting considerable attention. While several criteria have been proposed for selecting one or more relays, distributed mechanisms that perform the selection have received relatively less attention. In this paper, we develop a novel, yet simple, asymptotic analysis of a splitting-based multiple access selection algorithm to find the single best relay. The analysis leads to simpler and alternate expressions for the average number of slots required to find the best user. By introducing a new `contention load' parameter, the analysis shows that the parameter settings used in the existing literature can be improved upon. New and simple bounds are also derived. Furthermore, we propose a new algorithm that addresses the general problem of selecting the best $Q \ge 1$ relays, and analyze and optimize it. Even for a large number of relays, the algorithm selects the best two relays within 4.406 slots and the best three within 6.491 slots, on average. We also propose a new and simple scheme for the practically relevant case of discrete metrics. Altogether, our results develop a unifying perspective about the general problem of distributed selection in cooperative systems and several other multi-node systems.