Network-Level Performance Evaluation of a Two-Relay Cooperative Random Access Wireless System

TL;DR

This paper analyzes the network-level performance of a wireless system with two relays using random access, providing analytical stability conditions and demonstrating the benefits of deploying a second relay through both analysis and simulations.

Contribution

It extends previous single-relay results to a two-relay system, deriving stability conditions and showing advantages of relay deployment at the network level.

Findings

Two-relay deployment improves throughput and stability.

Analytical expressions for relay queue stability are derived.

Simulations confirm benefits in multi-packet reception scenarios.

Abstract

In wireless networks relay nodes can be used to assist the users' transmissions to reach their destination. Work on relay cooperation, from a physical layer perspective, has up to now yielded well-known results. This paper takes a different stance focusing on network-level cooperation. Extending previous results for a single relay, we investigate here the benefits from the deployment of a second one. We assume that the two relays do not generate packets of their own and the system employs random access to the medium; we further consider slotted time and that the users have saturated queues. We obtain analytical expressions for the arrival and service rates of the queues of the two relays and the stability conditions. We investigate a model of the system, in which the users are divided into clusters, each being served by one relay, and show its advantages in terms of aggregate and throughput per user. We quantify the above, analytically for the case of the collision channel and through simulations for the case of Multi-Packet Reception (MPR), and we provide insight on when the deployment of a second relay in the system can yield significant advantages.