Relay Selection and Power Allocation in Cooperative Cellular Networks

TL;DR

This paper investigates relay selection and power allocation in multiuser cooperative cellular networks, demonstrating that simple relay selection is nearly optimal and proposing heuristics that perform well in realistic scenarios.

Contribution

It formulates a convex optimization problem to analyze relay assignment, showing that selection is typically optimal, and introduces heuristics for near-optimal relay and power allocation.

Findings

Selection is nearly always optimal in multiuser relay scenarios.

Proposed heuristics achieve performance close to the upper bound.

Simulation results highlight the trade-offs between relaying gains and costs.

Abstract

We consider a system with a single base station communicating with multiple users over orthogonal channels while being assisted by multiple relays. Several recent works have suggested that, in such a scenario, selection, i.e., a single relay helping the source, is the best relaying option in terms of the resulting complexity and overhead. However, in a multiuser setting, optimal relay assignment is a combinatorial problem. In this paper, we formulate a related convex optimization problem that provides an extremely tight upper bound on performance and show that selection is, almost always, inherent in the solution. We also provide a heuristic to find a close-to-optimal relay assignment and power allocation across users supported by a single relay. Simulation results using realistic channel models demonstrate the efficacy of the proposed schemes, but also raise the question as to whether the gains from relaying are worth the additional costs.