Energy Efficiency in MIMO Underlay and Overlay Device-to-Device Communications and Cognitive Radio Systems

TL;DR

This paper develops algorithms for optimizing energy efficiency in spectrum-sharing systems involving primary and secondary users, applicable to cognitive radio and D2D communications, with solutions for both underlay and overlay scenarios.

Contribution

It introduces novel algorithms for resource allocation that maximize secondary energy efficiency under rate constraints, addressing non-convex fractional problems in both scenarios.

Findings

Algorithms achieve energy-efficient resource allocation

Proposed methods outperform existing solutions in complexity and performance

Overlay algorithms show similar results despite different complexities

Abstract

This paper addresses the problem of resource allocation for systems in which a primary and a secondary link share the available spectrum by an underlay or overlay approach. After observing that such a scenario models both cognitive radio and D2D communications, we formulate the problem as the maximization of the secondary energy efficiency subject to a minimum rate requirement for the primary user. This leads to challenging non-convex, fractional problems. In the underlay scenario, we obtain the global solution by means of a suitable reformulation. In the overlay scenario, two algorithms are proposed. The first one yields a resource allocation fulfilling the first-order optimality conditions of the resource allocation problem, by solving a sequence of easier fractional problems. The second one enjoys a weaker optimality claim, but an even lower computational complexity. Numerical results demonstrate the merits of the proposed algorithms both in terms of energy-efficient performance and complexity, also showing that the two proposed algorithms for the overlay scenario perform very similarly, despite the different complexity.