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

• Published in: IEEE transactions on signal processing Vol. 65; no. 4; pp. 1026 - 1041
• Main Authors: Zappone, Alessio, Matthiesen, Bho, Jorswieck, Eduard Axel
• Format: Journal Article
• Language: English
• Published: IEEE 15.02.2017
• Subjects: 5G technologies; Cognitive radio; device-to-device; Device-to-device communication; energy efficiency; Interference; MIMO; MIMO channels; Performance evaluation; resource allocation; Resource management; Signal processing algorithms
• ISSN: 1053-587X; 1941-0476
• DOI: 10.1109/TSP.2016.2626249

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 nonconvex, 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 programs. 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.