Energy Efficiency Optimization in Relay-Assisted MIMO Systems with Perfect and Statistical CSI

Alessio Zappone, Pan Cao, Eduard Jorswieck

Research output: Contribution to journalArticlepeer-review

94 Citations (Scopus)


A framework for energy-efficient resource allocation in a single-user, amplify-and-forward (AF), relay-assisted, multiple-input-multiple-output (MIMO) system is devised in this paper. Previous results in this area have focused on rate maximization or sum power minimization problems, whereas fewer results are available when bits/Joule energy efficiency (EE) optimization is the goal. Here, the performance metric to optimize is the ratio between the system's achievable rate and the total consumed power. The optimization is carried out with respect to the source and relay precoding matrices, subject to quality-of-service (QoS) and power constraints. Such a challenging non-convex optimization problem is tackled by means of fractional programming and alternating maximization algorithms, for various channel state information (CSI) assumptions at the source and relay. In particular the scenarios of perfect CSI and those of statistical CSI for either the source-relay or the relay-destination channel are addressed. Moreover, sufficient conditions for beamforming optimality are derived, which is useful in simplifying the system design. Numerical results are provided to corroborate the validity of the theoretical findings.
Original languageEnglish
Pages (from-to)443-457
Number of pages15
JournalIEEE Transactions on Signal Processing
Issue number2
Publication statusE-pub ahead of print - 20 Nov 2013


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