Energy Efficiency of the Cell-Free Massive MIMO Uplink with Optimal Uniform Quantization

Manijeh Bashar, Kanapathippillai Cumanan, Alister G. Burr, Hien Quoc Ngo, Erik G. Larsson

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)
214 Downloads (Pure)

Abstract

A cell-free Massive multiple-input multiple-output (MIMO) uplink is considered, where the access points (APs) are connected to a central processing unit (CPU) through limited-capacity wireless microwave links. The quantized version of the weighted signals are available at the CPU, by exploiting the Bussgang decomposition to model the effect of quantization. A closed-form expression for spectral efficiency is derived taking into account the effects of channel estimation error and quantization distortion. The energy efficiency maximization problem is considered with per-user power, backhaul capacity and throughput requirement constraints. To solve this non-convex problem, we decouple the original problem into two sub-problems, namely, receiver filter coefficient design and power allocation. The receiver filter coefficient design is formulated as a generalized eigenvalue problem whereas a successive convex approximation (SCA) and a heuristic sub-optimal scheme are exploited to convert the power allocation problem into a standard geometric programming (GP) problem. An iterative algorithm is proposed to alternately solve each sub-problem. Complexity analysis and convergence of the proposed schemes are investigated. Numerical results indicate the superiority of the proposed algorithms over the case of equal power allocation.
Original languageEnglish
JournalIEEE Transactions on Green Communications and Networking
Early online date30 Jul 2019
DOIs
Publication statusEarly online date - 30 Jul 2019

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