Accelerated Projected Gradient Method for the Optimization of Cell-Free Massive MIMO Downlink

Muhammad Farooq*, Hien Quoc Ngo, Le Nam Tran

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

We consider the downlink of a cell-free massive multiple-input multiple-output (MIMO) system where large number of access points (APs) simultaneously serve a group of users. Two fundamental problems are of interest, namely (i) to maximize the total spectral efficiency (SE), and (ii) to maximize the minimum SE of all users. As the considered problems are non-convex, existing solutions rely on successive convex approximation to find a sub-optimal solution. The known methods use off-the-shelf convex solvers, which basically implement an interior-point algorithm, to solve the derived convex problems. The main issue of such methods is that their complexity does not scale favorably with the problem size, limiting previous studies to cell-free massive MIMO of moderate scales. Thus the potential of cell-free massive MIMO has not been fully understood. To address this issue, we propose an accelerated projected gradient method to solve the considered problems. Particularly, the proposed solution is found in closed-form expressions and only requires the first order information of the objective, rather than the Hessian matrix as in known solutions, and thus is much more memory efficient. Numerical results demonstrate that our proposed solution achieves far less run-time, compared to other second-order methods.

Original languageEnglish
Title of host publication2020 IEEE 31st Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC 2020): Proceedings
PublisherInstitute of Electrical and Electronics Engineers Inc.
Number of pages6
ISBN (Electronic)9781728144900
DOIs
Publication statusPublished - 08 Oct 2020
Event31st IEEE Annual International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2020 - Virtual, London, United Kingdom
Duration: 31 Aug 202003 Sep 2020

Publication series

NameIEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC
PublisherIEEE
Volume2020-August
ISSN (Print)2166-9570
ISSN (Electronic)2166-9589

Conference

Conference31st IEEE Annual International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2020
CountryUnited Kingdom
CityVirtual, London
Period31/08/202003/09/2020

Keywords

  • Cell-free massive MIMO
  • Gradient
  • Power-control
  • Sum-rate

ASJC Scopus subject areas

  • Electrical and Electronic Engineering

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