Pilot Assignment for Joint Uplink-Downlink Spectral Efficiency Enhancement in Massive MIMO Systems With Spatial Correlation

• Published in: IEEE transactions on vehicular technology Vol. 70; no. 8; pp. 8292 - 8297
• Main Authors: Nguyen, Tien Hoa, Chien, Trinh Van, Ngo, Hien Quoc, Tran, Xuan Nam, Bjornson, Emil
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.08.2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Algorithms; Channel estimation; Closed-form expression; Combinatorial optimization; Combinatorial optimization problems; Contamination; Correlated Rayleigh fading channels; Data communication; Data transmission; Downlink; Downlinking; Efficiency; Ergodic spectral efficiencies; Fading channels; Heuristic algorithms; Interference; Massive MIMO; Massive multiple-input- multiple-output system (MIMO); max-min fairness optimization; MIMO systems; Optimization; Optimization problems; pilot assignment; Power control; Rayleigh fading; Sequential algorithm; Signal to noise ratio; Spectral efficiencies; Uplink; max-min fairness optimization; pilot assignment; Channel estimation; Interference; Massive MIMO; Downlink; Data communication; Uplink; Contamination; Signal to noise ratio
• ISSN: 0018-9545; 1939-9359; 1939-9359
• DOI: 10.1109/TVT.2021.3091020

This paper proposes a flexible pilot assignment method to jointly optimize the uplink and downlink data transmission in multi-cell Massive multiple input multiple output (MIMO) systems with correlated Rayleigh fading channels. By utilizing a closed-form expression of the ergodic spectral efficiency (SE) achieved with maximum ratio processing, we formulate an optimization problem for maximizing the minimum weighted sum of the uplink and downlink SEs subject to the transmit powers and pilot assignment sets. This combinatiorial optimization problem is solved by two sequential algorithms: a heuristic pilot assignment is first proposed to obtain a good pilot reuse set and the data power control is then implemented. Numerical results manifest that the proposed algorithm converges fast to a better minimum sum SE per user than the algorithms in previous works.