Uplink transmission design for crowded correlated cell-free massive MIMO-OFDM systems  

作　　者：Junyuan GAO Yongpeng WU Yongjian WANG Wenjun ZHANG Fan WEI 

机构地区：[1]The Department of Electronic Engineering,Shanghai Jiao Tong University,Shanghai 200240,China [2]The National Computer Network Emergency Response Technical Team/Coordination Center of China,Beijing 100029,China

出　　处：《Science China(Information Sciences)》2021年第8期123-138,共16页中国科学（信息科学）（英文版）

基　　金：National Key R&D Program of China(Grant No.2018YFB1801102);Jiangxi Key R&D Program(Grant No.20181ACE50028);National Natural Science Foundation of China(Grant No.61701301);Open Research Project of State Key Laboratory of Integrated Services Networks(Xidian University)(Grant No.ISN20-03);Shanghai Key Laboratory of Digital Media Processing and Transmission(Grant No.STCSM18DZ2270700);National Natural Science Foundation of China(Grant No.61931019);Shanghai Key Laboratory of Digital Media Processing and Transmission(Grant No.STCSM18DZ2270700).

摘　　要：In cell-free massive multiple-input multiple-output(MIMO)orthogonal frequency division multiplexing(OFDM)systems,user equipments(UEs)are served by many distributed access points(APs),where channels are correlated owing to finite angle-delay spread in realistic outdoor wireless propagation environments.Meanwhile,the number of UEs is growing rapidly for future fully networked society.In this paper,we focus on the uplink transmission design in crowded correlated cell-free massive MIMO-OFDM systems with a limited number of orthogonal pilots.For the pilot transmission phase,we identify active UEs based on non-orthogonal pilot phase shift hopping patterns and non-orthogonal adjustable phase shift pilots(APSP).We derive a closed-form expression of mean square error of channel estimation(MSE-CE)and obtain an optimal condition for minimizing MSE-CE.According to this condition,the APSP set allocation scheme is proposed.Furthermore,for the data transmission,the max-min power control algorithm is devised to maximize the minimum spectral efficiency(SE)lower bound among active UEs.Simulation results indicate significant performance gains in terms of MSE-CE for the proposed APSP set allocation scheme.The proposed power control scheme can further improve the minimum SE among active UEs.Hence,they are crucial for crowded correlated cell-free massive MIMO-OFDM systems.

关 键 词：APSP set allocation cell-free massive MIMO-OFDM correlated channels crowded scenarios power control 

分 类 号：TN929.53[电子电信—通信与信息系统]