A survey on user-centric cell-free massive MIMO systems  

作　　者：Shuaifei Chen Jiayi Zhang Jing Zhang Emil Björnson Bo Ai 

机构地区：[1]School of Electronic and Information Engineering,Beijing Jiaotong University,Beijing,100044,China [2]Frontiers Science Center for Smart High-speed Railway System,Beijing Jiaotong University,Beijing,100044,China [3]Department of Computer Science,KTH Royal Institute of Technology,SE-16440,Kista,Sweden [4]Department of Electrical Engineering(ISY),Linköping University,SE-58183,Linköping,Sweden [5]State Key Laboratory of Rail Traffic Control and Safety,Beijing Jiaotong University,Beijing,100044,China

出　　处：《Digital Communications and Networks》2022年第5期695-719,共25页数字通信与网络（英文版）

基　　金：This work was supported in part by National Key R&D Program of China under Grant 2020YFB1807201;in part by National Natural Science Foundation of China under Grants 61971027,U1834210,and 61961130391;in part by Beijing Natural Science Foundation under Grant L202013;in part by Frontiers Science Center for Smart High-speed Railway System under Grant 2020JBZD005;in part by the Royal Society Newton Advanced Fellowship under Grant NA191006.E.Björnson was supported by the Grant 2019-05068 from the Swedish Research Council.

摘　　要：The mobile data traffic has been exponentially growing during the last several decades.This was enabled by the densification of the network infrastructure in terms of increased cell density(i.e.,Ultra-Dense Network(UDN))and/or the increased number of active antennas per Access Point(AP)(i.e.,massive Multiple-Input Multiple-Output(mMIMO)).However,neither UDN nor mMIMO will meet the increasing demand for the data rate of the Sixth Generation(6G)wireless communications due to the inter-cell interference and large quality-of-service variations.Cell-Free(CF)mMIMO,which combines the best aspects of UDN and mMIMO,is viewed as a key solution to this issue.In such systems,each User Equipment(UE)is served by a preferred set of surrounding APs cooperatively.In this paper,we provide a survey of the state-of-the-art literature on CF mMIMO.As a starting point,the significance and the basic properties of CF mMIMO are highlighted.We then present the canonical framework to discuss the essential details(i.e.,transmission procedure and mathematical system model).Next,we provide a deep look at the resource allocation and signal processing problems related to CF mMIMO and survey the up-to-date schemes and algorithms.After that,we discuss the practical issues in implementing CF mMIMO and point out the potential future directions.Finally,we conclude this paper with a summary of the key lessons learned in this field.

关 键 词：6G network User-centric cell-free network Massive multiple-input multiple-output 

分 类 号：TP391.44[自动化与计算机技术—计算机应用技术] TN929.5[自动化与计算机技术—计算机科学与技术]