去蜂窝大规模MIMO系统研究进展与发展趋势
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摘要
去蜂窝大规模多天线(multiple input multiple output,MIMO)引入"以用户为中心"的思想,通过部署多个分布式接入点(access points,APs),利用相同的时频资源为所有用户服务,有效缩短AP与用户的距离,获得空间宏分集增益,大幅降低路径损耗,并利用大量AP带来的有利传播,减少多用户干扰,从而使全区域均匀覆盖并大幅提升用户体验。去蜂窝大规模MIMO技术刚刚提出,发展尚处于探索阶段。结合国内外移动通信发展的最新趋势,对去蜂窝大规模MIMO系统的基本特点、关键技术、核心挑战与发展趋势进行了介绍和展望,并分为信息理论分析和信号处理技术2个部分,重点论述了信道硬化、有利传播、空间相关、导频分配、信道估计、信号检测等关键技术。指出了去蜂窝大规模MIMO有望成为后5G(beyond 5G)和6G的核心关键技术之一。
Based on the user-centric approach,cell-free massive multiple input multiple output( MIMO) deploys a large number of distributed access points( APs) simultaneously and jointly serves a small number of users. It can efficiently reduce the distance between AP and users,achieve strong spatial macro diversity gain,dramatically decrease the path loss,and use favorable propagation to suppress the multiuser interference. It can also provide uniformly good service for all users in the network. However,the concept of cell-free massive MIMO has just been proposed recently. With the development of mobile communications around the world,this paper introduces the characteristics,key technologies,important challenging and future directions. From the aspects of information theory and signal processing,this paper investigates several key characteristics and technologies,such as channel hardening,favorable propagation,spatial correlation,pilot allocation,channel estimation and signal detection. Finally,cell-free massive MIMO can be one of the most promising technologies for B5 G and 6 G.
Based on the user-centric approach,cell-free massive multiple input multiple output( MIMO) deploys a large number of distributed access points( APs) simultaneously and jointly serves a small number of users. It can efficiently reduce the distance between AP and users,achieve strong spatial macro diversity gain,dramatically decrease the path loss,and use favorable propagation to suppress the multiuser interference. It can also provide uniformly good service for all users in the network. However,the concept of cell-free massive MIMO has just been proposed recently. With the development of mobile communications around the world,this paper introduces the characteristics,key technologies,important challenging and future directions. From the aspects of information theory and signal processing,this paper investigates several key characteristics and technologies,such as channel hardening,favorable propagation,spatial correlation,pilot allocation,channel estimation and signal detection. Finally,cell-free massive MIMO can be one of the most promising technologies for B5 G and 6 G.
引文
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[26]ZHANG J,WEI Y,BJRNSON E,et al.Performance analysis and power control of cell-free massive MIMO systems with hardware impairments[J].IEEE Access,2018(6):55302-55314.
[27]HOYDIS J,BRINK S,DEBBAH M.Massive MIMO in the UL/DL of cellular networks:How many antennas do we need?[J].IEEE J Sel Areas Commun,2013,31(2):160-171.
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[29]NGUYEN T H,NGUYEN T K,HAN H D,et al.Optimal power control and load balancing for uplink cell-free multi-user massive MIMO[J].IEEE Access,2018(6):14462-14473.
[30]MAI T C,NGO H Q,EGAN M,et al.Pilot power control for cell-free massive MIMO[J].IEEE Trans Veh Technol,2018,67(11):11264-11268.
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[32]SABBAGH R,PAN C,WANG J.Pilot allocation and sum-rate analysis in cell-free massive MIMO systems[C]//2018 IEEE International Conference on Communications Workshops(ICC Workshops).Kansas City,MO,USA:IEEE,2018:1-6.
[33]LI Y,BADUGE G A A.NOMA-aided cell-free massive MIMO systems[J].IEEE Wireless Commun Lett,2018,7(6):950-953.
[34]BASHAR M,CUMANAN K,BURR A G,et al.Enhanced max-min SINR for uplink cell-free massive MIMOsystems[C]//2018 IEEE International Conference on Communications Workshops(ICC Workshops).[S.l.]:IEEE,2018:1-6.
[35]PANDA S.Performance optimization of cell-free massive MIMO system with power control approach[J].AEU-Int J Electron Commun,2018(97):210-219.
[36]INTERDONATO G,FRENGE R P,LARSSON E G.Utility-based downlink pilot assignment in cell-free massive MIMO[C]//22ndInternational ITG Workshop on Smart Antennas(WSA 2018).Bochum,Germany:[s.n.],2018:1-8.
[37]INTERDONATO G,NGO H Q,LARSSON E G,et al.How much do downlink pilots improve cell-free massive MIMO?[C]//Proc.IEEE GLOBECOM.Washington,DC,USA:IEEE,2016:1-7.
[38]ATTARIFAR M,ABBASFAR A,LOZANO A.Modified conjugate beamforming for cell-free massive MIMO[J].IEEE Wireless Commun Lett,2019(1):1-1.
[39]HOANG T M,NGO H Q,DUONG T Q,et al.Cell-free massive MIMO networks:Optimal power control against active eavesdropping[J].IEEE Trans Commun,2018,66(10):4724-4737.
[40]PARK S,SIMEONE O,ELDAR Y C,et al.Optimizing pilots and analog processing for channel estimation in cell-free massive MIMO with one-bit ADCs[C]//Proc.IEEE SPAWC.[S.l.]:IEEE,2018:1-5.
[41]HE H,WEN C,JIN S,et al.Deep learning-based channel estimation for beamspace mm Wave massive MIMOsystems[J].IEEE Wireless Commun Lett,2018,7(5):852-855.
[42]HUANG H,YANG J,SONG Y,et al.Deep learning for super-resolution channel estimation and DOA estimation based massive MIMO system[J].IEEE Trans Veh Technol,2018,67(9):8549-8560.
[43]NAYEBI E,ASHIKHMIN A,MARZETTA T L,et al.Precoding and power optimization in cell-free massive MIMO systems[J].IEEE Trans Wireless Commun,2017,16(7):4445-4459.
[44]XIE H,GAO F,JIN S,et al.Channel estimation for TDD/FDD massive MIMO systems with channel covariance computing[J].IEEE Trans Wireless Commun,2018,17(6):4206-4218.
[45]NGO H Q,LARSSON E G.No downlink pilots are needed in TDD massive MIMO[J].IEEE Trans Wireless Commun,2017,16(5):2921-2935.
[46]BOROUJERDI M N,ABBASFAR A,GHANBARI M.Cellfree massive MIMO with limited capacity fronthaul[J].Wireless Personal Commun,2019,104(2):633-648.
[47]FEMENIAS G,RIERA-PALOU F.Cell-free millimeterwave massive MIMO systems with limited fronthaul capacity[EB/OL].[2019-04-11].https://arxiv.org/pdf/1902.07503v1.pdf.
[48]MASOUMI H,EMADI M J.Transmission strategies for cell-free massive MIMO with limited capacity fronthaul links[EB/OL].(2019-02-02)[2019-04-11].https://arxiv.org/abs/1902.00700.
[49]BASHAR M,CUMANAN K,BURR A G,et al.Cellfree massive MIMO with limited backhaul[C]//Proc IEEE ICC.Kansas City,MO,USA:IEEE,2018:1-7.
[50]HUANG Q,BURR A.Compute-and-forward in cell-free massive MIMO:Great performance with low backhaul load[C]//2017 IEEE International Conference on Communications Workshops(ICC Workshops).Paris,France:IEEE,2017:601-606.
[2]张平,牛凯,田辉,等.6G移动通信技术展望[J].通信学报,2019,40(1),141-148.ZHANG Ping,NIU Kai,TIAN Hui,et al.Technology prospect of 6G mobile communications[J].Journal of Communications,2019,40(1),141-148.
[3]TARIQ F,KHANDAKER M,WONG K-K,et al.Aspeculative study on 6G[EB/OL].(2019-02-18)[2019-03-15].https://arxiv.org/abs/1902.06700.
[4]SAAD W,BENNIS M,CHEN M.A vision of 6G wireless systems:Applications,trends,technologies,and open research problems[EB/OL].(2019-02-26)[2019-04-11].https://arxiv.org/abs/1902.10265.
[5]DAVID K,BERNDT H.6G vision and requirements:Is there any need for beyond 5G?[J].IEEE Veh Technol Mag,2018,13(3):72-80.
[6]RAGHAVAN V,LI J.Evolution of physical-layer communications research in the post-5G era[J].IEEE Access,2019(7):10392-10401.
[7]STRINATI E C,BARBAROSSA S,GONZALEZ-JIMEN-EZ J L,et al.6G:The next frontier[EB/OL].(2019-01-10)[2019-04-11].https://arxiv.org/abs/1901.03239?context=cs.NI.
[8]ZHOU S,ZHAO M,XU X,et al.Distributed wireless communication system:A new architecture for future public wireless access[J].IEEE Commun Mag,2003,41(3):108-113.
[9]SONG G,WANG W,CHEN D,et al.KPI/KQI-driven coordinated multipoint in 5G:Measurements,field trials,and technical solutions[J].IEEE Wireless Commun,2018,25(5):23-29.
[10]PAN C,ELKASHLAN M,WANG J,et al.User-centric C-RAN architecture for ultra-dense 5G networks:Challenges and methodologies[J].IEEE Commun,2018,56(6):14-20.
[11]NGO H Q,ASHIKHMIN A,YANGH,et al.Cell-free massive MIMO versus small cells[J].IEEE Trans.Wireless Commun,2017,16(3):1834-1850.
[12]INTERDONATOG,BJRNSON E,NGO H Q,et al.U-biquitous cell-free massive MIMO communications[EB/OL].(2019-02-27)[2019-04-11].https://arxiv.org/abs/1804.03421.
[13]ERICSSON.Radio Stripes:Re-thinking mobile networks[EB/OL].(2019-04-12).https://www.ericsson.com/en/blog/2019/2/radio-stripes.
[14]LIU P,LUO K,CHEN D,et al.Spectral efficiency analysis in cell-free massive MIMO systems with zero-forcing detector[EB/OL].(2018-05-27)[2019-04-13].https://arxiv.org/abs/1805.10621.
[15]NAYEBI E,ASHIKHMIN A,MARZETTA T L,et al.Performance of cell-free massive MIMO systems with MMSE and LSFD receivers[C]//2016 50th Asilomar Conference on Signals,Systems Computers.Pacific Grove,CA,USA:IEEE,2016:203-207.
[16]ZDOGAN,BJRNSON E,ZHANG J.Cell-Free massive MIMO with Rician fading:Estimation schemes and spectral efficiency[C]//Proc.52nd Asilomar Conference Signals,Systems Computers.Pacific Grove,CA,USA:IEEE,2018:975-979.
[17]NGUYEN L D,DUONG T Q,NGO H Q,et al.Energy efficiency in cell-free massive MIMO with zero-forcing precoding design[J].IEEE Commun Lett,2017,21(8):1871-1874.
[18]NGO H Q,TRAN L N,DUONG T Q,et al.On the total energy efficiency of cell-free massive MIMO[J].IEEETrans.Green Commun Netw,2018,2(1):25-39.
[19]YANG H,MARZETTA T L.Energy efficiency of massive MIMO:Cell-free vs.cellular[C]//Proc.IEEE VTC.[S.l]:IEEE,2018:1-5.
[20]CHEN Z,BJRNSON E.Channel hardening and favorable propagation in cell-free massive MIMO with stochastic geometry[J].IEEE Trans Commun,2018,66(11):5205-5219.
[21]ZHANG J,DAI L,HE Z,et al.Mixed-ADC/DAC multipair massive MIMO relaying systems:Performance analysis and power optimization[J].IEEE Trans Commun,2019,67(1):140-153.
[22]ZHANG J,DAI L,LI X,et al.On low-resolution ADCs in practical 5G millimeter-wave massive MIMO systems[J].IEEE Commun Mag,2018,56(7):205-211.
[23]ZHANG J,XUEX,BJRNSON E,et al.Spectral efficiency of multipair massive MIMO two-way relaying with hardware impairments[J].IEEE Wireless Commun Lett,2018,7(1):14-17.
[24]ZHANG J,DAI L,ZHANG X,et al.Achievable rate of Rician large-scale MIMO channels with transceiver hardware impairments[J].IEEE Trans Veh Technol,2016,65(10):8800-8806.
[25]ZHANG J,DAI L,SUN S,et al.On the spectral efficiency of massive MIMO systems with low-resolution ADCs[J].IEEE Commun Lett,2016,20(5):842-845.
[26]ZHANG J,WEI Y,BJRNSON E,et al.Performance analysis and power control of cell-free massive MIMO systems with hardware impairments[J].IEEE Access,2018(6):55302-55314.
[27]HOYDIS J,BRINK S,DEBBAH M.Massive MIMO in the UL/DL of cellular networks:How many antennas do we need?[J].IEEE J Sel Areas Commun,2013,31(2):160-171.
[28]KARLSSON M,BJRNSON E,LARSSON E G.Techniques for system information broadcast in cell-free massive MI-MO[J].IEEE Trans Commun,2019,67(1):244-257.
[29]NGUYEN T H,NGUYEN T K,HAN H D,et al.Optimal power control and load balancing for uplink cell-free multi-user massive MIMO[J].IEEE Access,2018(6):14462-14473.
[30]MAI T C,NGO H Q,EGAN M,et al.Pilot power control for cell-free massive MIMO[J].IEEE Trans Veh Technol,2018,67(11):11264-11268.
[31]ATTARIFAR M,ABBASFAR A,LOZANO A.Random vs structured pilot assignment in cell-free massive MIMOwireless networks[C]//2018 IEEE International Conference on Communications Workshops(ICC Workshops).Kansas City,MO,USA:IEEE,2018:1-6.
[32]SABBAGH R,PAN C,WANG J.Pilot allocation and sum-rate analysis in cell-free massive MIMO systems[C]//2018 IEEE International Conference on Communications Workshops(ICC Workshops).Kansas City,MO,USA:IEEE,2018:1-6.
[33]LI Y,BADUGE G A A.NOMA-aided cell-free massive MIMO systems[J].IEEE Wireless Commun Lett,2018,7(6):950-953.
[34]BASHAR M,CUMANAN K,BURR A G,et al.Enhanced max-min SINR for uplink cell-free massive MIMOsystems[C]//2018 IEEE International Conference on Communications Workshops(ICC Workshops).[S.l.]:IEEE,2018:1-6.
[35]PANDA S.Performance optimization of cell-free massive MIMO system with power control approach[J].AEU-Int J Electron Commun,2018(97):210-219.
[36]INTERDONATO G,FRENGE R P,LARSSON E G.Utility-based downlink pilot assignment in cell-free massive MIMO[C]//22ndInternational ITG Workshop on Smart Antennas(WSA 2018).Bochum,Germany:[s.n.],2018:1-8.
[37]INTERDONATO G,NGO H Q,LARSSON E G,et al.How much do downlink pilots improve cell-free massive MIMO?[C]//Proc.IEEE GLOBECOM.Washington,DC,USA:IEEE,2016:1-7.
[38]ATTARIFAR M,ABBASFAR A,LOZANO A.Modified conjugate beamforming for cell-free massive MIMO[J].IEEE Wireless Commun Lett,2019(1):1-1.
[39]HOANG T M,NGO H Q,DUONG T Q,et al.Cell-free massive MIMO networks:Optimal power control against active eavesdropping[J].IEEE Trans Commun,2018,66(10):4724-4737.
[40]PARK S,SIMEONE O,ELDAR Y C,et al.Optimizing pilots and analog processing for channel estimation in cell-free massive MIMO with one-bit ADCs[C]//Proc.IEEE SPAWC.[S.l.]:IEEE,2018:1-5.
[41]HE H,WEN C,JIN S,et al.Deep learning-based channel estimation for beamspace mm Wave massive MIMOsystems[J].IEEE Wireless Commun Lett,2018,7(5):852-855.
[42]HUANG H,YANG J,SONG Y,et al.Deep learning for super-resolution channel estimation and DOA estimation based massive MIMO system[J].IEEE Trans Veh Technol,2018,67(9):8549-8560.
[43]NAYEBI E,ASHIKHMIN A,MARZETTA T L,et al.Precoding and power optimization in cell-free massive MIMO systems[J].IEEE Trans Wireless Commun,2017,16(7):4445-4459.
[44]XIE H,GAO F,JIN S,et al.Channel estimation for TDD/FDD massive MIMO systems with channel covariance computing[J].IEEE Trans Wireless Commun,2018,17(6):4206-4218.
[45]NGO H Q,LARSSON E G.No downlink pilots are needed in TDD massive MIMO[J].IEEE Trans Wireless Commun,2017,16(5):2921-2935.
[46]BOROUJERDI M N,ABBASFAR A,GHANBARI M.Cellfree massive MIMO with limited capacity fronthaul[J].Wireless Personal Commun,2019,104(2):633-648.
[47]FEMENIAS G,RIERA-PALOU F.Cell-free millimeterwave massive MIMO systems with limited fronthaul capacity[EB/OL].[2019-04-11].https://arxiv.org/pdf/1902.07503v1.pdf.
[48]MASOUMI H,EMADI M J.Transmission strategies for cell-free massive MIMO with limited capacity fronthaul links[EB/OL].(2019-02-02)[2019-04-11].https://arxiv.org/abs/1902.00700.
[49]BASHAR M,CUMANAN K,BURR A G,et al.Cellfree massive MIMO with limited backhaul[C]//Proc IEEE ICC.Kansas City,MO,USA:IEEE,2018:1-7.
[50]HUANG Q,BURR A.Compute-and-forward in cell-free massive MIMO:Great performance with low backhaul load[C]//2017 IEEE International Conference on Communications Workshops(ICC Workshops).Paris,France:IEEE,2017:601-606.