CELL-FREE MASSIVE MIMO SYSTEMS WITH MULTI-ANTENNA USERS

In this paper, we investigate the impact of multiple-antenna deployment at access points (APs) and users on the performance of cell-free massive multiple-input multiple-output (MIMO). The transmission is done via time-division duplex (TDD) protocol. With this protocol, the channels are first estimated at each AP based on the received pilot signals in the training phase. Then these channel information will be used to decode the symbols before sending to all users. The simple and distributed conjugate beamforming technique is deployed. We derive a closed-form expression for the downlink spectral efficiency taking into account the imperfect channel state information (CSI), non-orthogonal pilots, and power control. This spectral efficiency can be achieved without the knowledge of instantaneous CSI at the users. In addition, the effects of the number antennas per APs and per users are analyzed in the case of using mutual orthogonal pilot sequences and data power control.

[1]  Emil Björnson,et al.  Massive MIMO with Non-Ideal Arbitrary Arrays: Hardware Scaling Laws and Circuit-Aware Design , 2014, IEEE Transactions on Wireless Communications.

[2]  Emil Björnson,et al.  Local Partial Zero-Forcing Precoding for Cell-Free Massive MIMO , 2020, IEEE Transactions on Wireless Communications.

[3]  Emil Björnson,et al.  Performance of Cell-Free Massive MIMO With Rician Fading and Phase Shifts , 2019, IEEE Transactions on Wireless Communications.

[4]  Alister G. Burr,et al.  Cell-Free Massive MIMO with Limited Backhaul , 2018, 2018 IEEE International Conference on Communications (ICC).

[5]  Erik G. Larsson,et al.  Downlink Training in Cell-Free Massive MIMO: A Blessing in Disguise , 2019, IEEE Transactions on Wireless Communications.

[6]  Symeon Chatzinotas,et al.  Performance Analysis of Cell-Free Massive MIMO Systems: A Stochastic Geometry Approach , 2020, IEEE Transactions on Vehicular Technology.

[7]  Emil Björnson,et al.  Can We Rely on Channel Hardening in Cell-Free Massive MIMO? , 2017, 2017 IEEE Globecom Workshops (GC Wkshps).

[8]  Stefano Buzzi,et al.  Cell-Free Massive MIMO: User-Centric Approach , 2017, IEEE Wireless Communications Letters.

[9]  Erik G. Larsson,et al.  Fundamentals of massive MIMO , 2016, SPAWC.

[10]  Thomas L. Marzetta,et al.  Noncooperative Cellular Wireless with Unlimited Numbers of Base Station Antennas , 2010, IEEE Transactions on Wireless Communications.

[11]  Andrea J. Goldsmith,et al.  Capacity and power allocation for fading MIMO channels with channel estimation error , 2006, IEEE Trans. Inf. Theory.

[12]  Erik G. Larsson,et al.  On the Total Energy Efficiency of Cell-Free Massive MIMO , 2017, IEEE Transactions on Green Communications and Networking.

[13]  Thomas M. Cover,et al.  Elements of Information Theory , 2005 .

[14]  Joint Power Allocation and Load Balancing Optimization for Energy-Efficient Cell-Free Massive MIMO Networks , 2020, IEEE Transactions on Wireless Communications.

[15]  Hien Quoc Ngo,et al.  Cell-Free Massive MIMO Networks: Optimal Power Control Against Active Eavesdropping , 2018, IEEE Transactions on Communications.

[16]  Emil Björnson,et al.  Ubiquitous cell-free Massive MIMO communications , 2018, EURASIP Journal on Wireless Communications and Networking.

[17]  Bhaskar D. Rao,et al.  Precoding and Power Optimization in Cell-Free Massive MIMO Systems , 2017, IEEE Transactions on Wireless Communications.

[18]  Antti Tölli,et al.  Fast Converging Algorithm for Weighted Sum Rate Maximization in Multicell MISO Downlink , 2012, IEEE Signal Processing Letters.

[19]  Erik G. Larsson,et al.  How Much Do Downlink Pilots Improve Cell-Free Massive MIMO? , 2016, 2016 IEEE Global Communications Conference (GLOBECOM).

[20]  Hien Quoc Ngo,et al.  Energy Efficiency in Cell-Free Massive MIMO with Zero-Forcing Precoding Design , 2017, IEEE Communications Letters.

[21]  S. Venkatesan,et al.  Network MIMO: Overcoming Intercell Interference in Indoor Wireless Systems , 2007, 2007 Conference Record of the Forty-First Asilomar Conference on Signals, Systems and Computers.

[22]  Emil Björnson,et al.  Channel Hardening and Favorable Propagation in Cell-Free Massive MIMO With Stochastic Geometry , 2017, IEEE Transactions on Communications.

[23]  Shlomo Shamai,et al.  Enhancing the cellular downlink capacity via co-processing at the transmitting end , 2001, IEEE VTS 53rd Vehicular Technology Conference, Spring 2001. Proceedings (Cat. No.01CH37202).

[24]  Erik G. Larsson,et al.  Massive MU-MIMO downlink TDD systems with linear precoding and downlink pilots , 2013, 2013 51st Annual Allerton Conference on Communication, Control, and Computing (Allerton).

[25]  Emil Björnson,et al.  Massive MIMO Networks: Spectral, Energy, and Hardware Efficiency , 2018, Found. Trends Signal Process..

[26]  Rasoul Nikbakht,et al.  Uplink Fractional Power Control and Downlink Power Allocation for Cell-Free Networks , 2020, IEEE Wireless Communications Letters.

[27]  Hien Quoc Ngo,et al.  Downlink Spectral Efficiency of Cell-Free Massive MIMO Systems With Multi-Antenna Users , 2020, IEEE Transactions on Communications.

[28]  Emil Björnson,et al.  Spectral and energy efficiency of cell-free massive MIMO systems with hardware impairments , 2017, 2017 9th International Conference on Wireless Communications and Signal Processing (WCSP).

[29]  Erik G. Larsson,et al.  Massive MIMO for next generation wireless systems , 2013, IEEE Communications Magazine.

[30]  Emil Björnson,et al.  Massive MIMO with multi-antenna users: When are additional user antennas beneficial? , 2016, 2016 23rd International Conference on Telecommunications (ICT).

[31]  Hien Quoc Ngo,et al.  Uplink Spectral Efficiency of Cell-free Massive MIMO with Multi-Antenna Users , 2019, 2019 3rd International Conference on Recent Advances in Signal Processing, Telecommunications & Computing (SigTelCom).

[32]  Erik G. Larsson,et al.  Cell-Free Massive MIMO Versus Small Cells , 2016, IEEE Transactions on Wireless Communications.

[33]  Michail Matthaiou,et al.  Power Scaling of Uplink Massive MIMO Systems With Arbitrary-Rank Channel Means , 2014, IEEE Journal of Selected Topics in Signal Processing.

[34]  Tao Jiang,et al.  Spectral Efficiency Analysis of Cell-Free Massive MIMO Systems With Zero-Forcing Detector , 2018, IEEE Transactions on Wireless Communications.

[35]  Hien Quoc Ngo,et al.  Pilot Power Control for Cell-Free Massive MIMO , 2018, IEEE Transactions on Vehicular Technology.

[36]  Emil Björnson,et al.  Making Cell-Free Massive MIMO Competitive With MMSE Processing and Centralized Implementation , 2019, IEEE Transactions on Wireless Communications.

[37]  Erik G. Larsson,et al.  Energy and Spectral Efficiency of Very Large Multiuser MIMO Systems , 2011, IEEE Transactions on Communications.