[en] Cell-Free Massive multiple-input multiple-output (MIMO) and reconfigurable intelligent surface (RIS) are two promising technologies for application to beyond-5G networks. This paper considers Cell-Free Massive MIMO systems with the assistance of an RIS for enhancing the system performance under the presence of spatial correlation among the engineered scattering elements of the RIS. Distributed maximum-ratio processing is considered at the access points (APs). We introduce an aggregated channel estimation approach that provides sufficient information for data processing with the main benefit of reducing the overhead required for channel estimation. The considered system is studied by using asymptotic analysis which lets the number of APs and/or the number of RIS elements grow large. A lower bound for the channel capacity is obtained for a finite number of APs and engineered scattering elements of the RIS, and closed-form expressions for the uplink and downlink ergodic net throughput are formulated in terms of only the channel statistics. Based on the obtained analytical frameworks, we unveil the impact of channel correlation, the number of RIS elements, and the pilot contamination on the net throughput of each user. In addition, a simple control scheme for optimizing the configuration of the engineered scattering elements of the RIS is proposed, which is shown to increase the channel estimation quality, and, hence, the system performance. Numerical results demonstrate the effectiveness of the proposed system design and performance analysis. In particular, the performance benefits of using RISs in Cell-Free Massive MIMO systems are confirmed, especially if the direct links between the APs and the users are of insufficient quality with high probability.
Disciplines :
Computer science
Author, co-author :
Van Chien, Trinh
Ngo, Hien Quoc
Chatzinotas, Symeon ; University of Luxembourg > Interdisciplinary Centre for Security, Reliability and Trust (SNT) > SigCom
Di Renzo, Marco
Ottersten, Björn ; University of Luxembourg > Interdisciplinary Centre for Security, Reliability and Trust (SNT)
External co-authors :
yes
Language :
English
Title :
Reconfigurable Intelligent Surface-Assisted Cell-Free Massive MIMO Systems Over Spatially-Correlated Channels
T. V. Chien, H. Q. Ngo, S. Chatzinotas, M. Di Renzo, and B. Ottersten, "RIS and cell-free massive MIMO: A marriage for harsh propagation environments," in Proc. IEEE GLOBECOM, Dec. 2021, pp. 1-6.
M. Giordani et al., "Toward 6G networks: Use cases and technologies," IEEE Commun. Mag., vol. 58, no. 3, pp. 55-61, Dec. 2020.
T. V. Chien and E. Björnson, Massive MIMO Communications. Cham, Switzerland: Springer, 2017, pp. 77-116.
T. Rappaport, Y. Xing, G. R. MacCartney, A. F. Molisch, E. Mellios, and J. Zhang, "Overview of millimeter wave communications for fifthgeneration (5G) wireless networks-with a focus on propagation models," IEEE Trans. Antennas Propag., vol. 65, no. 12, pp. 6213-6230, Dec. 2017.
E. Björnson, L. Sanguinetti, and M. Kountouris, "Deploying dense networks for maximal energy efficiency: Small cells meet massive MIMO," IEEE J. Sel. Areas Commun., vol. 34, no. 4, pp. 832-847, Apr. 2016.
T. V. Chien, T. N. Canh, E. Björnson, and E. G. Larsson, "Power control in cellular massive MIMO with varying user activity: A deep learning solution," IEEE Trans. Wireless Commun., vol. 19, no. 9, pp. 5732-5748, Sep. 2020.
G. Interdonato, E. Björnson, H. Q. Ngo, P. Frenger, and E. G. Larsson, "Ubiquitous cell-free massive MIMO communications," EURASIP J. Wireless Commun. Netw., vol. 2019, no. 1, pp. 1-13, Dec. 2019.
H. Q. Ngo, A. Ashikhmin, H. Yang, E. G. Larsson, and T. L. Marzetta, "Cell-free massive MIMO versus small cells," IEEE Trans. Wireless Commun., vol. 16, no. 3, pp. 1834-1850, Mar. 2017.
T. Van Chien, E. Bjornson, and E. G. Larsson, "Joint power allocation and load balancing optimization for energy-efficient cell-free massive MIMO networks," IEEE Trans. Wireless Commun., vol. 19, no. 10, pp. 6798-6812, Oct. 2020.
G. Interdonato, H. Q. Ngo, and E. G. Larsson, "Enhanced normalized conjugate beamforming for cell-free massive MIMO," IEEE Trans. Commun., vol. 69, no. 5, pp. 2863-2877, May 2021.
E. Björnson and L. Sanguinetti, "Scalable cell-free massive MIMO systems," IEEE Trans. Commun., vol. 68, no. 7, pp. 4247-4261, Jul. 2020.
Q. Wu and R. Zhang, "Intelligent reflecting surface enhanced wireless network via joint active and passive beamforming," IEEE Trans. Wireless Commun., vol. 18, no. 11, pp. 5394-5409, Nov. 2019.
T. A. Le, T. Van Chien, and M. Di Renzo, "Robust probabilisticconstrained optimization for IRS-aided MISO communication systems," IEEE Wireless Commun. Lett., vol. 10, no. 1, pp. 1-5, Jan. 2021.
M. Di Renzo et al., "Smart radio environments empowered by reconfigurable intelligent surfaces: How it works, state of research, and the road ahead," IEEE J. Sel. Areas Commun., vol. 38, no. 11, pp. 2450-2525, Nov. 2020.
Q. Wu et al., "Intelligent reflecting surface aided wireless communications: A tutorial," IEEE Trans. Commun., vol. 69, no. 5, pp. 3313-3351, May 2021.
M.-M. Zhao, Q. Wu, M.-J. Zhao, and R. Zhang, "Intelligent reflecting surface enhanced wireless networks: Two-timescale beamforming optimization," IEEE Trans. Wireless Commun., vol. 20, no. 1, pp. 2-17, Jan. 2021.
A. Zappone, M. Di Renzo, F. Shams, X. Qian, and M. Debbah, "Overhead-aware design of reconfigurable intelligent surfaces in smart radio environments," IEEE Trans. Wireless Commun., vol. 20, no. 1, pp. 126-141, Jan. 2021.
A. Abrardo, D. Dardari, and M. Di Renzo, "Intelligent reflecting surfaces: Sum-rate optimization based on statistical position information," IEEE Trans. Commun., vol. 69, no. 10, pp. 7121-7136, Oct. 2021.
B. Zheng and R. Zhang, "Intelligent reflecting surface-enhanced OFDM: Channel estimation and reflection optimization," IEEE Wireless Commun. Lett., vol. 9, no. 4, pp. 518-522, Apr. 2020.
X. Wei, D. Shen, and L. Dai, "Channel estimation for RIS assisted wireless communications-Part I: Fundamentals, solutions, and future opportunities," IEEE Commun. Lett., vol. 25, no. 5, pp. 1398-1402, May 2021.
N. S. Perovic, L. N. Tran, M. Di Renzo, and M. F. Flanagan, "Achievable rate optimization for MIMO systems with reconfigurable intelligent surfaces," IEEE Trans. Wireless Commun., vol. 20, no. 6, pp. 3865-3882, Jun. 2021.
T. Zhou, K. Xu, X. Xia, W. Xie, and J. Xu, "Achievable rate optimization for aerial intelligent reflecting surface-aided cell-free massive MIMO system," IEEE Access, vol. 9, pp. 3828-3837, 2021.
Z. Zhang and L. Dai, "Capacity improvement in wideband reconfigurable intelligent surface-aided cell-free network," in Proc. IEEE 21st Int. Workshop Signal Process. Adv. Wireless Commun. (SPAWC), May 2020, pp. 1-5.
M. Bashar, K. Cumanan, A. G. Burr, P. Xiao, and M. Di Renzo, "On the performance of reconfigurable intelligent surface-aided cellfree massive MIMO uplink," in Proc. GLOBECOM, Dec. 2020, pp. 1-6.
Y. Zhang, B. Di, H. Zhang, J. Lin, Y. Li, and L. Song, "Reconfigurable intelligent surface aided cell-free MIMO communications," IEEE Wireless Commun. Lett., vol. 10, no. 4, pp. 775-779, Apr. 2021.
Y. Zhang et al., "Beyond cell-free MIMO: Energy efficient reconfigurable intelligent surface aided cell-free MIMO communications," IEEE Trans. Cogn. Commun. Netw., vol. 7, no. 2, pp. 412-426, Jun. 2021.
T. Van Chien, L. T. Tu, S. Chatzinotas, and B. Ottersten, "Coverage probability and ergodic capacity of intelligent reflecting surfaceenhanced communication systems," IEEE Commun. Lett., vol. 25, no. 1, pp. 69-73, Jan. 2021.
T. Hou, Y. Liu, Z. Song, X. Sun, Y. Chen, and L. Hanzo, "Reconfigurable intelligent surface aided NOMA networks," IEEE J. Sel. Areas Commun., vol. 38, no. 11, pp. 2575-2588, Nov. 2020.
T. Van Chien, A. K. Papazafeiropoulos, L. T. Tu, R. Chopra, S. Chatzinotas, and B. Ottersten, "Outage probability analysis of IRSassisted systems under spatially correlated channels," IEEE Wireless Commun. Lett., vol. 10, no. 8, pp. 1815-1819, Aug. 2021.
M. Di Renzo et al., "Smart radio environments empowered by reconfigurable AI meta-surfaces: An idea whose time has come," EURASIP J. Wireless Commun. Netw., vol. 2019, no. 1, pp. 1-20, 2019.
Q.-U.-A. Nadeem, H. Alwazani, A. Kammoun, A. Chaaban, M. Debbah, and M.-S. Alouini, "Intelligent reflecting surface-assisted multi-user MISO communication: Channel estimation and beamforming design," IEEE Open J. Commun. Soc., vol. 1, pp. 661-680, 2020.
E. Björnson and L. Sanguinetti, "Rayleigh fading modeling and channel hardening for reconfigurable intelligent surfaces," IEEE Wireless Commun. Lett., vol. 10, no. 4, pp. 830-834, Apr. 2021.
B. Clerckx, G. Kim, and S. Kim, "Correlated fading in broadcast MIMO channels: Curse or blessing?" in Proc. IEEE GLOBECOM, Nov. 2008, pp. 1-5.
S. Kay, Fundamentals of Statistical Signal Processing: Estimation Theory. Upper Saddle River, NJ, USA: Prentice-Hall, 1993.
T. C. Mai, H. Q. Ngo, M. Egan, and T. Q. Duong, "Pilot power control for cell-free massive MIMO," IEEE Trans. Veh. Technol., vol. 67, no. 11, pp. 11264-11268, Nov. 2018.
T. Van Chien et al., "Joint pilot design and uplink power allocation in multi-cell massive MIMO systems," IEEE Trans. Wireless Commun., vol. 17, no. 3, pp. 2000-2015, Mar. 2018.
H. Cramér, Random Variables and Probability Distributions, no. 36. Cambridge, U.K.: Cambridge Univ. Press, 2004.
T. Van Chien, H. Q. Ngo, S. Chatzinotas, and B. Ottersten, "Reconfigurable intelligent surface-assisted massive MIMO: Favorable propagation, channel hardening, and rank deficiency," 2021, arXiv:2107.03434.
T. L. Marzetta, E. G. Larsson, H. Yang, and H. Q. Ngo, Fundamentals of Massive MIMO. Cambridge, U.K.: Cambridge Univ. Press, 2016.
G. Gradoni and M. Di Renzo, "End-to-end mutual coupling aware communication model for reconfigurable intelligent surfaces: An electromagnetic-compliant approach based on mutual impedances," IEEE Wireless Commun. Lett., vol. 10, no. 5, pp. 938-942, May 2021.
X. Qian and M. Di Renzo, "Mutual coupling and unit cell aware optimization for reconfigurable intelligent surfaces," IEEE Wireless Commun. Lett., vol. 10, no. 6, pp. 1183-1187, Jun. 2021.
G. Caire, "On the ergodic rate lower bounds with applications to massive MIMO," IEEE Trans. Wireless Commun., vol. 17, no. 5, pp. 3258-3268, May 2018.
G. Interdonato, H. Q. Ngo, P. Frenger, and E. G. Larsson, "Downlink training in cell-free massive MIMO: A blessing in disguise," IEEE Trans. Wireless Commun., vol. 18, no. 11, pp. 5153-5169, Nov. 2019.
E. Björnson, J. Hoydis, and L. Sanguinetti, "Massive MIMO networks: Spectral, energy, and hardware efficiency," Found. Trends Signal Process., vol. 11, nos. 3-4, pp. 154-655, Nov. 2017.
T. V. Chien and H. Q. Ngo, Massive MIMO Channels. Edison, NJ, USA: IET, 2020, ch. 11.