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Cellular Downlink Performance with Covariance-CSIT-Based MIMO precoding

WIRELESS PERSONAL COMMUNICATIONS 2012年第2期63卷 415-430页

作者： Wu, Kenneth Derham, Thomas Coupe, Patrice Orange Labs Shinjuku Ku Tokyo 1600022 Japan

The nature of the trade-off between reduced overhead of channel state information (CSI) and resultant performance losses influences the design of frequency-division duplexed practical cellular systems. One candidate for CSI feedback reduction is the use of covariance-matrix-based CSI at the transmitter (CSIT) in conjunction with linear precoding techniques. This paper analyzes the performance of such systems in the downlink for both single-user (SU-) and multiuser (MU-) multiple-input multiple output (MIMO) in comparison to those using optimal perfect-instantaneous-CSIT-based precoding. In addition, the effectiveness of techniques enforcing frequency domain diversity versus those based on the maximal ergodic channel capacity criterion is evaluated. A novel precoding scheme using covariance matrix information that supports spatial multiplexing in both SU- and MU-MIMO is proposed. Simulation results show that the spectral efficiency loss from covariance-CSIT-based techniques from those utilizing perfect, instantaneous CSIT is shown to be about 1 dB in a highly correlated urban channel environment for both SU- and MU-MIMO, whereas for microcell environments it is between 3 and 4 dB.

关键词： SU-MIMO MU-MIMO linear precoding Covariance CSIT

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Low-Complexity MIMO precoding for Finite-Alphabet Signals

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2017年第7期16卷 4571-4584页

作者： Wu, Yongpeng Ng, Derrick Wing Kwan Wen, Chao-Kai Schober, Robert Lozano, Angel Tech Univ Munich Inst Commun Engn D-80333 Munich Germany Shanghai Jiao Tong Univ Shanghai Key Lab Nav & Locat Based Minhang 200240 Peoples R China Univ New South Wales Sch Elect Engn & Telecommun Sydney NSW 2052 Australia Natl Sun Yat Sen Univ Inst Commun Engn Kaohsiung 804 Taiwan Univ Erlangen Nurnberg Inst Digital Commun Cauerstr 7 D-91058 Erlangen Germany Univ Pompeu Fabra Barcelona 08018 Spain

This paper investigates the design of precoders for single-user multiple-input multiple-output (MIMO) channels, and, in particular, for finite-alphabet signals. Based on an asymptotic expression for the mutual information of channels exhibiting line-of-sight components and rather general antenna correlations, precoding structures that decompose the general channel into a set of parallel subchannel pairs are proposed. Then, a low-complexity iterative algorithm is devised to maximize the sum mutual information of all pairs. The proposed algorithm significantly reduces the computational load of existing approaches with only minimal loss in performance. The complexity savings increase with the number of transmit antennas and with the cardinality of the signal alphabet, making it possible to support values thereof that were unmanageable with existing solutions. Most importantly, the proposed solution does not require instantaneous channel state information (CSI) at the transmitter, but only statistical CSI.

关键词： Finite alphabet inputs linear precoding multiple-input multiple-output (MIMO) replica method

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On Integer-Forcing precoding for the Gaussian MIMO Broadcast Channel

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2017年第7期16卷 4476-4488页

作者： Silva, Danilo Pivaro, Gabriel Fraidenraich, Gustavo Aazhang, Behnaam Univ Fed Santa Catarina Dept Elect & Elect Engn BR-88040900 Florianopolis SC Brazil Univ Estadual Campinas Dept Commun BR-13083852 Campinas SP Brazil Natl Inst Telecommun Radiocommun Reference Ctr BR-37540000 Santa Rita Do Sapucai Brazil Rice Univ Dept Elect & Comp Engn Houston TX 77005 USA

Integer-forcing (IF) precoding, also known as downlink IF, is a promising new approach to communication over multiple-input multiple-output (MIMO) broadcast channels. Inspired by the integer-forcing linear receiver for multiple-access channels, it generalizes linear precoding by inducing an effective channel matrix that is approximately integer, rather than approximately identity. Combined with lattice encoding and a pre-inversion of the channel matrix at the transmitter, the scheme has the potential to outperform any linear precoding scheme, despite enjoying similar low complexity. In this paper, a specific IF precoding scheme, called diagonally scaled exact IF (DIF), is proposed and shown to achieve maximum spatial multiplexing gain. For the special case of two receivers, in the high SNR regime, an optimal choice of parameters is derived analytically, leading to an almost closed-form expression for the achievable sum rate. In particular, it is shown that the gap to the sum capacity is upper bounded by 0.27 bits for any channel realization. For general SNR, a regularized version of DIF (RDIF) is proposed. Numerical results for two receivers under Rayleigh fading show that RDIF can achieve performance superior to optimal linear precoding and very close to the sum capacity.

关键词： Multiuser MIMO broadcast channel linear precoding beamforming compute-and-forward integer-forcing

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Iterative Matrix Inversion Methods for precoding in Cell-Free Massive MIMO Systems

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2022年第11期71卷 11972-11987页

作者： Ataeeshojai, Mahtab Elliott, Robert C. Krzymien, Witold A. Tellambura, Chintha Maljevic, Ivo Univ Alberta Dept Elect & Comp Engn Edmonton AB Canada TELUS Commun Scarborough ON Canada

Cell-free massive multiple-input multiple-output (mMIMO) systems are an alternative topology for mMIMO deployment, wherein a large number of access points are distributed over the coverage area to jointly serve users. linear precoding methods such as zero-forcing are sufficient to achieve near-optimal performance in mMIMO systems. However, a key challenge in implementing these precoders can be a channel matrix inversion operation, which results in significant computational complexity in systems with large-scale antenna arrays. Hence, instead of direct matrix inversion, we examine several iterative methods to calculate the precoding matrix in a cell-free mMIMO system. We investigate their computational complexity and convergence rate in the presence of small- and large-scale fading and spatial correlation between antennas. Notably, we demonstrate that some iterative methods previously proposed for conventional (co-located) mMIMO do not always converge for cell-free mMIMO. Our main focus is the hyper-power iterative inversion method, which can be applied to both matrix inverses and pseudoinverses with guaranteed convergence;its factorized version also reduces its computational complexity. Although the hyper-power method does not reduce the complexity compared to direct matrix inversion, it converges quickly with high accuracy and strong numerical stability, and is conducive to parallel computation. These qualities make it a good candidate for matrix inversion in cell-free mMIMO system precoders.

关键词： Cell-free massive MIMO computational com- plexity convergence iterative methods linear precoding matrix inversion parallel computation

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Jac-PCG Based Low-Complexity precoding for Extremely Large-Scale MIMO Systems

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2023年第12期72卷 16811-16816页

作者： Xu, Bokai Zhang, Jiayi Li, Jiaxun Xiao, Huahua Ai, Bo Beijing Jiaotong Univ Sch Elect & Informat Engn Beijing 100044 Peoples R China Beijing Jiaotong Univ Frontiers Sci Ctr Smart High Speed Railway Syst Beijing 100044 Peoples R China Intelligent Game & Decis Lab Beijing 100044 Peoples R China ZTE Corp State Key Lab Mobile Network & Mobile Multimedia T Shenzhen 518055 Peoples R China

Extremely large-scale multiple-input-multiple-output (XL-MIMO) has been reviewed as a promising technology for future sixth-generation (6G) networks to achieve higher performance. In practice, various linear precoding schemes, such as zero-forcing (ZF) and regularized ZF (RZF) precoding, are sufficient to achieve near-optimal performance in traditional massive MIMO (mMIMO) systems. It is critical to note that in large-scale antenna arrays the operation of channel matrix inversion poses a significant computational challenge for these precoders. Therefore, we explore several iterative methods for determining the precoding matrix for XL-MIMO systems instead of direct matrix inversion. Taking into account small- and large-scale fading as well as spatial correlation between antennas, we study their computational complexity and convergence rate. Furthermore, we propose the Jacobi-Preconditioning Conjugate Gradient (Jac-PCG) iterative inversion method, which enjoys a faster convergence speed than the CG method. Besides, the closed-form expression of spectral efficiency (SE) considering the interference between subarrays in downlink XL-MIMO systems is derived. In the numerical results, it is shown that the complexity given by the Jac-PCG algorithm has about 54 % reduction than the traditional RZF algorithm at basically the same SE performance.

关键词： XL-MIMO linear precoding matrix inversion iterative methods computational complexity

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precoding for Full Duplex Multiuser MIMO Systems: Spectral and Energy Efficiency Maximization

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2013年第16期61卷 4038-4050页

作者： Dan Nguyen Le-Nam Tran Pirinen, Pekka Latva-aho, Matti Univ Oulu Dept Commun Engn Oulu 90570 Finland Univ Oulu Ctr Wireless Commun Oulu 90570 Finland

We consider data transmissions in a full duplex (FD) multiuser multiple-input multiple-output (MU-MIMO) system, where a base station (BS) bidirectionally communicates with multiple users in the downlink (DL) and uplink (UL) channels on the same system resources. The system model of consideration has been thought to be impractical due to the self-interference (SI) between transmit and receive antennas at the BS. Interestingly, recent advanced techniques in hardware design have demonstrated that the SI can be suppressed to a degree that possibly allows for FD transmission. This paper goes one step further in exploring the potential gains in terms of the spectral efficiency (SE) and energy efficiency (EE) that can be brought by the FD MU-MIMO model. Toward this end, we propose low-complexity designs for maximizing the SE and EE, and evaluate their performance numerically. For the SE maximization problem, we present an iterative design that obtains a locally optimal solution based on a sequential convex approximation method. In this way, the nonconvex precoder design problem is approximated by a convex program at each iteration. Then, we propose a numerical algorithm to solve the resulting convex program based on the alternating and dual decomposition approaches, where analytical expressions for precoders are derived. For the EE maximization problem, using the same method, we first transform it into a concave-convex fractional program, which then can be reformulated as a convex program using the parametric approach. We will show that the resulting problem can be solved similarly to the SE maximization problem. Numerical results demonstrate that, compared to a half duplex system, the FD system of interest with the proposed designs achieves a better SE and a slightly smaller EE when the SI is small.

关键词： Energy efficiency full duplex linear precoding MIMO multiuser transmission spectral efficiency

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Robust precoding Schemes for Multi-User MISO-OFDM Downlink with Limited Time-Domain Feedback

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Tsinghua Science and Technology 2009年第6期14卷 725-731页

作者：苏泳涛张贤达 Department of Automation Tsinghua University

In multi-user multiple-input single-output orthogonal frequency-division multiplexing （MISO-OFDM） downlinks with limited feedback, both linear precoders （LP） and Tomlinson-Harashima precoders （THP） experience performance degradation due to inaccurate channel state information at the transmitter （CSIT）. This analysis treats the downlink channels as random quantities and exploits their second order statistics in robust precoding schemes to correct the errors introduced in the feedback procedure. The time-domain channel vectors are found to reduce the feedback overhead more than the frequency-domain vectors. A compression and restoration method and a codebook design are also given to obtain compact feedback quantities. Simulations show that the robust LP and THP are superior to the previous methods with tradeoffs possible between performance and feedback overhead.

关键词： linear precoding Tomlinson-Harashima precoding (THP) multiple-input single-output (MISO) orthogonal frequency-division multiplexing (OFDM)

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On the Equivalence Between SLNR and MMSE precoding Schemes with Single-Antenna Receivers

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IEEE COMMUNICATIONS LETTERS 2012年第7期16卷 1034-1037页

作者： Patcharamaneepakorn, Piya Armour, Simon Doufexi, Angela Univ Bristol Ctr Commun Res Bristol BS8 1UB Avon England

This letter considers transmit precoding schemes based on the maximum signal-to-leakage-and-noise ratio (SLNR) in multiuser MIMO systems with single-antenna receivers. The closed-form solution of SLNR design is generally given in the form of the eigenvector associated to the maximum eigenvalue. In this letter, analytic expressions of SLNR-based solutions and resulting SLNR are derived for a generic power allocation (GPA). The solution is shown to be a function of user-allocated power and an arbitrary phase shift. Under equal power allocation (EPA), the SLNR precoding scheme is shown to be equivalent to the minimum mean square error (MMSE) precoding scheme. Several useful implications in terms of the possible extension of existing algorithms and performance analysis are also discussed.

关键词： Multiuser MIMO linear precoding SLNR MMSE performance analysis

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Space-time precoding for downlink transmission in multiple antenna CDMA systems

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2007年第5期56卷 2590-2602页

作者： Razavizadeh, S. Mohammad Khandani, Amir K. Vakili, Vahid Tabataba Tong, Wen Iran Telecommun Res Ctr Tehran 14399 Iran Univ Waterloo Dept Elect & Comp Engn Waterloo ON N2L 3G1 Canada Iran Univ Sci Technol Dept Elect Engn Tehran 16846 Iran Wireless Technol Labs Nortel Networks Nepean ON K2G 6J8 Canada

This paper introduces a linear space-time precoding scheme for downlink transmission in a multiple-transmit single-receive antenna code-division multiple-access (CDMA) system. The proposed scheme relies on using space-time spreading sequences that are constructed from the time-domain user signatures combined with spatial channel information that corresponds to multiple transmit antennas. Numerical results show that the proposed scheme significantly reduces the multiple-access interference in both flat- and multipath-fading channels. At the same time, it achieves the maximum possible diversity order that is offered by the combination of multiple transmit antennas and multipath fading. To further improve the performance in overloaded CDMA systems, the proposed linear precoding method is. combined with a nonlinear operation known as vector perturbation (based on applying modulo operation to minimize the transmit energy). Throughout the paper, we assume that 1) the channel state information is known at the transmitter, 2) the modulation is binary phase-shift keying, and 3) the receivers are simply based on linear filters that are matched to the time-domain user signatures. We use a recent work of Reynolds et al. as a baseline for comparison. Numerical results show that our proposed method outperforms that of Reynolds et al. in both flat and multipath channels.

关键词： code-division multiple-access (CDMA) systems linear precoding modulo operation multiple-access interference (MAI) cancellation multiple antenna systems space-time spreading sequences vector perturbation

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Joint Channel Estimation and precoding for Faster-Than-Nyquist Signaling

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2020年第11期69卷 13139-13147页

作者： Li, Qiang Gong, Feng-Kui Song, Pei-Yang Li, Guo Zhai, Sheng-Hua Xidian Univ State Key Lab ISN Xian 710071 Peoples R China Beijing Inst Technol Sch Informat & Elect Beijing 100081 Peoples R China CAST Xian Inst Space Radio Technol Xian 710071 Peoples R China

The performance of existing frequency-domain channel estimation and equalization algorithms for faster-than-Nyquist (FTN) signaling is seriously hampered with the noise enhancement phenomenon that results from their inverse or pseudo-inverse operations. Through simulations, we show that the linear precoding can effectively mitigate the above-mentioned noise enhancement phenomenon. At first, a low complexity precoding-based channel estimation (PCE) algorithm is proposed for FTN signaling over frequency-selective fading channels. In contrast with most existing frequency-domain channel estimation algorithms, the proposed PCE algorithm has much better mean square error performance, and the performance improvement enlarges with the increase of signal to noise ratio. Furthermore, a joint channel estimation and precoding (JCEP) algorithm is proposed to perform data detection for FTN signaling over frequency-selective fading channels. On the one hand, compared with the existing frequency-domain channel estimation and equalization algorithms, the JCEP algorithm greatly reduces the complexity of signal processing at receivers since it performs the linear precoding processing at transmitters. On the other hand, even with estimated channel state information (CSI), the proposed JCEP algorithm can approach the bit error rate (BER) performance of the Nyquist signaling for all the modulation types adopted in digital video broadcasting-satellite-second generation extension (DVB-S2X). More precisely, the BER performance degradation with perfect and estimated CSI is 0.06dB and 0.07dB respectively when the time acceleration parameter equals to 0.7 and the rolling factor is 0.45.

关键词： Channel estimation precoding Frequency-domain analysis Signal processing algorithms Complexity theory Frequency-selective fading channels Receivers Faster-than-Nyquist (FTN) signaling frequency-selective fading channel frequency-domain channel estimation and equalization linear precoding

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