Multiple-Input Multiple-Output (MIMO) digital communications standards usually acquire Channel State Information (CSI) by means of supervised algorithms, which implies loss of performance since pilot symbols do not co...
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Multiple-Input Multiple-Output (MIMO) digital communications standards usually acquire Channel State Information (CSI) by means of supervised algorithms, which implies loss of performance since pilot symbols do not convey information. We propose obtaining this CSI by using semi-blind techniques, which combine both supervised and unsupervised (blind) methods. The key idea consists in introducing a decision criterion to determine when the channel suffered a significant change. In such a case, transmission of pilot symbols is required. The use of this criterion also allows us to determine the time instants in which CSI has to be sent to the transmitter from the receiver through a low-cost feedback channel.
We present a generalized singular value decomposition (GSVD) based multi-user (MU) multi-stream multiple-input multiple-output (MIMO) precoding scheme with limited feedback. Our precoding scheme maximizes the signal t...
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ISBN:
(纸本)9781467325691
We present a generalized singular value decomposition (GSVD) based multi-user (MU) multi-stream multiple-input multiple-output (MIMO) precoding scheme with limited feedback. Our precoding scheme maximizes the signal to leakage and noise ratio (SLNR), so that it does not require any iterations to obtain precoding matrices. However, in MU-MIMO system, the precoding matrix should be computed at transmit side, because the precoding matrix of a user affects those of other users. Accordingly, full channel state information (CSI) for all users is required at the transmitter, which prevents MU-MIMO precoding implementable. To overcome this problem, an efficient limited feedback algorithm optimized to the GSVD based MU-MIMO precoding is proposed. Here, by extracting the parameters to be utilized in GSVD based precoding from the full CSI, the amount of feedback information is reduced. Furthermore, by analyzing their statistical properties, the parameters are efficiently quantized according to their probability densities. Finally, we develop a modified GSVD based precoding considering the channel quantization errors due to the limited feedback.
A promising approach to deal with the high hardware cost and energy consumption of massive MIMO transmitters is to use low-resolution digital-to-analog converters (DACs) at each antenna element. This leads to a transm...
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A promising approach to deal with the high hardware cost and energy consumption of massive MIMO transmitters is to use low-resolution digital-to-analog converters (DACs) at each antenna element. This leads to a transmission scheme where the transmitted signals are restricted to a finite set of voltage levels. This paper is concerned with the analysis and optimization of a low-cost quantized precoding strategy, referred to as linear-quantized precoding, for a downlink massive MIMO system under Rayleigh fading. In linear-quantized precoding, the signals are first processed by a linear precoding matrix and subsequently quantized component-wise by the DAC. In this paper, we analyze both the signal-to-interference-plus-noise ratio (SINR) and the symbol error probability (SEP) performances of such linear-quantized precoding schemes in an asymptotic framework where the number of transmit antennas and the number of users grow large with a fixed ratio. Our results provide a rigorous justification for the heuristic arguments based on the Bussgang decomposition that are commonly used in prior works. Based on the asymptotic analysis, we further derive the optimal precoder within a class of linear-quantized precoders that includes several popular precoders as special cases. Our numerical results demonstrate the excellent accuracy of the asymptotic analysis for finite systems and the optimality of the derived precoder.
In this paper, linear precoding for non-orthogonal space time block codes (STBC) is investigated. A theoretical model of spatial correlation with a Laplacian distribution of AOA is first derived. The design of the pre...
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In this paper, linear precoding for non-orthogonal space time block codes (STBC) is investigated. A theoretical model of spatial correlation with a Laplacian distribution of AOA is first derived. The design of the precoder is based on the choice of the codeword error matrix according to a criterion. We propose here a new criterion based on the system outage probability to select the suitable codeword error matrix allowing to move rapidly from one diversity order to the next. Codeword selection points out the importance of the determinant and the eigenvalues of the error matrices. The proposed method is applied to the non-orthogonal optimal STBC: 2×2 Golden Code and 4×4 Perfect Code.
In this paper, we investigate low-complexity user scheduling schemes for the downlink (DL) massive multiuser multiple-input multiple-output (MU-MIMO) system, where an M-antenna (M is very large) base station (BS) serv...
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ISBN:
(纸本)9781479941452
In this paper, we investigate low-complexity user scheduling schemes for the downlink (DL) massive multiuser multiple-input multiple-output (MU-MIMO) system, where an M-antenna (M is very large) base station (BS) serves K (K > 2) N-antenna (N > 1) users with linear transceivers. Establishing the theoretical foundation of our scheduling schemes, we first investigate the asymptotic sum-rates of this system with both singular value decomposition (SVD) and regularized zero-forcing (RZF) precoders. In particular, we assume that both M and N go to infinity with a bounded ratio to perform the theoretical derivations with random matrix theory (RMT). In addition, the influence of imperfect channel estimation is also considered. Interestingly, the analysis indicates the existence of an optimal number of served users K~* in terms of asymptotic sum-rate, which motivates our low complexity user scheduling schemes. Unlike the conventional schemes with complicated computations and instantaneous channel state information, our user scheduling schemes are based on semi-analytical solutions with only statistic CSI. Simulation results validate our theoretical derivations and show the advantages of our schemes in the massive MU-MIMO system.
In this paper,several multi-user multiple-input multiple-output (MU-MIMO) linear precoding schemes with both perfect and imperfect channel state information (CSI) for downlink transmission are *** to nonlinear precodi...
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In this paper,several multi-user multiple-input multiple-output (MU-MIMO) linear precoding schemes with both perfect and imperfect channel state information (CSI) for downlink transmission are *** to nonlinear precoding schemes which need perfect CSI to achieve the channel capacity,we focus on systems which are restricted to use only linear precoding schemes due to complexity constraints and limited *** limited feedback and some improvement technologies have also been *** proposed MU-MIMO schemes extend the point-to-point single-user precoding to point-to-multipoint multi-user precoding.
Combining precoding and orthogonal space-time block codes(OSTBCs) can obtain full-diversity order and provide additional array *** paper proposes optimal linear precoding and quantization for OSTBCs with erroneous ***...
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Combining precoding and orthogonal space-time block codes(OSTBCs) can obtain full-diversity order and provide additional array *** paper proposes optimal linear precoding and quantization for OSTBCs with erroneous *** algorithm is used for designing codebooks with noisy quantized feedback in general *** two extreme cases,the transmitter can obtain perfect CSI and no CSI available,the optimal unquantized precoder for each case are presents and quantization scheme is *** result shows that the quantized codebook proposed in this paper can obtain better performance compared to open loop systems when feedback link is erroneous
Combining precoding and orthogonal space-time block codes (OSTBCs) can obtain full-diversity order and provide additional array gain. This paper proposes optimal linear precoding and quantization for OSTBCs with erron...
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ISBN:
(纸本)9781424448166
Combining precoding and orthogonal space-time block codes (OSTBCs) can obtain full-diversity order and provide additional array gain. This paper proposes optimal linear precoding and quantization for OSTBCs with erroneous feedback. Lloyd algorithm is used for designing codebooks with noisy quantized feedback in general case. In two extreme cases, the transmitter can obtain perfect CSI and no CSI available, the optimal unquantized precoder for each case are presents and quantization scheme is analysed. The result shows that the quantized codebook proposed in this paper can obtain better performance compared to open loop systems when feedback link is erroneous
Distributed antenna system(DAS) has emerged as a promising architecture for future mobile communications. Compared with collocated antenna system(CAS), DAS has advantages in reducing transmission power and improving t...
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ISBN:
(纸本)9781510814912
Distributed antenna system(DAS) has emerged as a promising architecture for future mobile communications. Compared with collocated antenna system(CAS), DAS has advantages in reducing transmission power and improving the cell coverage area. In this paper, the downlink performance of DAS with linear precoding is analyzed. The optimization problem of minimizing the total transmitted power while satisfying signal-to-interference-and-noise ratio(SINR) constraints is studied to optimize the beamforming for all user jointly, which can be solved by conic optimization method. However, the problem is non-convex and can not be solved efficiently. Suboptimal methods are proposed by optimizing power allocation after given the direction of precoding. In simulation, the performance of different linear precoding methods are analyzed for the downlink of DAS. Moreover, the performance of DAS and CAS are also compared with the same antenna configuration and direction of precoding. It is shown that compared with CAS, DAS achieves the same performance with much less transmission power.
Both channel coding over a finite field and linear precoding over a complex field can improve the system performance in wireless fading channels. In this paper, we investigate the potential benefit of linear precoding...
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ISBN:
(纸本)9781467308298
Both channel coding over a finite field and linear precoding over a complex field can improve the system performance in wireless fading channels. In this paper, we investigate the potential benefit of linear precoding in a nonbinary LDPC coded underwater acoustic OFDM system. Real precoders of small sizes are selected in different setups, in order to avoid any complexity increase at the receiver. Simulations and emulated experimental results demonstrate the benefits of linear precoding, particularly when the receiver has a small number of hydrophones.
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