• Title/Summary/Keyword: Multiuser MIMO

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Precoding Method for Increasing System Capacity in Multiuser MIMO Downlink Channels (다중사용자 MIMO 하향링크 채널 환경에서 시스템 용량 향상을 위한 프리코딩 기법)

  • Kim, Kwang-Yoon;Lee, Jong-Sik;Koo, Sung-Wan;Yang, Jea-Su;Kim, Jin-Young
    • 한국정보통신설비학회:학술대회논문집
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    • pp.12-16
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    • 2008
  • In this paper, we study precoding techniques for co-channel interference suppression in multiuser MIMO systems. DPC is optimal techniques to achieve the system capacity of multiuser MIMO downlink channels. DPC is not proper in practical wireless systems because complexity is very high. So block diagonal precoding for multiuser MIMO downlink channel is studied. The block diagonal precoding is used to suppress co-channel interference between multiuser. Block diagonal precoding method, whose complexity is reduced by modified null space operation, change multiuser MIMO channel to multiple single-user MIMO channel. We also use V-BLAST decoder in receiver. V-BLAST decoder can achieve increased system capacity in proportion to the number of users. We show improved system performance by using computer simulation.

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Adaptive Opimization of MIMO Codebook to Channel Conditions for Split Linear Array (분할된 선형배열안테나를 위한 채널 환경에 적응하는 MIMO 코드북 최적화)

  • Mun, Cheol;Jung, Chang-Kyoo;Kwak, Yun-Sik
    • Journal of Advanced Navigation Technology
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    • v.13 no.5
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    • pp.736-741
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    • 2009
  • In this paper, adaptive optimizations of precoder codebook to channel conditions is proposed for a multiuser multiple-input multiple-output (MIMO) system with split linear array and limited feedback. We propose adaptive method for constructing a precoder codebook by coloring the random vector quantization codebook at each link by using limited long-term feedback information on transmit correlation matrix of each link. It is shown that the proposed multiuser MIMO codebook design scheme outperforms existing multiuser MIMO codebook design schemes for various channel conditions in terms of the average sum throughput of multiuser MIMO systems using zero-forcing maximum eigenmode transmission and limited feedback.

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Data Stream Allocation Algorithm for Maximizing Sum Capacity in Multiuser MIMO Systems (다중 사용자 MIMO 시스템에서 전체 채널 용량을 최대화하기 위한 데이터 스트림 할당 기법)

  • Kim, Bong-Seok;Choi, Kwon-Hue
    • Journal of Satellite, Information and Communications
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    • v.6 no.1
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    • pp.19-27
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    • 2011
  • In this paper, we propose the data stream allocation algorithms for maximizing sum capacity of downlink multiuser MIMO (Multiple-input Multiple-output) systems with BD (Block Diagonalization). The conventional BD precoding algorithms maximize the capacity by controlling power against channel gain of each user. In multiuser MIMO systems, however, the number of data streams for each user can be used to as another control parameter, which determines the capacity. This paper proposes the data stream allocation algorithm of BD for increasing capacity in multiuser MIMO systems. The proposed algorithm allocates unequal bit stream to each user based on channel matrix of each user for maximizing sum capacity. It is proved that proposed algorithm can achieve the significantly improved sum capacity by computer simulation.

Joint Lattice-Reduction-Aided Precoder Design for Multiuser MIMO Relay System

  • Jiang, Hua;Cheng, Hao;Shen, Lizhen;Liu, Guoqing
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.10 no.7
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    • pp.3010-3025
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    • 2016
  • Lattice reduction (LR) has been used widely in conventional multiple-input multiple-output (MIMO) systems to enhance the performance. However, LR is hard to be applied to the relay systems which are important but more complicated in the wireless communication theory. This paper introduces a new viewpoint for utilizing LR in multiuser MIMO relay systems. The vector precoding (VP) is designed along with zero force (ZF) criterion and minimum mean square error (MMSE) criterion and enhanced by LR algorithm. This implementable precoder design combines nonlinear processing at the base station (BS) and linear processing at the relay. This precoder is capable of avoiding multiuser interference (MUI) at the mobile stations (MSs) and achieving excellent performance. Moreover, it is shown that the amount of feedback information is much less than that of the singular value decomposition (SVD) design. Simulation results show that the proposed scheme using the complex version of the Lenstra--Lenstra--Lovász (LLL) algorithm significantly improves system performance.

Interpolation-based Precoding Approximation Algorithm for Low Complexity in Multiuser MIMO-OFDM Systems (다중 사용자 MIMO-OFDM 시스템에서 계산양 감소를 위한 선형 보간법 기반 프리코딩 근사화 기법)

  • Lim, Dong-Ho;Kim, Bong-Seok;Choi, Kwon-Hue
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.11A
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    • pp.1027-1037
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    • 2010
  • In this paper, we propose the linear interpolation-based BD (Block Diagonalization) precoding approximation algorithm for low complexity in downlink multiuser MIMO-OFDM (Multiple-input Multiple-output Orthogonal Frequency Division Multiplexing) systems. In the case of applying the general BD precoding algorithm to multiuser MIMO-OFDM systems, the computational complexity increases in proportional to the number of subcarriers. The proposed interpolation-based BD precoding approximation algorithm can be achieved similar SER performance with general BD algorithm and can decrease the computational complexity. It is proved that proposed algorithm can achieve the significantly decreased computational complexity by computer simulation.

Triangulation Algorithm for Multi-user Spatial Multiplexing in MIMO Downlink Channels (MIMO 다운링크 채널에서 다중사용자 공간다중화를 위한 알고리즘)

  • Lee, Heun-Chul;Paulraj, Aroyaswami;Lee, In-Kyu
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.1C
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    • pp.45-54
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    • 2010
  • This paper studies the design of a multiuser multiple-input multiple-output (MIMO) system, where a base station (BS) transmits independent messages to multiple users. The remarkable "dirty paper coding (DPC)" result was first presented by Costa that the capacity does not change if the Gaussian interference is known at the transmitter noncausally. While several implementable DPC schemes have been proposed recently for single-user dirty-paper channels, DPC is still difficult to implement directly in practical multiuser MIMO channels. In this paper, we propose a network channel matrix triangulation (NMT) algorithm for utilizing interference known at the transmitter. The NMT algorithm decomposes a multiuser MIMO channel into a set of parallel, single-input single-output dirty-paper subchannels and then successively employs the DPC to each subchannel. This approach allows us to extend practical single-user DPC techniques to multiuser MIMO downlink cases. We present the sum rate analysis for the proposed scheme. Simulation results show that the proposed schemes approach the sum rate capacity of the multiuser MIMO downlink at moderate signal-to-noise ratio (SNR) values.

Recent Trend of the Technology Development for Multiuser MIMO based on LTE-Advanced Standard (LTE-Advanced 표준에 바탕을 둔 다중사용자 MIMO의 기술개발 현황)

  • Lee, Byung-Ju;Lim, Chae-Man;Shim, Byong-Hyo
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.49 no.4
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    • pp.18-25
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    • 2012
  • As the demand for smart phone user is rapidly increasing in recent years, the development of new mobile communication system which provides more improved quality compared to existing 3G standard is highly requested. In this point, the long-term evolution (LTE) system, which was being developed in mid of 2000's, has attracted a considerable attention. The LTE has been developed continuously to result a release 10 which is called as LTE-Advanced (LTE-A) in 2010. Among various features in LTE-A, the multiuser MIMO (MU-MIMO) design is expected to give better quality for throughput, spectral efficiency, and latency. In this paper, we first review the development process from LTE to LTE-A. We also provide the overview of design challenges and specific solutions for MU-MIMO systems developed in LTE-Advanced standard.

Multiuser Heterogeneous-SNR MIMO Systems

  • Jo, Han-Shin
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.8 no.8
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    • pp.2607-2625
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    • 2014
  • Previous studies on multiuser multiple-input multiple-output (MIMO) mostly assume a homogeneous signal-to-noise ratio (SNR), where each user has the same average SNR. However, real networks are more likely to feature heterogeneous SNRs (a random-valued average SNR). Motivated by this fact, we analyze a multiuser MIMO downlink with a zero-forcing (ZF) receiver in a heterogeneous SNR environment. A transmitter with Mantennas constructs M orthonormal beams and performs the SNR-based proportional fairness (S-PF) scheduling where data are transmitted to users each with the highest ratio of the SNR to the average SNR per beam. We develop a new analytical expression for the sum throughput of the multiuser MIMO system. Furthermore, simply modifying the expression provides the sum throughput for important special cases such as homogeneous SNR, max-rate scheduling, or high SNR. From the analysis, we obtain new insights (lemmas): i) S-PF scheduling maximizes the sum throughput in the homogeneous SNR and ii) under high SNR and a large number of users, S-PF scheduling yields the same multiuser diversity for both heterogeneous SNRs and homogeneous SNRs. Numerical simulation shows the interesting result that the sum throughput is not always proportional to M for a small number of users.

A Low Complexity Scheduling of Uplink Multiuser MIMO/FDD System (FDD 기반 상향링크 다중사용자 MIMO 시스템 상에서의 낮은 복잡도의 스케줄링 기법)

  • Cho, Sung-Yoon;Kim, Yohan;Kim, Dong-Ku
    • Journal of Advanced Navigation Technology
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    • v.11 no.4
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    • pp.430-436
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    • 2007
  • In this paper, we assume the uplink multiuser MIMO system based on FDD. Considering the implementation of practical system, Antenna selection and Transmit Beamforming scheme are suggested. System model of both two schemes are introduced and the scheduling algorithm which approaches the optimal performance with affordable computational complexity is proposed for each transmission scheme. Simulation results show that the sum-rate of the proposed low complexity scheduler approaches the performance of brute-force scheduler which is believed to be the optimal scheme.

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Regularized Channel Inversion for Multiple-Antenna Users in Multiuser MIMO Downlink (다중 안테나 다중 사용자 하향 링크 환경에서 Regularized Channel Inversion 기법)

  • Lee, Heun-Chul;Lee, Kwang-Won;Lee, In-Kyu
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.3A
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    • pp.260-268
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    • 2010
  • Channel inversion is one of the simplest techniques for multiuser downlink systems with single-antenna users. In this paper, we extend the regularized channel inversion technique developed for the single-antenna user case to multiuser multiple-input multiple-output (MIMO) channels with multiple-antenna users. We first employ the multiuser preprocessing to project the multiuser signals near the null space of the unintended users based on the MMSE criterion, and then the single-user preprocessing is applied to the decomposed MIMO interference channels. In order to reduce the complexity, we focus on non-iterative solutions for the multiuser transmit beamforming and use a linear receiver based on an MMSE criterion. Simulation results show that the proposed scheme outperforms existing joint iterative algorithms in most multiuser configurations.