• Title/Summary/Keyword: Massive-MIMO

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Efficient Transmit Antenna Selection Method for Massive MIMO system (Massive MIMO 시스템을 위한 효율적인 송신 안테나 선택 기법)

  • Ju, Sang-Lim;Lee, Byung-Jin;Kim, Young-Jae;Kim, Jin-Up;Bang, Young-Jo;Kim, Kyungseok
    • Journal of Satellite, Information and Communications
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    • v.11 no.3
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    • pp.58-64
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    • 2016
  • This paper proposes the efficient transmit antenna selection (TAS) scheme considering trade-off between the performance and the complexity in massive MIMO system. The massive MIMO system is a core technology to achieve performance objectives for 5 generation wireless communication. It achieve high spectral efficiency, a reliability, and a diversity gain. However many RF chains required by massive transmit antennas equipped in a base station create the problem such as high hardware cost and complexity. Therefor we investigates the transmit antenna selection scheme, in which the number of RF chains of BS is reduced, and the trade-off between the performance and the complexity is considered for proposed scheme. And, the spectral efficiency and complexity are analysed by transmit antenna selection schemes.

System-Level Performance of Limited Feedback Schemes for Massive MIMO

  • Choi, Yongin;Lee, Jaewon;Rim, Minjoong;Kang, Chung Gu;Nam, Junyoung;Ko, Young-Jo
    • ETRI Journal
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    • v.38 no.2
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    • pp.280-290
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    • 2016
  • To implement high-order multiuser multiple input and multiple output (MU-MIMO) for massive MIMO systems, there must be a feedback scheme that can warrant its performance with a limited signaling overhead. The interference-to-noise ratio can be a basis for a novel form of Codebook (CB)-based MU-MIMO feedback scheme. The objective of this paper is to verify such a scheme's performance under a practical system configuration with a 3D channel model in various radio environments. We evaluate the performance of various CB-based feedback schemes with different types of overhead reduction approaches, providing an experimental ground with which to optimize a CB-based MU-MIMO feedback scheme while identifying the design constraints for a massive MIMO system.

Optimal Number of Base Station Antennas and Users in MF Based Multiuser Massive MIMO Systems (MF 기반 다중 사용자 Massive MIMO 시스템의 최적 기지국 안테나 수 및 사용자 수 분석)

  • Jung, Minchae;Choi, Sooyong
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.38A no.8
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    • pp.724-732
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    • 2013
  • In this paper, we analyze a performance of multiuser massive multiple-input and multiple-output (MIMO) system. We derive the ergodic cell capacity based on a downlink frame structure and analyze the ergodic cell capacity with respect to the number of base station (BS) antennas and the number of users. This paper shows that the ergodic cell capacity is a concave function with respect to the number of BS antennas and the number of users, and also derives the optimal numbers of BS antennas and users for the maximum cell capacity. The simulation results verify the derived analyses and show that the derived numbers of BS antennas and users provide the maximum cell capacity.

Energy-efficient mmWave cell-free massive MIMO downlink transmission with low-resolution DACs and phase shifters

  • Seung-Eun Hong;Jee-Hyeon Na
    • ETRI Journal
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    • v.44 no.6
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    • pp.885-902
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    • 2022
  • The mmWave cell-free massive MIMO (CFmMIMO), combining the advantages of wide bandwidth in the mmWave frequency band and the high- and uniform-spectral efficiency of CFmMIMO, has recently emerged as one of the enabling technologies for 6G. In this paper, we propose a novel framework for energy-efficient mmWave CFmMIMO systems that uses low-resolution digital-analog converters (DACs) and phase shifters (PSs) to introduce lowcomplexity hybrid precoding. Additionally, we propose a heuristic pilot allocation scheme that makes the best effort to slash some interference from copilot users. The simulation results show that the proposed hybrid precoding and pilot allocation scheme outperforms the existing schemes. Furthermore, we reveal the relationship between the energy and spectral efficiencies for the proposed mmWave CFmMIMO system by modeling the whole network power consumption and observe that the introduction of low-resolution DACs and PSs is effective in increasing the energy efficiency by compromising the spectral efficiency and the network power consumption.

Massive MIMO TWO-Hop Relay Systems Over Rician Fading Channels

  • Cao, Jian;Yu, Shujuan;Yang, Jie;Zhang, Yun;Zhao, Shengmei
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.13 no.11
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    • pp.5410-5426
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    • 2019
  • With the advent of the fifth-generation (5G) era, Massive multiple-input multiple-output (MIMO) relay systems have experienced the rapid development. Recently, the performance analysis models of Massive MIMO relay systems have been proposed, which are mostly based on Rayleigh fading channels. In order to create a more suitable model for 5G Internet of Things scenarios, our study is based on the Rician fading channels, where line-of-sight (LOS) path exists in the channels. In this paper, we assume the channel state information (CSI) is perfect. In this case, we use statistical information to derive the analytical exact closed-form expression for the achievable sum rate of the uplink for the Massive MIMO two-hop relay system over Rician fading channels. Moreover, considering the different communication scenarios, we derive the analytical exact closed-form expression for the achievable sum rates of the uplink for other three scenarios. Finally, based on these expressions, we make simulations and analyze the performance under different transmit powers and Rician-factors, which provides a theoretical basis and reference for further research.

Iterative Detection and Decoding of LDPC-Coded Multiuser Uplink Massive-MIMO Systems (LDPC 부호화된 멀티유저 상향링크 Massive-MIMO 시스템의 반복 검출 및 복호 수신기)

  • Park, Jin Soo;Kim, Inseon;Song, Hong-Yeop;Han, Sung Woo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.39A no.9
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    • pp.528-534
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    • 2014
  • In this paper, we propose an iterative detection and decoding scheme for the LDPC coded multiuser uplink massive-MIMO systems. We consider the simple maximal ratio combining (MRC) detector and LDPC decoder. We formulate the soft output of MRC detector and the relation between the extrinsic informations of the detector and decoder. The performance improvement of the proposed iterative detection and decoding scheme is shown by computer simulation.

Adaptive Channel Estimation Techniques for FDD Massive MIMO Systems (FDD Massive MIMO 시스템에서의 적응 채널 추정 기법)

  • Chung, Jinjoo;Han, Yonghee;Lee, Jungwoo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.7
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    • pp.1239-1247
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    • 2015
  • In frequency-division duplex (FDD) massive multiple-input multiple-output (MIMO) system, the computational complexity of downlink channel estimation is proportional to the number of antennas at a base station. Therefore, effective channel estimation techniques may have to be studied. In this paper, novel channel estimation algorithms using adaptive techniques such as Kalman and least mean square (LMS) filters are proposed in a channel model with temporal and spatial correlation.

Pilot Sequence Assignment for Spatially Correlated Massive MIMO Circumstances

  • Li, Pengxiang;Gao, Yuehong;Li, Zhidu;Yang, Dacheng
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.13 no.1
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    • pp.237-253
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    • 2019
  • For massive multiple-input multiple-output (MIMO) circumstances with time division duplex (TDD) protocol, pilot contamination becomes one of main system performance bottlenecks. This paper proposes an uplink pilot sequence assignment to alleviate this problem for spatially correlated massive MIMO circumstances. Firstly, a single-cell TDD massive MIMO model with multiple terminals in the cell is established. Then a spatial correlation between two channel response vectors is established by the large-scale fading variables and the angle of arrival (AOA) span with an infinite number of base station (BS) antennas. With this spatially correlated channel model, the expression for the achievable system capacity is derived. To optimize the achievable system capacity, a problem regarding uplink pilot assignment is proposed. In view of the exponential complexity of the exhaustive search approach, a pilot assignment algorithm corresponding to the distinct channel AOA intervals is proposed to approach the optimization solution. In addition, simulation results prove that the main pilot assignment algorithm in this paper can obtain a noticeable performance gain with limited BS antennas.

Alternating-Projection-Based Channel Estimation for Multicell Massive MIMO Systems

  • Chen, Yi Liang;Ran, Rong;Oh, Hayoung
    • Journal of information and communication convergence engineering
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    • v.16 no.1
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    • pp.17-22
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    • 2018
  • In massive multiple-input multiple-output (MIMO) systems, linear channel estimation algorithms are widely applied owing to their simple structures. However, they may cause pilot contamination, which affects the subsequent data detection performance. Therefore, herein, for an uplink multicell massive multiuser MIMO system, we consider using an alternating projection (AP) for channel estimation to eliminate the effect of pilot contamination and improve the performance of data detection in terms of the bit error rates as well. Even though the AP is nonlinear, it iteratively searches the best solution in only one dimension, and the computational complexity is thus modest. We have analyzed the mean square error with respect to the signal-to-interference ratios for both the cooperative and non-cooperative multicell scenarios. From the simulation results, we observed that the channel estimation results via the AP benefit the following signal detection more than that via the least squares for both the cooperative and non-cooperative multicell scenarios.

Before/After Precoding Massive MIMO Systems for Cloud Radio Access Networks

  • Park, Sangkyu;Chae, Chan-Byoung;Bahk, Saewoong
    • Journal of Communications and Networks
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    • v.15 no.4
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    • pp.398-406
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    • 2013
  • In this paper, we investigate two types of in-phase and quadrature-phase (IQ) data transfer methods for cloud multiple-input multiple-output (MIMO) network operation. They are termed "after-precoding" and "before-precoding". We formulate a cloud massive MIMO operation problem that aims at selecting the best IQ data transfer method and transmission strategy (beamforming technique, the number of concurrently receiving users, the number of used antennas for transmission) to maximize the ergodic sum-rate under a limited capacity of the digital unit-radio unit link. Based on our proposed solution, the optimal numbers of users and antennas are simultaneously chosen. Numerical results confirm that the sum-rate gain is greater when adaptive "after/before-precoding" method is available than when only conventional "after-precoding" IQ-data transfer is available.