• Title, Summary, Keyword: CSI Feedback

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A Channel State Information Feedback Method for Massive MIMO-OFDM

  • Kudo, Riichi;Armour, Simon M.D.;McGeehan, Joe P.;Mizoguchi, Masato
    • Journal of Communications and Networks
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    • v.15 no.4
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    • pp.352-361
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    • 2013
  • Combining multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) with a massive number of transmit antennas (massive MIMO-OFDM) is an attractive way of increasing the spectrum efficiency or reducing the transmission energy per bit. The effectiveness of Massive MIMO-OFDM is strongly affected by the channel state information (CSI) estimation method used. The overheads of training frame transmission and CSI feedback decrease multiple access channel (MAC) efficiency and increase the CSI estimation cost at a user station (STA). This paper proposes a CSI estimation scheme that reduces the training frame length by using a novel pilot design and a novel unitary matrix feedback method. The proposed pilot design and unitary matrix feedback enable the access point (AP) to estimate the CSI of the signal space of all transmit antennas using a small number of training frames. Simulations in an IEEE 802.11n channel verify the attractive transmission performance of the proposed methods.

Performance Improvement on Adaptive OFDM System with a Multi-Step Channel Predictor over Mobile Fading Channels (이동 페이딩 채널하의 멀티 스텝 채널 예측기를 이용한 적응 OFDM 시스템의 성능개선)

  • Ahn, Hyun-Jun;Kim, Hyun-Dong;Choe, Sang-Ho
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.12A
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    • pp.1182-1188
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    • 2006
  • Adaptive OFDM(Orthogonal Frequency Division Multiplexing) improves data capacity and system performance over multipath fading by adaptively changing modulation schemes according to channel state information(CSI). To achieve a good performance in adaptive OFDM systems, CSI should be transmitted from receiver to transmitter in real time through feedback channel. However, practically, the CSI feedback delay d which is the sum of the data processing delay and the propagation delay is not negligible and damages to the reliability of CSI such that the performance of adaptive OFDM is degraded. This paper presents an adaptive OFDM system with a multistep predictor on the frequency axis to effectively compensate the multiple feedback delays $d(\geq2)$. Via computer simulation we compare the proposed scheme and existing adaptive OFDM schemes with respect to data capacity and system performance.

Channel State Information Feedback Scheme Based on Non-Convex Compressed Sensing for Massive MIMO Systems (거대 다중 안테나 시스템을 위한 넌컨벡스 압축센싱 기반채널 정보 피드백 기법)

  • Kim, Jung-Hyun;Kim, Inseon;Park, Jin Soo;Song, Hong-Yeop;Han, Sung Woo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.4
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    • pp.628-636
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    • 2015
  • In this paper, we propose a non-convex compressed sensing(NCCS)-based channel state information(CSI) feedback scheme for massive multiple-input multiple-output(MIMO) systems. Combining the random vector quantization(RVQ), the proposed scheme permits a transmitter to obtain CSI with acceptable accuracy under substantially reduced feedback load. Furthermore, it recovers CSI from fewer measurements than that of existing convex compressed sensing(CCS)-based schemes even if the measurements are inaccurate and incomplete. Simulation results show that the proposed scheme achieves higher throughput than both existing CCS-based feedback scheme and random vector quantization(RVQ) feedback scheme with the same feedback load.

Reducing Feedback Overhead in Opportunistic Scheduling of Wireless Networks Exploiting Overhearing

  • Baek, Seung-Jun
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.6 no.2
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    • pp.593-609
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    • 2012
  • We propose a scheme to reduce the overhead associated with channel state information (CSI) feedback required for opportunistic scheduling in wireless access networks. We study the case where CSI is partially overheard by mobiles and thus one can suppress transmitting CSI reports for time varying channels of inferior quality. We model the mechanism of feedback suppression as a Bayesian network, and show that the problem of minimizing the average feedback overhead is NP-hard. To deal with hardness of the problem we identify a class of feedback suppression structures which allow efficient computation of the cost. Leveraging such structures we propose an algorithm which not only captures the essence of seemingly complex overhearing relations among mobiles, but also provides a simple estimate of the cost incurred by a suppression structure. Simulation results are provided to demonstrate the improvements offered by the proposed scheme, e.g., a savings of 63-83% depending on the network size.

A Robust Adaptive MIMO-OFDM System Over Multipath Transmission Channels (다중경로 전송 채널 특성에 강건한 적응 MIMO-OFDM 시스템)

  • Kim, Hyun-Dong;Choe, Sang-Ho
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.32 no.7A
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    • pp.762-769
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    • 2007
  • Adaptive MIMO-OFDM (Orthogonal Frequency Division Multiplexing) system adaptively changes modulation scheme depending on feedback channel state information (CSI). The CSI feedback channel which is the reverse link channel has multiple symbol delays including propagation delay, processing delay, frame delay, etc. The unreliable CSI due to feedback delay degrades adaptive modulation system performance. This paper compares the MSE and data capacity with respect to delay and channel signal to noise ratio for the two multi-step channel prediction schemes, CTSBP and BTSBP, such that robust adaptive SISO-OFDM/MIMO-OFDM is designed over severe mobile multipath channel conditions. This paper presents an interpolation method to reduce feedback overhead for adaptive MIMO-OFDM and shows MSE with respect to interpolation interval.

Compressed Channel Feedback for Correlated Massive MIMO Systems

  • Sim, Min Soo;Park, Jeonghun;Chae, Chan-Byoung;Heath, Robert W. Jr.
    • Journal of Communications and Networks
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    • v.18 no.1
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    • pp.95-104
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    • 2016
  • Massive multiple-input multiple-output (MIMO) is a promising approach for cellular communication due to its energy efficiency and high achievable data rate. These advantages, however, can be realized only when channel state information (CSI) is available at the transmitter. Since there are many antennas, CSI is too large to feed back without compression. To compress CSI, prior work has applied compressive sensing (CS) techniques and the fact that CSI can be sparsified. The adopted sparsifying bases fail, however, to reflect the spatial correlation and channel conditions or to be feasible in practice. In this paper, we propose a new sparsifying basis that reflects the long-term characteristics of the channel, and needs no change as long as the spatial correlation model does not change. We propose a new reconstruction algorithm for CS, and also suggest dimensionality reduction as a compression method. To feed back compressed CSI in practice, we propose a new codebook for the compressed channel quantization assuming no other-cell interference. Numerical results confirm that the proposed channel feedback mechanisms show better performance in point-to-point (single-user) and point-to-multi-point (multi-user) scenarios.

Channel Prediction and Estimation based Feedback Overhead Reduction for Adaptive OFDM System (채널 예측 및 추정을 이용한 적응 전송 OFDM 시스템의 피드백 오버헤드 감소 기법)

  • Kim, Hyun-Dong;Choe, Sang-Ho
    • Proceedings of the IEEK Conference
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    • pp.213-214
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    • 2006
  • To reduce the feedback overhead of predicted CSI (channel status information) of adaptive OFDM (orthogonal frequency division multiplexing), we use partial data of CSI and employ linear interpolation. Simulation results show estimated CSI and its MSE.

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Low-Overhead Feedback Topology Design for the K-User MIMO Interference Alignment

  • Jin, Jin;Gao, Xiang-Chuan;Li, Xingwang;Cavalcante, Charles Casimiro;Li, Lihua
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.12 no.11
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    • pp.5304-5322
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    • 2018
  • Since designing a feedback topology is a practical way to implement interference alignment at reduced cost of channel state information (CSI) feedback, six feedback topologies have been presented in prior works for a K-user multiple-input multiple-output interference channel. To fully reveal the potential benefits of the feedback topology in terms of the saving of CSI overhead, we propose a new feedback topology in this paper. By efficiently performing dimensionality-decreasing at the transmitter side and aligning interference signals at a subset of receivers, we show that the proposed feedback topology obtains substantial reduction of feedback cost over the existing six feedback designs under the same antenna configuration.

Channel Quantization for Block Diagonalization with Limited Feedback in Multiuser MIMO Downlink Channels

  • Moon, Sung-Hyun;Lee, Sang-Rim;Kim, Jin-Sung;Lee, Inkyu
    • Journal of Communications and Networks
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    • v.16 no.1
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    • pp.1-9
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    • 2014
  • Block diagonalization (BD) has been proposed as a simple and effective technique in multiuser multiple-input multiple-output (MU-MIMO) broadcast channels. However, when channel state information (CSI) knowledge is limited at the transmitter, the performance of the BD may be degraded because inter-user interference cannot be completely eliminated. In this paper, we propose an efficient CSI quantization technique for BD precoded systems with limited feedback where users supported by a base station are selected by dynamic scheduling. First, we express the received signal-to-interference-plus-noise ratio (SINR) when multiple data streams are transmitted to the user, and derive a lower bound expression of the expected received SINR at each user. Then, based on this measure, each user determines its quantized CSI feedback information which maximizes the derived expected SINR, which comprises both the channel direction and the amplitude information. From simulations, we confirm that the proposed SINR-based channel quantization scheme achieves a significant sum rate gain over the conventional method in practical MU-MIMO systems.

Ordered Interference Alignment in MIMO Interference Channel with Limited Feedback (제한된 궤환 채널 기반 MIMO 간섭 채널에서의 순서화 된 간섭 정렬 기법 설계)

  • Cho, Sungyoon;Yang, Minho;Yang, Janghoon;Kim, Dong Ku
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.37B no.10
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    • pp.938-946
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    • 2012
  • Interference alignment (IA) is a data transmission technique that achieves the maximum degrees-of-freedom (DoF) in the multiuser interference channel for high signal-to-noise ratios (SNRs). However, most prior works on IA are based on the unrealistic assumption that perfect and global channel-state information (CSI) is available at all transmitters and receivers. In this paper, we propose the efficient design of feedback framework for IA that substantially suppresses the feedback overhead. While the feedback overhead in the conventional IA quadratically increases with K, the proposed feedback scheme supports the sequential exchange of computed IA precoders between transmitters and receivers and reduces the feedback overhead that linearly scales with K. Moreover, we analyze the residual interference due to the quantization error in limited feedback and propose the ordered IA algorithm that selects IA pair to minimize the sum residual interference in given channel realizations.