The Experts below are selected from a list of 2454 Experts worldwide ranked by ideXlab platform

Lingjia Liu - One of the best experts on this subject based on the ideXlab platform.

  • multi cell multi user massive fd mimo downlink precoding and throughput analysis
    IEEE Transactions on Wireless Communications, 2019
    Co-Authors: Rubayet Shafin, Lingjia Liu
    Abstract:

    In this paper, downlink (DL) precoding and power allocation strategies are identified for a time-division-duplex multi-cell multi-user massive full-dimension MIMO network. Utilizing Channel Reciprocity, DL Channel state information feedback is eliminated and the DL multi-user MIMO precoding is linked to the uplink (UL) direction of arrival (DoA) estimation through the estimation of signal parameters via rotational invariance technique. Assuming non-orthogonal/non-ideal spreading sequences of the UL pilots, the performance of the UL DoA estimation is analytically characterized and the characterized DoA estimation error is incorporated into the corresponding DL precoding and power allocation strategy. The simulation results verify the accuracy of our analytical characterization of the DoA estimation and demonstrate that the introduced multi-user MIMO precoding and power allocation strategy outperforms the existing zero-forcing-based massive MIMO strategies.

  • multi cell multi user massive fd mimo downlink precoding and throughput analysis
    arXiv: Information Theory, 2018
    Co-Authors: Rubayet Shafin, Lingjia Liu
    Abstract:

    In this paper, downlink (DL) precoding and power allocation strategies are identified for a time-division-duplex (TDD) multi-cell multi-user massive Full-Dimension MIMO (FD-MIMO) network. Utilizing Channel Reciprocity, DL Channel state information (CSI) feedback is eliminated and the DL multi-user MIMO precoding is linked to the uplink (UL) direction of arrival (DoA) estimation through estimation of signal parameters via rotational invariance technique (ESPRIT). Assuming non-orthogonal/non-ideal spreading sequences of the UL pilots, the performance of the UL DoA estimation is analytically characterized and the characterized DoA estimation error is incorporated into the corresponding DL precoding and power allocation strategy. Simulation results verify the accuracy of our analytical characterization of the DoA estimation and demonstrate that the introduced multi-user MIMO precoding and power allocation strategy outperforms existing zero-forcing based massive MIMO strategies.

Ming Lei - One of the best experts on this subject based on the ideXlab platform.

  • Retrieving Channel Reciprocity for Coordinated Multi-Point Transmission with Joint Processing
    IEEE Transactions on Communications, 2014
    Co-Authors: Gang Wang, Ming Lei
    Abstract:

    In time division duplex coordinated multi-point transmission with joint processing (CoMP-JP) systems, the uplink-downlink Channels are no longer reciprocal. Due to the difficulty of antenna calibration among the coordinated base stations (BSs), practical downlink Channels differ from uplink Channels by multiplicative ambiguity factors, which lead to severe performance degradation. In this paper, we propose an inter-BS antenna calibration strategy to facilitate downlink CoMP-JP transmission, whose basic idea is to estimate the ambiguity factors. To establish the observation equations for estimation, an extra uplink training frame except for the regular uplink and downlink frames is introduced, and existing signalling framework of limited feedback can also be reused. To improve the estimation performance, we can either select multiple users or employ multiple frames of one user to assist the calibration. After establishing the observation equations respectively with uplink training or limited feedback, the weighted least square criterion is used for estimation. We proceed to analyze and compare the mean square errors of the estimators, and provide a principle to select the users for assisting calibration. Simulation results show that the Channel Reciprocity is largely retrieved by the proposed antenna calibration strategy, which provides substantial throughput gain over the CoMP-JP systems without inter-BS calibration.

  • coordinated multi point transmission strategies for tdd systems with non ideal Channel Reciprocity
    IEEE Transactions on Communications, 2013
    Co-Authors: Shengqian Han, Gang Wang, Dalin Zhu, Chenyang Yang, Ming Lei
    Abstract:

    This paper studies transmission strategies for downlink time division duplex coordinated multi-point (CoMP) systems with non-ideal uplink-downlink Channel Reciprocity, where several multi-antenna base stations (BSs) jointly serve multiple single-antenna users. Due to the inherent antenna calibration errors among different BSs, the uplink-downlink Channels are no longer reciprocal such that the Channel information at the BSs is with multiplicative noises. To mitigate the performance degradation caused by the imperfect Channels, we employ a weighted sum rate estimate as the objective function for robust precoder design. To show the impact of data sharing on the performance of CoMP under the non-ideal Channel Reciprocity, we provide a unified framework for designing precoder for CoMP systems with different amount of data sharing. The optimal parametric linear precoder structure that maximizes the weighted sum rate estimate under per-BS power constraints is characterized, based on which a closed-form robust signal-to-leakage-plus-noise ratio (SLNR) precoder is proposed to exploit the statistics of the calibration errors. Simulation results show that the proposed precoder in conjunction with user scheduling provides substantial performance gain over Non-CoMP transmission and the CoMP transmission with non-robust precoders.

  • retrieving Channel Reciprocity for coordinated multi point transmission
    Wireless Communications and Networking Conference, 2013
    Co-Authors: Chenyang Yang, Gang Wang, Ming Lei
    Abstract:

    Due to the difficulty of self antenna calibration among different base stations (BSs), the uplink-downlink Channels are no longer reciprocal in time division duplex coordinated multi-point transmission with joint processing (CoMP-JP) systems. To retrieve the Channel Reciprocity, we propose an inter-BS antenna calibration method. Specifically, we estimate the inter-BS ambiguity factors with weighted least square criterion by using the uplink and downlink Channel estimates and the received signal of a calibration sounding signal of multiple supporting users or multiple frames. We then analyze the mean square error of the proposed estimator, and compare the performance of the estimators with multiple supporters and with multiple frames. Simulation results show that the Channel Reciprocity is largely retrieved by the proposed antenna calibration method, which provides substantial throughput gain over the CoMP-JP systems without calibration.

  • coordinated multi point transmission with non ideal Channel Reciprocity
    Wireless Communications and Networking Conference, 2012
    Co-Authors: Shengqian Han, Gang Wang, Dalin Zhu, Ming Lei
    Abstract:

    This paper studies robust transmission strategies for downlink time division duplex coordinated multi-point (CoMP) systems with non-ideal uplink-downlink Channel Reciprocity due to imperfect antenna calibration. By exploiting the statistics of antenna calibration errors, we first characterize the optimal parametric precoder structure that maximizes the weighted sum rate, based on which a closed-form robust signal-to-leakage-plus-noise ratio (RSLNR) precoder with properly selected parameters is then proposed. Simulation results show that the proposed precoder together with user scheduling provides near-optimal performance and data sharing among coordinated BSs may become detrimental depending on the employed precoders and the accuracy of antenna calibration.

  • robust multiuser precoder for base station cooperative transmission with non ideal Channel Reciprocity
    Global Communications Conference, 2010
    Co-Authors: Shengqian Han, Gang Wang, Chenyang Yang, Ming Lei
    Abstract:

    In this paper we present a method to alleviate the performance degradation led by non-ideal Channel Reciprocity in TDD downlink base station (BS) cooperative transmission systems, which comes from imperfect antenna calibration among BSs. By exploiting the statistics of the ambiguity factors between uplink and downlink Channels, a robust multiuser precoder is proposed aimed at maximizing the lower bound of the average signal-to-leakage-plus-noise ratio (SLNR). The precoder is able to adaptively control the cooperation level among the coordinated BSs according to the antenna calibration accuracy among BSs. Simulation results demonstrate an evident performance gain of the proposed robust precoder over the non-robust precoder.

Rubayet Shafin - One of the best experts on this subject based on the ideXlab platform.

  • multi cell multi user massive fd mimo downlink precoding and throughput analysis
    IEEE Transactions on Wireless Communications, 2019
    Co-Authors: Rubayet Shafin, Lingjia Liu
    Abstract:

    In this paper, downlink (DL) precoding and power allocation strategies are identified for a time-division-duplex multi-cell multi-user massive full-dimension MIMO network. Utilizing Channel Reciprocity, DL Channel state information feedback is eliminated and the DL multi-user MIMO precoding is linked to the uplink (UL) direction of arrival (DoA) estimation through the estimation of signal parameters via rotational invariance technique. Assuming non-orthogonal/non-ideal spreading sequences of the UL pilots, the performance of the UL DoA estimation is analytically characterized and the characterized DoA estimation error is incorporated into the corresponding DL precoding and power allocation strategy. The simulation results verify the accuracy of our analytical characterization of the DoA estimation and demonstrate that the introduced multi-user MIMO precoding and power allocation strategy outperforms the existing zero-forcing-based massive MIMO strategies.

  • multi cell multi user massive fd mimo downlink precoding and throughput analysis
    arXiv: Information Theory, 2018
    Co-Authors: Rubayet Shafin, Lingjia Liu
    Abstract:

    In this paper, downlink (DL) precoding and power allocation strategies are identified for a time-division-duplex (TDD) multi-cell multi-user massive Full-Dimension MIMO (FD-MIMO) network. Utilizing Channel Reciprocity, DL Channel state information (CSI) feedback is eliminated and the DL multi-user MIMO precoding is linked to the uplink (UL) direction of arrival (DoA) estimation through estimation of signal parameters via rotational invariance technique (ESPRIT). Assuming non-orthogonal/non-ideal spreading sequences of the UL pilots, the performance of the UL DoA estimation is analytically characterized and the characterized DoA estimation error is incorporated into the corresponding DL precoding and power allocation strategy. Simulation results verify the accuracy of our analytical characterization of the DoA estimation and demonstrate that the introduced multi-user MIMO precoding and power allocation strategy outperforms existing zero-forcing based massive MIMO strategies.

Zhi Ding - One of the best experts on this subject based on the ideXlab platform.

  • deep learning phase compression for mimo csi feedback by exploiting fdd Channel Reciprocity
    IEEE Wireless Communications Letters, 2021
    Co-Authors: Yuchien Lin, Zhenyu Liu, Tasung Lee, Zhi Ding
    Abstract:

    Large scale MIMO FDD systems are often hampered by bandwidth required to feedback downlink CSI. Previous works have made notable progresses in efficient CSI encoding and recovery by taking advantage of FDD uplink/downlink Reciprocity between their CSI magnitudes. Such framework separately encodes CSI phase and magnitude. To further enhance feedback efficiency, we propose a new deep learning architecture for phase encoding based on limited CSI feedback and magnitude-aided information. Our contribution features a framework with a modified loss function to enable end-to-end joint optimization of CSI magnitude and phase recovery. Our test results show superior performance in indoor/outdoor scenarios.

  • exploiting bi directional Channel Reciprocity in deep learning for low rate massive mimo csi feedback
    IEEE Wireless Communications Letters, 2019
    Co-Authors: Zhenyu Liu, Lin Zhang, Zhi Ding
    Abstract:

    Channel state information (CSI) feedback is important for multiple-input multiple-output (MIMO) wireless systems to achieve their capacity gain in frequency division duplex mode. For massive MIMO systems, CSI feedback may consume too much bandwidth and degrade spectrum efficiency. This letter proposes a learning-based CSI feedback framework based on limited feedback and bi-directional reciprocal Channel characteristics. The massive MIMO base station exploits the available uplink CSI to help recovering the unknown downlink CSI from low rate user feedback. We propose two deep learning architectures, DualNet-MAG and DualNet-ABS, to significantly reduce the CSI feedback payload based on the multipath Reciprocity. DualNet-MAG and DualNet-ABS can exploit the bi-directional correlation of the magnitude and the absolute value of real/imaginary parts of the CSI coefficients, respectively. The experimental results demonstrate that our architectures bring an obvious improvement compared with the downlink-based architecture.

Gang Wang - One of the best experts on this subject based on the ideXlab platform.

  • Retrieving Channel Reciprocity for Coordinated Multi-Point Transmission with Joint Processing
    IEEE Transactions on Communications, 2014
    Co-Authors: Gang Wang, Ming Lei
    Abstract:

    In time division duplex coordinated multi-point transmission with joint processing (CoMP-JP) systems, the uplink-downlink Channels are no longer reciprocal. Due to the difficulty of antenna calibration among the coordinated base stations (BSs), practical downlink Channels differ from uplink Channels by multiplicative ambiguity factors, which lead to severe performance degradation. In this paper, we propose an inter-BS antenna calibration strategy to facilitate downlink CoMP-JP transmission, whose basic idea is to estimate the ambiguity factors. To establish the observation equations for estimation, an extra uplink training frame except for the regular uplink and downlink frames is introduced, and existing signalling framework of limited feedback can also be reused. To improve the estimation performance, we can either select multiple users or employ multiple frames of one user to assist the calibration. After establishing the observation equations respectively with uplink training or limited feedback, the weighted least square criterion is used for estimation. We proceed to analyze and compare the mean square errors of the estimators, and provide a principle to select the users for assisting calibration. Simulation results show that the Channel Reciprocity is largely retrieved by the proposed antenna calibration strategy, which provides substantial throughput gain over the CoMP-JP systems without inter-BS calibration.

  • coordinated multi point transmission strategies for tdd systems with non ideal Channel Reciprocity
    IEEE Transactions on Communications, 2013
    Co-Authors: Shengqian Han, Gang Wang, Dalin Zhu, Chenyang Yang, Ming Lei
    Abstract:

    This paper studies transmission strategies for downlink time division duplex coordinated multi-point (CoMP) systems with non-ideal uplink-downlink Channel Reciprocity, where several multi-antenna base stations (BSs) jointly serve multiple single-antenna users. Due to the inherent antenna calibration errors among different BSs, the uplink-downlink Channels are no longer reciprocal such that the Channel information at the BSs is with multiplicative noises. To mitigate the performance degradation caused by the imperfect Channels, we employ a weighted sum rate estimate as the objective function for robust precoder design. To show the impact of data sharing on the performance of CoMP under the non-ideal Channel Reciprocity, we provide a unified framework for designing precoder for CoMP systems with different amount of data sharing. The optimal parametric linear precoder structure that maximizes the weighted sum rate estimate under per-BS power constraints is characterized, based on which a closed-form robust signal-to-leakage-plus-noise ratio (SLNR) precoder is proposed to exploit the statistics of the calibration errors. Simulation results show that the proposed precoder in conjunction with user scheduling provides substantial performance gain over Non-CoMP transmission and the CoMP transmission with non-robust precoders.

  • retrieving Channel Reciprocity for coordinated multi point transmission
    Wireless Communications and Networking Conference, 2013
    Co-Authors: Chenyang Yang, Gang Wang, Ming Lei
    Abstract:

    Due to the difficulty of self antenna calibration among different base stations (BSs), the uplink-downlink Channels are no longer reciprocal in time division duplex coordinated multi-point transmission with joint processing (CoMP-JP) systems. To retrieve the Channel Reciprocity, we propose an inter-BS antenna calibration method. Specifically, we estimate the inter-BS ambiguity factors with weighted least square criterion by using the uplink and downlink Channel estimates and the received signal of a calibration sounding signal of multiple supporting users or multiple frames. We then analyze the mean square error of the proposed estimator, and compare the performance of the estimators with multiple supporters and with multiple frames. Simulation results show that the Channel Reciprocity is largely retrieved by the proposed antenna calibration method, which provides substantial throughput gain over the CoMP-JP systems without calibration.

  • coordinated multi point transmission with non ideal Channel Reciprocity
    Wireless Communications and Networking Conference, 2012
    Co-Authors: Shengqian Han, Gang Wang, Dalin Zhu, Ming Lei
    Abstract:

    This paper studies robust transmission strategies for downlink time division duplex coordinated multi-point (CoMP) systems with non-ideal uplink-downlink Channel Reciprocity due to imperfect antenna calibration. By exploiting the statistics of antenna calibration errors, we first characterize the optimal parametric precoder structure that maximizes the weighted sum rate, based on which a closed-form robust signal-to-leakage-plus-noise ratio (RSLNR) precoder with properly selected parameters is then proposed. Simulation results show that the proposed precoder together with user scheduling provides near-optimal performance and data sharing among coordinated BSs may become detrimental depending on the employed precoders and the accuracy of antenna calibration.

  • robust multiuser precoder for base station cooperative transmission with non ideal Channel Reciprocity
    Global Communications Conference, 2010
    Co-Authors: Shengqian Han, Gang Wang, Chenyang Yang, Ming Lei
    Abstract:

    In this paper we present a method to alleviate the performance degradation led by non-ideal Channel Reciprocity in TDD downlink base station (BS) cooperative transmission systems, which comes from imperfect antenna calibration among BSs. By exploiting the statistics of the ambiguity factors between uplink and downlink Channels, a robust multiuser precoder is proposed aimed at maximizing the lower bound of the average signal-to-leakage-plus-noise ratio (SLNR). The precoder is able to adaptively control the cooperation level among the coordinated BSs according to the antenna calibration accuracy among BSs. Simulation results demonstrate an evident performance gain of the proposed robust precoder over the non-robust precoder.