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Hang Long - One of the best experts on this subject based on the ideXlab platform.

  • ICCC - Precoding and Destination-Aided Cooperative Jamming in MIMO Untrusted Relay Systems
    2020 IEEE CIC International Conference on Communications in China (ICCC), 2020
    Co-Authors: L. Zhang, Hang Long, Li Huang
    Abstract:

    In this paper, secrecy communications with cooperative jamming in a two-hop one-way untrusted relay system is studied. Assuming that all nodes are equipped with multiple antennas, new Precoding designs are proposed to increase the secrecy capacity. Two situations are considered, namely only designing Precoding Vector for jamming signal when user signal has been determined, and designing Precoding Vectors for both user and jamming signals by jointly considering the source node. For each situation, two alignment algorithms are proposed, namely zero-forcing-based (ZF) alignment algorithm and minimum-mean-squared-error-based (MMSE) alignment algorithm. Both algorithms are designed to ensure that the equivalent wiretap channel matrix forms two aligned Vectors. The channel Vector from the destination node is designed to be aligned with that from the source node, so that the eavesdropping node cannot decode user signals. Analytical and simulation results show that all proposed scheme can achieve secure communication, and the MMSE algorithm performs better than the ZF. In addition, the destination-relay link has greater impact on the secrecy performance than the relay-destination link.

  • Precoding Vector distribution under spatial correlated channel and nonuniform codebook design
    International Conference on Communications, 2008
    Co-Authors: Hang Long, Wenbo Wang, Hui Zhao, Kan Zheng
    Abstract:

    In this paper, influence of spatial correlation on codebook-based Precoding technology is analyzed. Optimum pre- coder distribution under spatial correlated channel is achieved at first, which is no longer isotropical on the unitary matrix (Vector) set. Selection probability of the matrix (Vector) in codebook is not uniform too. Then, a novel codebook design is presented for spatial correlated channel, which is termed as nonuniform codebook. Codebook is designed as function of spatial correlation characteristic of channel and presents a nonuniform quantization of unitary Vector set. Smaller quantization error and higher spectral efficiency can be achieved by proposed codebook design than that of traditional fixed uniform codebook design, with the cost of slight feedback overhead increasing.

  • ICC - Precoding Vector Distribution under Spatial Correlated Channel and Nonuniform Codebook Design
    2008 IEEE International Conference on Communications, 2008
    Co-Authors: Hang Long, Wenbo Wang, Hui Zhao, Kan Zheng
    Abstract:

    In this paper, influence of spatial correlation on codebook-based Precoding technology is analyzed. Optimum pre- coder distribution under spatial correlated channel is achieved at first, which is no longer isotropical on the unitary matrix (Vector) set. Selection probability of the matrix (Vector) in codebook is not uniform too. Then, a novel codebook design is presented for spatial correlated channel, which is termed as nonuniform codebook. Codebook is designed as function of spatial correlation characteristic of channel and presents a nonuniform quantization of unitary Vector set. Smaller quantization error and higher spectral efficiency can be achieved by proposed codebook design than that of traditional fixed uniform codebook design, with the cost of slight feedback overhead increasing.

H Taoka - One of the best experts on this subject based on the ideXlab platform.

  • VTC Fall - Effect of Intra-Subframe Frequency Hopping on Closed-Loop Type Transmit Diversity with Precoding for Uplink DFT-Precoded OFDMA
    2011 IEEE Vehicular Technology Conference (VTC Fall), 2011
    Co-Authors: Lianjun Deng, Teruo Kawamura, H Taoka, Mamoru Sawahashi
    Abstract:

    This paper proposes applying intra-subframe frequency hopping (FH) to closed-loop (CL) type transmit diversity using codebook based Precoding for a shared channel carrying user traffic data in the uplink discrete Fourier transform (DFT)-precoded Orthogonal Frequency Division Multiple Access (OFDMA). In the paper, we present two types of Precoding schemes associated with intra-subframe FH: individual Precoding Vector selection between 2 slots where a 1-msec subframe comprises 2 slots among the reduced Precoding codebooks, and common Precoding Vector selection between 2 slots. We investigate the effect of intra-subframe FH on the CL type transmit diversity with Precoding in terms of the block error rate (BLER) performance while maintaining the same number of feedback bits required for notification of the selected Precoding Vector as that for CL type Precoding based transmit diversity without FH. Computer simulation results show that CL type transmit diversity with Precoding using intra-subframe FH is very effective in reducing the required average received signal-to-noise power ratio (SNR) when the fading maximum Doppler frequency, fD, is higher than approximately 50 Hz both for 2- and 4-antenna transmission in the uplink DFT-precoded OFDMA.

  • a multi stage hybrid scheduler for codebook based Precoding system
    Wireless Communications and Networking Conference, 2008
    Co-Authors: Jingxiu Liu, Xiaoming She, Lan Chen, H Taoka
    Abstract:

    Significant throughput gains can be obtained in multi-user wireless system by exploiting the combination of multi-user scheduling in media access control (MAC) layer and MIMO spatial multiplexing using Precoding in physical (PHY) layer. In this paper, we propose a multi-stage hybrid scheduling scheme for codebook-based Precoding system, which applies different scheduling methods at different scheduling stages for selecting user equipments (UEs). In detail, we employ different scheduling algorithms when the appropriate UE or UE sets are selected within the same Precoding Vector, within the same Precoding matrix, and within the codebook, respectively, so that we could finely adjust the balance between capacity and fairness. Computer simulation results show that the proposed scheme effectively fills the performance gap between pure maximum carrier-to-interference (C/I) power ratio and pure proportional fairness (PF) methods, and provides an important means at the MAC layer to lever between aggregate cellular throughput and geometry-specific per-user fairness, in order to meet the requirements of more precise quality of service (QoS) provision for future mobile communication systems.

  • WCNC - A Multi-Stage Hybrid Scheduler for Codebook-Based Precoding System
    2008 IEEE Wireless Communications and Networking Conference, 2008
    Co-Authors: Jingxiu Liu, Xiaoming She, Lan Chen, H Taoka
    Abstract:

    Significant throughput gains can be obtained in multi-user wireless system by exploiting the combination of multi-user scheduling in media access control (MAC) layer and MIMO spatial multiplexing using Precoding in physical (PHY) layer. In this paper, we propose a multi-stage hybrid scheduling scheme for codebook-based Precoding system, which applies different scheduling methods at different scheduling stages for selecting user equipments (UEs). In detail, we employ different scheduling algorithms when the appropriate UE or UE sets are selected within the same Precoding Vector, within the same Precoding matrix, and within the codebook, respectively, so that we could finely adjust the balance between capacity and fairness. Computer simulation results show that the proposed scheme effectively fills the performance gap between pure maximum carrier-to-interference (C/I) power ratio and pure proportional fairness (PF) methods, and provides an important means at the MAC layer to lever between aggregate cellular throughput and geometry-specific per-user fairness, in order to meet the requirements of more precise quality of service (QoS) provision for future mobile communication systems.

Kan Zheng - One of the best experts on this subject based on the ideXlab platform.

  • Precoding Vector distribution under spatial correlated channel and nonuniform codebook design
    International Conference on Communications, 2008
    Co-Authors: Hang Long, Wenbo Wang, Hui Zhao, Kan Zheng
    Abstract:

    In this paper, influence of spatial correlation on codebook-based Precoding technology is analyzed. Optimum pre- coder distribution under spatial correlated channel is achieved at first, which is no longer isotropical on the unitary matrix (Vector) set. Selection probability of the matrix (Vector) in codebook is not uniform too. Then, a novel codebook design is presented for spatial correlated channel, which is termed as nonuniform codebook. Codebook is designed as function of spatial correlation characteristic of channel and presents a nonuniform quantization of unitary Vector set. Smaller quantization error and higher spectral efficiency can be achieved by proposed codebook design than that of traditional fixed uniform codebook design, with the cost of slight feedback overhead increasing.

  • ICC - Precoding Vector Distribution under Spatial Correlated Channel and Nonuniform Codebook Design
    2008 IEEE International Conference on Communications, 2008
    Co-Authors: Hang Long, Wenbo Wang, Hui Zhao, Kan Zheng
    Abstract:

    In this paper, influence of spatial correlation on codebook-based Precoding technology is analyzed. Optimum pre- coder distribution under spatial correlated channel is achieved at first, which is no longer isotropical on the unitary matrix (Vector) set. Selection probability of the matrix (Vector) in codebook is not uniform too. Then, a novel codebook design is presented for spatial correlated channel, which is termed as nonuniform codebook. Codebook is designed as function of spatial correlation characteristic of channel and presents a nonuniform quantization of unitary Vector set. Smaller quantization error and higher spectral efficiency can be achieved by proposed codebook design than that of traditional fixed uniform codebook design, with the cost of slight feedback overhead increasing.

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

  • intelligent reflecting surface assisted millimeter wave communications joint active and passive Precoding design
    IEEE Transactions on Vehicular Technology, 2020
    Co-Authors: Peilan Wang, Jun Fang, Xiaojun Yuan, Zhi Chen
    Abstract:

    Millimeter wave (MmWave) communications is capable of supporting multi-gigabit wireless access thanks to its abundant spectrum resource. However, severe path loss and high directivity make it vulnerable to blockage events, which can be frequent in indoor and dense urban environments. To address this issue, in this paper, we introduce intelligent reflecting surface (IRS) as a new technology to provide effective reflected paths to enhance the coverage of mmWave signals. In this framework, we study joint active and passive Precoding design for IRS-assisted mmWave systems, where multiple IRSs are deployed to assist the data transmission from a base station (BS) to a single-antenna receiver. Our objective is to maximize the received signal power by jointly optimizing the BS's transmit Precoding Vector and IRSs’ phase shift coefficients. Although such an optimization problem is generally non-convex, we show that, by exploiting some important characteristics of mmWave channels, an optimal closed-form solution can be derived for the single IRS case and a near-optimal analytical solution can be obtained for the multi-IRS case. Our analysis reveals that the received signal power increases quadratically with the number of reflecting elements for both the single IRS and multi-IRS cases. Simulation results are included to verify the optimality and near-optimality of our proposed solutions. Results also show that IRSs can help create effective virtual line-of-sight (LOS) paths and thus substantially improve robustness against blockages in mmWave communications.

  • intelligent reflecting surface assisted millimeter wave communications joint active and passive Precoding design
    arXiv: Signal Processing, 2019
    Co-Authors: Peilan Wang, Zhi Chen, Jun Fang, Xiaojun Yuan, Huiping Duan
    Abstract:

    Millimeter wave (MmWave) communications is capable of supporting multi-gigabit wireless access thanks to its abundant spectrum resource. However, the severe path loss and high directivity make it vulnerable to blockage events, which can be frequent in indoor and dense urban environments. To address this issue, in this paper, we introduce intelligent reflecting surface (IRS) as a new technology to provide effective reflected paths to enhance coverage of mmWave signals. In this framework, we study joint active and passive Precoding design for IRS-assisted mmWave systems, where multiple IRSs are deployed to assist the data transmission from a base station (BS) to a single-antenna receiver. Our objective is to maximize the received signal power by jointly optimizing the transmit Precoding Vector at the BS and the phase shift parameters used by IRSs for passive beamforming. Although such an optimization problem is generally non-convex, we show that, by exploiting some important characteristics of mmWave channels, an optimal closed-form solution can be derived for the single IRS case and a near-optimal analytical solution can be obtained for the multi-IRS case. Our analysis reveals that the received signal power increases quadratically with the number of reflecting elements for both the single IRS and multi-IRS cases. Simulation results are included to verify the optimality and near-optimality of our proposed solutions. Results also show that IRSs can help create effective virtual LOS paths and thus substantially improve robustness against blockages in mmWave communications.

  • WTS - Successive Precoding and user selection in MU-MIMO broadcast channel with limited feedback
    2014 Wireless Telecommunications Symposium, 2014
    Co-Authors: Long Chen, Zhi Chen, Bin Fu
    Abstract:

    In this paper, we propose a joint successive pre-coding and user selection algorithm in multi-user multiple-input multiple-output (MIMO) broadcast channel with limited feedback. The proposed scheme recalculates each user's best Precoding Vector by projecting the original Precoding Vector, which is obtained by limited feedback, onto the orthogonal complement space of the Precoding Vectors of the selected users. The base station (BS) then calculates the estimated signal-to-interference-plus-noise ratio (SINR) for each unselected user using the best Precoding Vector, and choose the one with the largest SINR. Numerical results illustrate the performance of the scheme.

Hui Zhao - One of the best experts on this subject based on the ideXlab platform.

  • Precoding Vector distribution under spatial correlated channel and nonuniform codebook design
    International Conference on Communications, 2008
    Co-Authors: Hang Long, Wenbo Wang, Hui Zhao, Kan Zheng
    Abstract:

    In this paper, influence of spatial correlation on codebook-based Precoding technology is analyzed. Optimum pre- coder distribution under spatial correlated channel is achieved at first, which is no longer isotropical on the unitary matrix (Vector) set. Selection probability of the matrix (Vector) in codebook is not uniform too. Then, a novel codebook design is presented for spatial correlated channel, which is termed as nonuniform codebook. Codebook is designed as function of spatial correlation characteristic of channel and presents a nonuniform quantization of unitary Vector set. Smaller quantization error and higher spectral efficiency can be achieved by proposed codebook design than that of traditional fixed uniform codebook design, with the cost of slight feedback overhead increasing.

  • ICC - Precoding Vector Distribution under Spatial Correlated Channel and Nonuniform Codebook Design
    2008 IEEE International Conference on Communications, 2008
    Co-Authors: Hang Long, Wenbo Wang, Hui Zhao, Kan Zheng
    Abstract:

    In this paper, influence of spatial correlation on codebook-based Precoding technology is analyzed. Optimum pre- coder distribution under spatial correlated channel is achieved at first, which is no longer isotropical on the unitary matrix (Vector) set. Selection probability of the matrix (Vector) in codebook is not uniform too. Then, a novel codebook design is presented for spatial correlated channel, which is termed as nonuniform codebook. Codebook is designed as function of spatial correlation characteristic of channel and presents a nonuniform quantization of unitary Vector set. Smaller quantization error and higher spectral efficiency can be achieved by proposed codebook design than that of traditional fixed uniform codebook design, with the cost of slight feedback overhead increasing.