The Experts below are selected from a list of 222 Experts worldwide ranked by ideXlab platform

A. Lee Swindlehurst - One of the best experts on this subject based on the ideXlab platform.

  • Spectral Efficiency of One-Bit Sigma-Delta Massive MIMO
    IEEE Journal on Selected Areas in Communications, 2020
    Co-Authors: Hessam Pirzadeh, Gonzalo Seco-granados, Shilpa Rao, A. Lee Swindlehurst
    Abstract:

    Author(s): Pirzadeh, H; Seco-Granados, G; Rao, S; Swindlehurst, AL | Abstract: IEEE We examine the uplink spectral efficiency of a massive MIMO base station employing a one-bit Sigma-Delta (Σ) sampling scheme implemented in the spatial rather than the temporal domain. Using spatial rather than temporal oversampling, and feedback of the quantization error between adjacent antennas, the method shapes the spatial spectrum of the quantization noise away from an angular sector where the signals of interest are assumed to lie. It is shown that, while a direct Bussgang analysis of the ΣΔ approach is not suitable, an alternative Equivalent Linear Model can be formulated to facilitate an analysis of the system performance. The theoretical properties of the spatial quantization noise power spectrum are derived for the ΣΔ array, as well as an expression for the spectral efficiency of maximum ratio combining (MRC). Simulations verify the theoretical results and illustrate the significant performance gains offered by the ΣΔ approach for both MRC and zero-forcing receivers.

  • Spectral Efficiency of One-Bit Sigma-Delta Massive MIMO
    eScholarship University of California, 2020
    Co-Authors: Pirzadeh H, Seco-granados G, Rao S, A. Lee Swindlehurst
    Abstract:

    © 1983-2012 IEEE. We examine the uplink spectral efficiency of a massive MIMO base station employing a one-bit Sigma-Delta ( \Sigma \Delta ) sampling scheme implemented in the spatial rather than the temporal domain. Using spatial rather than temporal oversampling, and feedback of the quantization error between adjacent antennas, the method shapes the spatial spectrum of the quantization noise away from an angular sector where the signals of interest are assumed to lie. It is shown that, while a direct Bussgang analysis of the \Sigma \Delta approach is not suitable, an alternative Equivalent Linear Model can be formulated to facilitate an analysis of the system performance. The theoretical properties of the spatial quantization noise power spectrum are derived for the \Sigma \Delta array, as well as an expression for the spectral efficiency of maximum ratio combining (MRC). Simulations verify the theoretical results and illustrate the significant performance gains offered by the \Sigma \Delta approach for both MRC and zero-forcing receivers

Izuru Takewaki - One of the best experts on this subject based on the ideXlab platform.

  • soil structure random response reduction via tmd vd simultaneous use
    Computer Methods in Applied Mechanics and Engineering, 2000
    Co-Authors: Izuru Takewaki
    Abstract:

    A new systematic method for optimal viscous damper (VD) placement in building structures with a tuned mass damper (TMD) is developed taking into account the response amplification due to the surface ground. Non-Linear amplification of the surface ground is described by an Equivalent Linear Model and local interaction with the surrounding soil is incorporated with a horizontal spring and a dashpot. Hysteretic damping of the surface ground and radiational damping into the semi-infinite visco-elastic ground are included in the Model. An original steepest direction search algorithm is applied to the interaction Model with a TMD. Closed-form expressions of the inverse of the coefficient matrix (tri-diagonal matrix) enable one to compute the transfer function and its derivative with respect to design variables very efficiently. It is shown that simultaneous use of a TMD and added viscous dampers is very effective in response reduction and the ratio of the fundamental natural period of the structure to that of the surface ground is a key parameter for characterizing the optimal damper placement. Several examples with and without a TMD for different soil conditions are presented to demonstrate the effectiveness and validity of the present method.

  • Equivalent Linear ductility design of soil-structure interaction systems
    Engineering Structures, 1998
    Co-Authors: Izuru Takewaki
    Abstract:

    The purpose of this paper is to propose a new semi-explicit ductility design method for a shear building Model taking into account dynamic soil-structure interaction. The shear building Model is supported by swaying and rocking springs and by the corresponding dashpots. Design earthquakes are defined as a set of spectrum-compatible earthquakes at the ground surface level. The normal biLinear rule is adopted as the story shear force-interstory drift relationship. It is shown that the introduction of an Equivalent Linear Model and application of the hybrid inverse eigenmode problem, due to the present author, to this Equivalent Linear Model enable one to construct a new efficient ductility design method for an elastically supported shear building Model. This design method, although approximate, does neither require any eigenvalue analysis nor any repetitive procedure including elastic-plastic time-history response analysis. The validity and accuracy of this design method is demonstrated by elastic-plastic time-history response analysis.

Swindlehurst A. Lee - One of the best experts on this subject based on the ideXlab platform.

  • Massive MIMO Channel Estimation with Low-Resolution Spatial Sigma-Delta ADCs
    2021
    Co-Authors: Rao Shilpa, Pirzadeh Hessam, Seco-granados Gonzalo, Nossek, Josef A., Swindlehurst A. Lee
    Abstract:

    We consider channel estimation for an uplink massive multiple-input multiple-output (MIMO) system where the base station (BS) uses an array with low-resolution (1-2 bit) analog-to-digital converters and a spatial Sigma-Delta ($\Sigma\Delta$) architecture to shape the quantization noise away from users in some angular sector. We develop a Linear minimum mean squared error (LMMSE) channel estimator based on the Bussgang decomposition that reformulates the nonLinear quantizer Model using an Equivalent Linear Model plus quantization noise. We also analyze the uplink achievable rate with maximal ratio combining (MRC), zero-forcing (ZF), and LMMSE receivers and provide a lower bound for the achievable rate with the MRC receiver. Numerical results show superior channel estimation and sum spectral efficiency performance using the $\Sigma\Delta$ architecture compared to conventional 1- or 2-bit quantized massive MIMO systems.Comment: Submitted to IEEE Transactions on Signal Processing after revisio

  • Spectral Efficiency of One-Bit Sigma-Delta Massive MIMO
    'Institute of Electrical and Electronics Engineers (IEEE)', 2020
    Co-Authors: Pirzadeh Hessam, Seco-granados Gonzalo, Rao Shilpa, Swindlehurst A. Lee
    Abstract:

    We examine the uplink spectral efficiency of a massive MIMO base station employing a one-bit Sigma-Delta sampling scheme implemented in the spatial rather than the temporal domain. Using spatial rather than temporal oversampling, and feedback of the quantization error between adjacent antennas, the method shapes the spatial spectrum of the quantization noise away from an angular sector where the signals of interest are assumed to lie. It is shown that, while a direct Bussgang analysis of the Sigma-Delta approach is not suitable, an alternative Equivalent Linear Model can be formulated to facilitate an analysis of the system performance. The theoretical properties of the spatial quantization noise power spectrum are derived for the Sigma-Delta array, as well as an expression for the spectral efficiency of maximum ratio combining (MRC). Simulations verify the theoretical results and illustrate the significant performance gains offered by the Sigma-Delta approach for both MRC and zero-forcing receivers.Comment: Published in IEEE JSA

  • Massive MIMO Channel Estimation with Low-Resolution Spatial Sigma-Delta ADCs
    2020
    Co-Authors: Rao Shilpa, Pirzadeh Hessam, Seco-granados Gonzalo, Swindlehurst A. Lee
    Abstract:

    We consider channel estimation for an uplink massive multiple input multiple output (MIMO) system where the base station (BS) uses an array with low-resolution (1-2 bit) analog-to-digital converters and a spatial Sigma-Delta ($\Sigma\Delta$) architecture to shape the quantization noise away from users in some angular sector. We develop a Linear minimum mean squared error (LMMSE) channel estimator based on the Bussgang decomposition that reformulates the nonLinear quantizer Model using an Equivalent Linear Model plus quantization noise. We also analyze the uplink achievable rate with maximal ratio combining (MRC) and zero-forcing (ZF) receivers and provide a closed-form expression for the achievable rate with the MRC receiver. Numerical results show superior channel estimation and sum spectral efficiency performance using the $\Sigma \Delta$ architecture compared to conventional 1- or 2-bit quantized massive MIMO systems

Hessam Pirzadeh - One of the best experts on this subject based on the ideXlab platform.

  • Spectral Efficiency of One-Bit Sigma-Delta Massive MIMO
    IEEE Journal on Selected Areas in Communications, 2020
    Co-Authors: Hessam Pirzadeh, Gonzalo Seco-granados, Shilpa Rao, A. Lee Swindlehurst
    Abstract:

    Author(s): Pirzadeh, H; Seco-Granados, G; Rao, S; Swindlehurst, AL | Abstract: IEEE We examine the uplink spectral efficiency of a massive MIMO base station employing a one-bit Sigma-Delta (Σ) sampling scheme implemented in the spatial rather than the temporal domain. Using spatial rather than temporal oversampling, and feedback of the quantization error between adjacent antennas, the method shapes the spatial spectrum of the quantization noise away from an angular sector where the signals of interest are assumed to lie. It is shown that, while a direct Bussgang analysis of the ΣΔ approach is not suitable, an alternative Equivalent Linear Model can be formulated to facilitate an analysis of the system performance. The theoretical properties of the spatial quantization noise power spectrum are derived for the ΣΔ array, as well as an expression for the spectral efficiency of maximum ratio combining (MRC). Simulations verify the theoretical results and illustrate the significant performance gains offered by the ΣΔ approach for both MRC and zero-forcing receivers.

Xinglong Gong - One of the best experts on this subject based on the ideXlab platform.

  • the rheology of shear thickening fluid stf and the dynamic performance of an stf filled damper
    Smart Materials and Structures, 2008
    Co-Authors: Xianzhou Zhang, Xinglong Gong
    Abstract:

    This paper presents a study of the rheological properties of shear thickening fluid (STF) and its application as a damper. The STF samples, with different weight fractions, were prepared by dispersing nanosized silica particles in a solvent. By using a parallel-plate rheometer, both steady-state and dynamic experiments were carried out to investigate the rheological properties of STFs. Experimental results indicated that these suspensions show an abrupt increase in complex viscosity beyond a critical dynamic shear rate, as well as this increase being reversible. Working with the fabricated STF materials, a prototype damper was fabricated and its dynamic performances were experimentally evaluated. An Equivalent Linear Model through effective elastic stiffness and viscous damping was developed to address both the damping and the stiffness capabilities of the damper. Also, a mathematical Model was developed to investigate working mechanisms of STF-based devices.