Conference Paper

WLC31-3: Adaptive Modulation in MIMO Eigen beamforming with Outdated Channel State Information

Dept. of ECE, Univ. of Massachusetts, Amherst, MA
DOI: 10.1109/GLOCOM.2006.795 Conference: Global Telecommunications Conference, 2006. GLOBECOM '06. IEEE
Source: IEEE Xplore


Channel state information(CSI) at the transmitter, even imperfect, can improve the capacity of a multiple-input multiple-output(MIMO) communication system and substantially reduce the receiver complexity. Eigenbeamforming has been proven to be the preceding scheme that not only achieves the channel capacity, but also minimizes the mean square error (MSE) at the output of the receiver in this case. This paper presents a novel adaptive modulation scheme that loads power and integer bits over the eigenmodes in a MIMO communication system according to outdated CSI at the transmitter. An un- coded narrowband system is considered in a time-varying and spatially uncorrelated fading channel. Simulations indicate that the proposed scheme provides a much higher spectral efficiency than the standard strategy which simply adds energy margin to achieve the target error performance.

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    • "In this paper, we present a more deterministic design approach that uses the per-subchannel SINR expression derived in [6] (also see [5]) to ┬┐nd a subchannel power-loading scheme and multiplexing thresholds for SVD-based MIMO signaling with M-QAM constellations under ICSI conditions. "
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    ABSTRACT: In narrowband multiple-input multiple-output (MIMO) communication systems with perfectly known channel state information (CSI), the singular value decomposition (SVD) is commonly used to decompose the MIMO channel into independent single-input single-output subchannels. In theory, optimal interference-free data multiplexing may then be carried out using the subchannel power levels provided by the well-known waterfilling solution. In practice, however, when finite codebooks are used and perfect CSI is unavailable, adaptations to power levels and bit-loading schemes are often needed to maintain reasonable performance. In this paper, we use expressions for the per-subchannel signal-to-interference- and-noise ratio for the imperfect CSI case to derive approximately optimal subchannel power levels and thresholds on the amount of CSI imperfections and noise tolerable in SVD-based multiplexing systems using M-ary quadrature amplitude modulation. Numerical simulations demonstrate the usefulness of the derived expressions.
    Full-text · Conference Paper · Apr 2010
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    ABSTRACT: This letter studies peak-to-average power ratio (PAPR) reduction for orthogonal frequency-division multiplexing (OFDM) signals in eigenbeamformed multiple antenna systems. The weak eigenmodes abandoned by the waterfilling allocation are intentionally filled in order to offset signal peaks in the time domain.Numerical results indicate that this method can significantly increase the efficiency of peak power constrained systems with no modification of the receiver required.
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    ABSTRACT: A number of techniques are now available for the characterization of solid surfaces using an Optical Laser Microscope (OLM). It has firmly established its role in industry and elsewhere for routing high-resolution studies of surface structure and topography. One of the most common operations in machine vision is finding the connected components in an image. In this work, a component-labeling algorithm will find all connected components in an image and assigns a unique label to all points in the same component. After capturing the image from OLM, various grains features were extracted at the first step and shipped to the second step for the final statistical analysis, performed with the aid of MATLAB software. The raster graphics is used to visualize the surface data which is one of the best techniques that has occupied computer graphics analysis. All observable features in material sample can be counted and measured with the aid of the (computerized optical laser microscope).
    No preview · Article · Jan 2013