Capacity scaling and Coverage of Repeater-Aided MIMO Systems in Line-of-Sight Environments
Date Issued
2010
Date
2010
Author(s)
Tsai, Lung-Sheng
Abstract
Multiple-input multiple-output (MIMO) technique provides
capacity improvement which scales linearly with the number of antennas. However, such improvement cannot be realized in line-of-sight (LOS) environments due to lack of scattering. It had been proposed that, in LOS environments, if a mobile station can receive signal from multiple repeaters, the artificial multipath could render an equivalent high-rank end-to-end MIMO channel. In this dissertation, we first investigate whether fixed-location repeaters can induce significant MIMO capacity gain throughout the coverage of
a cell in a LOS environment. Our results indicate that, for a wide range of repeater locations and antenna parameters, the majority of the coverage area of a cell can support a high-order capacity scaling factor. We further show that for a capacity scaling factor of 2, the corresponding coverage consists of a small number of simply-connected areas. We present the expressions for the contour of these areas as a function of base station and repeater locations, antenna spacings, and antenna orientations. Next we investigate the effect of antenna geometry and orientation on the capacity scaling behavior. A MIMO system aided by two repeaters in a LOS environment is considered. For a particular MS location, the supporting MIMO gain can be quite different depending on the array orientation. Due to the mobile nature, the MS antenna array may not usually orient to a suitable direction to enable the MIMO gain. In light of this concern, we derive the formulation of the two-eigenmode availability, defined to be the probability of a mobile location enjoying two
useful spatial degrees of freedom given a random antenna orientation. Regardless of the antenna geometry, locations of the same eigenmode availability must constitute one or more horseshoe curves. Our result shows that the repeaters can provide MIMO gain with a high probability over a large
area.
Subjects
MIMO
relay
repeater
LOS
capacity scaling
multiplexing
coverage
geometry
orientation
Type
thesis
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