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Capacity and interference analysis of multicell CDMA systems using 3-dimensional smart antennas Cheung, Titus Tin Hing

Abstract

In this thesis, we derive analytical expressions for the interference and estimate the capacity of a CDMA based wireless system for indoor mobiles in 6 groups of high riser buildings occupying 6 building blocks of a typical high density downtown city environment. The analysis compares the performances of a single element panel antenna, a 1-dimensional linear array, and a 3-dimensional vertical planar array. We further consider an appropriate 3-dimensional urban model representative for such an environment, and based upon this model, a more accurate 3-dimensional user distribution is introduced. Our work has shown that, for such an environment, the traditional assumption of uniform user distribution is not valid. It is found that by arranging smart antenna elements in specific 2- and 3-dimensional geometries, reduction of sidelobes and significant improvements in the directivity can be achieved with the same number of elements traditionally used in a 1-dimensional linear array. For a more accurate analysis, short dipoles and panel antenna elements are used instead of isotropic point sources. Surface plots for the interference and capacity from the 6 building groups for different vertical and azimuth angles are produced. The capacity with the use of a 3-dimensional smart antenna and the improvement over a linear array are then compared, taken into account of different building materials' and dimensional effects. These performance evaluation results have shown that, as compared to the 1-dimentional linear array employing the same number of antennas, significant capacity improvements are achievable.

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