Augmented antenna arrays for CDMA cellular systems

In this paper, a CDMA cellular system with an adaptive minimum redundancy array (MRA) at base stations is proposed. This system is based on the high-resolution signal angle of arrival algorithm, ESPRIT, in conjunction with array augmentation techniques, and linear least squares adaptation. For the MRA, we propose to use virtual array elements at the locations where there is no sensor element. All real and virtual sensor outputs are weighted and combined to extract the desired signal components and suppress interference. We use the Gaussian approximation to model all interference. To simplify the evaluation of the interference from adjacent cells, the concentric circle cell geometry is employed in place of the common hexagonal cell geometry. The performance of the proposed system is quantified by comparison with the omnidirectional antenna, and the adaptive uniform linear array (ULA) with the same number of elements and same array aperture, using realistic simulations. It is shown that there is around 4 dB and 1 dB improvement in the despread output signal to interference plus noise ratio of the proposed system over the omnidirectional antenna and the conventional ULA, respectively