Semi-blind interference suppression for frequency selective DS-CDMA systems employing space-time block codes

This paper considers the problem of interference suppression in short-burst frequency selective direct-sequence code-division multiple access (DS-CDMA) systems that employ space-time block codes in the transmitter. It is assumed that attached to each burst are a certain number of training symbols that can be used in the receiver to recover the unknown data in a training-based (least squares) or semi-blind (combination of training and blind) manner. We propose a semi-blind algorithm that works by combining subspace-based estimation with an iterative CMA routine. The algorithm is tested for the special case of Alamouti´s space-time block code. Simulation results demonstrate significant gains for the proposed semi-blind procedure over least-squares (training-only) interference suppression.