A single beamformer for antenna array CDMA systems

In order to combine the signals distributed in the space and time domains, various space-time processing techniques have been proposed. For code division multiple access systems with antenna arrays, the 2D-RAKE combiner has been proposed to combine the signals in the space and time domains. The combiner has multiple beamformers and the number of beamformers is equal to the number of multipaths. In order to reduce the number of beamformers, we propose a combiner with a single beamformer in this paper. Using the maximum signal strength criterion, the spatial and temporal weight vectors are derived for the proposed combiner. It is shown that the proposed combiner can be efficient if the distribution of the multipath signals in the space domain is narrow. To track time-variant channels, an adaptive method to recursively find the spatial and temporal weight vectors is also considered. (C) 2001 Elsevier Science B.V. All rights reserved.