Downlink beamforming for TD/CDMA multipath channels

Downlink beamforming has been proposed for high-capacity and spectrally-efficient DS-CDMA wireless systems. It mitigates the effects of multiple access interference, self interference and inter-cell interference. In this paper we propose a new direction-based downlink beamforming algorithm for frequency selective TD/CDMA multipath channels. It minimises the radiated array power while suppressing dominant interferers. By considering the directivity of the beam pattern, improved robustness and good spatial filtering properties are achieved. This approach also supports path diversity, assuming that a conventional rake is deployed at the mobile. Moreover, it can easily be expanded to facilitate space division multiple access (SDMA).