MIMO Adaptive Beamforming for MC-CDMA System

We combine an adaptive beamforming with the Alamouti space-time block code transmission. An adaptive beamforming is a smart antenna system capable of suppressing interferences in a multi-user multiple-input multiple-output (MIMO) communications scenario. For the Alamouti space-time block code, it allows the systems transmit diversity. The beamformer suppress interferences by beamspace processing called generalize sidelobe cancellation (GSC). By minimizing the output power of interference signals, the adaptive beamformer achieves an array pattern corresponding to the directions of arrival (DOAs) of desired user while steering null toward interfering users. Combined with space-time coding, the smart antenna forms multi-mainbeams toward the same desired user. The system performance is evaluated by simulation in terms of beampatterns and bit error rates (BERs). It is shown that the proposed hybrid system outperforms (1) MIMO systems without beamforming, (2) smart system without MIMO; (3) transmit diversity technique (only the Alamouti coding), and (4) no diversity (conventional receiver) in Rayleigh frequency selective environments.