Blind MIMO Adaptive Beamforming Techniques for DS-CDMA Systems

M. Hefnawi (Canada)


Adaptive-beamforming, space-time coding, transmit diversity, code-filtering approach, LS-CMA. beamforming techniques [1]-[5] are attracting a lot of attention in increasing data rates and enhancing the performance of wireless systems in terms of power and spectral efficiency. In conventional beamforming systems, digital signal processing algorithms are employed to adaptively update the beamforming weights, so that a single beam radiation pattern of the array can be dynamically and adapt


In this paper we focus on adaptive beamforming Algorithms in a direct sequence-code division multiple access (DS-CDMA) system using Multiple Input Multiple Output (MIMO) technology. The system is based on an adaptive beamformer at the base station and the Alamouti’s transmit diversity at the mobile users. Two blind algorithms, the Least Squares Constant Modulus Algorithm (LS-CMA) and the code filtering approach (CFA) are examined and compared. The system performance is evaluated by simulation in terms of Bit Error Rate (BER) and beampattern. It is shown that the proposed hybrid system significantly outperforms MIMO systems without beamforming and that the CFA can offer a better beampattern and bit error rate performance compared to the LS-CMA.

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