Beam forming Algorithm for Smart Antenna in WCDMA Network

The capacity of cellular system is limited by two different phenomena namely, multipath fading and multi-access interference. The Third Generation based Wide Band Code Division Multiple Access (W-CDMA) Networks use smart antenna techniques that include Direction of Arrival (DOA) approach and adaptive beamforming algorithm to remove multipath fading, multi-access interference and to increase the Signal to Interference Noise Ratio (SINR), and system capacity to improve the communication quality. In this paper, DOA is estimated using Multiple Signal Classification (MUSIC) method which makes use of the Eigen structure. Subsequently, the adaptive beam forming algorithm is employed which comprises of complex weightings, time delays and the summer. Here, we improve on the Minimum Variance Distortion less Response (MVDR) method in order to assign the weightings. We have proposed a new method to compute the complex weighting coefficients based on certain data-dependent criteria known as constraints. Instead of using a single linear equality constraint, as in MVDR, multiple constraints that broaden the null area of interferers have been used to calculate the optimum weights. Simulations have been carried out in the presence of noise to compute BER for the conventional MVDR method and proposed method by varying (i) the number of antenna elements, and (ii) the spacing between the antenna elements. For both the cases, the performance of the proposed method is better than MVDR method.