A new adaptive algorithm for MSNR beamforming in WCDMA system

In a code division multiple access (CDMA) system, the optimum weight vector of an adaptive antenna array is the principal eigenvector (eigenvector corresponding to the maximum eigenvalue) of the covariance matrix of the received signal at the output of the despreader [S. Choi & D. Yun, Sept. 1997]. Consequently the weight vector can be computed by solving a simple eigenvalue problem (SE) [F. Alam et al., May 2002]. In this paper we develop a new adaptive algorithm based on the Lagrange multiplier technique to solve the SE. The computational complexity of the proposed algorithm is linear with the number of antenna elements. We investigate different aspects like the convergence and tracking property of the proposed algorithm. We employ a beamformer-RAKE [A. F. Naguib, Aug. 1996] receiver at the uplink of a wideband CDMA (WCDMA) [UMTS, 3G TS 25.213 V3.2.0 (2000-03)], [UMTS, 3G TS 25.211 V3.2.0 (2000-03)] system to test the performance of the adaptive algorithm. We compare the proposed algorithm with another Lagrange multiplier based algorithm [S. Choi & D. Shim, Sept. 2000] in terms of computational complexity, rate of convergence and bit error rate (BER) performance of the beamformer-RAKE receiver in multipath environment.