This paper analyses the performance of a joint receiving structure for DS-CDMA communications systems. To reduce undesirable performance degradation due to the multiple access interferences and the near-far problem in multipath fading channel environment, this paper exploits the receiving structure for the multiuser communication composed of a beamformer-RAKE receiver and a decorrelating multiuser detector. The proposed DS-CDMA receiving structure mitigates the performance impairment invoked from the noise enhancement and reveals less computational complexity by utilizing the multipath temporal combiner prior to accessing the decorrelating detection. Also an efficient block Toeplitz inversion technique using the matrix Levinson polynomials is introduced to further diminish the computational burden encountered from applying the decorrelating multiuser detection process as in usual. Simulation results are conducted to demonstrate the superior performance of the proposed multiuser detection structure in multipath fading CDMA channel.

This paper introduces an efficient affine projection algorithm (APA) using iterative hyperplane projection. The inherent effectiveness against the rank deficient problem has led APA to be the preferred algorithm to be employed for various applications over other variety of fast converging adaptation algorithms. However, the amount of complexity of the conventional APA could not be negligible because of the accomplishment of sample matrix inversion (SMI). Another issue is that the "shifting invariance property," which is typically exploited for single channel case, does not hold ground for space-time decision-directed equalizer (STDE) application deployed in single-input-multi-output (SIMO) systems. Therefore, fast adaptation schemes, such as fast traversal filter based APA (FTF-APA), becomes impossible to utilize. The motivation of this paper deliberates on finding an effective algorithm on the basis of APA, which yields low complexity while sustaining fast convergence as well as excellent tracking ability. The performance of the proposed method is evaluated under wireless SIMO channel in respect to bit error rate (BER) behavior and computational complexity, and upon completion, the validity is confirmed. The performance of the proposed method is evaluated under wireless SIMO channel in respect to bit error rate (BER) behavior and computational complexity, and upon completion, the validity is confirmed.