Variable Step Size Affine Projection Algorithm for Adaptive Multiuser DS-CDMA MMSE Receiver |
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Authors: | Aditya Trivedi Daljit Kumar Mehra |
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Institution: | (1) Department of Electronics Engineering, Madhav Institute of Technology and Science, Gwalior, Madhya Pradesh, 474 005, India;(2) Department of Electronics and Computer Engineering, Indian Institute of Technology, Roorke, 247667, India |
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Abstract: | In this paper, we consider the use of affine projection algorithm (APA) for interference suppression in direct sequence code-division
multiple-access (DS-CDMA) system. We first derive the multiuser fixed step-size APA (FSS-APA) algorithm. The computational
complexity offered by the APA algorithm is linear in terms of the number of taps with additional terms of O (L
2) and a matrix inversion of dimension L, where L is known as the order of the filter. The value of L is chosen very small as compared to the number of filter-taps N
T
. We next propose a novel variable step-size APA (VSS-APA) algorithm, which further improves the performance of the FSS-APA
algorithm with very small increase in computational complexity as compared to the FSS-APA. It is demonstrated that the performance
of the APA based minimum mean-square error (MMSE) receivers is far superior to that of the normalized least-mean-square (NLMS)
based receivers. Though, the recursive-least-square (RLS) algorithm based adaptive receivers offer better performance but
at the cost of much higher computational complexity. |
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Keywords: | DS-CDMA systems MMSE receivers adaptive algorithms interference suppression |
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