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An Adaptive MSINR Filter for Cochannel Interference Suppression in DS/CDMA Systems
Yutaro MINAMI Kohei OTAKE
Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Vol.E86A
No.1
pp.235243 Publication Date: 2003/01/01
Online ISSN:
DOI:
Print ISSN: 09168508 Type of Manuscript: PAPER Category: Spread Spectrum Technologies and Applications Keyword: DS/CDMA, spreadspectrum communication, adaptive filter, interference suppression, SINR,
Full Text: PDF>>
Summary:
Many types of adaptive algorithms based on the MMSE criterion for cochannel interference suppression in DS/CDMA systems have been studied in great detail. However, these algorithms have such a problem that the training speed is greatly dropped under the strong nearfar problem. In this paper, we propose and analyze an adaptive filter based on the Maximum Signal to Interference and Noise Ratio (MSINR) criterion, called adaptive MSINR filter. This filter is basically equivalent to the adaptive filter based on the MMSE criterion. However, due to the structual difference, the convergence speed is greatly improved. Specifically, the despreading vector in this filter is so renewed as to maximize the Signal to Interference and Noise Ratio (SINR) by minimizing the despread interference and noise power under the condition that the despread desired signal power keeps constant. So the proposed filter uses the estimated interference and noise signal calculated by subtracting the estimated desired signal from the received signal. It is just the reason why the adaptive MSINR filter shows remarkable convergence speed. And to satisfy the constant signal power condition, the projection matrix onto the orthogonal complement of the desired signal space is used for the despreading vector. For the proposed filter, we analyze the convergence modes and also investigate the despread interfernce and noise power for calculating the theoretical SINR curve. Then, we conduct some computer simulations in order to show the difference between this filter and the conventional one in terms of the SINR convergence speed. As the result, we confirm that the adaptive filter based on the MSINR criterion achieves significant progress in terms of the SINR convergence speed.

