| Summary: | 碩士 === 國立清華大學 === 電機工程研究所 === 84 === Narrowband interference cancellation or suppression is
important in design of a wireless spread-spectrum code-
division multiple-access (CDMA) system. Most related
techniques described previously are either with
unsatisfactory performance or difficult for hardware
implementation. In this thesis, we propose some methods with
comparable computational/hardware complexity to suppress
narrowband interference in wireless direct-sequence CDMA
systems, including a basic scheme and two performance-
enhanced versions. The basic scheme is a nonlinear predictor
that consists of an (N+1)-level quantizer and an adaptive
linear filter, where N is the number of users in the CDMA
system. The first enhanced scheme is an adaptive nonlinear
interpolator, and the second one is an adaptive nonlinear
predictor with offset outputs. Computer simulation results
show that these two approaches have approximately the
same performance for high signal-to-noise-ratio (SNR) cases,
regardless of the number of users. However, the proposed
interpolator outperforms the proposed offset predictor for
most low SNR cases, except for the case where the SNR is very
low and the number of users is large. Both approaches have
much better performance than the conventional linear
filtering approach. As compared to the approximate
conditional mean (ACM) nonlinear filter, they achieve
comparable performance when the SNR is large, but involve
much less computational/hardware complexity.
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