Filter-Bank-Based Narrowband Interference Detection and Suppression in Spread Spectrum Systems
- PDF / 866,513 Bytes
- 14 Pages / 600 x 792 pts Page_size
- 108 Downloads / 186 Views
Filter-Bank-Based Narrowband Interference Detection and Suppression in Spread Spectrum Systems Tobias Hidalgo Stitz Institute of Communications Engineering, Tampere University of Technology, P.O. Box 553, 33101 Tampere, Finland Email: [email protected]
Markku Renfors Institute of Communications Engineering, Tampere University of Technology, P.O. Box 553, 33101 Tampere, Finland Email: [email protected] Received 29 October 2002; Revised 27 October 2003; Recommended for Publication by Xiang-Gen Xia A filter-bank-based narrowband interference detection and suppression method is developed and its performance is studied in a spread spectrum system. The use of an efficient, complex, critically decimated perfect reconstruction filter bank with a highly selective subband filter prototype, in combination with a newly developed excision algorithm, offers a solution with efficient implementation and performance close to the theoretical limit derived as a function of the filter bank stopband attenuation. Also methods to cope with the transient effects in case of frequency hopping interference are developed and the resulting performance shows only minor degradation in comparison to the stationary case. Keywords and phrases: narrowband interference cancellation, complex PR filter banks, DS-SS.
1.
INTRODUCTION
Direct sequence spread spectrum (DS-SS) systems have several applications, for example, CDMA communications and advantages, low power spectral density, privacy of the communications, and an inherent immunity to narrowband interferences, due to the processing gain [1]. Nevertheless, this immunity is only effective up to certain interference power, making it necessary to apply additional techniques to suppress the effect of strong narrowband interferences if a degradation of the performance is to be avoided. Several interference suppression techniques have been proposed to process the signal in the time domain (e.g., adaptive transversal filtering) [2, 3, 4, 5, 6] and in the transform domain [2, 7, 8, 9]. These techniques take advantage of the knowledge of the wide spectral shape of the desired signal’s spectrum as compared to the interferer’s narrow spectrum. There are also methods in the spatial domain, using techniques like antenna diversity or beamforming [2, 10], although these methods are not exclusive to narrowband interference on a wideband SS signal. There exist more advanced approaches in the time-frequency domain [11, 12], like wavelet transformation-based methods. In situations in which the interfering environment changes quickly, time-domain techniques are too slow to work correctly. In these cases, frequency-domain techniques like the
FFT-based or the filter-bank-based methods perform better [8, 12]. The purpose of this paper is to analyse the performance of a filter-bank-based interference suppression system. To eliminate the effects of narrowband interference, a perfect reconstruction (PR) filter bank with interference detection and subband suppression logic is used. Efficient implementation of the complex, cri
Data Loading...
