Abstract
This paper analyses frequency tracking characteristics of a complex-coefficient adaptive infinite-impulse response (IIR) notch filter used for suppression of narrow-band interference (NBI) with a randomly-varying frequency in a quadriphase shift keying (QPSK) modulated direct-sequence code-division multiple-access (DS-CDMA) communication system. The QPSK DS-CDMA signals are transmitted over a frequency non-selective Rayleigh fading channel. The analysis is based on a first-order real-coefficient difference equation with respect to steady-state instantaneous frequency tracking error from which a closed-form expression that relates frequency tracking mean square error (MSE) with number of DS-CDMA active users and NBI power is obtained. Closed-form expressions for optimum notch bandwidth coefficient and step size constant that minimize the frequency tracking MSE are also derived. Computer simulations are included to substantiate the accuracy of the analyses.
Highlights
Direct-sequence code-division multiple-access (DS-Code-Division Multiple Access (CDMA)) is a preferred multiplexing technique in cellular telecommunications services as it exhibits desired features that are not inherently found in other multiple access techniques, i.e., time-division multiple-access (TDMA) and frequency-division multiple-access (FDMA)
This paper analyses frequency tracking characteristics of a complex-coefficient adaptive infinite-impulse response (IIR) notch filter used for suppression of narrow-band interference (NBI) with a randomly-varying frequency in a quadriphase shift keying (QPSK) modulated direct-sequence code-division multiple-access (DS-CDMA) communication system
Its application in the suppression of NBI in quadriphase shift keying (QPSK) direct-sequence spread-spectrum (DSSS) communication system was shown to result in a better signal-to-noise ratio (SNR) improvement factor than that achieved by finite-impulse response (FIR) adaptive prediction filter
Summary
Direct-sequence code-division multiple-access (DS-CDMA) is a preferred multiplexing technique in cellular telecommunications services as it exhibits desired features that are not inherently found in other multiple access techniques, i.e., time-division multiple-access (TDMA) and frequency-division multiple-access (FDMA). Its application in the suppression of NBI in quadriphase shift keying (QPSK) direct-sequence spread-spectrum (DSSS) communication system was shown to result in a better signal-to-noise ratio (SNR) improvement factor than that achieved by finite-impulse response (FIR) adaptive prediction filter. In [11] a complex coefficient adaptive IIR notch filter with a simplified gradient-based algorithm that does not require any matrix inversion was presented. This paper investigates frequency tracking characteristics of the complex-coefficient adaptive IIR notch filter in [11] that is used for suppression of NBI with randomly-varying frequency in a synchronous QPSK DSCDMA communication system communicating over a frequency non-selective Rayleigh fading channel.
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