PN code chip time tracking with smart antennas

This paper proposes to employ a smart antenna to improve pseudonoise (PN) code chip time tracking loop (PNCTL), and analyzes its performance in the third generation (3G) wideband code division multiple access wireless communications channel (W-CDMA). Since a smart antenna can improve the signal-to-interference-plus-noise power ratio (SINR), the smart antenna may also improve the PNCTL performance as well as the bit error rate (BER) and capacity of the CDMA system. We consider the mean-time-to-lose-lock (MTLL) as the performance criteria. The PNCTL takes the smart antenna array output as its input. We examine both the first and second order PNCTLs, and employ a normalized least mean square (NLMS) algorithm to update the weight vector for the smart antenna. A flat Rayleigh Jakes fading multipath is taken as the channel model, and independent additive white Gaussian noise (AWGN) is added at each antenna element. Through both analysis and simulation, we demonstrate that the MTLL can be significantly improved under fading and AWGN environments, compared to a single antenna element, e.g., a 6 dB improvement in SINR with four antenna elements.