A novel ekf-based recovery in ds scheme for ds/cdma systems tracking code delay

Abstract

Classical delay-lock loops (DLL) have beenwidely considered for code synchronization purposes inDS/CDMA systems, although they have not been devised foroperation when channel fading is present. This paper describes a new code synchronizationscheme based on a previously proposed extended Kalmanfilter (EKF) approach. The scheme proposed in this paperis able to operate under low signal-to-interference ratios (SIR), usual at the receiver input incellular CDMA mobile environments, and it outperformsthe behavior of previously proposed EKF-based schemes,which failed in such environments. Performance results under realistic mobile environment conditionsare shown in terms of the mean time to lose lock (MTLL)and the tracking error variancest2 for a wide range ofSIR values and under Rayleigh fading. Moreover, the Cramer-Rao lower boundonst2 is also computed inorder to validate the results obtained viasimulations