A modified non-coherent delay-locked loop for CDMA systems

A PN code tracking loop for DS-CDMA is presented with main focus on the third generation cdma2000 system. The proposed tracking scheme is based on a modified early-late delay-locked loop (DLL) structure that utilizes three non-coherent correlators and post-detection accumulations. A lock detector is used to maintain the signals aligned for a long period of time and to determine when a loss of synchronization has occurred. Analytical and simulation results for the mean hold-in time performance in AWGN and Rayleigh fading conditions are presented. It is shown that the loop can maintain lock with the incoming signal at very low signal-to-noise ratio. Tracking of time varying delays is also demonstrated.