Pulse Shaping in Non-Coherent DLL Tracking of CDMA Signals

摘要

The paper analyses the impact of pulse shaping on code tracking for direct-sequence code division multiple access (DS-CDMA) signal synchronization using non-coherent delay-lock loops (NC-DLL). The dependency of the residual timing error variance on the chip waveform is emphasized, and the performance of several non-rectangular pulse shapes is presented. The design of optimized chip waveforms for minimizing the DLL tracking error variance is then formulated using a cost function expressed in frequency-domain and highlighting the dependency of the tracking jitter on the chip waveform Fourier transform. A solution methodology is introduced based on the use of Prolate Spheroidal Wave Functions. Some illustrative design examples are presented, establishing theoretical limits for the best achievable performance (minimum jitter). In particular, it is shown that the half-sine and Hamming pulses are near-optimum when considering pulses with 99% and 99.9% in-band power bandwidth occupancies, respectively.