Design and implementation of all-digital CDMA code tracking loops

Code Division Multiple Access (CDMA) code tracking performance has been shown to depend on both the correlation properties of the spreading codes and the actual pulse shape utilized. This work quantifies the impact of pulse shaping on the performance of the noncoherent delay lock loop used in code tracking in direct sequence spread spectrum systems. Several families of pulses are considered. The effect of pulse shaping is demonstrated in the presence of multiple access interference. Optimization based on the use of Prolate Spheroidal Wave Functions is carried out to determine optimal pulse shapes in terms of minimum tracking jitter. The optimized pulse shapes are obtained and their performance compared to conventional pulse shapes. Finally, the implementation of the digital tracking loop is carried out using a Digital Signal Processor (DSP).