Assessing the effect of DS-CDMA chip rate on RAKE branch statistics using a ray-tracing propagation model

An important improvement in the performance of CDMA and other wideband digital communication systems can be achieved using a RAKE receiver architecture and diversity combining of its branches. The paper presents an analysis of RAKE branch statistics as a function of chipping or channel symbol transmission rate for urban microcells. A deterministic ray-tracing model is used to provide realistic, site-specific estimates of the time dispersion in the dynamic fading channel. The results of the analysis show that increased chipping rates produce increasingly Ricean fading distributions on the diversity branches along with increased power in the higher order diversity branches. Increased diversity branch power results in more effective diversity combining and improved signal-to-noise ratios of the combined branch signals.