Broad-band propagation channel analysis for DS and hybrid CDMA system design

The paper describes analysis carried on frequency-selective channels to establish and quantify the performance improvements offered by broadband channels. The work focuses on the two types of diversity, frequency and path, which are offered only by wideband communications systems. For this reason a geometric propagation channel model is developed enabling the performance study of frequency-selective channels to be carried out at their operating frequencies; i.e. at bandpass. The channel model provides the transfer function and parameters such as coherence bandwidth and multipath spread of broadband channels. Based on these transfer functions the time responses of communication channels, separated by one or more signalling bandwidths, are compared and statistically quantified. The results indicate that, depending on the channel bandwidth, there is considerable correlation between broadband communications which are centred at different carrier frequencies. The high correlation between the different broadband channels can be used for propagation path-loss estimation for transmission power control applications in DS and hybrid CDMA systems.