EFFECT OF DELAY SPREAD ON MULTI-BANDWIDTH CDMA SYSTEM WITH MULTIPLE ORDER SELECTION COMBINING

In a multi-bandwidth CDMA system, the performance of a multiple order selection combining rake receiver is analyzed according to the spreadi ng bandwidth of the system and the delay spread of a Rayleigh fading c hannel. The results for various channel environments indicate a tradeo ff between total received signal energy and multipath fading immunity. Increasing the occupied bandwidth of the system (wide-bandwidth sprea ding) gives better performance for small delay spread environments, wh ile gathering more energy (narrow-bandwidth spreading) gives better pe rformance for large delay spread environments. It is also shown that t he performance difference between low and high order selection combini ng grows larger as the spreading bandwidth is increased. It is noted t hat performance degrades by increasing the bandwidth above a certain p oint and the optimum spreading bandwidth for each channel environment decreases as the delay spread of the channel increases.