Average Orthogonality Factor in WCDMA Downlinks for Independent Rayleigh Fading Multipath Channels

In wideband code division multiple access (WCDMA) system capacity analysis and simulations, downlink interference due to loss of orthogonality between spreading codes is modeled by means of the orthogonality factor (OF). This study derives closed-form expressions for the time-averaged OF over independent Rayleigh fading multipath channels, in which the average power gains of each path can be distinct or identical. Two approximation approaches proposed in related literature are tested against the analytical results presented here