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The presence of multipath leads to a loss of orthogonality between the signals transmitted simultaneously on a wideband code-division multiple access (WCDMA) downlink. We derive general analytical expressions for the orthogonality factor (OF), which quantifies this loss of orthogonality, as a function of the instantaneous multipath fade realization of the channel. We show that the OF exhibits a significant temporal variation for the three channel profiles suggested in the WCDMA standard, namely, typical urban, rural area, and hilly terrain, which span a wide range of realistic cases. Moreover, its temporal variations and statistics vary significantly from one channel profile to another. Also, while the pulse shape and the number of Rake fingers has only a marginal impact on the OFs statistics, the granularity in setting the finger positions has a considerable impact. The results of the work can be directly used for evaluation of the system performance of WCDMA cellular systems.Index Terms-Code-division multiple access (CDMA), intracell interference, multipath channels, orthogonality factor, Rake receiver.

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A computer method for determining the scattering, absorption, and internal field structure of thin flat disks of arbitrary refractive index is described. The code is shown to be accurate for all angles of incidence for radii up to at least two free space wavelengths and for media ranging from pure dielectric to highly conductive ones. The accuracy of the method is assessed by comparison with published experimental data and with results computed by other methods. The applicability of this technique for analyzing clouds of disk-shaped aerosols is also discussed.

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