On the capacity of cellular DS/CDMA systems under slow Rician/Rayleigh-fading channels

Abstract

Power control is essential for code-division multiple-access (CDMA) cellular systems to overcome the near-far problem. Fast power control tracks multipath fading perfectly which increases the intercell interference and thus reduces the capacity. If there is a line of sight (LOS) component between the mobile and the base station with which it is communicating, the fading will be of Rician type and less deep fades will be encountered which reduces the intercell interference. In this paper, we investigate the system capacity assuming the fading between a mobile and the base station with which it is communicating to be Rician with a Rician factor K with the fading between the same mobile and other base stations to be Rayleigh. We show a large increase in the capacity even for small Rician factors. A Rician fading is usually encountered when the mobile is close to the base station and thus the path-loss exponent can be less than four. Thus, we investigate the effect of changing the path-loss exponent value on the system capacity. Finally, we reduce the intercell interference by imposing a limit on the maximum increase in power to compensate for multipath fading and show how can this increase the capacity by more than 100%.