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

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%.

[1]  Andrew J. Viterbi,et al.  On the capacity of a cellular CDMA system , 1991 .

[2]  Edward R. Dougherty,et al.  Probability and Statistics for the Engineering, Computing and Physical Sciences , 1990 .

[3]  K. Sohrabi,et al.  Wideband channel measurements at 900 MHz , 1995, 1995 IEEE 45th Vehicular Technology Conference. Countdown to the Wireless Twenty-First Century.

[4]  Michele Zorzi.  Power control and diversity in mobile radio cellular systems in the presence of Ricean fading and log-normal shadowing , 1996 .

[5]  Asrar U. H. Sheikh,et al.  Outage probability analysis for microcell mobile radio systems with cochannel interferers in Rician/Rayleigh fading environment , 1990 .

[6]  Roberto Padovani,et al.  The application of spread spectrum to PCS has become a reality: Reverse Link Performance of 1S-95 Based Cellular Systems , 1994, IEEE personal communications.

[7]  L. F. Chang,et al.  Signal and interference statistics of a CDMA system with feedback power control , 1991, IEEE Global Telecommunications Conference GLOBECOM '91: Countdown to the New Millennium. Conference Record.

[8]  B. Hashem,et al.  On the capacity of a cellular DS/CDMA system under slow multipath fading and fixed step power control , 1997, Proceedings of ICUPC 97 - 6th International Conference on Universal Personal Communications.

[9]  M. Wallace,et al.  CDMA radio network planning , 1994, Proceedings of 1994 3rd IEEE International Conference on Universal Personal Communications.

[10]  Michele Zorzi.  On the analytical computation of the interference statistics with applications to the performance evaluation of mobile radio systems , 1997, IEEE Trans. Commun..