Statistical nature of behavior and performance of DS-CDMA cellular mobile communications

In this paper, the statistical nature of DS-CDMA cellular radio systems is studied. Many different behaviors of the system result from its statistical nature. Since DS-CDMA is an averaging method, In a qualitative discussion about it, the average behavior of the system is usually considered. But, the capacity criterion is usually the 1st percentile of the `C/I´ (carrier to interference ratio) distribution function. This criterion is a function of both the mean and the variance of C/I. Any parameter which increases the randomness of the system, increases the variance and decreases the capacity of the system with the same `C/I´ mean. The most important effects of this fact are: (i) dividing the available spectrum into sub-channels reduces the total capacity of the system, (ii) the capacity improvement due to the voice activity is less than 1/(VoiceActivity), (iii) in the downtown of big cities with tall buildings, the capacity is lower