Direct-sequence spread-spectrum code-division-multiple-access cellular systems in Rayleigh fading and log-normal shadowing channel

Direct-sequence spread-spectrum code-division-multiple-access (DS-SS-CDMA) techniques for personal and mobile communications are considered. A service area is divided into cells. The radio link is modeled as an additive white Gaussian noise channel with Rayleigh fading and log-normal shadowing, and is also corrupted by mutual interferences due to other users. L-branch microscopic diversity combining, K-site macroscopic diversity selection, and uplink power control are assumed. Under these assumptions, for uplink and downlink transmissions between users and cell-sites, analytical expressions of the probability distribution of the ratio of bit-energy to noise-plus-interference-density are derived. By numerically evaluating the derived expressions, the number of users per cell as a function of outage probability are obtained. Numerical results indicate that DS-SS-CDMA provides high capacity