Antenna downtilt effects on CDMA cell-site capacity

Antenna downtilt is often used in cellularized mobile wireless communications systems to reduce inter-cell interference, particularly in a CDMA-based network where all call traffic in all cell sites is simultaneously supported using the same carrier frequency. While the inter-cell interference is indeed reduced through such downtilt the sectorization efficiency may also be reduced with increased downtilt. For a CDMA system, interference reduction increases cell-site capacity whereas reduced sectorization efficiency decreases cell-site capacity. Since the net effect on capacity is of interest, an analytical treatment of the effects of antenna downtilt on the reverse-link capacity for a CDMA cell site has been performed. Results from a parametric study for various cell-site configurations are presented in this paper.