Cochannel interference reduction by using a notch in tilted antenna pattern

Publisher Website
Google Scholar
Abstract
In a mobile radio environment, the height of a cell site antenna is usually two order of magnitude less than the distance between the cell site and the mobile unit. The elevation angle as observing the cell-site antenna from the mobile unit then is very small. Therefore, the portion of an antenna gain pattern which affects a remote edge of a serving cell region is substantially the same as the portion affecting a nearby cochannel interfering cell. Consequently, antennas in cellular systems have been typically oriented to direct their principal radiation along a plane which is essentially horizontal, i.e., parallel to a plane that is tangent to the average curvature of the earth at the base of the antenna site. Reliance has been placed upon propagation loss effect and the placement of cochannel antenna sites at a sufficient spacing to assure acceptable low levels of cochannel interference. To arrange a sufficient geographical spacing between two cochannel cells in a cellular system, is costly. At present, the conventional cochannel-cell spacing of a cellular system is 4.6 times the cell radius. Under this situation, the cochannel interference sometimes are strongly existing. The scheme of dividing a cell into three sectors and using directional antenna in each sector does reduce the cochannel interference. Sometimes it is still not enough. The following scheme introduced here is to further reduce the cochannel interference. In this paper, we find that the average S/I ratio in a cell region served by a serving cell antenna site is improved by tilting the antenna gain pattern downward by a predetermined amount at every cell site in the cellular system.

This publication has 0 references indexed in Scilit: