TABLE OF CONTENTS In wireless system design and planning, one has to deal with two main problems, coverage and capacity. Coverage designs include, among other parameters, the selection of the number of base station sites, locations, heights, antenna orientation, and transmit power required to provide service in a given geographic area. When the system is first deployed, the number of subscribers is low and the aim is to maximize the coverage area of each site. As the number of network users grows, the number of users per site and sector also grows. As more users are added to a sector, the base station transmit power as well as the total power transmitted by those users increases, which effectively increases the interference on both the forward and reverse links. The system then becomes capacity or interference limited. One of the most common ways to deal with this interference problem is sectorization.
In base stations employing omnidirectional antennas, the transmit power is equally radiated in all directions. The equal distribution leads to a portion of the power being transmitted throughout the cell but not received by the user. This wasted power then becomes forward link interference to other base stations or users in other cells. Similarly, each new user added to a cell increases the interference and noise levels on the reverse link. This results in a reduction in the signal-to-noise ratio, which in turn degrades the performance of the detection and demodulation operations. One way to reduce interference...
