educe interference with its neighbors. With this change in function, the high-gain antennas that served well for wider cover- age use their narrow-vertical-beam property to concentrate on their smaller service area and to reject signals from further away. Lowering antennas on their towers also reduces the radio range and shrinks cell size. We lean more toward downtilting because downtilting improves local radio perfor- mance, whereas lowering antennas does not. Lowering antennas reduces everybody's radio path gain but affects shorter paths less than longer ones. Also, lowering anten- nas is more expensive because it requires moving the antennas and possibly installing a new platform, whereas downtilting requires only adjusting the antennas on their cur- rent platform. Aside from lowering existing antennas, we do sometimes choose to place antennas at a lower height than our planning would indicate is best. The primary reason for this is political: Neighborhood residents often do not like high towers nearby. They like cellu- lar phones and they want good service, but they can fight hard to keep the radio tow- ers out of their neighborhoods. Using a shorter tower is a good way to make neighbors feel better by reducing the visual intrusion of cellular in the communities. In the ini- tial system deployment phase, a shorter tower may make the difference between a suc- cessful and an unsuccessful zoning application. When downtilting or lowering antennas, each sector can be treated separately. It is possible to downtilt the antennas on just one face, affecting only one sector. This could be done to resolve a pilot-pollution problem at the edge of that sector without mak- ing changes to other sectors on the same cell. A program of downtilting and lowering Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Base Station Planning Base Station Planning ante