with hundreds of base stations to having the same num- ber of sectors in all the cells. The sector plan has to work for the cell layout. Sector boundaries are pilot-pollution zones, just as cell boundaries are. Each sector is its own CDMA server with its own car- riers and pilots. Thus we should orient the sector antennas so that the equal-path-gain lines between sectors do not cross cell triple-points and four-cell zones. The good news for cellular planners is that the sector boundaries are clean, straight lines. Neighbor- ing sectors are in the same place, served by the same base station, so the radio path gains should be exactly the same. The only difference is the comparative antenna gains, and this difference should depend only on the serving signal direction. Thus, while cell boundaries are made fuzzy by terrain, obstructions, and vegetation, realistic sector boundaries should be drawn easily on a map. 3 As we discussed in Sec. 30.1, this is in direct contrast to conventional reuse (FDMA and TDMA), where sectorization is used to manage interference. 4Note that the omnidirectional cell in this discussion is hypothetical. We do not expect to find many omnidirectional CDMA cells actually out there serving calls, but we start with the omnicell as a point of comparison for our capacity calculations. 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 Planning for CDMA Capacity When we need a high-gain antenna for a tough area with low radio path gain, we can create a narrow sector for coverage. Or when there is a small area of high demand, we can create a narrow sector for capacity. The narrow sector goes between two existing sectors as part of the sector plan, not as some kind of overlay sector in the middle of another sector. The next technology step in cell sectorization is introducing adaptive phased arrays, or smart a