rve an equal share. This would be a very efficient growth scheme. Small Figure 32.5 Grid representation of a three-to-one cell split. Downloaded from Digital Engineering Library @ McGraw-Hil (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. Planning Locations for Base Stations Planning for CDMA Capacity Small Figure 32.6 Three-to-one cell split creates a triangular cell. Small Figure 32.7 Grid representation of a four-to-one cell split. Downloaded from Digital Engineering © 2004 The Library McGraw-Hill @ McGraw-Hill Companies. (www.digitalengineeringlibrary.com) All rights reserved. Copyright Any use is subject to the Terms of Use as given at the website. Planning Locations for Base Stations Planning Locations for Base Stations Just as three-to-one splitting produced triangular rather than hexagonal cells, four- to-one cell splitting produces oblong, rectangular cells, as shown in Fig. 32.8. These rec- tangles eventually are whittled down to hexagons as their neighboring cells are added to the small-cell grid, but the initial growth cell is a long rectangle. The good news about these rectangles is that they are large, half the area of a large cell. The two cells being relieved are reduced to 79 percent of their former area, SO the growth cell pro- vides substantial capacity relief. The other good news is that the rectangular growth cell usually does not produce any four-cell zones. When using four-to-one cell splitting, we can create four-cell zones. This happens when the small-cell grid has holes in it, as shown in Fig. 32.9. As long as the small-cell grid regions are convex areas, regions without any boundary U shapes or internal holes, then four-to-one cell splitting should grow a CDMA system with very few four-cell zones of high pilot pollution. 4 Its ability to grow a CDMA system with less pilot pollution than three-to-one splitting causes us to favor four-to-one cell splitting for CDMA growth. 