keting and business plans. 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. Planning Locations for Base Stations Planning Locations for Base Stations In Fig. 27.15 we showed a cellular system adding cells on a smaller grid at the triple- points of its existing large-cell grid. Since the small-cell grid has three times as many cells as the large-cell grid, we call this three-to-one cell splitting. In the grid represen- tation we show the new, small cell as a smaller hexagon, as shown in Fig. 32.5. The ra- dius of this hexagon is V3 times smaller than the large hexagons surrounding it, and it has one-third the area. The reality of a three-to-one cell split is not a small hexagon, however. It is the tri- angle shown in Fig. 32.6. The good news about the triangle cell shape is that it is big- ger than the hexagon, so instead of serving one-third of a large-cell area, it serves one- half a large-cell area. Three large cells are reduced by one-sixth by the new cell, so they cover 83 percent of their former area. 3 The bad news about the triangle cell shape is that it creates three four-cell zones at its corners. These particular areas will go away as the small-cell grid expands, but the interface between the small-cell grid and the large-cell grid will continue to have four-cell zones. The alternative grid-based growth scheme is four-to-one cell splitting, as we saw in Fig. 27.14. Instead of adding cells at triple-points, we add small cells midway between existing large cells. These cells form a grid half the radius and one-quarter the area of the large-cell grid, so we call this four-to-one cell splitting. In our grid mindset, we rep- resent the new cell with a hexagon four times smaller, as shown in Fig. 32.7. Superscript(3)In some ideal vision of cellular growth, we would like to add a new cell to relieve n busy cells so that n + 1 cells each se