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v2009.01.01 - Convex Optimization

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374 CHAPTER 5. EUCLIDEAN DISTANCE MATRIX<br />

ˇx 7<br />

x 1<br />

ˇx 2<br />

ˇx 3<br />

ˇx 4<br />

ˇx 6<br />

ˇx 5<br />

Figure 101: Regions of coverage by base stations ◦ in a cellular telephone<br />

network. The term cellular arises from packing of regions best covered<br />

by neighboring base stations. Illustrated is a pentagonal cell best covered<br />

by base station ˇx 2 . Like a Voronoi diagram, cell geometry depends on<br />

base-station arrangement. In some US urban environments, it is not unusual<br />

to find base stations spaced approximately 1 mile apart. There can be as<br />

many as 20 base-station antennae capable of receiving signal from any given<br />

cell phone • ; practically, that number is closer to 6.<br />

Figure 102: Some fitted contours of equal signal power in R 2 transmitted<br />

from a commercial cellular telephone • over about 1 mile suburban terrain<br />

outside San Francisco in 2005. Data courtesy Polaris Wireless. [279]

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