ls at the busy hour are the only calls with a significant incremental cost to the service provider. 2We could consider a targeted campaign that aired during Buffy: Vampires, don't get caught without a cell phone. 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. Regional Growth in a Specific Area Regional Growth in a Specific Area Mobile telephone service is particularly popular on major routes of travel. These would include highways and commuter rail routes. Some of these routes go through ar- eas where it is difficult to get base stations to provide adequate coverage. Sometimes it is the lack of telephone transport or even available electrical power that makes it dif- ficult to reach these areas. And sometimes it is that communities try to put noisy roads and rails in sound-protected areas so that their residential neighbors do not have to lis- ten to the noise. Those sound-protected areas are often well protected from radio sig- nals as well. We want to spend some effort figuring out where demand is cheap to serve. Those are the areas where we want to promote subscriber demand SO that we get a greater rev- enue stream while paying less for it. This is the kind of engineering that makes finan- cial investors very happy. 3 The best areas to promote are those where we have excess capacity in a base station that is already operating. The next best areas are those where transport is cheap and easy to get. And the third best areas are those where have plenty of capacity in the mobile switching center (MSC). 45.1.1 Existing base stations While we have been writing about base stations being installed for capacity expansion, even a large and populous wireless telephone system has a lot of base stations whose purpose is coverage. Without these base stations in the system, areas that are currently green areas would have been red or yellow, as describe