inuously changing backhaul environment of a growing wireless telephone system. The fan-out backhaul network design is complete when we have evaluated all reasonable transport links, assigned them cost values taking into account the fixed cost and recurring expenses discussed in Sec. 35.1, and completed this heuristic until there are no improvements found in the iterative search. 35.3 Backbone Backhaul Networks In areas where there is a backbone of cheap and plentiful telephone transport, the backhaul problem is easier. 1 The transport backbone makes itself visible at specific Superscript(1)Planners in major industrialized cities can take this kind of transport for granted, but the fu- ture of wireless telephone is worldwide, with much of its development expected in places where telephone transport is neither readily available nor cheap. 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. Backhaul Planning Planning for CDMA Capacity places called points of presence (POPs). Transport from POP to POP is enormously cheaper than transport from anywhere else to anywhere else. There can be a single line of POPs, or the backbone can be a complicated network of transport with POPs all over the city. The backhaul design from the base stations to the MSC becomes a backhaul design from the base stations to the nearest and cheapest POP. It is like driving in a town with a few major highways: Everybody gives directions from the nearest major highway, and most trips involve getting to the highway, a few minutes of high speed motoring, and getting from the highway to the destination. Because of its transport requirements, the MSC will be on the backbone, SO it suffices to find the least expensive way to get each base station's packets to the nearest POP. We expect the backhaul solution to consist of daisy-chained packet links as before. This means that one larg