ime of day. In this way, we can figure out the true limit- ing factors that determine how many MSCs will be needed. The result of this study should be a multiple-service, time-of-day analysis that tells us how many MSCs we ex- pect to need at the end of the planning horizon. 1We are assuming that speech coders are bidirectional. 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. Mobile Switching Center (MSC) Planning Planning for CDMA Capacity 34.2 Location Planning for MSCs It is important to find a good place for the MSCs. Because there is no radio link, MSC site selection is far less important than base station site selection, but it is still an im- portant part of the wireless telephone system planning process. An MSC has to have reliable electrical power. This may sound obvious, but it is an important consideration. The less reliable the source of electrical power, the more im- portant it becomes to have a good power backup. The real cost issue in MSC location is the availability of telephone transport. In ad- dition to the base stations, the MSC has to communicate with the PSTN, the PPDN, any private networks, the ANSI-41 signaling network, and other MSCs. Clearly, we want the MSC to be in a place where large-volume telephone transport is available and cheap. Most areas, particularly where there is an extensive landline telephone system, have transport backbones, networks of very high speed telephone transport. 2 In a system with more than one MSC, we can put all of them in one place. This keeps administrative costs down because all the equipment is in one place, so one service visit can attend to all the MSCs. Having all the MSCs together means being able to share the electrical power supply. And any communication between MSCs is going to be cheaper and simpler when the MSCs are all in the same building. Distributing the MSCs allows them