. Thus a traffic accident not only generates more voice-mail traffic from drivers sitting in their cars, but it also generates voice mail to those drivers when the air interface is blocking wireless call terminations. 34.7 Anticipating System Growth We can design a wireless telephone system to serve forecast traffic at a specified qual- ity of service (QoS). We can do our financial planning based on these designs and form a clear picture for investors and stockholders. We expect our wireless telephone system to grow, however, to serve more traffic over time. We expect voice call traffic to increase and new 3G services to increase even faster. The financial plan of a system should include not only the expected initial traf- fic but also the growth of that traffic over time. Our base station plan already should be designed for growth in demand and evolution of service mix. Adding a new MSC is a big deal. It costs a lot of money, of course, but it also involves a lot of engineering work. The new MSC requires transport links to the PSTN, the PPDN, private networks, signaling, and other MSCs. New MSC regions have to be formed, and new inter-MSC borders have to be managed. If MSC regions are thought of as giant cells, then adding a new MSC is giant-cell splitting. If the system design with m MSCs is close to requiring m + 1 MSCs, then the ini- tial deployment probably should install the extra MSC up front. Just as we did with base stations in Chap. 31, we should plan the initial system for a deployment time horizon. Anticipating growth in demand for a time horizon gives us a breathing spell to get the system working well before we have to start changing it to satisfy more subscribers. 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 34.8 Conclusion Following the methods in this chapt