 an MSC must be robust, well supported, and well protected. In this text we use the term MSC to refer to the switch. The term also can refer to the building, the physical facility that houses one or more MSC switches and related equipment. When we count MSCs, we are counting the number of switches needed to support all the base stations on the network. In Sec. 34.2 we will discuss the physical housing of MSCs. In this chapter we will also discuss component planning for MSCs and for auxiliary equipment. 34.1 Estimating MSC Count Just as we did with base stations, we want to estimate the total number of MSCs re- quired for a wireless telephone system. The issues are less complex for MSCs than for base stations because MSCs do not depend so heavily on the CDMA air interface, but there are more issues. Switches cost money, and more switches cost more money. To put MSC cost into per- spective, if one MSC costs US$5 million and serves 200 base stations that cost $500,000 each, then the MSC cost is 5 percent of the base station cost. Thus MSC cost is a sig- nificant fraction of total equipment cost, enough to merit some attention. While some of the MSC cost depends on the number of base stations, there are enough fixed costs of installing an MSC that we want to avoid having extra MSCs in the system. Each time we add an MSC to a wireless system, we add to the administrative work- load. Telephone switches have internal databases and maintenance schedules. There are more connections and more transport pipes as well. Finally, having more MSCs in a wireless system means having more MSC bound- aries and more inter-MSC communication. This affects call originations and termina- tions because dividing the system into more MSC regions makes more of the wireless 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