est simply to engineer them well and to consider their failures as emergencies outside routine reliability studies. However, in supporting a large network, it is important both to reduce the likelihood of and to be ready for rare crises. We can reduce the likelihood of rare failures by adhering to a well-designed maintenance schedule. In fact, proper management and maintenance are crucial factors that generally do not fit into our neat equations. 11 4.9 Conclusion In the last two chapters we have discussed the systems on the two sides of the air in- terface: the user terminal and the base station that connects the cellular link to the PSTN. In the next chapter we will discuss the basics of wireless telephony. That dis- cussion will lay the groundwork for descriptions of AMPS, GSM, and CDMA. 11 11Maintenance and management may not sound like capacity issues until somebody sends the bill to the wrong place, the electric company cuts off the service, and the batteries run out several hours later. 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. The Base Station 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. Source: CDMA CAPACITY AND QUALITY OPTIMIZATION Chapter Basic Wireless Telephony Interference used to be a bad thing in radio, a disease to be minimized rather than a phenomenon to be managed. The fundamental idea of managing, rather than avoiding, interference gave birth to the cellular phone networks that have sprouted up in the last two decades, growing to about 130,000,000 cell phones in the United States and 1,000,000,000 worldwide in the year 2002. A key component in managing radio interference is the cell, a small transmission area where all mobile phones are serve