f the network over the air interface. In current capacity planning, the relative benefit improving the quality of mobile telephones versus improving the quality of base sta- tions depends on the ratio of mobile telephones to base stations. If a system has 1000 subscribers per base station, it is probably more cost-effective to implement system performance improvements at the base stations because there are so many mobile Older readers will recall Dick Tracy and his two-way wrist radio from the comics. This inno- vation in cellular technology probably will be much more welcome in the market than the shoe phone made popular in the television show "Get Smart." 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 User Terminal The User Terminal telephones served by each base station. However, if a system has only 100 subscribers per base station, it can be more cost-effective to improve the quality of the mobile units, even if this might mean offering customers a free trade-in for a new unit.9 In AMPS and GSM, a poor radio results in poor call quality for that user, making easy for the customer to accept an upgrade to a new phone. However, in CDMA, each mobile unit transmitter is a source of interference for all the other callers on the cell. As a result, a poor radio or, for example, a radio with poor power control interferes with other users on the same cell. In these situations, the problem does not affect the cell phone owner; it affects other users. As a result, it may be more difficult to convince a customer to trade up to a new phone. Overall, however, better radios in CDMA mobile telephones mean more calls per tor, requiring fewer base stations in a given area to provide the same quality of service to the same number of users. This is a factor in planning in that if phones are devel- oped with better radios, it will be possible to slow th