arge supply of dual- mode user terminals and then switch on the CDMA carrier for them. We also make the CDMA carrier their first choice for setting up calls. The legacy system now serves two roles, the overflow for the dual-mode CDMA user terminals and the primary server for the legacy cell phones. If we have sold enough dual-mode user terminals, then this combined system should be more efficient than the legacy technology using the full spectrum. Knowing that we can overflow traffic, we should engineer the CDMA system for high blocking, perhaps very high blocking. As we move traffic from FDMA and TDMA to CDMA, the legacy system will become lightly loaded, and we can grab another piece of spectrum for another CDMA carrier. We can keep doing this until there is only a small amount of legacy bandwidth left. We want to leave some small piece of FDMA or TDMA bandwidth for those stubborn subscribers who hang onto their old cell phones for many years. 7 As the market develops for 3G services, the service provider may want to reserve some capacity for data and other services. It may make sense to put more voice traffic on the legacy system SO that CDMA capacity is available for these advanced services. The service provider may decide to give priority to data and other services on the CDMA carrier to develop these markets. One of us (Rosenberg) still has the AMPS car phone he bought in 1986 and still uses it occa- sionally. 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. Base Station Planning Planning for CDMA Capacity 33.6.3 Evolution starts with a small CDMA system It is very expensive to deploy a partial-spectrum CDMA system on every cell of a legacy system. Using our earlier example, a 5-MHz CDMA carrier handles twice the traffic of 25 MHz of GSM. Thus we may want to start the CDMA evolution on only a fraction of the legacy cells, a larger CDMA 