ning may keep first-time planners and engineers busy for 6 months, so they do not want to be combating growth issues during that time. More experienced CDMA ven- dors may be comfortable with a 2-month initial planning horizon because they can be ready to deal with growth issues sooner. Taking into consideration the four sources of subscribers and the other issues just mentioned, the planners for the service provider should form a clear estimate of the number of voice subscribers they expect to be using the system at the end of their ini- tial planning horizon. This is important not only for system planning but also for esti- mating how many cell phones are needed. The next step in estimating demand is to form a time-of-day picture of telephone us- age. There will be several distinct groups of voice subscribers, commuters, shoppers, mobile businesspeople, and so on. Each of these groups has its own time-of-day behav- ior and its own busy-hour usage pattern. CDMA planners should form a clear forecast of the different groups using cellular telephones and their usage patterns. One factor in estimating time-of-day usage is the variety of calling plans and packages offered 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. Estimating Wireless Telephone Demand Estimating Wireless Telephone Demand by the service provider. Demand for voice capacity is different depending on whether subscribers are using minutes they view as a limited or an unlimited resource or if they are paying for calls by the minute. 31.1.1 Estimating voice call demand in other world markets In estimating demand outside Europe and North America, the same four elements ap- ply, but the market situation is very different. In the former Soviet Union, called the second world, cellular telephony is a growth market. The People's Republic of China is the world's largest potential market fo