otal voice demand in erlangs. This demand in erlangs is the primary determinant of how much CDMA capacity is required to serve our voice telephone calls. Another important component of voice traffic in CMDA is subscriber motion. The CDMA channel is 2 dB less efficient for a moving user terminal than for a stationary one. Drivers and rail commuters are going to use 1.6 times as much CDMA resource (2 dB more) than callers sitting or standing still. Once we have the busy-hour voice traffic loads in erlangs, with subscriber mo- tion taken into account, the next step is to convert that demand into CDMA resource 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 Planning for CDMA Capacity consumption. In Sec. 30.7 we described the estimation of CDMA resource used. We can quantify the CDMA resource as a gross chip rate y in Eq. (31.1): y eR Nou (31.1) where y = chip-per-second estimate e = demand in erlangs R = data rate U = activity factor We can say the gross chip rate of a service is the value of y for one erlang, e = 1. Later on (in Eq. 31.2) we will turn the gross chip estimate y into a cell count estimate. The final part of the estimation process is to derive a geographic picture of the voice call demand. Knowing the total demand is important for estimating equipment re- quirements, including cell counts. However, the CDMA planning process is going to need a lot more than this. Later stages of system planning depend on having as accu- rate a forecast picture of the regional distribution of demand as possible. 31.2 Estimating Data Service Demand The market for data service is harder to predict than the market for voice. We have his- torical data that tell us what kinds of people got cell phones and how much those peo- ple used their cell phones. As we move into the 3G world of data services, we move into uncha