low lower radio conditions once in a while because the condition is temporary. If the average call lasts 2 minutes and the carrier supports 20 calls, then the expected time until somebody hangs up is 6 seconds, not terribly long, probably not long enough for subscribers to notice. Even if the service provider does not deliberately overload the CDMA carrier, radio conditions can change. A subscriber can walk into a building or truck can drive between a user terminal and its antenna face. The CDMA channel flexible enough that it probably will be able to maintain all the calls, perhaps in a slightly degraded state, until somebody hangs up and relieves the overloaded condition. 30.7 CDMA Radio Capacity Estimation In this section we look at eight CDMA carrier environments, forward and reverse for cdmaOne, cdma2000, W-CDMA, and time division synchronized CDMA (TD-SCDMA). The capacity values we get will have fractional values such as 20.7 voice users cdmaOne. The fractional call, the extra 0.7, would not be important if this value were While this is not good news about CDMA, we should not forget how much more efficient CDMA is than conventional reuse. 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. Capacity Issues Specific to CDMA Capacity and Quality Principles derived for a single serving sector in isolation. After all, it is of no use to the twenty- first caller that there is room for seven-tenths of a voice call. However, these values rep- resent CDMA carrier capacity taking into account interference from other cells and other sectors on the same cell, so a carrier with 20.7 call capacity is 0.7 users better than one with only 20.0. Let us look at several variables that determine CDMA carrier capacity. The values we used in our capacity analysis are in Table 30.1. W is the chip rate. R is the information data rate. Eb/No is the energy per bit d