h an av- erage load on neighboring cells and sectors, the cdmaOne carrier supports about 21 users, but we will keep three extra channels to carry more traffic when neighbors are more lightly loaded. We are engineering our system for a busy-hour blocking rate of be- tween 2 and 5 percent, high enough to serve 19 erlangs of busy-hour demand. This means that each equipped channel can serve 40 subscribers and that each cdmaOne carrier with 24 equipped channels can serve 960 subscribers. Each equipped carrier has a low-power combiner that costs $3600. Our base station design allows us to use one big power amplifier and one set of antennas for all the car- riers serving one sector. The low-power combiner adds up all the modulated signals from the channel cards and sends the combined signal to the power amplifier for the forward direction. Our wireless telephone system has five cdmaOne carriers, but not all cells have all five carriers. In our example, the average number of carriers per sector is four. Thus each sector serves four carriers at 960 subscribers per carrier, which works out to 3840 subscribers per sector. Each equipped sector has the full array of radio equipment. The three antennas, one transmit and two receive, are $3000 each; there are $2000 worth of cables and connec- tors; and the power amplifier is $13,000. Each sector also gets charged for half a chan- nel backplane using the postage-stamp model because each sector has to have a chan- nel backplane for each 32 channel cards. The half a backplane is marked with (P) in Table 46.1. 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. Business-Case Models Modeling for CDMA TABLE 46.1 CDMA Component Costs Cost per subscriber summary Ratio Per Subscriber Per-subscriber costs User terminal 50 subscribers/erlang $ 300.00 $300.00 Per-channel costs 0.8 erlangs/channel Channel card 200.00 1/32 