 Tones and listen to a minute or more of forward-direction speech. But we have a hard time believing that this sort of traffic rep- resents a serious fraction of wireless voice traffic. Of course, many of us experience listening to people who talk a lot on the other end of the phone. Statistically, however, this balances out be- cause there are as many talkative people on each end of each telephone call, landline or cellular. 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. Special Situations Planning for CDMA Capacity favoring the reverse direction. Video broadcast services create a similar asymmetric demand. If a roving reporter sends a live video feed using four cellular carriers in one direction plus one two-way voice link, then the demand is much greater in the reverse direction. While it is tempting to evade the issue by suggesting that the two asymmetries will cancel each other out and leave a perfectly balanced data channel, we believe that the imbalance issue deserves a little more scrutiny than this. The decision of how much ca- pacity to allocate in each direction depends on the estimated market for various kinds of data services. Time division synchronized CDMA (TD-SCMDA) offers the advantage that it can allocate forward and reverse data capacity dynamically so that the service provider can engineer the total two-way traffic without having to make the decision advance of how much traffic will go in each direction. 38.1.1 Carrier asymmetry cdma2000 and wideband CDMA (W-CDMA) allow the service provider to use more CDMA carriers in one direction than the other. This gives one-time control to a service provider, who can estimate the service mix and the traffic in both directions. cdma2000 offers a variety of carrier options, 1x, 3x, 6x, and so on. The service provider is allowed to use a different carrier in the forward and reverse di