be more revealing when we consider splitting cells. We use the propagation models to find out which bins are in each sector and then add up the total demand for each sector. This may be done on a service-by-service basis or for the total code division multiple access (CDMA) air-interface resources. Once we have the total demand for each cell sector, we can look at how the sector is equipped, how many CDMA carriers it has, and estimate its blocking rate. If the blocking rate is too high, then we can add carriers, add sectors, or even split cells, as described in Chaps. 41 and 42. It is important to remember that 3G CDMA systems serve a variety of services. It may not be enough that the total CDMA air interface has enough capacity for the total demand. There may be specific requirements for one service that are not met by a to- tal capacity analysis. A simple example is a wireless laptop user buying a premium wireless data service that guarantees fast access to the Internet. Even if there are more than enough bits available on the CDMA carrier, there may not be enough at a given time to meet this subscriber's quality-of-service (QoS) requirement. 48.2 CDMA-Specific Factors CDMA has its own specific issues with both radio propagation and subscriber demand that we can deal with in predictive models. The more we can analyze these issues in the planning stages with computer models, the less we have to deal with them in the field in a working system. In conventional reuse (FDMA and TDMA), the same-channel interference is coming from a cochannel cell several cells away. In CDMA, the neighboring cells are using the same carrier. This means that the planning model has to be able to add up the inter- ference from neighboring cells. These cells are close enough to require summing their interference on a bin-by-bin basis. These sums are reflected in the CDMA equations we saw in Sec. 28.1. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. A