13.6 Traffic Model

The capacity for a CDMA2000 cell site is determined through the interaction of several parameters and is driven by the radio access portion of the system, provided the fixed network has the requite number of modules for each platform. The parameters for determining the traffic load at CDMA2000 site are similar to those used for an IS-95 system with the exception that CDMA2000 introduces packet data and the inclusion of 128/256 Walsh code, to mention a few of the previously covered issues.

As with IS-95 base stations, the use of channel element cards is essential for the handling of traffic whether it is for voice or data. The desired result from traffic engineering for a CDMA2000 base station is to be able to determine the amount of channel elements and cards required to support the expected traffic. Another factor that fits into the traffic calculations for the site involves system noise. There is a simple relationship between system noise and the capacity of the cell site. Typically the load of the cell site design is somewhere in the vicinity of 40 to 50 percent of the pole capacity, maximum 75 percent.

The next major element in determining the capacity for a CDMA cell is the soft and softer handoff factor. Because CDMA2000, like IS-95, relies on soft and softer handoffs as part of the fundamental design for the network, this must also be factored into the usable capacity at the site. The reason for factoring soft and...