34.1.5 Packet switching The packet-switching load on a 3G wireless switch includes all the base station com- munications because they are almost certainly all packet pipes, all data services, and most of the other services. The packet handler is a queuing system, so the packet pacity of one MSC is limited not just by the volume of packet data but also by the de- lay requirements of the data services, as described in Sec. 24.4. Once we have an esti- mate of the packet capacity of the MSC, we divide that into the total system packet load in the forecast to get a final lower bound for the MSC count. 34.1.6. Total MSC count Main processor capacity, transport load capacity, circuit switching, speech coding, and packet switching are five factors that limit the capacity of an MSC. The final MSC count estimate is simply the largest of the five lower bounds based on the MSC components. In second-generation (2G) systems, we have real-world experience with MSCs and base stations. Even here, the MSC count can vary considerably depending on the num- ber of carriers and the distribution of traffic by time of day. However, code division mul- tiple access (CDMA) providers tell us that a rough rule of thumb is one MSC for 200 cells in a system with eight cdmaOne carriers. In the new generation of 3G systems, we have new services and new markets to con- sider. The mix of data services in the market is uncertain. A mix favoring high-rate data subscribers will keep the MSC packet-switching components busy while leaving the processor nearly idle. On the other hand, a larger community of low-rate data ser- vices, heavy e-mail and SMS activity, for example, will limit the MSC processor first. As we did with base stations, we should leave some room for initial system growth. If we install three MSCs all operating at 97 percent of their capacity, then it is virtu- ally certain that we will need a fourth MSC almost immediately. To refine the MSC count estimate, we need to quantify the mix of voice, data, and other services by region and t