chapter  2
12 Pages

The Path to IMS—Evolution of the Cellular Switching System to 3G

The first-generation switch was the backbone of the analog cellular network. While vendors were able to build products with this model in order to introduce cellular service commercially, it had numerous drawbacks. Its principle drawback was one of scaling. Because of processor or memory constraints, early switches were greatly constrained in the number of subscribers that could be supported per switch. Switches in the late 1980s were size-limited to 50K to 75K subscribers, based on the HLR capacity of the switch. Thus, every time an operator approached these limits a completely new switch was required to be added to their network.1