16.3. Telephony and Its Rapid Evolution
Figure 16.2 provides a schematic overview of the existing PSTN. This architecture provides a cost-effective method of delivering voice connectivity throughout the world. When combined with digital wireless (cellular) architectures, nearly universal access is available, certainly in the developed world and in large parts of the economically developing and even underdeveloped areas. However, there are a number of changes that are occurring that are causing rapid evolution to this architecture. These changes are among the important drivers for development and deployment of VoDSL:
The deployment of fiber and “digital remotes” in the access network
Support for voice-over packet and cell-based networks
Novel signaling ...