Table of Contents:

Definition and Overview

1. History of Subscriber Carriers

2. Early Next-Generation Digital Loop Carriers

3. Next-Generation Digital Loop Carriers for Rural and Suburban Applications

4. NGDLC Applications

5. Future Directions

6. Economics

7. The Multiservice DLC

Self-Test

Glossary

PDF of this tutorial

The NGDLC will soon be replaced by a multiservice DLC. The multiservice NGDLC will become a network cloud that consists of a couple of different networks: a data network and a TDM network, which is the Class-5 switching infrastructure. The multiservice NDGLC will have to be able to take in wideband ATM frame relay video. It will need to be able to split that traffic off back at the network POTS, possibly sending the POTS subscribers to the Class-5 infrastructure. The data customers can be sent through data network—an ATM network or a frame relay network, whatever the case may be.

The local access network topologies of the future will be yet another extension of what was seen in the earlier 1990s DLC topologies. As shown in Figure 12, there will be a number of OC–12 and OC–48 type of rings going in, which currently does not exist in the local loop at all.

Figure 12. Local Access Topologies—Multiservice NGDLC

Housing developments are not deploying ring topologies; they are deployed in mesh topologies. So a key attribute of the system that needs to be available very soon is the ability to support high-bandwidth services and transmission facilities (i.e., T1, T3, etc.) and mix them in anyway the network is configured—in a mesh, or a ring. Another key attribute will be not overlaying the network topology onto the system architecture.

The future evolution of the multiservice DLC network will be another extension of what has already been discussed. However, not only are analog POTS, T1/E1, and ISDN supported, there is also some frame-relay and ATM traffic. That is where the future is, and the multiservice DLC will need to be able to support those frame-type traffic rates. On the network side, there will probably be a need for wireless local loop service since there will be some places where there is no infrastructure. Where copper or fiber cannot be delivered to subscribers, the use of spread-spectrum between terminals is becoming prevalent. For high-bandwidth services there will be a need for capabilities such as OC–3, OC–12, OC–48, and xDSL as a transport between terminals. If all of those elements can be utilized, there will be an ideal, cost-effective solution for the short term and an excellent migration strategy for the long term.