DSL Advances

4.1. Review of First-Generation HDSL

The driving application of HDSL is to transport a DS1 payload without repeaters on loops that meet carrier serving area (CSA) requirements. CSA loops basically define a range of 9 kft on 26-gauge wire and 12 kft on 24-gauge wire. Meeting this goal would greatly simplify and cost reduce the provisioning of “high-capacity” DS1 Service to end customers. Hence, HDSL would be an alternative choice for the network operator in provisioning a DS1 access line.

Figure 4.1 shows a diagram of a DS1 access loop using repeatered T1 alternate mark inversion (AMI) technology. Conventional T1 AMI is deployed on a specially engineered repeatered line. The loop uses two wire pairs. One loop carries the full 1.544 Mb/s bit rate ...