Feasibility and problems of DSL loop topology identification via single-ended line tests

Abstrac t Digital subscriber lines (DSL) offer the possibility to deliver broadband services over the existing telephone network. Yet, before deploying DSL, the subscriber loops must be tested to see whether they can support high-speed data services, and at what rate. Single-ended automatic qualification is essential for achieving low-cost deployment of DSL, since it allows loops to be qualified in bulk without human intervention at the customer’s location. An even more ambitious challenge is to fully characterize the loop, i.e. to identify its loop topology (number of loop sections, length and cable type of each section). This paper discusses the feasibility and the problems of loop topology identification via single-ended measurements.