A combined correlation TDR and FDR procedure for Single Ended Loop topology estimation in DSL

Single Ended Loop Testing (SELT) is generally the most preferred and economical way for estimating loop topology. In this paper we implement a combination of Correlation Time Domain Reflectometry (CTDR) and Frequency Domain Reflectometry (FDR) for loop topology estimation. SELT loop estimation is performed in two phases, a measurement phase and an interpretation phase. The major advantage of the proposed method is that the measurement is done by reusing most of firmware modules in a typical DSL broadband modem without affecting the other services in the bundle. As the measurement is done online the effect of cross talk noise and AWGN noise is also considered. No prior knowledge of the network topology is required. While CTDR is used for an initial estimate, FDR proceeds further to obtain more exact estimates. Simulations performed on a typical ANSI loops using this method shows good prediction capability.