Patent ID: 7835431

Claim:
A method to estimate a loop length of a transmission line comprising: estimating a first channel transfer function using one or more downstream signals from an initialization; estimating a second channel transfer function using one or more upstream signals from the initialization, the initialization occurring between a first broadband multicarrier modem on a first end of the transmission line and a second broadband multicarrier modem on a second end of the transmission line, the one or more downstream signals from the initialization having been transmitted or received using a first multiplicity of discrete frequency carriers and the one or more upstream signals from the initialization having been transmitted or received using a second multiplicity of discrete frequency carriers; determining a first theoretical channel transfer function; determining a second theoretical channel transfer function; comparing the first theoretical channel transfer function and the first estimated channel transfer function; comparing the second theoretical channel transfer function and the second estimated channel transfer function; determining a first estimated loop length of the transmission line based upon said comparison of the first theoretical channel transfer function and the first estimated channel transfer function; and determining a second estimated loop length of the transmission line based upon said comparison of the second theoretical channel transfer function and the second estimated channel transfer function.