Optimal downstream power back-off for digital subscriber lines

A method comprising:

• optimizing downstream power backoff (DPBO) parameters of a plurality of cabinet-deployed digital subscriber lines (DSLs) based on crosstalk coupling parameters among the cabinet-deployed DSLs,
• wherein the DPBO parameters include a plurality of cutoff frequencies, each of which corresponds to one of the plurality of DSLs, and
• wherein optimizing the DPBO parameters comprises:
• for each line n, where n equals 1 to N, where N is a total number of the plurality of DSLs:
• for each subcarrier k, where k equals 1 to K, where K is a number of subcarriers:
• determining a gain hkn,n and a background noise parameter σkn, and
• for each line m, where m equals 1 to N, where m≠n:
• determining a crosstalk coupling parameter hkn,m from line m into line n, and
• setting initial values of variables DPBOFMAXmaxn DPBOFMAXminn, and
• DPBOFMAXtoln, wherein the initial values satisfy a constraint (DPBOFMAXmaxn−DPBOFMAXminn>DPBOFMAXtoln;
• for each line i, where i equals 1 to N, iteratively repeating the following steps until DPBOFMAXmaxi−DPBOFMAXmini≦DPBOFMAXtoli:
• for each line n, where n equals 1 to N, performing the following steps if DPBOFMAXmaxn−DPBOFMAXminn>DPBOFMAXtoln:
• determining an intermediate cutoff frequency DPBOFMAXintn as DPBOFMAXintn=(DPBOFMAXmaxn+DPBOFMAXminn)/2,
• for each subcarrier fk, where k equals 1 to K, where K is a number of subcarriers, determining a transmit power spectral density (PSD) parameter skn based on the intermediate cutoff frequency,
• determining a data rate Rn based on the transmit PSD parameters and a plurality of the crosstalk coupling functions corresponding to all DSLs, and
• if, Rn>Rtargetn, set DPBOFMAXminn equal to DPBOFMAXintn, and otherwise set DPBOFMAXmaxn equal to DPBOFMAXintn, where Rtargetn is a required data rate;
• and
• determining the cutoff frequency of the PSD profile as a final intermediate cutoff frequency produced by the iterative steps.