A device for identifying an impaired communication line (701, 702) from a plurality of communication lines (101, 301, 302); said device being configured to perform the following steps: - obtaining heatmap coefficients for said communication lines with respect to said communication lines; wherein a heatmap coefficient for a first communication line with respect to a second communication line is indicative for an amount of cross-talk between said first and second communication lines normalized by an attenuation value for said first communication line; and - identifying one or more impaired communication lines (701, 702) comprising said impaired communication line from said heatmap coefficients; and - splitting said heatmap coefficients in non-impaired heatmap coefficients for non-impaired communication lines and impaired heatmap coefficients for said impaired communications lines (701, 702); and - grouping said non-impaired communication lines into topology elements (341, 342) determined from said non-impaired heatmap coefficients; and - calculating averaged heatmap values (401, 402) for each topology element with respect to said non-impaired communication lines; and wherein a respective averaged heatmap value for a respective topology element with respect to a respective communication line is calculated from heatmap coefficients for all non-impaired communication lines of said respective topology element with respect to said respective non-impaired communication line; - correlating, for each topology element, impaired heatmap coefficients for said impaired communication line (701, 702) with respect to said non-impaired communication lines with averaged heatmap values (401, 402) for said each topology element with respect to said non-impaired communication lines thereby obtaining a best correlated topology element to which said impaired communication line belongs (701, 702); wherein said topology elements correspond to binders each binding a subset of said communication lines into a separate bundle. - obtaining heatmap coefficients for said communication lines with respect to said communication lines; wherein a heatmap coefficient for a first communication line with respect to a second communication line is indicative for an amount of cross-talk between said first and second communication lines normalized by an attenuation value for said first communication line; and - identifying one or more impaired communication lines (701, 702) comprising said impaired communication line from said heatmap coefficients; and - splitting said heatmap coefficients in non-impaired heatmap coefficients for non-impaired communication lines and impaired heatmap coefficients for said impaired communications lines (701, 702); and - grouping said non-impaired communication lines into topology elements (341, 342) determined from said non-impaired heatmap coefficients; and - calculating averaged heatmap values (401, 402) for each topology element with respect to said non-impaired communication lines; and wherein a respective averaged heatmap value for a respective topology element with respect to a respective communication line is calculated from heatmap coefficients for all non-impaired communication lines of said respective topology element with respect to said respective non-impaired communication line; - correlating, for each topology element, impaired heatmap coefficients for said impaired communication line (701, 702) with respect to said non-impaired communication lines with averaged heatmap values (401, 402) for said each topology element with respect to said non-impaired communication lines thereby obtaining a best correlated topology element to which said impaired communication line belongs (701, 702);