Patent ID: 8588285

Claim:
A modem comprising: circuitry arranged to obtain measurements of attenuation of signals at a plurality of different frequencies, to combine the measurements together to form a combined attenuation measure and to use the combined attenuation measure to form an electrical length estimation, and then to use the electrical length estimation to generate an upstream power back of mask for use in controlling an amount of power used when transmitting signals upstream over a copper pair connection to which the modem is connected in one or more upstream transmission bands, wherein the combined attenuation measure is formed by generating a plurality of values associated with different frequencies and selecting one value of the plurality of values as the combined attenuation measure according to relative magnitudes of the plurality of values such that the selected value corresponds to a predetermined non-zeroth and non-hundredth percentile of the plurality of values, wherein the selection is made by finding a percentile value.