Patent ID: 7573935

Claim:
A method for performing ranging operations in a cable modem system that includes two or more cable modems, comprising the steps of: (a) receiving at a cable modem, a ranging response generated by a cable modem termination system, the ranging response comprised of a plurality of ranging parameters including an upstream communications parameter, a timing adjust parameter, a power level adjust parameter, a carrier frequency offset parameter, and a plurality of equalization parameters, the equalization parameters including a number of ranging response equalizer coefficients, wherein the ranging response is the first ranging response received since the cable modem was initialized; (b) setting a current pre-equalizer coefficient for each one of a plurality taps at the cable modem equal to the ranging response equalizer coefficients to generate new pre-equalizer coefficients, wherein one of said plurality of taps is designated a main tap and the remaining number of said plurality of taps are referred to as non-main taps and further wherein each one of said plurality of taps has a real part and an imaginary part; (c) derotating the new pre-equalizer coefficients so that the imaginary part of the main tap is equal to zero; (d) identifying each non-main tap having a determined magnitude squared value below a specified threshold and setting the new pre-equalizer coefficients for the real part and the imaginary part of each identified non-main tap to zero; (e) generating scaled coefficients using the new pre-equalizer coefficients for the main tap and non-main taps obtained from steps (c) and (d); and (f) adjusting a transmit power of the cable modem using an equalizer coefficient gain change value, the equalizer coefficient gain change value being determined from a current equalizer coefficient gain value and a new equalizer coefficient gain value in accordance with Δ P (dB)=10 log 10 ( P cur /P new ), wherein the new equalizer coefficient gain value is determined from P = ∑ i = 1 N ⁢ ( ( C _ real ⁢ i ) 2 + ( C _ imag ⁢ i ) 2 ) wherein P new represents a new equalizer coefficient gain value, P cur is a current equalizer gain value, N refers to a number of feedforward taps, and C i refers to the generated scaled coefficients.