Patent ID: 7573947

Claim:
A method for weighting samples in a sub band of frequencies in a narrowband excision system for transmissions from a plurality of cable modems in a DOCSIS compatible digital data transmission system to a cable modem termination system, comprising the steps: 1) decomposing the signal received over a hybrid fiber coaxial cable system from a cable modem into a plurality of sub bands using a bank of analysis filters or a fast fourier transform calculation circuit; 2) estimating the transmitted signal power in each of a plurality of sub bands of the transmitted signal from the cable modem whose transmissions are being processed; 3) calculating the average received signal power in each sub band of the signal received at said cable modem termination system from the cable modem; 4) for each said sub band, divide the estimated transmitted signal power in said sub band calculated in step 2 by the average received signal power calculated in step 3 to derive the weighting factor for each sub band, wherein deriving the weighting factor comprises calculating a running average of the product of each sample's complex number times its conjugate; and 5) multiply the samples in each sub band by the weighting factor calculated in step 4 for said sub band, wherein step 2 is done for each sub band in the transmission from the cable modem by performing the following steps: A) averaging the received signal power in each sub band; B) computing the sum of the power of all N sub bands; C) subtracting the sum of the power of a predetermined number L of the strongest sub bands from the total power calculated in step B; D) scale the total power calculated by step C by the factor N/(N-L) so as to account for the signal lost by eliminating the signal power of said L strongest sub bands to derive a new total power; and E) for each sub band, scale the new total power by a predetermined factor corresponding to the spectral power of the transmit filter in the Kth sub band to derive the transmitted signal power in the Kth sub band.