| 摘要 |
Provided are methods and apparatuses for quickly and efficiently locating a frequency band for upstream transmission of data in a data communications network system utilizing cable modems. In a preferred embodiment, a cable modem termination system (CMTS) at the headend performs a lookahead in order to determine the noise power spectrum allocated to its upstream channels. Free bands (noise-free bands available for upstream data transmission) may then be determined based on the noise power spectrum and the upstream channel capacity requirements according to a process that is preferably implemented in computer code at the headend. The lookahead is preferably accomplished by using a spectrum analyzer, which is preferably incorporated into the CMTS at the headend, to collect a table of samples of the noise power versus frequency. This table of samples is input to a computational algorithm which determines free band sets for one or more preferred modulation formats rapidly and efficiently in software without the stepping of the upstream receiver frequency as in the blind frequency hop process. Once a band has been located, the CMTS assigns its frequency to an upstream channel and signals the cable modem of the frequency update.
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