RF Requirements For A Reliable Zenith Network
Carrier/anything of at least 25 dB at the receive port of all modems. To support the time varying nature of an HFC network, 35 dB C/anything was required at the input to the frequency translator in the headend.
Carrier/anything is not a technical term, but is intended to include: C/Noise, C/Interference, and distortion products.
Downstream input to each cable modem of +5 dBmV +/- 2 dB. Due to the non-existence of any real input AGC, the lack of a re-modulating frequency translator, and lack of upstream transmit power control, the tight receive level range accommodated upstream path variation.
In comparison, a 2003 DOCSIS 2.0 compliant CMTS operating at 0.5 to 1 dB from theory will provide both 16QAM and 64 QAM in 6.4 MHz at 25 dB C/noise, and in some cases negative C/I. Next-Gen CMTSs
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