B-4
Cisco uBR7200 Series Universal Broadband Router Hardware Installation Guide
OL-5421-03
Appendix B RF Specifications
DOCSIS 1.1 Transmission Characteristics
DOCSIS 1.1 Transmission Characteristics
The following tables provide information on the assumed downstream RF channel transmission
characteristics for DOCSIS 1.1.
Downstream RF Channel Transmission Characteristics
Transmission is from the headend combiner to the cable modem input at the customer location.
Measurement methods are defined in NCTA or CableLabs2 documentation.
Go to URL
http://www.ncta.com/
. Search on “transmission”.
Go to URL
http://www.cablelabs.com/.
Table B-5
DOCSIS 1.1 Assumed Downstream RF Channel Transmission Characteristics
Parameter
Value
Frequency range
Cable system normal downstream operating range is from
50 MHz to as high as 860 MHz. However, the values in this
table apply only at frequencies
≥
88 MHz.
RF channel spacing (design bandwidth)
6 MHz
Transit delay from headend to most distant customer
≤
0.800 msec (typically much less)
Carrier-to-noise ratio in a 6-MHz band
Not less than 35 dB
1
1.
Measured relative to a QAM signal that is equal to the nominal video level in the plant.
Carrier-to-composite triple beat distortion ratio
Not less than 41 dB
1
Carrier-to-composite second order distortion ratio
Not less than 41 dB
1
Carrier-to-cross-modulation ratio
Not less than 41 dB
1
Carrier-to-any other discrete interference (ingress)
Not less than 41 dB
1
Amplitude ripple
3 dB within the design bandwidth
Group delay ripple in the spectrum occupied by the CMTS
75 ns within the design bandwidth
Micro-reflections bound for dominant echo
–10 dBc @
≤
0.5 microsecond
–15 dBc @
≤
1.0 microsecond
–20 dBc @
≤
1.5 microsecond
–30 dBc @
>
1.5 microsecond
Carrier hum modulation
Not greater than –26 dBc (5%)
Burst noise
Not longer than 25microseconds at a 10-Hz average rate
Maximum analog video carrier level at the cable modem input 17 dBmV
Maximum number of analog carriers
121
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