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Cisco uBR7225VXR Universal Broadband Router Hardware Installation Guide
OL-17309-02
Appendix B RF Specifications
DOCSIS 1.0 Transmission Characteristics
DOCSIS 1.0 Transmission Characteristics
The following tables provide information on the assumed downstream RF channel transmission
characteristics for DOCSIS 1.0.
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 the following URL: http://www.ncta.com/. Search on “transmission”.
Go to the following URL: http://www.cablelabs.com/.
1280 1.60 2.56 ~2.3 5.12 ~4.6
2560 3.20 5.12 ~4.6 10.24 ~9.0
Table B-2 Upstream Channel Data Rates (continued)
Symbol Rate,
ksym/sec
Channel
Bandwidth,
MHz
QPSK Raw
Data Rate,
Mbps
QPSK Nominal
Data Rate,
Mbps
QAM-16 Raw
Data Rate,
Mbps
QAM-16
Nominal Data
Rate, Mbps
Table B-3 DOCSIS 1.0 Assumed Downstream RF Channel Transmission Characteristics
Parameter Value
Frequency range
1
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 (analog video level) Not less than 35 dB
2
Carrier-to-interference ratio for total power (discrete and
broadband ingress signals)
Not less than 35 dB within the design bandwidth
Composite triple beat distortion for analog modulated carriers Not greater than –50 dBc
3
within the design bandwidth
Composite second-order distortion for analog modulated
carriers
Not greater than –50 dBc within the design bandwidth
Cross-modulation level Not greater than –40 dBc within the design bandwidth
Amplitude ripple 0.5 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 microseconds
–15 dBc @ ≤ 1.0 microseconds
–20 dBc @ ≤ 1.5 microseconds
–30 dBc @ >1.5 microseconds
Carrier hum modulation
4
Not greater than –26 dBc (5%)
Burst noise Not longer than 25 μsec at a 10-Hz average rate
Signal level slope, 50-750 MHz 16 dB