Specifications

The downstream and upstream frequencies used•
The noise measurements in dB. Make certain that they are correct and within the allowed limits. A
table of the noise limits is included below:
•
DOCSIS Cable Upstream RF Specifications
Note: *n indicates additional information below.
Specifications
UPSTREAM
DOCSIS Specifications *1 Minimum Settings *2
System/Channel
Frequency range
5 to 42 MHz (North
America) 5 to 65 MHz
(Europe)
5 to 42 MHz (North
America) 5 to 65 MHz
(Europe)
Transit delay from
the most distant CM
to the nearest CM or
CMTS.
< 0.800 µsec < 0.800 µsec
Carrier to noise
ratio
25 dB 25 dB
Carrier to ingress
power ratio
> 25 dB > 25 dB
Carrier to
interference ratio
> 25 dB (QPSK) *4
> 25 dB (16 QAM) *4
> 21 dB (QPSK) *4
> 24 dB (16 QAM) *4
Carrier hum
modulation
< −23 dBc *6 (7%) < −23 dBc (7%)
Burst noise
Not longer than 10 µsec at a
1 kHz average rate for most
cases.
Not longer than 10 µsec
at a 1 kHz average rate
for most cases.
Amplitude ripple
0.5 dB/MHz 0.5 dB/MHz
Group delay ripple
200 ns/MHz 200 Ns/MHz
Micro reflections
(single echo)
−10 dBc @ < 0.5 µsec
−20 dBc @ < 1.0 µsec
30 dBc @ 1.0 µsec
−10 dBc @ < 0.5 µsec
−20 dBc @ < 1.0 µsec
30 dBc @ 1.0 µsec
Seasonal/diurnal
signal level
variation Not greater that 8 dB min to
max.
Not greater than 8 dB
min to max.
Digital Signal Levels
From cable modem
(upstream)
+8 to +58 dBmV (QPSK)
+8 to +55 dBmV (16 QAM)
+8 to +58 dBmV
(QPSK)
Cisco − Determining RF or Configuration Issues On the CMTS