Specifications

14 Release Notes for Cisco uBR904 Cable Access Router for Cisco IOS Release 12.0(7)T
Important Notes
DOCSIS configuration files are created at the headend typically by using a configuration file editor
of your choice. Using the FastStep utility at a subscriber site to locally configure the unit is not
supported.
The DOCSIS configuration file defines the Cisco uBR904 cable access router’s operating mode,
such as the provisioned downstream and upstream service assignments, including assigned
frequencies, data rates, modulation schemes, Class of Service (CoS), type of services to support, and
other parameters.
Note An incorrect configuration file can cause the Cisco uBR904 cable access router to constantly
cycle off-line. Such errors include: wrong downstream frequency, wrong Upstream Channel
Descriptor (UCD), wrong downstream Channel ID, invalid CoS, and incorrect BPI privacy
configurations or shared secret strings.
The Cisco uBR904 cable access router supports the following service classes:
• The first CoS in the DOCSIS configuration file is configured as the “Tiered Best Effort Type
Class” used by the Cisco uBR904 cable access router as the primary QoS for all regular data
traffic. The class has no minimum upstream rate specified for the channel.
Signal-to-Noise Ratio
(SNR)
64 QAM:
>23.5 dB @ BER<10^8
256 QAM*:
>30 dB @ BER <10^-8
(For input level between +15 and -8 dBmV,
SNR must be greater than 30 dB. For input
level between -8 and -15 dBmV, SNR must be
greater than 33 dB.)
Note These performance numbers are in
laboratory-controlled conditions, against
statistically pure noise sources (AWGN).
Because such conditions do not exist in
practice, a 6 or more dB SNR margin is
required for reliable operation. Check with
your local system guidelines.
QPSK:
>15 dB @ BER<10^-8
(QPSK will work at 98% successful
ping rate for SNR>13 dB. An SNR of
15 dB is needed to get almost optimal
packets per minute transition.)
16 QAM:
>22 dB @ BER <10^-8
(For 16 QAM, an SNR>22 dB makes
the grade for 98% ping efficiency. To
get a good packet rate, you need
SNR>25 dB).
Note These measurements were done
for 0 and -10 dBmV input to the CMTS,
1280 ksym/sec and 64 bytes packet size
with a Cisco uBR904 cable access
router and laboratory-controlled
conditions.
Security DES decryption: DOCSIS Baseline Privacy
(BPI), 40 bit- and 56 bit-encryption, as
controlled by the headend and configuration
files.
Note Cisco IOS images must contain
encryption software at both the CMTS router
and the Cisco uBR904 cable access router.
Enable and configure both routers to support
encryption.
DES encryption.
Table 3 Cisco uBR904 Cable Access Router Data Specifications (continued)
Description Downstream Values Upstream Values