A-3
Cisco uBR924 Router Hardware Installation Guide
OL-0338-01 (3/2000)
Appendix A Technical Specifications
Data Specifications
Data Specifications
Table A-2 lists the specifications for the Cisco uBR924 cable access router’s data ports.
Table A-2
Cisco uBR924 Cable Access Router Data Specifications
Description
Downstream Values
Upstream Values
Frequency Range
88 to 860 MHz
5 to 42 MHz
Modulation
64 QAM
256 QAM
QPSK
16 QAM
Data Rate
30 Mbps/64 QAM
(27 Mbit/sec after FEC overhead)
42.8 Mbps/256 QAM
(36 Mbit/sec after FEC overhead)
QPSK—320 Kbit/sec to 5 Mbit/sec
16 QAM—640 Kbit/sec to 10 Mbit/sec
Bandwidth
6 MHz
200K, 400K, 800K, 1.6M,
3.2 MHz
FEC
RS (122, 128) Trellis
Signal-to-Noise Ratio
(SNR)
64 QAM:
>23.5 dB @ BER<10^8
256 QAM*:
>30 dB @ BER <10^-8
(For input level b15 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). Since such
conditions do not exist in practise, 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 will be 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 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 and laboratory-controlled
conditions.
