Cisco Systems UBR900 Data Specifications, Description Downstream Values Upstream Values

Feature Overview

Note Interactive games are the exception. Although low latency is required in gaming applications, high upstream data throughput is not demanded since the volume of data transmitted upstream is typically small.

Data Specifications

Table 1	Cisco uBR900 Series Cable Access Router Data Specifications
Description	Downstream Values	Upstream Values
Frequency Range	88 to 860 MHz	5 to 42 MHz
Modulation	64 QAM	QPSK
	256 QAM	16 QAM
Data Rate	30 Mbps/64 QAM	QPSK—320 Kbit/sec to 5 Mbit/sec
	(27 Mbit/sec after FEC overhead)
	42.8 Mbps/256 QAM	16 QAM—640 Kbit/sec to 10 Mbit/sec
	(36 Mbit/sec after FEC overhead)
Bandwidth	6 MHz	200K, 400K, 800K, 1.6M,
		3.2 MHz
FEC	RS (122, 128) Trellis	Reed Solomon
One Channel	Receive level of digital signal	QPSK— +8 to +58 dBmV
	-15 to +15 dBmV

Note Most field measurements are of nearby	16 QAM— +8 to +55 dBmV
or adjacent analog signal which is normally
+6 to +10 dB (system specific) above the
digital signal level

Signal-to-Noise Ratio	64 QAM:
(SNR)	>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). Since
	such conditions do not exist in practise, a 6 dB
	or more 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. A 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, a SNR>22 dB makes the grade for 98% ping efficiency. To get good packet rate, you need

SNR>25 dB)

Note These measurements were made 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.

6Cisco IOS Release 12.0(7)T