Setting The Upstream Channel Width - Cisco uBR10012 Software Configuration Manual

Configuring the Upstream Cable Interface
Tx Backoff Start 0, Tx Backoff End 4
Modulation Profile Group 1
part_id=0x3137, rev_id=0x03, rev2_id=0xFF
nb_agc_thr=0x0000, nb_agc_nom=0x0000
Range Load Reg Size=0x58
Request Load Reg Size=0x0E
Minislot Size in number of Timebase Ticks is = 8
Minislot Size in Symbols = 64
Bandwidth Requests = 0xFE
Piggyback Requests = 0xD
Invalid BW Requests= 0x2
Minislots Requested= 0x2963
Minislots Granted
Minislot Size in Bytes = 16
Map Advance = 4000 usecs
UCD Count = 32964
DES Ctrl Reg#0 = C000C043, Reg#1 = 0

Setting the Upstream Channel Width

Use the commands below to enter the upstream channel width in hertz (Hz). For NTSC operations, valid
values are 200000 Hz (160 kilo symbols per second [ksps]), 400,000 Hz (320 ksps), 800,000 Hz
(640 ksps), 1,600,000 Hz (1280 ksps), and 3,200,000 Hz (2560 ksps). The default is 1,600,000 Hz.
If no acceptable channels of the specified width are found, the spectrum management card automatically
begins to scan the upstream spectrum for the next largest available channel width; for example, if the
spectrum management card is unable to find a usable 1.6 MHz upstream channel, it automatically begins
searching for usable 800 kHz channels.
Higher symbol rates are more susceptible to RF noise and interference. If you use a symbol rate or
Caution
modulation format beyond the capabilities of your HFC network, you might experience packet loss
or loss of cable interface connectivity.
For QAM-16 channel widths of 400 kHz (320 ksps) or greater, Cisco recommends that you use
Note
QAM-16 modulation for long and short data, and that you use QPSK for request, initial, and station
communications. For QAM-16 channel widths of 200 kHz (160 ksps), all communication must be
able to use QAM-16. That is, 160 ksps with QAM-16 requires an exceptional signal-to-noise ratio
(SNR) in your upstream channels. When you use QAM-16 for request, initial, and station
maintenance messages with channel widths greater than 400 kHz, the QAM-16 preamble and
message data take longer to transmit than the QPSK format.
Note To set the upstream channel width, use the following commands in cable interface configuration mode.
Command
Step 1
Router(config-if)# cable upstream usport
channel-width width
Step 2
Router(config-if)# no cable upstream usport
channel-width
Cisco uBR10012 Universal Broadband Router Software Configuration Guide
3-20
Chapter 3 Configuring Cable Interface Features for the Cisco uBR10012 Router
= 0x2963
Purpose
Enters the channel width for your upstream RF carrier in Hz.
Returns the channel width to its default setting of 1,600,000 Hz.
OL-1520-05