3-24
Cisco uBR10012 Universal Broadband Router Software Configuration Guide
OL-1520-05
Chapter 3 Configuring Cable Interface Features for the Cisco uBR10012 Router
Configuring the Upstream Cable Interface
Tx Backoff Start 0, Tx Backoff End 4
Modulation Profile Group 1
Perform these steps if you are having difficulty with verification:
1.
Verify that the upstream amplitude of an optimal RF carrier (injected at the fiber node reference
input point) reaches the cable interface line card input point at a consistent level (node-to-node and
port-to-port).
2.
Verify that this absolute level, as installed, matches both the design and software settings on the
Cisco uBR10000 series CMTS.
Note
Software adjustments of 1 to 3 dB can be used to adjust for minor variations in measurement or setup
and port-to-port calibration differences. These adjustments can significantly improve cable interface
performance, particularly in marginal situations. Larger adjustments should be made in conjunction
with spectrum analyzer support at the headend or distribution hub.
Specifying Upstream Minislot Size
To specify the minislot size (in ticks) for specific upstream cable interfaces, use the following command
in cable interface configuration mode. Acceptable values are 2, 4, 8, 16, 32, 64, and 128. The default is 8.
Router(config-if)#
cable
upstream
usport
minislot-size
size
For additional information about channel width and minislot size, refer to the
Cable Radio Frequency
(RF) FAQs
at
http://www.cisco.com/en/US/customer/tech/tk86/tk319/technologies_q_and_a_item09186a0080134faa
.shtml
Verifying Upstream Minislot Size
To verify upstream minislot size, enter the
show controllers cable
command for the upstream port you
have just configured:
Router#
show controllers cable5/0/0 u0
Cable5/0/0 Upstream 0 is up
Frequency 24.016 MHz, Channel Width 1.600 MHz, QPSK Symbol Rate 1.280 Msps
Spectrum Group is overridden
SNR 33.2560 dB
Nominal Input Power Level 0 dBmV, Tx Timing Offset 2288
Ranging Backoff automatic (Start 0, End 3)
Ranging Insertion Interval automatic (60 ms)
Tx Backoff Start 0, Tx Backoff End 4
Modulation Profile Group 1
part_id=0xFFFF, rev_id=0xFF, 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 = 0x2963
Minislot Size in Bytes = 16
Map Advance = 4000 usecs
UCD Count = 32964
DES Ctrl Reg#0 = C000C043, Reg#1 = 0