Chapter 9: Upstream Cable Access Modules (UCAMs)
STANDARD Revision 1.0
C4® CMTS Release 8.3 User Guide
© 2016 ARRIS Enterprises LLC. All Rights Reserved.
306
Parameter
Description
int-
stepsize
SCDMA Interleaver Step Size In an SCDMA upstream channel, interleaving is performed on a sub-frame basis. The
interleaver step size determines the manner in which symbols are interleaved within the sub-frame. This option
must be present for a SCDMA channel and must not be present for all other upstream channel types. Range = 1–31.
spreader
SCDMA Spreader In an SCDMA upstream channel, there are two modes of spreader operation: on and off.
According to the RFI specification, IUC 3 must use spreader off, and IUCs 1, 9, 10 and 11 must use spreader on. And
IUC 4 can use either on or off. However, the CMTS only supports the usage of spreader off for IUC 4. This option
must be present for an SCDMA channel and must not be present for all other upstream channel types.
subframe-
code
SCDMA Codes per Sub-Frame In an SCDMA upstream channel, interleaving is performed on a sub-frame basis. The
codes per sub-frame define the size of the sub-frame. A sub-frame can vary in size from 1 code up to the total
number of active codes. This option must be present for an SCDMA channel and must not be present for all other
upstream channel types.
docsis-
mode
Upstream DOCSIS-Mode This parameter contains the type of the upstream channel which must correspond to one
of the following values:
• tdma (default)
• atdma
• tdma-atdma
According to the DOCSIS RFI Specification, another value that is typically associated with upstream modulation profiles is
the preamble offset start value. It indicates where in the possible string of the preamble bits the actual preamble actually
starts. This value is determined by the CMTS. The string of possible preamble bits is included in the UCD message.
Once you have equipped the CMTS with CAMs and put them in service, the upstream channels have to be configured. Use
the following command to choose the desired modulation profile and other parameters that determine the upstream
channel’s characteristics:
configure interface cable-upstream <slot/port> cable <parameter>
Note: Logical channels are sometimes called subinterfaces. When changing the following upstream parameters, if no
logical channel (n.0) is specified, then the command syntax assumes logical channel 0.
• Modulation profile ID
• SCDMA active codes
• Ranging backoff range
• SCDMA frame size
• Data backoff range
• SCDMA hopping seed