Chapter 8: Downstream Cable Access Modules (DCAMs)
STANDARD Revision 1.0
C4® CMTS Release 8.3 User Guide
© 2016 ARRIS Enterprises LLC. All Rights Reserved.
265
This feature is supported only by Annex A; it cannot be used by Annex B customers. This is because in Annex B 64-QAM
and 256-QAM run at different symbol rates. The XD-CAM cannot generate different symbol rates for different channels
on the same port.
Mixed modulation is not enabled or disabled: it is configured on a per-port basis.
A port enters mixed modulation mode when a modulation type is configured for an unused channel that differs
from the modulation used by the channels that are already configured.
If the last remaining mixed modulation channel is unconfigured or removed from the cable-mac, then this port is
no longer in mixed modulation mode.
There are four F-connectors (ports) on the XD-CAM. The following restrictions apply when mixed modulation is used on
a given connector (port):
From 1-4 DS channels can be 64-QAM and 1-4 can be 256-QAM
The lowest 4 numbered channels on a connector must all use the same modulation; the highest 4 numbered
channels on a connector must all use the same modulation.
On a 32D XD-CAM in Annex A the channel numbering is shown in the table below:
Table 33.
Channel Numbering per Connector on the Annex A XD CAM
Connector
Lower Four Channels
Upper Four Channels
0
0-3
4-7
1
8-11
24-27
2
12-15
16-19
3
20-23
28-31
This feature causes no frequency agility restrictions: any channel of either modulation type may be assigned to any
available 8 MHz slot in the port’s frequency window.
Impact on RF Power Levels
Operators using this feature should be aware that this feature affects RF power levels as follows:
