© 2016 ARRIS Enterprises LLC. All Rights Reserved. 390
The set of upstream and downstream RF channels that connect to the fiber node is known
as the SG.
An SG is the set of upstream and downstream RF channels that can provide service to a
single subscriber device. This could include channels from different DOCSIS MAC domains
and even different C4/c CMTSs as well as video EQAMs.
The SG is an important DOCSIS 3.0 concept, but it is not directly used or represented in
the C4/c CMTS provisioning.
The DOCSIS protocol has always employed the use of a downstream channel to carry the
channel access control information for each upstream channel. This control information is
carried in two messages:
The first is the Upstream Channel Descriptor, which contains information about the
physical properties of an upstream channel.
The second is the MAP, a message which allocates upstream minislot transmission
opportunities to individual cable modem requests.
For any upstream channel, these two types of control messages are always transmitted on
the same downstream channel. The C4/c CMTS CLI refers to the set of UCD and MAP
messages sent to an upstream channel as upstream channel supervision.
In order to receive the upstream channel supervision for one upstream channel, a DOCSIS
3.0 CM locates the supervision on one of the downstream channels to which it is tuned
and monitors that one downstream channel for the complete set of MAP and UCD
messages. The DOCSIS 3.0 CM repeats this process for each of the upstream channels that
have been assigned.
The CM may find the supervision for different US channels on different DS channels. The
CM may also find duplicate supervision for the same US on multiple DS channels. In such a
case the CM chooses only one DS channel as the source of the supervision for that
particular US channel.
The C4/c CMTS allows the operator to provision any downstream channel to provide
supervision for an upstream channel.
a. Information source is CableLabs® CM-SP-MULPIv3.0-I15-110210 Specifications.
To Next Page
Loading...
