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.
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Parameter
Description
4 Periodic Ranging (Also called Station Maintenance). Cable modems use this IE to perform station maintenance.
This IE is unicast. Only the range request message — no other data — can be sent using this IE.
5 Short Data Grants This unicast IE gives permission to a specific cable modem to transmit one or more Protocol
Data Units (PDUs). The cable modem uses this region in the upstream map interval if the number of minislots
required to send the message is less than or equal to the maximum burst interval specified for a short data grant in
the Upstream Channel Descriptor (UCD) message. The reason that grants can be split into short and long data grants
is for the sake of FEC encoding. Short data grants are used only when a cable modem is transmitting via an upstream
channel that is compatible with DOCSIS 1.X.
6 Long Data Grants This unicast IE gives permission to a specific cable modem to transmit one or more PDUs. The
cable modem uses this region in the upstream map interval if the number of minislots required to send the message
is greater than the maximum burst interval for a short data grant in the Upstream Channel Descriptor (UCD)
message. The reason that grants can be split into short and long data grants is for the sake of FEC encoding. Long
data grants are used only when a cable modem is transmitting via an upstream channel that is compatible with
DOCSIS 1.X.
Note: The following Advanced PHY types are provided for channels carrying combined DOCSIS 1.x and DOCSIS 2.0
bursts and also for channels carrying DOCSIS 2.0 bursts.
9 Advanced PHY Short This IE is the same as a short data grant except that it is used when the cable modem is
communicating via an upstream channel that is DOCSIS 2.0 compatible.
10 Advanced PHY Long This IE is the same as a long data grant except that it is used when the cable modem is
communicating via an upstream channel that is DOCSIS 2.0 compatible.
11 Advanced PHY UGS This IE is new with DOCSIS 2.0. It allows parameters to be optimized for UGS flows, which
normally carry VoIP.
diff
Differential Encoding True = enabled; False = disabled.
mod
Modulation type Values 3–6 must not be used when the upstream channel is only DOCSIS 1.X compatible. A DOCSIS
1.X only compatible channel is signified in the UCD message with a descriptor encoded with a type 4 TLV. A type 5
TLV signifies that the channel is DOCSIS 2.0 compatible.
1 = QPSK
3 = 8QAM
5 = 64QAM
2 = 16QAM
4 = 32QAM
6 = 128QAM (not currently supported)