Comtech EF Data CTOG-250 - Manual (Page 128)

CTOG-250 Comtech Traffic Optimization Gateway Revision 1
Ethernet-based Remote Product Management MN-CTOG250
7–26
• Symbol Rate – Enter the Tx Symbol Rate in ksps, and then click [Submit] to save. Once the
Symbol Rate is selected, then range of valid MODCODs is as follows:
o 1000 to 62000 for MODCODs QPSK 1/4 through 8PSK 9/10.
o 1000 to 47000 for MODCODs QPSK 1/4 through 16APSK 9/10.
o 1000 to 38000 for MODCODs QPSK 1/4 through 32APSK 9/10.
When you are operating in ACM/VCM mode on the Outbound Carrier, the per-remote
MODCOD assignment follows these rate restrictions. Specifically, if the Tx Symbol Rate is
above 38 Msps, the ACM Controller will not assign any of the 16APSK or 32APSK MODCODs
to a Remote Site. Likewise, if the symbol rate is above 47 Msps, none of the 32APSK
MODCODs will be assigned to a Remote Site.
If you are not operating in ACM Mode on the Outbound Carrier, the range of acceptable
MODCODs allowed for the “VCM Only” field for each Group QoS are limited as detailed
previously. See Sect. 7.4.4.3.2.2 for further details.
• FEC Type – DVB-S2 is the sole available FEC type.
• Frame – Use the drop-down menu to select the Frame type as Normal or Short. This field
will be forced to Normal if any MODCOD enabled in Group QoS (see Sect. Sect. 7.4.4.3.2.2)
has a code rate of 9/10.
Short Frame operation is recommended for latency- and jitter-sensitive applications when
the Outbound Symbol rate is below 5Msps. Otherwise, Normal Frame operation is
recommended.
The CDM-840 automatically detects the framing, so no additional configuration is required.
• Pilots (read-only) – This feature is always ON.
• Gold Code (000000 to 262141) – The Gold-n Index indicates the Physical Layer spreading
sequence number. The default setting is all 0s.
If a non-zero Gold Code is configured, you must be sure that the receiving
CDM-840s are also configured with the same Gold Code. If they are not, then
traffic will not pass.
• Roll Off – The Tx Alpha Rolloff (α) dictates how fast the spectral edges of the carrier are
attenuated beyond the 3 dB bandwidth. With 20% rolloff, the edge falls off more quickly
than with 25% and 35%.
Use the drop-down menu to set the expected filter Tx Alpha Rolloff (α) of the carrier as 20%,
25%, or 35%. The default selection is 20%.