Comtech EF Data SLM-5650A Installation And Operation Manual page 490

G.6 Carrier-in-Carrier Summary
Comtech EF Data's DoubleTalk Carrier-in-Carrier can provide significant savings in operational
expenses. The following should be considered when evaluating CnC:
•
CnC can only be used for full duplex links where the transmitting earth station is able to
receive itself.
•
CnC can be used in both bandwidth limited and power limited situations.
•
The maximum savings is generally achieved when the original link is symmetric in data
rate.
G.7 Glossary of Terms
Bandwidth, Allocated or Occupied:
Bandwidth or Allocated Bandwidth or Occupied Bandwidth is the frequency space required by a
carrier on a transponder.
For example: A Duplex 10 Mbps Circuit with 8PSK Modulation, FEC Rate 3/4 and 1.4 Spacing
requires:
•
Allocated BW = (DR / SE) * CSF [(Data Rate / Spectral Efficiency) * Carrier Spacing
Factor]
•
Allocated BW = 6.222 MHz = (10 / 2.25) * 1.4
For a 36 MHz transponder, 6.222 MHz corresponds to 17.3% Bandwidth Utilization.
Bandwidth, Leased (LBW):
Almost all satellite operators charge for the Leased Bandwidth (LBW). Leased Bandwidth or
Leased Resource is the greater of the Allocated Bandwidth and Power Equivalent Bandwidth.
For example: If a carrier requires 3 MHz of Allocated BW and 4.5 MHz of PEB, the Leased
Bandwidth is 4.5 MHz.
Bandwidth, Power Equivalent (PEB):
Power Equivalent Bandwidth (PEB) is the transponder power used by a carrier, represented as
bandwidth equivalent.
PEB Calculation Example:
•
Transponder EIRP = 37 dBW
•
Output Backoff (OBO) = 4 dB
•
Available EIRP = 37 – 4 = 33 dBW = 10
•
Transponder Bandwidth = 36 MHz
•
Power Available / MHz = 1995.26 / 36 = 55.424 W
•
If a carrier uses 24 dBW, its PEB = 10
This corresponds to 12.59% of available transponder power.
Appendix H
3.3
= 1995.26 Watts
2.4
/ 55.424 = 4.532 MHz
G–24
SLM-5650A Satellite Modem
Revision 10
MN-SLM-5650A