Comtech EF Data CDM-425, Инструкция по установке и эксплуатации

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CDM-425 Advanced Satellite Modem
Revision 0
Appendix F F–33 MN-CDM-425
F.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 DoubleTalk Carrier-in-Carrier:
•
DoubleTalk Carrier-in-Carrier can only be used for full duplex links where the transmitting
earth station is able to receive itself.
•
DoubleTalk Carrier-in-Carrier 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.
F.7 Glossary
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
3.3
= 1995.26 Watts
•
Transponder Bandwidth = 36 MHz
•
Power Available / MHz = 1995.26 / 36 = 55.424 W
•
If a carrier uses 24 dBW, its PEB = 10
2.4
/ 55.424 = 4.532 MHz
This corresponds to 12.59% of available transponder power.