Comtech EF Data CDM-800 - Manual (Page 124)

CDM-800 Gateway Router Revision 1
Appendix B MN-CDM800
B–2
• DVB‐S2 standard: "Quasi Error Free" (QEF) is defined as "less than one uncorrected
error‐event per transmission hour at the level of a 5 Mbits/s single TV service decoder",
approximately corresponding to a Transport Stream Packet Error Ratio equal to a
PER<10
‐7 before demultiplexer. A packet is defined as block of 188 byte MPEG frame
size data.
• Es/No vs. Eb/No: The DVB‐S2 standard commonly refers to the use of Es/No instead of
Eb/No. When links operate at a constant symbol rate this is a good method for comparing
the performance of different modulation types and code rates.
The relation between the two quantities is given by:
Eb/No = Es/No – 10
log
(Spectral Efficiency)
• Occupied Bandwidth: Occupied bandwidth is defined as the bandwidth between ‐10 dB
points of the power spectral density, which are approximately:
Occupied Bandwidth = 1.19 x Symbol Rate, for 35% Rolloff
= 1.15 x Symbol Rate, for 25% Rolloff
= 1.12 x Symbol Rate, for 20% Rolloff
* Taken at the -10 dB points on the plot of power spectral density, the occupied bandwidth is 1.19 x Symbol
Rate for 35%, and 1.15 x Symbol Rate for 25%.
B.3 CDM-800 Error Performance Characteristics
On the pages that follow, Figure B‐1 through Figure B‐4 illustrate the guaranteed error
performance characteristics of the CDM‐800 for DVB‐S2 operation while receiving with Normal
frames (64,800 bits), Pilots ON.