Comtech EF Data CTOG-250 - Manual (Page 196)

CTOG-250 Comtech Traffic Optimization Gateway Revision 1
Appendix B MN-CTOG250
B–2
bits and, for lower data rate applications, a short frame block at 16,800 bits suffers only a small
error correcting loss (0.2 to 0.5 dB) compared to the standard block.
B.2.1 Range of Data Rates
See S
ect. 1.4 CTOG-250 SPECIFICATIONS
for the range of available data rates
B.2.2 BER, QEF, Eb/No, Es/No Spectral Efficiency, and Occupied Bandwidth
Depending upon the operating mode, the DVB standard uses different modes of specifying
performance with a unit in IF Loop and Additive White Gaussian Noise (AWGN):
• 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.