Cdm-800 Error Performance Characteristics - Comtech EF Data CDM-800 Installation And Operation Manual

CDM-800 Gateway Router
Forward Error Correction
•
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 Mbit/s single TV service decoder",
approximately corresponding to a Transport Stream Packet Error Ratio equal to a
PER<10
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:
•
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
* 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%.
6.3

CDM-800 Error Performance Characteristics

On the pages that follow, Figure 6-1 through Figure 6-4 illustrate the guaranteed error
performance characteristics of the CDM-800 for DVB-S2 operation while receiving with Normal
frames (64,800 bits), Pilots ON.
-7
before demultiplexer. A packet is defined as block of 188 byte MPEG frame
Eb/No = Es/No – 10
Symbol Rate, for 35% Rolloff
x
= 1.15
x
= 1.12 x Symbol Rate, for 20% Rolloff
(Spectral Efficiency)
log
Symbol Rate, for 25% Rolloff
6–2
Revision 0
MN-CDM800