Comtech EF Data CDM-800 Spezifikationen PDF herunterladen (Seite 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mo

dulation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Sy mbol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.



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