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Anything else >> General and other topics >> Difference Between kbps and ksps https://www.satsig.net/cgi-bin/yabb/YaBB.pl?num=1377516060 Message started by martin.amara on Aug 26th, 2013 at 12:21pm |
Title: Difference Between kbps and ksps Post by martin.amara on Aug 26th, 2013 at 12:21pm
What is the difference between bits per second and symbols per second? Can anyone explain how these terms are used for defining data rate of VSAT terminal.
Thanks & Regards Martin |
Title: Re: Difference Between Kbps and Ksps Post by USN - Retired on Aug 26th, 2013 at 12:39pm |
Title: Re: Difference Between kbps and ksps Post by Eric Johnston on Aug 26th, 2013 at 1:24pm
Assume 27.5 Msps (mega symbols per second) for typical large outlink download carrier.
If BPSK modulation then 1 bit/symbol ( 27.5 Mbit/s) If QPSK modulation then 2 bit/symbol ( 55 Mbit/s) If 8PSK modulation then 3 bit/symbol ( 82.5 Mbit/s) If 16QAM modulation then 4 bit/symbol ( 110 Mbit/s) Above bits are transmission rate bits. If using 7/8 FEC the information rate is less, by factor of 7/8 Information rate is what matters to the end user, less overheads due to IP headers etc. What is information rate for 27.5 Msps, 8PSK, 3/4 rate FEC ? Higher order modulation a need higher C/N 7/8 FEC has less effect than 1/2 FEC In heavy rain or small dish use BPSK and 1/2 rate FEC In clear sky, very big dish, use 16QAM, 7/8 FEC Hope that helps Best regards, Eric |
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