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Fringe Reception General
Nilesat 201
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<blockquote data-quote="Huevos" data-source="post: 714644" data-attributes="member: 301161"><p>Hi dx qwer,</p><p>What are those dB figures referring to? S/N, C/N, MER?</p><p></p><p>In the case of QPSK & 8PSK, if MER is the same on both, C/N has to be much higher for 8PSK, or if C/N is the same, MER will be much worse on 8PSK. This is due to higher precision required to decide which of the 8 zones of the IQ constellation an 8PSK bit belongs to, compared to only 4 zones for QPSK. Shannon's theorem explains this. Basically it says for a particular noise floor it is only possible to get so much data down the pipe. If you want to send more data down the same size pipe you must lower the noise floor or increase the power. 8PSK is double the data per symbol so requires a bigger margin between signal and noise.</p><p></p><p>In the case of DVB-S & DVB-S2 when both are QPSK the required C/N is lower for DVB-S2, i.e. DVB-S2 requires a less powerful signal.</p></blockquote><p></p>
[QUOTE="Huevos, post: 714644, member: 301161"] Hi dx qwer, What are those dB figures referring to? S/N, C/N, MER? In the case of QPSK & 8PSK, if MER is the same on both, C/N has to be much higher for 8PSK, or if C/N is the same, MER will be much worse on 8PSK. This is due to higher precision required to decide which of the 8 zones of the IQ constellation an 8PSK bit belongs to, compared to only 4 zones for QPSK. Shannon's theorem explains this. Basically it says for a particular noise floor it is only possible to get so much data down the pipe. If you want to send more data down the same size pipe you must lower the noise floor or increase the power. 8PSK is double the data per symbol so requires a bigger margin between signal and noise. In the case of DVB-S & DVB-S2 when both are QPSK the required C/N is lower for DVB-S2, i.e. DVB-S2 requires a less powerful signal. [/QUOTE]
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Fringe Reception General
Nilesat 201
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