Finally DirecTV News
- Thread starter Scott Greczkowski
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True 50% is what it should be, but I was basing my 33% on what Dish is doing now:
QPSK 20m sym 5/6 FEC 188/204 RS = 30.7 mbit/sec
8PSK 21.5m sym 2/3 FEC 188/204 RS = 39.6 mbit/sec
Dish is actually getting less than 33% more... 28% but at 2/3 FEC turbo coded they actually need less signal than 5/6 QPSK. Now if they had enough ERP on the transponder to do what VOOM does 22m 5/6 FEC 188/204 RS they would get 50.7 mbit/sec or 65% more. There are a lot of factors.
QPSK 20m sym 5/6 FEC 188/204 RS = 30.7 mbit/sec
8PSK 21.5m sym 2/3 FEC 188/204 RS = 39.6 mbit/sec
Dish is actually getting less than 33% more... 28% but at 2/3 FEC turbo coded they actually need less signal than 5/6 QPSK. Now if they had enough ERP on the transponder to do what VOOM does 22m 5/6 FEC 188/204 RS they would get 50.7 mbit/sec or 65% more. There are a lot of factors.
silversurfer01973 said:Just what the heck did he say??:shocked
I'm not sure, but I think it was something smart. It also made me like 8PSK.
~Alan
In practice, that doesn't hold true. At least not at typical power, receiver sensitivities, and noise levels. Because the higher data density is achieved from more subtle differences in modulation states, an 8PSK modulated signal is more easily corrupted by noise. Therefore, more forward error correction is typically needed on an 8psk signal, negating some of the bandwidth advantage, resulting in a more typical NET USABLE percentage increase around the thirties. More power output at the satellite, and newer, better receiver designs could help to improve the real world 8psk advantage.red hazard said:
What he said 
Seriously though, both red and darin are right.. The key in red's statement was "If all other variables stay constant". Unfortunatly FEC doesn't stay constant. It has to be increased to account for the more easily damaged signal. If they made the satellite higher powered and used entirely new LNB's on the additionally required round dish, then they could lower FEC and utilize even more bandwidth.
As for me, if 8PSK is only going to be a way to squeeze extra locals onto the far slot, it doesn't matter for me one way or another... though for those of you it does affect it would be nice to get 33%-50% more channels.. you will need a new dish anyway, just make it a special sat "d" setup...
Seriously though, both red and darin are right.. The key in red's statement was "If all other variables stay constant". Unfortunatly FEC doesn't stay constant. It has to be increased to account for the more easily damaged signal. If they made the satellite higher powered and used entirely new LNB's on the additionally required round dish, then they could lower FEC and utilize even more bandwidth.
As for me, if 8PSK is only going to be a way to squeeze extra locals onto the far slot, it doesn't matter for me one way or another... though for those of you it does affect it would be nice to get 33%-50% more channels.. you will need a new dish anyway, just make it a special sat "d" setup...
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