Quote:
Originally Posted by Sephiroth
The only way of making serious inroads into top end speeds is to mimprove the infrastructure quality so that it can run at a higher QAM rating. IMO that is almost a survival matter for VM.
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Not so much, past 256QAM you get into increasingly diminishing returns.
256QAM -> 1024QAM = 25% increase
The SNR including coding gain to make this happen is 37dB - 6dB above that for 256QAM.
2048QAM = 10% increase over 1024QAM but increases SNR requirement by 3dB - now up to 40dB.
4096QAM = 9% increase over 2048QAM and you're now in need of 43dB SNR.
So in return for an increase from 50Mb/s per channel to 75Mb/s per channel you've increased downstream SNR requirements by 12dB.
Increasing the number of downstream channels is, on the whole, a better way to go. VM can get RF bandwidth back by shifting TV channels from 64QAM to 256QAM and using the freed up multiplexes for additional downstreams.
My own area has tons of room free now having a 1GHz network, even 750MHz networks have 300MHz+ free thanks to analogue switch off - each analogue channel consumed 8MHz, enough for 4 HD channels.