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General Maximus · 15-07-2015, 16:49

it doesn't work like that dude. The modulation directly corresponds to bandwidth and the amount of data that can go over that channel (it is to do with the number of bits per symbol). To keep it nice and simple qam64 provides a 50% increase in bandwidth from qam16 so I think you are roughly looking at going from 20mbits/channel to 30mbits/channel.

If you are using three channels (on qam16) then it is 3x20mbits=60mbits. Using your example, adding the three channel modulations to make qam48 would give you far less than what you currently have access to. What you are missing out on is 3 x qam64 channels which is 3x30mbits/channel=90mbits potential bandwidth.

You haven't got anything to worry about being stuck on qam16, it has been the normal for the last couple of years. In order to achieve the higher modulations your (or VM's network) has got to be a far higher standard and there has got to be less noise. This is why we have seen upstream channels fall back to qpsk in the past; slower connections but more noise tolerant. What some users have already reported seeing is being moved to qam64, but as issues crop up with noise they temporarily fall back to qam16. Things are moving in the right direction and as the shubs re only capable of using 4 bonded upstream channels the way forward for VM is to change the modulation and try and squeeze as much juice out of it as they can.

15-07-2015, 16:49	#43
General Maximus cf.mega poster Join Date: Nov 2008 Location: Lincoln Services: phone + 1gbit BB + SkyQ Posts: 11,021	Re: Uddingston upstream 3 channels? it doesn't work like that dude. The modulation directly corresponds to bandwidth and the amount of data that can go over that channel (it is to do with the number of bits per symbol). To keep it nice and simple qam64 provides a 50% increase in bandwidth from qam16 so I think you are roughly looking at going from 20mbits/channel to 30mbits/channel. If you are using three channels (on qam16) then it is 3x20mbits=60mbits. Using your example, adding the three channel modulations to make qam48 would give you far less than what you currently have access to. What you are missing out on is 3 x qam64 channels which is 3x30mbits/channel=90mbits potential bandwidth. You haven't got anything to worry about being stuck on qam16, it has been the normal for the last couple of years. In order to achieve the higher modulations your (or VM's network) has got to be a far higher standard and there has got to be less noise. This is why we have seen upstream channels fall back to qpsk in the past; slower connections but more noise tolerant. What some users have already reported seeing is being moved to qam64, but as issues crop up with noise they temporarily fall back to qam16. Things are moving in the right direction and as the shubs re only capable of using 4 bonded upstream channels the way forward for VM is to change the modulation and try and squeeze as much juice out of it as they can.