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General Maximus · 25-02-2016, 13:47

You will see a lot of threads about qam64 on the upstream because it is something new which VM are in the process of implementing. People are talking about it because it is something new and exciting which they have just got (just like the downstream upgrades) and they are also talking about it because it is coming and going as VM play around with it. QAM64 is a new standard which VM are still implementing and trying to achieve. QAM16 has been used for years and I am sure many millions of customers will still be on upstream channels which are QAM16. We all keep harping on about upstream upgrades and how VM are far behind the competition and that is because it is harder and more expensive to provide additional upstream bandwidth on HFC networks.
You can do it one of two ways; either by adding more channels or squeezing as much juice out of each channel as possible. VM are trying both atm, I believe that most areas have now been moved from two upstream channels up to three (and some even four). In addition to this, VM are also trying to squeeze as much bandwidth out of each channel as possible and that is why we are seeing qam64 appear. QAM64 provides a 50% increase in throughput versus qam16. I can't remember what the exact numbers are but as an example you would be looking at 20mbits per channel on qam16 versus 30mbits on qam64. When you scale this up and look at your 3 channel bonding group then you are looking at 60mbits versus 90mbits. (those aren't exact numbers because I can't remember the exact throughput per channel).
The reason why people still see QAM32, 16 and maybe even qpsk is because the modulation of the channel is entirely noise dependant. QAM64 is very noise sensitive and rather than just throwing a wobbly and you losing your connection when there is a lot of noise on the network, it will drop down to lower modulations in order to maintain a stable connection. This is why you will see (and sometimes I do) one of the channels dropping to qam32 for a day or right back down to qam16. A couple of years ago both channels would drop down to qpsk and when that happened you knew VM had some big problems.
QAM16 is nothing to worry about. Physical upgrade work has to be done on the network in order to achieve qam64 and I imagine it is will work in progress.

25-02-2016, 13:47	#4
General Maximus cf.mega poster Join Date: Nov 2008 Location: Lincoln Services: phone + 1gbit BB + SkyQ Posts: 11,021	Re: Qam 16 upstream You will see a lot of threads about qam64 on the upstream because it is something new which VM are in the process of implementing. People are talking about it because it is something new and exciting which they have just got (just like the downstream upgrades) and they are also talking about it because it is coming and going as VM play around with it. QAM64 is a new standard which VM are still implementing and trying to achieve. QAM16 has been used for years and I am sure many millions of customers will still be on upstream channels which are QAM16. We all keep harping on about upstream upgrades and how VM are far behind the competition and that is because it is harder and more expensive to provide additional upstream bandwidth on HFC networks. You can do it one of two ways; either by adding more channels or squeezing as much juice out of each channel as possible. VM are trying both atm, I believe that most areas have now been moved from two upstream channels up to three (and some even four). In addition to this, VM are also trying to squeeze as much bandwidth out of each channel as possible and that is why we are seeing qam64 appear. QAM64 provides a 50% increase in throughput versus qam16. I can't remember what the exact numbers are but as an example you would be looking at 20mbits per channel on qam16 versus 30mbits on qam64. When you scale this up and look at your 3 channel bonding group then you are looking at 60mbits versus 90mbits. (those aren't exact numbers because I can't remember the exact throughput per channel). The reason why people still see QAM32, 16 and maybe even qpsk is because the modulation of the channel is entirely noise dependant. QAM64 is very noise sensitive and rather than just throwing a wobbly and you losing your connection when there is a lot of noise on the network, it will drop down to lower modulations in order to maintain a stable connection. This is why you will see (and sometimes I do) one of the channels dropping to qam32 for a day or right back down to qam16. A couple of years ago both channels would drop down to qpsk and when that happened you knew VM had some big problems. QAM16 is nothing to worry about. Physical upgrade work has to be done on the network in order to achieve qam64 and I imagine it is will work in progress.