Superhub : Qam 16 upstream

[Broken Hope]

Is Qam 16 bad for upstream? I hear people complaining when it drops from 64, yet I've never noticed mine being any higher.

Does it depend on what area you're in and such?

[Taf]

I get QAM 16 during the first hour of on-off-on-off connection most days, then it settles down to QAM32 (6Mbps up).

[ianch99]

Mine has never been anything else than 16QAM ...

[General Maximus]

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.

[Martin_D]

Just like General Maximus says it take a lot of work to get 64QAM running on the network, It took them about 6 months to make it stable in this area.

31000000 ATDMA 44.8 64 qam 6400000 5120

37600000 ATDMA 44.8 64 qam 6400000 5120

[SnoopZ]

Originally Posted by General Maximus

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.

Are You sure about that as i thought most areas are still on 2?

QAM16 here even though i am on the new CMTS with 16 downstreams.

[General Maximus]

Originally Posted by SnoopZ

Are You sure about that as i thought most areas are still on 2?

ya, they spent most of last year concentrating on the upstream work for the public wifi thing they ended up knocking on the head. I went up to 3 upstreams along with many other peeps but when they decided to cancel the rollout then I dropped back down to two. Now I think about it most peeps are probably back down on two because I remember the increase in channels was tied to a firmware update for the public wifi which they ended up rolling back.
They also pushed ahead with the QAM upgrades and I had one QAM64 last summer and two QAM16s and now I have got two QAM64s.

[SnoopZ]

I took it as most users moved to 3-4 upstreams not areas.

[General Maximus]

it is the same thing. By August last year most areas (and thus users) were on 3 upstreams in their bonding group before VM rolled back the firmware. Although we all thought it was upgrade work they were doing in preparation for the speed upgrades, it turned out it was to add extra capacity for their public wifi plan.

[SnoopZ]

I wonder why i never saw it in my area(old cambridge cable network).

[General Maximus]

I am surprised you didn't notice it because everyone was talking about it at the time. There were cheers when we went up to three upstreams and qam64 and there were tears when we went back to two and qam16 . I can remember making several posts with screen dumps myself as I went to 3 upstreams, then one was qam64, then I lost the qam64, then I went to two upstreams and then both went to qam64.

[SnoopZ]

Originally Posted by General Maximus

I am surprised you didn't notice it because everyone was talking about it at the time. There were cheers when we went up to three upstreams and qam64 and there were tears when we went back to two and qam16 . I can remember making several posts with screen dumps myself as I went to 3 upstreams, then one was qam64, then I lost the qam64, then I went to two upstreams and then both went to qam64.

I cant notice it if it didnt come my way as I check my levels weekly so I don't think it ever came to me unless it was just a day or so!

Obviously I knew it was about as I live on this site and have also trialed the last 3 SHs so it is not as if I didn't know about what was going on.

[Martin_D]

Originally Posted by SnoopZ

I cant notice it if it didnt come my way as I check my levels weekly so I don't think it ever came to me unless it was just a day or so!

Obviously I knew it was about as I live on this site and have also trialed the last 3 SHs so it is not as if I didn't know about what was going on.

It may have been you were on the SH2ac at the time as it did not get the new firmware, only the SH2 got the update and let it use 3 upstreams

[Ignitionnet]

Originally Posted by SnoopZ

I cant notice it if it didnt come my way as I check my levels weekly so I don't think it ever came to me unless it was just a day or so!

Why ever not? It's apparently truly enthralling. Avid power level watching alongside avid speed testing seems to be the done thing.

No idea what people will do when we're all on FTTP. No power levels to look at so I presume it'll just be hourly speed tests.

---------- Post added at 00:25 ---------- Previous post was at 00:24 ----------

Originally Posted by SnoopZ

I took it as most users moved to 3-4 upstreams not areas.

Indeed. The upstreams are already there. Just a configuration change to move users onto them.

[pip08456]

Originally Posted by Ignitionnet

Why ever not? It's apparently truly enthralling. Avid power level watching alongside avid speed testing seems to be the done thing.

I think you'll find it's only VM customers who do it though.

I wonder why?