PDA

View Full Version : 50mb to 5? Good SNR and Power levels?


50to5wtf
03-06-2009, 18:09
If you're in yorkshire area you may be affected by inadequate UBR cards. 2nd line and networks are aware of the issue but will give you the run around for months.

I had 50mb installed over 2 months ago and have been seeing the PL to UBR + massive speed drop outs since the very same day. I've had Modem, Splitter, Attenuator and drop cable all replaced, PT with laptop who ruled out all my equipment being at fault and network engineers to the cab. Nothing has resolved the issue, or even improved it one iota.

From what i've been able to find out, it's something to do with the UBR cards only supporting 64QAM and not 256QAM which is what most everywhere else in the country is set to. Frankly i am not entirely convinced that's the issue either, but that's what 2nd line suspect and what Networks are aware of. Aparently much of Yorkshire is affected, and perhaps other areas too, but they're dragging their feet on funding new equipment to resolve the issue.

If you've got the above symptoms, suffered multiple engineer visists only to report perfect power levels, AND know how to "PROPERLY" speed test your connection (i.e NOT speedtest.net), then you should bring the issue of inadequate UBR cards up.

Hopefully if enough ppl complain then things might get fixed.

HEADRAT
03-06-2009, 18:10
Maybe post your experiences in:-

http://www.cableforum.co.uk/board/12/33650861-views-on-50-mb.html

you are not alone ;)

Ignitionnet
03-06-2009, 18:51
Not likely, Yorkshire does not magically have different line cards from the rest of the network, all of which I might add support 256QAM given that it's been a requirement of DOCSIS since the very beginning of the standard.

You might be in an area which due to local network issues struggles with 256QAM and has to be on 64QAM but it's absolutely nothing to do with the CMTS cards. They are without exception able to support 256QAM on both the old and the newer overlay network.

Sounds more like 2nd line are clutching at straws to be honest. I'm not aware of a DOCSIS 3 deployment that doesn't use 256QAM, and you'd see errors at your modem, bursts or constant streams uncorrectable codewords if that were the issue.

50to5wtf
03-06-2009, 18:58
Not likely, Yorkshire does not magically have different line cards from the rest of the network, all of which I might add support 256QAM given that it's been a requirement of DOCSIS since the very beginning of the standard.

You might be in an area which due to local network issues struggles with 256QAM and has to be on 64QAM but it's absolutely nothing to do with the CMTS cards. They are without exception able to support 256QAM on both the old and the newer overlay network.

Sounds more like 2nd line are clutching at straws to be honest. I'm not aware of a DOCSIS 3 deployment that doesn't use 256QAM, and you'd see errors at your modem, bursts or constant streams uncorrectable codewords if that were the issue.


Frequency 299000000 307000000 315000000 N/A
Lock Status
(QAM Lock/FEC Sync/MPEG Lock) Y/Y/Y Y/Y/Y Y/Y/Y N/N/N
Channel Id 60 61 62 N/A
Modulation 64QAM 64QAM 64QAM N/A
Symbol Rate
(Msym/sec) 6.952 6.952 6.952 N/A
Interleave Depth I=12
J=17 I=12
J=17 I=12
J=17 N/A
Power Level
(dBmV) 4.62 4.51 4.68 N/A
RxMER
(dB) 34.72 34.87 35.20 N/A
Correctable
Codewords 0 1 0 N/A
Uncorrectable
Codewords 1005 252 717 N/A



If you read the support NG, check the submissions of modem pages and check the IPs. All reside in Yorkshire. I was told by my PT that Network Managers were aware of the issue, new equipment had to be bought and it was with the finance department.

Having said that, i dont hold out much hope for that actually resolving the issue as i see other user on here with identical symptoms to me, perfect SNR and power all the time, like me, and speed drop outs and PL like me and yet his UBR has had his card replaced AND he's on 256QAM.

Ignitionnet
03-06-2009, 19:05
This is nothing to do with the CMTS cards, it's an issue with downstream lasers, etc on your local network.

If it were as simple as a card replacement it would have been done, the equipment they are waiting on will be optical equipment I imagine. If it were a CMTS card fault that card would have been replaced under warranty.

I've seen a few posts on the support NG from all over the country, nothing Yorkshire specific. Yorkshire has a few different networks on it, there's bits of ex-Telewest, ex-ntl Langley and ex-ntl Bromley, so it's nothing personal to Yorkshire at all.

Which bit of Yorkshire are you in just out of interest? I know bits of Sheffield with those superbly maintained ex-Telewest local networks that got totally ignored until they palmed them off on ntl were stuck on 64QAM.

Can't help but think you've heard this vague rumour about CMTS cards and you're posting it as fact - it's not. You are on a Cisco 10k and don't even have a downstream CMTS card as such. The downstreams are generated by a device external to the CMTS, an E-QAM. If this is malfunctioning it would affect performance for masses of 20 and 50Mbit customers over a pretty wide area. Regardless the E-QAM will, 100%, support 256QAM without any issues. If it's on 64AM it's an issue with the network local to you and the capability of the lasers feeding your local area, absolutely not the E-QAM itself.

50to5wtf
03-06-2009, 19:09
Bradford UBR, Ex-Blueyonder.

My PT actually said "there were a few bits", so perhaps the optical was what he was referring to.

Network engineers came out at one point and tuned the amp in the cab, altho he said it wasn't bad enough to cause problems, he did say it was an uncommon amp and had to go get other equipment to tune it. Perhaps another suspect?

PL and Speed drop outs seem to go hand in hand. It either works at 50mb solid for a while perfectly, or speed drops to around 5mb (or higher) and PL goes through the roof. SNR and power levels never change. Browsing is impossible, pages wont load until downloads are stopped, at which point PL disappears too.

Ignitionnet
03-06-2009, 19:15
Bradford was mentioned to me by a friend as being an area that had bits running at 64QAM. It's an ex-Telewest area and a victim of the fantastic care Telewest took of their network :(

The fault is that the lasers that transmit the signals from where they are generated down the fibre optics to the local nodes that feed homes could not carry 256QAM as it would have driven them too hard, corrupting the signals they transmitted so they are running at 64QAM until these have been upgraded. The lasers aren't really good enough for all the data and channels they are required to transmit.

I know it's no help to you but hope that clarifies things a bit :(

50to5wtf
03-06-2009, 19:22
I updated my other post with additional information regarding the problem, but.

PL and Speed drop outs seem to go hand in hand. It either works at 50mb solid for a while perfectly, or speed drops to around 5mb (or higher) and PL goes through the roof. SNR and power levels never change. Browsing is impossible, pages wont load until downloads are stopped, at which point PL disappears too.


So, you agree then that 50mb on 64QAM is likely to cause these sorts of problems?

The local nodes meaning the street side cabs? My cab is literally right on my doorstep. So would that mean that every cab on a cable would need it's equipment upgraded before they could transmit 256QAM with the E-QAM?

Drat
03-06-2009, 19:38
Thought I would add my twopenny worth
Cable Modem Downstream

DS-1 DS-2 DS-3 DS-4
Frequency 299000000 307000000 315000000 N/A
Lock Status
(QAM Lock/FEC Sync/MPEG Lock) Y/Y/Y Y/Y/Y Y/Y/Y N/N/N
Channel Id 57 58 59 N/A
Modulation 64QAM 64QAM 64QAM N/A
Symbol Rate
(Msym/sec) 6.952 6.952 6.952 N/A
Interleave Depth I=12
J=17 I=12
J=17 I=12
J=17 N/A
Power Level
(dBmV) -5.78 -6.15 -5.75 N/A
RxMER
(dB) 32.44 32.53 32.72 N/A
Correctable
Codewords 0 0 0 N/A
Uncorrectable
Codewords 231 252 246 N/A


From that wonderful ex Telewest region of Sheffield that Broadbandings highlighted.

Ignitionnet
03-06-2009, 19:39
So, you agree then that 50mb on 64QAM is likely to cause these sorts of problems?

No, even at 64QAM and 3 downstreams there's still 114Mbit to share between the customers on the group and if it's congestion you should see a nice graceful degredation at peak times not bursts of tons of packet loss.

The local nodes meaning the street side cabs? My cab is literally right on my doorstep. So would that mean that every cab on a cable would need it's equipment upgraded before they could transmit 256QAM with the E-QAM?

No, meaning the cabinets that have fibre going to them. You would only need to upgrade the lasers in the hubsite or headend that transmit to the nodes, not the nodes themselves. It's the transmitter that is the problem, and the transmitter will be in a small or not so small VM building and not a street cabinet, in those are the receiver and the upstream transmitter only.

50to5wtf
03-06-2009, 20:00
Well i am kind of at a dead end then. Sounds like there are multiple issues that need fixing and they may or may not be the cause of the problems. 64QAM issue is what i've been left with and no one seems to want to look any further than that.

What bothers me is i am able to get a few minutes of good solid 50mb before it dies out. What might be causing that? Something works then just degrades... Seems very strange.

http://nemon.myby.co.uk/20-04-2009%2011-05-17.png
http://nemon.myby.co.uk/16-04-2009%2013-12-53.png

Ignitionnet
03-06-2009, 20:03
It's not the 64QAM that's causing your issues, there is something else going on which might be related but just being on 64QAM will not be causing that. The obsession with the downstream laser issue strikes me as laziness and they should be working on getting you a decent service while waiting for the laser upgrade.

The alternative, of course, was to not release the damn thing on a network that wasn't ready in the first place.

50to5wtf
03-06-2009, 20:06
So the call out engineers aren't trained or equipped to find anything, so those are a waste of time. I'll need network engineers out at my cab again to run more tests i guess, although they were certain there was nothing wrong with networks then.

king000000
11-06-2009, 21:29
Hi my speeds are going up and down is my power settings ok ?



Download Failed (1)
---------- Post added at 20:29 ---------- Previous post was at 20:06 ----------

Peter_
11-06-2009, 21:51
Hi my speeds are going up and down is my power settings ok ?



Download Failed (1)
---------- Post added at 20:29 ---------- Previous post was at 20:06 ----------
You need an engineer as your Downstream is way to high at around 17 so call Tech Support.

What is the Upstream, we only need you to copy the figures not the page.

king000000
11-06-2009, 22:02
found a 15db att from old modem put it on the modem and levels down to 3.95 power level dBmV and rxMER is 38.61 my speeds are a bit quicker at 34mb/s on speed test

Upstream is symbol rate 2560 and power level 58.21db
are those power levels ok or do i need a engineer still?

Peter_
11-06-2009, 22:04
found a 15db att from old modem put it on the modem and levels down to 3.95 power level dBmV and rxMER is 38.61 my speeds are a bit quicker at 34mb/s on speed test are those power levels ok or do i need a engineer still?
Thats a lot better and well within the normal range.

What is the Upstream.

Ignitionnet
11-06-2009, 22:06
Upstream is symbol rate 2560 and power level 58.21db

Too high, probably due to the attenuator. You still need an engineer sadly.

You meant 58.25dBmV, right?

Peter_
11-06-2009, 22:08
Upstream is symbol rate 2560 and power level 58.21db
are those power levels ok or do i need a engineer still?
As broadbanding said you still need the engineer and remove the attenuator to see what the Downstream is without it.

Ignitionnet
11-06-2009, 22:13
I'm somewhat astounded that they just shonked a 15dB attenuator on to the previous modem without making any attempts to balance the signal forward and return to the home. If you have DTV and the set top doesn't have a heavy duty attenuator also it will probably be quite unhappy. Cowboy install of the old service, even worse install of the new one to be honest.

king000000
11-06-2009, 22:32
ok give virgin a call get them to check it out, I do have tv box as well and no att on it but that seems to work fine.