Does noise margin change depending on speed profile?

Xcellor

Yesterday I was on the 7.6 speed profile with the following results:

/ # adsl info
Current Training Status : Showtime
Current trained adsl mode : G.Dmt
Current trained adsl path : Interleaved
Downstream Bit Rate : 7616000 bps
Downstream Noise Margin : 15.0 dB
Downstream Attenuation : 8.0 dB
Upstream Bit Rate : 672000 bps
Upstream Noise Margin : 12 dB
Upstream Attenuation : 15.0 dB

Today it seems my ISP bumped me down and now its the following.

/ # adsl info
Current Training Status : Showtime
Current trained adsl mode : G.Dmt
Current trained adsl path : Interleaved
Downstream Bit Rate : 5120000 bps
Downstream Noise Margin : 23.5 dB
Downstream Attenuation : 8.0 dB
Upstream Bit Rate : 512000 bps
Upstream Noise Margin : 12 dB
Upstream Attenuation : 15.0 dB

Seems like my Downstream noise margin has jumped. The others have remained as is. Since I reported an issue with my broadband U.TV put me up to 7.6mb profile, reduced me to 6mb, put me back up to 7.6 now they have put me down to 5mb... I'm starting to wonder what for............


Frustrated......

X

DECEiFER

Xcellor wrote: »

Yesterday I was on the 7.6 speed profile with the following results:

/ # adsl info
Current Training Status : Showtime
Current trained adsl mode : G.Dmt
Current trained adsl path : Interleaved
Downstream Bit Rate : 7616000 bps
Downstream Noise Margin : 15.0 dB
Downstream Attenuation : 8.0 dB
Upstream Bit Rate : 672000 bps
Upstream Noise Margin : 12 dB
Upstream Attenuation : 15.0 dB

Today it seems my ISP bumped me down and now its the following.

/ # adsl info
Current Training Status : Showtime
Current trained adsl mode : G.Dmt
Current trained adsl path : Interleaved
Downstream Bit Rate : 5120000 bps
Downstream Noise Margin : 23.5 dB
Downstream Attenuation : 8.0 dB
Upstream Bit Rate : 512000 bps
Upstream Noise Margin : 12 dB
Upstream Attenuation : 15.0 dB

Seems like my Downstream noise margin has jumped. The others have remained as is. Since I reported an issue with my broadband U.TV put me up to 7.6mb profile, reduced me to 6mb, put me back up to 7.6 now they have put me down to 5mb... I'm starting to wonder what for............


Frustrated......

X

Indeed it does. I just got upgraded to UTV 7.6Mb today, and it's been nothing but disastrous. However, in light of DSL needing a few days of stable line sync, I'm going to wait and see if it improves. If not, I will be onto them like lightning, and I will make damn well sure that they do not lower my sync to whatever. There is no need, my line is capable of the full 7.6Mb. I hate half-assed workarounds. It's unacceptable.

My stats after today's upgrade:
Noise Margin: 15.1 dB (Down) / 12.0 dB (Up)
Line Attenuation: 3.0 dB (Down) / 2.0 dB (Up)


Please read on...

---

I believe your line is more than capable of the full 7.6Mb too, given your stats. Get onto them and tell them to fix the problem, and not work around it.

I swear, if they pull this crap on me again, there will be war. In-fact, the more people bitching at them about it, the more likely they'll cop themselves on and push Eircom into fixing it properly. Give them a call tomorrow is my advice.

Everyone on UTV experiencing issues related to sloppy speeds or needless sync downgrades, call UTV Support on 1890-926-111, and give 'em hell until you're satisfied with a resolution.

If you're getting nowhere on the phone, email a strong but dignified letter to support@u.tv and CC it to consumerline@comreg.ie (to attempt to put the s**ts up them).

dub45

Xcellor wrote: »

Yesterday I was on the 7.6 speed profile with the following results:

/ # adsl info
Current Training Status : Showtime
Current trained adsl mode : G.Dmt
Current trained adsl path : Interleaved
Downstream Bit Rate : 7616000 bps
Downstream Noise Margin : 15.0 dB
Downstream Attenuation : 8.0 dB
Upstream Bit Rate : 672000 bps
Upstream Noise Margin : 12 dB
Upstream Attenuation : 15.0 dB

Today it seems my ISP bumped me down and now its the following.

/ # adsl info
Current Training Status : Showtime
Current trained adsl mode : G.Dmt
Current trained adsl path : Interleaved
Downstream Bit Rate : 5120000 bps
Downstream Noise Margin : 23.5 dB
Downstream Attenuation : 8.0 dB
Upstream Bit Rate : 512000 bps
Upstream Noise Margin : 12 dB
Upstream Attenuation : 15.0 dB

Seems like my Downstream noise margin has jumped. The others have remained as is. Since I reported an issue with my broadband U.TV put me up to 7.6mb profile, reduced me to 6mb, put me back up to 7.6 now they have put me down to 5mb... I'm starting to wonder what for............


Frustrated......

X

http://www.kitz.co.uk/adsl/lowSNR.htm

Traditional Fixed 512/1Mb/2Mb
For each upgrade between the speeds you can expect to lose on average 6dB. Therefore if you upgraded from 512kbps to 2Mbps then your SNR Margin is likely to have dropped in the region of 12dB.
Once your SNR Margin starts to drop below 10dB on a traditional fixed rate line then you can experience problems.

DECEiFER

dub45 wrote: »

http://www.kitz.co.uk/adsl/lowSNR.htm

Traditional Fixed 512/1Mb/2Mb
For each upgrade between the speeds you can expect to lose on average 6dB. Therefore if you upgraded from 512kbps to 2Mbps then your SNR Margin is likely to have dropped in the region of 12dB.
Once your SNR Margin starts to drop below 10dB on a traditional fixed rate line then you can experience problems.

Exactly! Therefore his line is capable of the full 7.6Mb sync, and downgrading it is just a load of bulls**t, no matter what excuse they pull out for it.


Best of luck with it, Xcellor.

dub45

DECEiFER wrote: »

Exactly! Therefore his line is capable of the full 7.6Mb sync, and downgrading it is just a load of bulls**t, no matter what excuse they pull out for it.


Best of luck with it, Xcellor.

Yes in theory but don't forget his internal wiring could be in a mess:)

DECEiFER

dub45 wrote: »

Yes in theory but don't forget his internal wiring could be in a mess:)

True, but surely that would deteriorate the signal and up the noise?

dub45

The op has not told us exactly what the issue was that lead to UTV changing his profile. The attenuation figure would suggest that he is living very close to the exchange. The SNR figure would suggest that give that proximity to the exchange there must be an issue of line quality somewhere. That problem may be contributing to the already low snr figure.

Grommet

DECEiFER wrote: »

Exactly! Therefore his line is capable of the full 7.6Mb sync, and downgrading it is just a load of bulls**t, no matter what excuse they pull out for it.

Modems are normally set to "Rate Adaptive" mode by the operator, which means that the modem will be set to a maximum speed (probably 7Mbps in this case) but can re-synch at lower speeds if noise is introduced onto the line. It sounds as if there is some RF interference somewhere that is causing the op's line to degrade on occasion. I doubt if UTV (or eircom) have actually provisioned a lower speed profile.

As suggested above, I would check all internal wiring and try to clean that up (or plug into master socket with rest of wiring removed) and see if it improves.

Xcellor

Grommet wrote: »

Modems are normally set to "Rate Adaptive" mode by the operator, which means that the modem will be set to a maximum speed (probably 7Mbps in this case) but can re-synch at lower speeds if noise is introduced onto the line. It sounds as if there is some RF interference somewhere that is causing the op's line to degrade on occasion. I doubt if UTV (or eircom) have actually provisioned a lower speed profile.

As suggested above, I would check all internal wiring and try to clean that up (or plug into master socket with rest of wiring removed) and see if it improves.

It's a new home build and the Eircom box outside my house is drilled directly to the socket I am plugging into. The length of the cable to the socket is less than 1 meter. It's an estate so all the cables run underground to the exchange.

Just a bit of history to fill in the gaps:

About 8 weeks ago (actually longer) my 3mb connection went from being near perfect, top download speeds, 30ms pings all day to a very slow 0.5-1mb. The ping jumped to 100ms-200ms. However this would only occur between 5-12:30am. The rest of the time the connection would be perfect.

After much complaining U.TV upgraded me to 7.6 since it had lower contention 12:1. Again, the download speeds and ping were perfect through the day. As soon as the evening hit the same problem. Issue escalated to Eircom. Eircom come back saying nothing wrong. This circle went around a couple of times.

U.TV then suggest putting me down to 6mb profile. I questioned the logic of this but decided to try it out so no one can say I was a difficult customer. Same problem. Perfect through the day, sh*t when evening came. The ping now could easily reach 500ms and even 1000ms.

Roll a few more weeks Eircom still saying No problem. So on Tuesday U.TV phone me and say they are going to try and put me down to 3mb to see if that stabilizes my connection. This is where I said "NO WAY." The issue was reported when I was AT 3MB there is no way putting me back on that would fix the problem. So instead they seem to put me on a 5mb profile. (I phoned them to confirm this action was carried out by them).

The issue is clearly capacity/load related. I start off with 3mb and the speed etc was great, then one night it goes to sh*te, then I go up to 7.6 have the problem, go down to 6mb have the problem, go back up to 7.6 have the problem, go down to 5mb still have the problem. It's like I'm jumping through pointless hoops and getting no closer to the problem being resolved.

My exchange is Newtownforbes CAB011 (043 33 38xxx), I guess it must be a subexchange of Longford. It was only BB enabled in January.

It's really starting to get me down now!!

X

Grommet

Grommet wrote: »

Modems are normally set to "Rate Adaptive" mode by the operator, which means that the modem will be set to a maximum speed (probably 7Mbps in this case) but can re-synch at lower speeds if noise is introduced onto the line. It sounds as if there is some RF interference somewhere that is causing the op's line to degrade on occasion. I doubt if UTV (or eircom) have actually provisioned a lower speed profile.

As suggested above, I would check all internal wiring and try to clean that up (or plug into master socket with rest of wiring removed) and see if it improves.

I've seen some people's modems constantly sync at 6144/512 or 5120/512 so this would make me think that there are multiple profiles. I'd just find it highly unlikely that a modem would, on its own accord, sync at exactly 5 or 6 megs.

Grommet

Karsini wrote: »

I've seen some people's modems constantly sync at 6144/512 or 5120/512 so this would make me think that there are multiple profiles. I'd just find it highly unlikely that a modem would, on its own accord, sync at exactly 5 or 6 megs.

It depends on the modem manufacturer. The various synch speeds are defined within the modem firmware. The max profile is set by the operator, the modem then synchs to one of the lower values it supports as determined by the S/N.

Xcellor wrote: »

My exchange is Newtownforbes CAB011 (043 33 38xxx), I guess it must be a subexchange of Longford. It was only BB enabled in January.

It's really starting to get me down now!!

X

Hi X - as per my post in the other recent thread - there was certainly congestion at the BRAS node in Mullingar through which your exchange is connected. This was fixed earlier this week, so definitely the better ping times you are seeing now should continue. Definitely I am certain that the very bad ping times you were getting of half a second were down to that congestion at the aggregation node.

I don't know the specific cause of your poor download speeds however as you say they are continuing. It could be a function of your ISP (UTV in your case) or indeed some interference on your local line. Having said that, if it is consistently evening time that you see the issue then it is unlikely to be your local line (which is not shared) but is likely to be congestion on either the link between the DSLAM and the BRAS or somewhere within UTV's network. Some more traceroutes might help to pinpoint the issue.

EDIT: come to think of it - if your exchange was only enabled in June then there is no way the link between the DSLAM and the BRAS would be anywhere near full already. So almost certainly not congestion there.

Sponge Bob

Grommet wrote: »

EDIT: come to think of it - if your exchange was only enabled in June then there is no way the link between the DSLAM and the BRAS would be anywhere near full already. So almost certainly not congestion there.

Absolutely . Another possibility and one that would be have been masked by the congestion upstream would be 'Crosstalk' .

In other words too many people out your direction from the exchange have signed up for eircom DSL and interfere with each other copper to copper .

Shut the modem down before you leave tomorrow and start it up as late as you possibly can tomorrow and see how it goes . If OK at 7pm and ****e at 8 maybe a better modem than a Netopia is required. Netopias are only middling grade modems and they do run hot requiring good ventilation .

Report in tomorrow .

lucernarian

Crosstalk would do nothing except lower signal margin. Aka it's not noticeable until the signal margin spikes down towards 0.

The fact that the speed issues only appear in the evenings, and stop by 1am, means that contention/backhaul issues in some form or other are the problem. The line is grand.

Btw, I've found the signal margin changes unpredictably when sync rate is changed. As good as the Kitz website is, the "rule of thumb" about upgrades is very much just that. It assumes that thermal and other sorts of electrical noise are evenly spread and that the only difference between the available tones in downstream is each one's attenuation. (attenuation higher for higher tones obviously)

I've seen with the way some people can't get stable 1 mbps at 5.5 km while others can just about reach stable 2 mbps at the same distance. Goes to show that locale conditions and even what modem you use can make a big difference.

Btw OP, I suggest you simply leave UTV by hook or crook. If you lodge an official complaint with them, and they won't take action, then forward corrospondence to ComReg, like the other poster said.