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Standard User Bald_Eagle1
(committed) Tue 08-May-12 08:43:21
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Re: New speeds upgrade question


[re: RobertoS] [link to this post]
 
In reply to a post by RobertoS:
It was Bald_Eagle's 4dB drop sometimes when using the phone that had come into my head.

If that had been on your connection I would have been wondering if the filter in the faceplate had given up. Hence the suggestion of adding a dangly smile.

In his case, it looks more like a D-side problem.


When this happens, I do try a dangly filter in the usual phone socket (no improvement) & also in the user accessible test socket (again, no improvement).

I think engineers have also suspected the master socket filtering as the cause as one replaced the whole thing & another replaced the filter pcb.

It just has to be a D-Side issue (unless it's the DSLAM itself or the patch cable connections in the fibre cabinet).

Modems have been replaced.
My drop wire has been replaced, removing the engineer installed data extension in the process.
I have run my connection with everything except VDSL2 disconnected for 2 week periods.
Twisted D-Side pairs have been swapped.
Exchange side Lift & Shift has been done.
Double-jumpered cabinet connection has been removed.
Engineers have run TDR tests & other "basic" tests - All result in LTOK.

There isn't much left to test & getting an engineer on site just when the issue is evident seems impossible.

It usually lasts for 3 or 4 days or so, completely ruining my connection speeds, but it takes more or less a week to organise an engineer visit, so the issue has gone again by the time they arrive.

More recently it appears that dry & warm weather starts it off (which seems to be the complete opposite to the usual water in the cable/joints issues).
Simply dialling in seems to effect a temporary cure (after initially causing a disconnection & banding my connection at a ridiculously low sync speed)frown
Standard User qasdfdsaq
(member) Tue 08-May-12 17:30:48
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Re: New speeds upgrade question


[re: Bald_Eagle1] [link to this post]
 
I've just found your epic thread on the other forum you mentioned - sounds like you're getting pretty decent support from Plusnet on the whole, but unfortunate the problem itself hasn't been fixed...

Anyhow. Your attenuation would have to be lower to get higher speeds, yes, but your attenuation for an ~850m long line is unusually high.

It's not as easy to quote a single attenuation value for the whole spectrum on VDSL2 as it is on ADSL - there's huge variations across the different bands, then there's the fact there's multiple bands to begin with, which can vary. There's no standard for combining the readouts for the different bands either, so the per-band and per-tone readings off the HG612 are the best we can get. To be honest I think they provide a much better reading than any individual or per-band attenuation figure anyway.

I see you've posted elsewhere "good" and "bad" line stats examples, I presume the bad one is yours - not sure where the "good" one is from, but I'd expect an 850m line to be around halfway between those two, with full usage of the D2 band and maybe a touch of D3.

Given you've basically replaced everything except the cab and underground cable, you're right to suspect one of the two. I recall you mentioned an engineer once tested your line at the cab, and got a full 80mb sync. Do you happen to know what the max attainable rate was showing in that test? 80 doesn't really say much at the cab, it should really be around over 150mbps to be meaningful.

Incidentally I've decided to report a fault on my line now, as it's not just the DLM speed capping getting in my way. I've noticed picking up the phone causes a spike of FEC errors on my modem stats and packet loss on my TBB BQM as well as a short-term drop in SNRM from ~7 down to ~2, before it gradually recovers. That's even with the line synced at ~47 out of 90mbps and a dangly filter.

Edited by qasdfdsaq (Tue 08-May-12 17:33:25)

Standard User Bald_Eagle1
(committed) Tue 08-May-12 18:16:35
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Re: New speeds upgrade question


[re: qasdfdsaq] [link to this post]
 
In reply to a post by qasdfdsaq:
I've just found your epic thread on the other forum you mentioned - sounds like you're getting pretty decent support from Plusnet on the whole, but unfortunate the problem itself hasn't been fixed...

Anyhow. Your attenuation would have to be lower to get higher speeds, yes, but your attenuation for an ~850m long line is unusually high.

The main problem seems to be that the faults(s) are intermittent, apart from what does appear to be quite consistently high attenuation over a relatively short distance.


It's not as easy to quote a single attenuation value for the whole spectrum on VDSL2 as it is on ADSL - there's huge variations across the different bands, then there's the fact there's multiple bands to begin with, which can vary. There's no standard for combining the readouts for the different bands either, so the per-band and per-tone readings off the HG612 are the best we can get. To be honest I think they provide a much better reading than any individual or per-band attenuation figure anyway.

Agreed.
A few of us have tied to suss out a formula for combining the split attenuation values into a single value as that is what most engineers are familiar with.
I believe a JDSU can actually report split attenuation values, just like the HG612 modem, so I was most disappointed when the latest engineer turned up with an Exfo instead of the usual JDSU.
He was a most helpful engineer, who did look for the split figures to compare against my modem stats & relate back to his single values, but it appears the Exfo doesn't report that.


I see you've posted elsewhere "good" and "bad" line stats examples, I presume the bad one is yours - not sure where the "good" one is from, but I'd expect an 850m line to be around halfway between those two, with full usage of the D2 band and maybe a touch of D3.

I'd now be quite happy to achieve a 40Mb & stable connection as I never really expected to exceed that anyway.
I only wish I had recorded the connection stats at installation time for comparison against my current stats.
At that time I had no idea that I would not be able to see my own connection stats.


Given you've basically replaced everything except the cab and underground cable, you're right to suspect one of the two. I recall you mentioned an engineer once tested your line at the cab, and got a full 80mb sync. Do you happen to know what the max attainable rate was showing in that test? 80 doesn't really say much at the cab, it should really be around over 150mbps to be meaningful.

The engineer said his Exfo (not a JDSU that time) had synced at 80Mb at the cab, so I don't know what the Max Rate was at the cab.

By the time my D-Side had attenuated it, these were the modem stats:-

Text
1
23
45
67
89
1011
1213
1415
1617
1819
2021
22
# xdslcmd info --pbParams 
xdslcmd: ADSL driver and PHY statusStatus: Showtime
Retrain Reason: 2Max:    Upstream rate = 6376 Kbps, Downstream rate = 35864 Kbps
Path:   0, Upstream rate = 6372 Kbps, Downstream rate = 35322 Kbps 
Discovery Phase (Initial) Band PlanUS: (0,95) (868,1207) (1972,2783) 
DS: (32,859) (1216,1963) (2792,3939) Medley Phase (Final) Band Plan
US: (0,95) (868,1207) DS: (32,859) (1216,1963) 
       VDSL Port Details       Upstream        DownstreamAttainable Net Data Rate:       6376 kbps         35864 kbps
Actual Aggregate Tx Power:        6.2 dBm          12.2 dBm============================================================================
  VDSL Band Status        U0      U1      U2      U3      D1      D2      D3  Line Attenuation(dB):  8.2     53.0    64.1     N/A    21.6    63.2    0.1    
Signal Attenuation(dB):  14.4    52.5     N/A     N/A    21.6    63.2     N/A           SNR Margin(dB):  6.0     6.1      N/A     N/A    6.3     6.4      N/A   
         TX Power(dBm): -4.3     5.8      N/A     N/A    10.9    6.4      N/A



Incidentally I've decided to report a fault on my line now, as it's not just the DLM speed capping getting in my way. I've noticed picking up the phone causes a spike of FEC errors on my modem stats and packet loss on my TBB BQM as well as a short-term drop in SNRM from ~7 down to ~2, before it gradually recovers. That's even with the line synced at ~47 out of 90mbps and a dangly filter.

Sounds very similar to my current intermittent issue(s).
Please keep us posted as to how you get on with matters.


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Standard User BatBoy
(legend) Tue 08-May-12 20:00:24
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Re: New speeds upgrade question


[re: Bald_Eagle1] [link to this post]
 
In reply to a post by Bald_Eagle1:
A few of us have tied to suss out a formula for combining the split attenuation values into a single value as that is what most engineers are familiar with.
The way I would do it is to convert them to milliwatts, add them up and take the average or the mean. Then convert the result back.


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Standard User qasdfdsaq
(member) Wed 09-May-12 15:16:23
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Re: New speeds upgrade question


[re: Bald_Eagle1] [link to this post]
 
In reply to a post by Bald_Eagle1:
Sounds very similar to my current intermittent issue(s).
Please keep us posted as to how you get on with matters.

BT's online fault tracker seems to claim they fixed the fault in about an hour, despite them having done nothing of note or contacted me. No phone call, no engineer, not even a resync of my line. Until...

Right on time at 6am this morning, DLM changed my cap and triggered another resync - now I'm at 53998 down, 20000 up. Interleaving appears to be even higher, which is a pain since my main uses for my connection are gaming and remote desktop/ssh.

Picking up the phone still reduces my DL attainable rate by 5mbps, but increases upstream SNR and doesn't cause any packet loss or errors now. Perhaps DLM increased impulse noise protection and interleaving for that, which simply stinks.

All in all... DLM = total PITA and BT support = meh.
Standard User Bald_Eagle1
(committed) Wed 09-May-12 16:49:57
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Re: New speeds upgrade question


[re: qasdfdsaq] [link to this post]
 
In reply to a post by qasdfdsaq:
Picking up the phone still reduces my DL attainable rate by 5mbps, but increases upstream SNR and doesn't cause any packet loss or errors now. Perhaps DLM increased impulse noise protection and interleaving for that, which simply stinks.

That really is peculiar.
What happens to upstream attainable rates when upstream SNR(M) increases & what happens to downstream SNR(M) when downstream attainable rate reduces by 5Mb?



All in all... DLM = total PITA and BT support = meh.

I Can't comment on BT support as I'm with Plusnet, but I agree 100% that DLM = total PITA.

Perhaps you need a connection like mine:-

Stable Connection???

Despite simply using the phone sometimes causing disconnections, this is apparently the current status of my connection:-

"With your line we can see the sync rate and stability is within limits and so it is unlikely that further engineers will be able to find any problems."
Standard User qasdfdsaq
(member) Wed 09-May-12 17:53:41
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Re: New speeds upgrade question


[re: Bald_Eagle1] [link to this post]
 
In reply to a post by Bald_Eagle1:
In reply to a post by qasdfdsaq:
Picking up the phone still reduces my DL attainable rate by 5mbps, but increases upstream SNR and doesn't cause any packet loss or errors now. Perhaps DLM increased impulse noise protection and interleaving for that, which simply stinks.

That really is peculiar.
What happens to upstream attainable rates when upstream SNR(M) increases

No real change, it goes from 30400 down to maybe 29800. Certainly nowhere near the drop down to 15000 I was getting yesterday.

& what happens to downstream SNR(M) when downstream attainable rate reduces by 5Mb?

About 1dB reduction.



I Can't comment on BT support as I'm with Plusnet, but I agree 100% that DLM = total PITA.

Perhaps you need a connection like mine:-

Stable Connection???

Honestly I'd rather have a slow and unstable connection with interleaving off so my pings stay low. That's the main reason I switched from VM - despite them having slightly lower minimum latency, the horrendous jitter 24/7 meant the average ended up 50% higher, and the pathetic 1.5mbps upload didn't help either.

Despite simply using the phone sometimes causing disconnections, this is apparently the current status of my connection:-

"With your line we can see the sync rate and stability is within limits and so it is unlikely that further engineers will be able to find any problems."

Perhaps you should try using your phone repeatedly so disconnections get to the point where it is no longer within limits? tongue

Edited by qasdfdsaq (Wed 09-May-12 18:12:14)

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