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Opti
(newbie) Sat 15-Aug-09 23:52:47

Half the sync I should have

[link to this post]

Hi all, first post here. I'll try and keep this post short despite the length of the on-going issue.

My area can only get around 5Mbps on LLU (Even less on BT Wholesale ISP's due to a very high training target SNR), but this doesn't add up because I've seen people getting ~14Mbps with the same attenuation (~38dB) as me on ADSL2+, and many many people getting full 8Mbps sync with the same attentuation on ADSL2.

On top of this, my line works how I'd expect it to every time there is a power-cut. (UPS smile

) It even lasts for 10 minutes after a power-cut, at which point suddenly the SNR plummets until Sync is lost. It then re-syncs and I'm back to my laggy 4meg of throughput.

BT point-blank denied any issues until recently when a Engineer confirmed the line gives several more megabips at the nearest CAB. However they have still yet to do fix the source of this problem.

My full router stats are posted below, and i'm hoping some of you can help finally solve this. I have a portable AM radio here if that can help at all?

Power-Cut Performance
[IMG]http://speed.io/pics/2179/0434/speed.io.png[/img]
Normal Performance
[IMG]http://speed.io/pics/2327/3185/speed.io.png[/img]

Text

ADSL driver and PHY status
Status: ShowtimeRetrain Reason: 1Channel: INTR, Upstream rate = 768 Kbps, Downstream rate = 5024 Kbps
Link Power State: L0Mode:                   G.DMT
Channel:                InterleaveTrellis:                ON
Line Status:            No DefectTraining Status:        Showtime
                Down            UpSNR (dB):       6.9             14.0
Attn(dB):       38.0            25.0Pwr(dBm):       19.8            9.4
Max(Kbps):      5696            1216Rate (Kbps):    5024            768
                        G.dmt framingK:              158(0)          25
R:              16              16S:              1               8
D:              64              8                        ADSL2 framing
MSGc:           51              68B:              58              23
M:              4               8T:              3               1
R:              12              16S:              1.5145          7.7037
L:              1310            216D:              64              8
                        CountersSF:             305618          305622
SFErr:          0               0RS:             20782090                2596784
RSCorr:         2112185         0RSUnCorr:       0               0
 HEC:            0               0
OCD:            0               0LCD:            0               0
Total Cells:    61562444                0Data Cells:     2100432         0
Drop Cells:     0Bit Errors:     0               0
 ES:             49              1
SES:            8               0UAS:            7412            30
AS:             5196 
INP:            2.34            2.37PER:            16.18           17.81
delay:          24.23           15.40OR:             28.17           33.23
 Bitswap:        0               0
 Total time = 1 days 14 hours 3 min 23 sec
SF  = 328973CRC = 1325
LOS = 8LOF = 72
ES  = 49Latest 1 day time = 14 hours 3 min 23 sec
SF  = 328973CRC = 1325
LOS = 5LOF = 45
ES  = 5

deleted
(deleted) Sun 16-Aug-09 00:05:07

Re: Half the sync I should have

[re: Opti] [link to this post]

I'm not entirely sure what your question is.

You say that:
1. your area usually gets ~5Mbps on LLU.
2. 38dB gives ~14Mbps on ADSL2+
3. 38dB gives 8Mbps on ADSL 2

Your line is using ADSL1 as per this:
Mode: G.DMT

And you are in synch at just a shade under 5Mbps (using old fashioned/corrrect 1Mb = 1024Kb):
Rate (Kbps): 5024

So what actually is the problem?

Maybe I missed the point?

Opti
(newbie) Sun 16-Aug-09 00:11:59

Re: Half the sync I should have

[re: deleted] [link to this post]

My sync is MUCH higher during and after a powercut, as well as being MUCH higher from the nearest CAB. The last part of my loop loses me over 3Megabips as confirmed by BT. Yet no solution is in-sight.

XRaySpeX
(committed) Sun 16-Aug-09 00:13:00

Re: Half the sync I should have

[re: Opti] [link to this post]

I doubt that "38dB gives ~14Mbps on ADSL2+"; more like 10 Mbps.

But you are on ADSL1 anyway.

1999: Freeserve 44K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg BB

Opti
(newbie) Sun 16-Aug-09 00:22:11

Re: Half the sync I should have

[re: XRaySpeX] [link to this post]

I am refering to stats I've seen people post on another DSL-related site, one person clearly was getting 14Mbps on Be There with a SNR of around 3dB on a 36-39dB line. Do I have to find the exact post just to satisfy you?

The graph on Wikipedia also shows ~12Mbps for ADSL2+ at 37-38dB.

Edited by Opti (Sun 16-Aug-09 00:22:43)

deleted
(deleted) Sun 16-Aug-09 00:29:36

Re: Half the sync I should have

[re: Opti] [link to this post]

In reply to a post by Opti:
My sync is MUCH higher during and after a powercut, as well as being MUCH higher from the nearest CAB. The last part of my loop loses me over 3Megabips as confirmed by BT. Yet no solution is in-sight.

In perfect conditions 38dB attenuation should give about 7Mbps.

Interesting about the power cut scenario. All I can suggest is that after the power cut a lot of electrical equipment doesn't come back into life until someone switches it on - so less background noise.

How long is the loop to your nearest cab?
Has the engineer tried switching you to a different pair in a different bundle from that cab (if possible)?
What kind of area is it? Any light industry around etc.?
Why do you get so many powercuts???

laugh

For reference attenuation vs synch speed (ideal conditions):

http://adsl.yesyes.info/pics/att_vs_speed.jpg

XRaySpeX
(committed) Sun 16-Aug-09 00:34:46

Re: Half the sync I should have - EDITED

[re: Opti] [link to this post]

In reply to a post by Opti:
Do I have to find the exact post just to satisfy you?

Don't bother! I was merely expressing an opinion; admittedly based on the usual NM of 6 db.

Also GeeTee's just posted "ideal conditions" referenced graph confirms my view. So, there is no need to be so antagonistic!

1999: Freeserve 44K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg BB

Edited by XRaySpeX (Sun 16-Aug-09 00:42:24)

deleted
(deleted) Sun 16-Aug-09 00:45:54

Re: Half the sync I should have

[re: XRaySpeX] [link to this post]

I'd love to be able to run a 6dB NM, but it just isn't possible where I live - too much noise. I have to be up at 12dB to keep the errors to a manageable level, anything less and whilst it maintains synch, it is pretty horrible to use as the error count goes through the roof.

Such is life... and I'm certainly not going to be wasting any effort getting engineers out about it - nothing they can do laugh

Opti
(newbie) Sun 16-Aug-09 00:47:53

Re: Half the sync I should have

[re: deleted] [link to this post]

Nearest CAB is not far at all (~200meters) and the last BT Engineer confirmed these issues are completly gone from that point.

Only one cable goes from that CAB to this Building to my knowledge, only one cable comes up from underground, which is within 2cm of this buildings mains cable as well at least.

The area is residential, no commercial buildings near by that I'm aware of. And powercuts are rare here, I was lucky to be at the PC during the powercut I had last month. The previous powercut before that was years ago and after that power cut I logged into the router to discover it was synced at over 7Mbps, which is why I then bought the UPS.

Edited by Opti (Sun 16-Aug-09 00:51:39)

deleted
(deleted) Sun 16-Aug-09 00:55:33

Re: Half the sync I should have

[re: Opti] [link to this post]

Well if that incoming bundle runs parallel to the mains incomer for any distance - therein lies your problem - and explains the behaviour post power-cut... the noise and cross talk will grow and grow as people power things back on - at least presuming it is a multi-occupancy building (flats etc.).

If it is a block of flats, what state is the cabling in from the incoming bundle to the flat itself... and is it correct grade telco cabling or some dicky alarm cabling used to save costs (all too common unfortunately!)?

Only option I see you have left to try is trying a different pair in the bundle.

edit - typo

Edited by deleted (Sun 16-Aug-09 00:56:33)

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