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Should I upgrade?

magicofthemind
Dabbler
Posts: 23
Registered: 30-07-2007

Should I upgrade?

I've just received an invitation to apply for a free upgrade from 2Mb and 8Mb. I'm confused by comments that upgrading could leave me with a worse service than before - the last speed test I tried came out at around 1.8Mb. I'm also concerned by references to rebooting the router - I'm using an internal PCI modem. I can only disconnect it from the splitter or reboot the PC.

So should I stick with a more or less reliable service or upgrade?
17 REPLIES
Community Veteran
Posts: 26,339
Thanks: 595
Fixes: 8
Registered: 10-04-2007

Should I upgrade?

Can you get hold of the statistics (noise margin etc.) from your modem and post them. We can then make a guess about the likely speed you would get from upgrading.

This page may help you find the stats: http://www.kitz.co.uk/adsl/frogstats.htm
jelv (a.k.a Spoon Whittler)
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magicofthemind
Dabbler
Posts: 23
Registered: 30-07-2007

Should I upgrade?

Thanks, but my MRI PCI modem isn't listed on that page.

Connexant "Physical Layer Statistics" are currently showing

Noise up: +30
Noise down: around +16

Attenuation: up 14.5 down 22.9

Bits per frame: up 269 down 1473

Max Tx PSD -38

Does that help?

Barry
Plusnet Staff
Plusnet Staff
Posts: 12,169
Thanks: 18
Fixes: 1
Registered: 04-04-2007

Should I upgrade?

Hi,

That downstream noise figure is a little on the low side especially considering the attenuation.

I'd suggest taking a look through this:

http://usertools.plus.net/tutorials/id/13

just to make sure that all the wiring is set up correctly as that could easily cause a lower SNR. If the SNR goes up a bit then I would say there shouldn't be any problems with Max on your line, but I would very much recommend checking everything out first to ensure there's no wiring or setup problems.
magicofthemind
Dabbler
Posts: 23
Registered: 30-07-2007

Should I upgrade?

Thanks. My wiring looks OK to me. It is complicated, but my ADSL line only passes through one splitter, at the extension socket. The extension cable is hard-wired from the back of my master socket and does not pass through the splitter there. All phones are connected through one of my two splitters, one at each main socket.

Barry
Plusnet Staff
Plusnet Staff
Posts: 12,169
Thanks: 18
Fixes: 1
Registered: 04-04-2007

Should I upgrade?

If you can, it's worth testing at the master socket with nothing else connected to the line, just as a test to see if it makes any difference to that SNR figure.

Your attenuation isn't far off mine (mine's around 18-19dB), but before Max I had an SNR of about 30dB, now I get a sync of 8128kbps and SNR about 10dB.

As such I would say that something is causing your SNR to be lower than it should be, probably by 10-15dB, an extension cable or damaged wiring can easily cause that so it would be useful to compare.

Based on your line figures at the moment you'd probably be looking at 3-4Mbps with Max, the SNR is high enough now not to cause any real problems but I think if you find anything wrong and the SNR increases towards 30dB you should be looking at a rock solid 8Mbps.
magicofthemind
Dabbler
Posts: 23
Registered: 30-07-2007

Should I upgrade?

I've now done the testing. The problem seems to be my dial-up LT Win modem, which I still use at least once a week. If I disconnect it, the noise margin goes up from around 15 to around 25. I've tried disabling it, but that has no effect; it has to be physically unplugged, which is a nuisance as I can't easily get behind the PC!

Any suggestions please?
Plusnet Staff
Plusnet Staff
Posts: 12,169
Thanks: 18
Fixes: 1
Registered: 04-04-2007

Should I upgrade?

I presume the modem is connected to a filter (and it doesn't get doubley filtered)? If not then that'll be the reason. If it is connected to filter then I'd suggest trying a different modem lead or swapping the filter to see if it makes any difference.

Certainly at 25dB you should have absolutely no problems with Max, but with the modem causing a 10dB loss in the SNR it could easily cause problems.
N/A

8Mb upgrade

Hi, I've also just received an invitation to apply for a free upgrade from 2Mb and 8Mb. Can some one help me decipher the results below, ie; if my setup would ok, or perhaps offer some advice? Thanks

BusyBox v0.61.pre (2005.05.16-03:05+0000) Built-in shell (ash)
Enter 'help' for a list of built-in commands.

# cat/proc/avalanche/avsar_modem_stats
cat/proc/avalanche/avsar_modem_stats: No such file or directory
#
# cat /proc/avalanche/avsar_modem_stats

AR7 DSL Modem Statistics:
--------------------------------
[DSL Modem Stats]
US Connection Rate: 288 DS Connection Rate: 2272
DS Line Attenuation: 43 DS Margin: 7
US Line Attenuation: 28 US Margin: 29
US Payload : 4025280 DS Payload: 16108752
US Superframe Cnt : 3898497 DS Superframe Cnt: 3898498
LOS errors: 0 SEF errors: 0
Frame mode: 3 Max Frame mode: 0
Trained Path: 0 US Peak Cell Rate: 679
Trained Mode: 3 Selected Mode: 1
ATUC Vendor Code: 414C4342 ATUC Revision: 1
Hybrid Selected: 1 Trellis: 1
Showtime Count: 4 Max Attenable Bit Rate: 24894746
96

[Upstream (TX) Interleave path]
CRC: 0 FEC: 0 NCD: 1
LCD: 0 HEC: 0

[Downstream (RX) Interleave path]
CRC: 0 FEC: 0 NCD: 0
LCD: 0 HEC: 0

[Upstream (TX) Fast path]
CRC: 11 FEC: 68 NCD: 0
LCD: 0 HEC: 0

[Downstream (RX) Fast path]
CRC: 484 FEC: 0 NCD: 0
LCD: 0 HEC: 0

[ATM Stats]
[Upstream/TX]
Good Cell Cnt: 83860
Idle Cell Cnt: 44932747


[Downstream/RX)]
Good Cell Cnt: 335599
Idle Cell Cnt: 354795202
Bad Hec Cell Cnt: 278
Overflow Dropped Cell Cnt: 0

[SAR AAL5 Stats]
Tx PDU's: 650490
Rx PDU's: 800476
Tx Total Bytes: 88309516
Rx Total Bytes: 692609134
Tx Total Error Counts: 0
Rx Total Error Counts: 22


[OAM Stats]
Near End F5 Loop Back Count: 0
Near End F4 Loop Back Count: 0
Far End F5 Loop Back Count: 0
Far End F4 Loop Back Count: 0
#
#
Plusnet Staff
Plusnet Staff
Posts: 12,169
Thanks: 18
Fixes: 1
Registered: 04-04-2007

Should I upgrade?

These are the important figures

Quote
DS Line Attenuation: 43 DS Margin: 7


The Attenuation figure isn't too bad, it's on the borderline for a fixed rate 2Mbps service, but Max will often give higher than the fixed rate, however the Margin figure is pretty low.

By default BT will aim for the SNR to be 6dB which would mean that on Max your downstream speed probably won't be any faster and if that SNR figure goes down another couple of dB (which it can easily do) then you may even get a lower downstream speed.

The figure is a lot lower than I would probably expect so I would recommend checking all your wiring and filters and see if connecting at the master socket with nothing else connected to the line makes a difference. If you can find something that increases that SNR to maybe 15dB or higher than you shouldn't have a problem with Max, but at 7dB it's a bit low.
magicofthemind
Dabbler
Posts: 23
Registered: 30-07-2007

Should I upgrade?

Quote
I presume the modem is connected to a filter (and it doesn't get doubley filtered)? If not then that'll be the reason. If it is connected to filter then I'd suggest trying a different modem lead or swapping the filter to see if it makes any difference.



Thanks. I've tried changing the filter and the lead to the dial-up modem. I've also tried putting the leads for the two modems through different filters. No effect.

It seems that the two modems are somehow interfering with each other. Any ideas as to what may be causing this please?
N/A

Should I upgrade?

If one is a dial-up modem (ie old school 56k) then you must ensure that this goes into the voice side of the ADSL filter. (Its classed as voice as it uses audible tones only to communicate)

The ADSL modem should be the *only* thing plugged into the ADSL side.
magicofthemind
Dabbler
Posts: 23
Registered: 30-07-2007

Should I upgrade?

Yes, it's plugged into the voice side.
Plusnet Staff
Plusnet Staff
Posts: 12,169
Thanks: 18
Fixes: 1
Registered: 04-04-2007

Should I upgrade?

Sounds like it could be a fault with the 56k modem, worth checking the socket to make sure there's no dirt or something causing a "loop" the copper's touching. If you're able to try/borrow another modem then that would prove one way or another.
N/A

Should I upgrade?

I have also been told that I will be upgraded but reading all the stuff online is beginning to concern me. Should I stick at the 2MB service or go for the 8MB service?

Looking at my router stats they are as follows:

ADSL Link Downstream Upstream
Connection Speed 7616 kbps 448 kbps
Line Attenuation 26 db 8.5 db
Noise Margin 7 db 21 db

The noise margin is varying from 7db to 4db.

Any advice will be gratefully received. My current 2MB service has been great so I don't want to go for something that's supposed to be faster and then find I get something slower.