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shaaaaaamo
Aspiring Contributor
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Message 1 of 13

Line Rate vs Attainable Rate?

So, I've had infinity for appraoching 18 months now, and live a considerable distance from the Cab.

 

I unlocked the modem almost immediately and despite my distance I achieved full sync of 39999 (not on I2) and an upload of 74xx which I was over the moon with.

 

The attainable rate has always been around 45mb so decided it was not worth upgrading to 80mb.

 

However - over the recent months I have notived that there is a BT van parked at the exchange just about every other day (or so it seems!), and my line rate is slowly plummeting.  The lowest its been is 20mb and its currently hovering around 32mb. 

 

Yes the speed is ok, but its not what I used to enjoy.  SNR is 6.1db.  Why would line rate start a slippery slope of decline but the Attainable still stay as it used to?

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12 REPLIES 12
Distinguished Expert
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Message 2 of 13

Re: Line Rate vs Attainable Rate?

The decline may be to do with crosstalk, which has a very bad effect on vdsl2. But I'm struggling with the obsession with attainable rate that everyone has as this is just a calculation based on ideal line conditions, presumably the speed for the attenuation at 0dB snrm.

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Ratty2012
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Message 3 of 13

Re: Line Rate vs Attainable Rate?

I think this is one of the reasons why the openreach modem was locked so that people did not get obsessive over attainable rates.

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Guru
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Message 4 of 13

Re: Line Rate vs Attainable Rate?


@Ratty2012 wrote:

I think this is one of the reasons why the openreach modem was locked so that people did not get obsessive over attainable rates.


Not true, if they were displayed in the hub attinable isn't displayed. Only sync speeds, errors and noise margins are displayed.

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Ratty2012
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Message 5 of 13

Re: Line Rate vs Attainable Rate?


@ryant704 wrote:

@Ratty2012 wrote:

I think this is one of the reasons why the openreach modem was locked so that people did not get obsessive over attainable rates.


Not true, if they were displayed in the hub attinable isn't displayed. Only sync speeds, errors and noise margins are displayed.


I did not say the hub, I said modem 😛

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Guru
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Message 6 of 13

Re: Line Rate vs Attainable Rate?


@Ratty2012 wrote:

@ryant704 wrote:

@Ratty2012 wrote:

I think this is one of the reasons why the openreach modem was locked so that people did not get obsessive over attainable rates.


Not true, if they were displayed in the hub attinable isn't displayed. Only sync speeds, errors and noise margins are displayed.


I did not say the hub, I said modem 😛


The stats are displayed in hub, like they were when the service was first released. Hence this leading to locking the modem as people found tutorials online on how to get there stats from there. Now we are in unlocking phase of the modem.

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chrcoluk
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Message 7 of 13

Re: Line Rate vs Attainable Rate?


@legitimise_sailing wrote:

The decline may be to do with crosstalk, which has a very bad effect on vdsl2. But I'm struggling with the obsession with attainable rate that everyone has as this is just a calculation based on ideal line conditions, presumably the speed for the attenuation at 0dB snrm.


people are obsessed as its a product they have paid for and noone likes to see a declining service.  I agree the reported attainable rate is a guess by the modem, it guesses I believe based on the amount of available snrm above the target snrm.  so one can have an attainable sync below their actual sync. if eg. their noise margin in 5.5db and the target noise margin is 6db then the attainable will be lower than the current sync speed.

 

I think its harsh to tell someone whos signal strength has gone from 45mbit down to 20mbit as obsessed as thats a serious degradation.

 

BT do seem to have higher crosstalk issues than the international average, which doesnt say much about the quality of the local loop.  But whats also possible is BT could be using power back in the dslam equipment which will also reduce attainable sync speeds.  Its possible BT configured power cutback to try and combat crosstalk but have been a bit overzealous with it, or it could all be crosstalk which is pretty severe if it is.  Vectoring is a technology that is expected to massively improve crosstalk loss but no sign of it yet in on BT's service.

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shaaaaaamo
Aspiring Contributor
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Message 8 of 13

Re: Line Rate vs Attainable Rate?

I think most of the posters have missed the point entirely...

 

my connection speed i.e. line rate and hence profile has declined by almost 50% for no obvious reason. (not obvious in that attainable is not impacted.

 

im not a connection junkie obsessed with any kind of rates, I Just want what I pay for and what I used to get.

 

as it happens, this is about the 3rd time in 18 months I've bothered looking, specifically because my On Demand is dog slow and on speed testers I'm struggling to get about 3-4mb.

 

 

can I assume there is no useful insight beyond the possibility of the Cab getting loaded up and cross talk?

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Guru
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Message 9 of 13

Re: Line Rate vs Attainable Rate?

There are very similar posts to yours, your best option would be to contact the moderators.

 

They will take personal ownership over your case until it's resolved, they normally take 3 days to respond.

 

You can contact them here.

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Matt197
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Message 10 of 13

Re: Line Rate vs Attainable Rate?

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