Max rate Premium 880 up

have been working on a few max rate premium circuits recently, seem to get very low snr upstream on this product, typically 3db upstream, the line is about 3.8k/m and has a downstream loss of 45db with an snr of 12.5db, downstream speed is 5.7 meg.
Diagnostics have sent the fault to OR to check suspect low up snr of 3db.

line is stable with no errors at all at e/u, helpdesk said that they wanted us to check the circuit at the exchange with loads and without.

I dont think there is anything wrong with the circuit as every max premium circuit i have worked on has a low up snr.

At the exch the snr was the same with 60db attenuators 3.5db snr and without them it was only at 4.5db.

No one in the helpdesk or BOU can tell me what i should be getting.

The question I am after an answer to is , can someone explain why we have such a low snr on this 880k max premium , is this correct or is it that we are only seeing results on circuits that are faulty.

I dont think the line is faulty as it passes Hawk pair quality checks and the e/u is complaining of loss of internet session and has to reboot his router to get the session going again, he never loses sync at any time when his problem arises on this lynksys router.


many thanks in anticipation

max premium is 832k upstream, innit ?

In achieving that the SNR margin will be reasonably low, especially on a long line. It should however synch at 6 dB margin with as lower speed than 832k rather than have a 3 dB SNR.

Try a different bit of kit to see if the result is the same, or ask someone to read off what the DSLAM thinks the upstream SNR is.

many thanks for the reply.
my problem isnt about achieving the 832 up speed, it is should the upstream snr be as low as 3db, on all the max premiums i have worked on it has always been low, but as i say i only get to work on them when they are reporting some kinds of fault, which each time we have put our kit on and not seen any problems at all .

it is the s/p that is sending us out for a low upstream snr, so they are seeing 3db even with the e/u kit in sync and assuming it is a faulty line in openreaches remit.

when we co-oped with the s/p today it was clear that they had no idea what the snr SHOULD be on a max premium 832 product, and whether this was proper to this product.

the 3db up snr is the same at the exch as well as out at the e/u, and this can be seen via the diagnostic teams (whoosh tests ???? if they use it ) and our remote Apts kit.

Didnt know that they could set the upstreamsnr on a max product, even the 440 standard max, i thought they only set the downstream snr.

still unsure from your response whether 3db ( low up snr ) is standard on the max product or whether is is a sign that it is faulty.

3 dB is not standard, 6 dB is standard on BT Wholesale Max Premium.

If it can't do 832 at 6dB or more then it should slow down to a lower speed and 6 dB. If it syncs at 6dB then sees more noise it will report less than 6 dB of course.

I'm not clear if this is LLU as 880 isn't a Wholesale speed.

If it's BTw you should ask a Wholesale tech to get the SNR off the DSLAM - they can access trends with time etc. I have had 6 dB upstream SNR margin reported on the CPE and the DSLAM has seen 9 dB for example. The upstream is set and measured at the DSLAM.

A low upstream SNR can't really be an Openreach problem on a rate adaptive service. The DSLAM and CPE set and arrange the SNR. If the line had issues then the speed would be lower than it ought to be for the line length.

Last week I looked at a Max Premium line that wouldn't connect unless the phone was off-hook. When off-hook it was at 64k upstream and 6 dB SNR. Another line across the road connects happily at 832k :-

Connection Speed 3904 kbps 832 kbps
Line Attenuation 52 db 15 db
Noise Margin 10 db 8 db

so we got Openreach to address the line issue and now the line is solid at 832 upstream also.

To summarise, the CPE and DSLAM should sync to achieve their target margin by reducing the speed accordingly. If the SNR is low it is either a) the target is low b) noise has increased since syncing or c) it isn't rate adaptive and has a fixed upstream speed.

I wonder then, if the Voyager105/APtS software is giving poor/duff readings ? Mine will always report a downstream snr of 2 to 2.5db higher than the target, and like Smifffy will always shows low upstream snr on a Max premium circuit.

Phil, the 880 Smiffy refers to was just a generalisation, it was a BTw product he was working on.