How does the C&W LLU speed selection work

OK with BT it was simple, you sync'd and you ran at a set ADSL/ADSL2/ADSL2+ line speed. You knew if you made the line better it would go to the next step up (most of the time ) and if you made it worse it would go down a step. Sometimes the speed was 'fixed' or 'stuck' at a step and would not move, but at least we knew the steps.

What is the logic / steps for the C&W LLU network?

In reply to a post by iand:

What is the logic / steps for the C&W LLU network?

If you're speaking about DLM, there isn't any.

The default profile 9db, will look at the line on sync and make a split second decision if to use interleaving or not - this can change from sync to sync. If it chooses interleaving, it will be at 8ms.

Some exchanges don't have:

- non-interleaved profile at all but their national fast profile trials are going well
- 6db profiles

Matt

Edited by uno (Sat 01-May-10 18:12:43)

LLU doesn't have the steps, and it doesn't have the delay in download speed increases when you get a higher connection speed.

So far as I know neither does C & W have the aggressive BT sync-time noise margin management, where a few problems like in a thunderstorm can cause a rise of several dB and 10-14 days to get each drop of 3dB to recover from it.

I think C & W is basically the same as O2/Be in that the maximum download speed is about 84% of connection speed. Most of that is hiddden inside the reduction caused by the BT IP Profiling system, as the overheads of 13%-18% on both systems are basically the same.

On O2/Be we expect to get that maximum 24/7. On C & W I don't know.

In reply to a post by RobertoS:

LLU doesn't have the steps, and it doesn't have the delay in download speed increases when you get a higher connection speed.

So far as I know neither does C & W have the aggressive BT sync-time noise margin management, where a few problems like in a thunderstorm can cause a rise of several dB and 10-14 days to get each drop of 3dB to recover from it.

I think C & W is basically the same as O2/Be in that the maximum download speed is about 84% of connection speed. Most of that is hiddden inside the reduction caused by the BT IP Profiling system, as the overheads of 13%-18% on both systems are basically the same.

On O2/Be we expect to get that maximum 24/7. On C & W I don't know.

C&W was fine when I was on Bulldog. The default margin was 9dB IIRC.
And they refused to accept payment too

Does look like the C&W network does have some form of SNR steps in it. I went from 9SNR up to 14 and have been stuck on this for a while.

Up Speed Down Speed SNR Margin Loop Att.
511 5976 14.0 29.0

I have had 'problems' with the line that now look to be fixed and was wondering how to get back down to 9snr/6snr

I would guess that the problems are fixed due to the profile applied. If a default profile is re-applied, the problems may come back?

Matt

I assume replacing the exchange line card means the 'problems' were not of the lines making and hence I could get the line reset to the default settings I think I will ask for that. I am getting a solid connection now and this is running with <= 1/200,000 error retry on the line.

In either case it does look to me that the C&W lines do have set steps it uses to correct line issues, it is just we do not know them.