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[bb billy]

Hi,
    First post. Have been reading forum topics and have found the discussions extreemly informative. I have been having frustrating problems with my connexion over the last 3 months and have picked up much useful info from this site and from personal experinces, which I have noted.

My connexion is now what I class as perfection, since my last find 2 days ago. Since then my sync has been locked at 8096, and the BRAS risen to 7000k from 5500k after only just 24hrs of being stable. I can only now keep my fingers crossed and hope my connexion remains stable , and now for the first time feel confident that it will do so. My stability has been acheived as my down noise margin on my Home Hub only varies betweeen 11 and 11.5 db. and approx 1crc and 1 hec error per hour. This I finally reached by changing out my cable from the BT block on my wall, direct to the NTE, rather than send it via the roof indoors, where I found it went into different types of cable to reach the NTE.
My question to any Knowledgeable person on this forum is :-

SNR/SNR MARGIN

With Max a target SNR margin is set on the DSLAM and its your router and the DSLAM that agree the best way of meeting this target margin. The target margin range is between 3dB and 15dB and rises in 3dB increments - although it is normal for it to fluctuate either side during the training period. The default is 6dB without interleaving.

The above statment is cut from this site, call anyboby tell me the answer to my question?

From your router/Hub stats ,how can you tell what setting the DSLAM and Router has set on your line?

The reason I ask is that I have found that if a 6db rate is applied then the full 8096 is sent from the exchange, and as the rate swiches down to 9,12, 15db then the output sync speed from the exchange is reduced by approx 800hz. per 3db drop.

I have a 6db interleaved on my line, but would like to know how this equates to my 11db margin I have at present. I know my line is set to 6db asI have gained some inside info,but would like to know how you can tell if this info from within were not availalbe.

BB Billy

[roseway]

Hi Billy and welcome.

As far as I know, the only way to tell from your router stats what the target margin is, is to check the stats immediately after a re-sync. At that point in time the actual margin should be very close to the target margin (unless of course you have a wildly fluctuating noise situation).

After the router has connected the noise margin will drift up and down, depending on noise conditions, so your level of 11 dB (compared to a target of 6 dB) suggests that your local noise conditions change a fair bit over time.

[bb billy]

Thanks for your reply.  I had read this on the forum somewhere,and hence checked my stats as soon as i re-syncd my line. as you can see from the enclosed info my line started at 11.5db and over the last 2days has never moved more than 11-11.5db.

Previously when I was loosing sync every few days my margin was varing by around a 8.5-2.5db swing, but the Dslam setting was always 6db interleaved. at this time I was gettinng many crc and hec errors along with errored seconds.  After doing the cable reroute my Hub just decided to go to 11db margin and stay stable.

Uptime:   0 days, 0:02:22
 

Modulation:   G.992.1 annex A
 

Bandwidth (Up/Down) [kbps/kbps]:   448 / 8,096
 

Data Transferred (Sent/Received) [KB/KB]:   110.00 / 558.00
 

Output Power (Up/Down) [dBm]:   12.0 / 19.5
 

Line Attenuation (Up/Down) [dB]:   17.0 / 33.0
 

SN Margin (Up/Down) [dB]:   23.0 / 11.5
 

Vendor ID (Local/Remote):   TMMB / TSTC
 

Loss of Framing (Local/Remote):   0 / 0
 

Loss of Signal (Local/Remote):   0 / 0
 

Loss of Power (Local/Remote):   0 / 0
 

Loss of Link (Remote):   0
 

Error Seconds (Local/Remote):   0 / 0
 

FEC Errors (Up/Down):   0 / 0
 

CRC Errors (Up/Down):   0 / 0
 

HEC Errors (Up/Down):   0 / 0
 

Line Profile:   Interleaved
 

[roseway]

In that case, it's almost certain that your target noise margin is now 12 dB. As a result of your earlier problems with instability the DLM process will have increased the target margin to stabilise the connection.

If your connection is now really stable, what should happen is that over a period of some weeks the target should be reduced again in stages, but I don't know exactly what the operating rules are for this.

[bb billy]

Many thanks again Roseway, I am having a little trouble getting my head around this one,so sorry if i am seem to be being a little dense.
From your last replyam I thinking on the right lines as follows:-

The exchange is set to 6db, as I am receiving the max sync speed available. (The max sync would be lower if it was permanatly set at 12db.)
As I had had sync problems, the line managment is trying me on 12db to see if the situation improves. ( which it certainly has, due to my new cable route,which was causing the instability )

In time will the line managment temp change my setting to 9db so as to see if stability can still be obtained.

If yes after a period thenwill it perhaps step to 6db to see if stability can be obtained.(This time with my cable fixed I feel there is a good chance it will )

If the answer is no to either the temp 9db or 6db am I thinking that the line managment will then having found its best setting reduce permanantly to that selected db setting, and consequently reduce the output sync speed to match.

I think I can see what I am trying to say I hope you canunderstand also. It seems a difficult thing to get your head around. (Pehaps I am looking into things to deep, and should just accept things more. )

Thanks Chris

[roseway]

The exchange is set to 6db, as I am receiving the max sync speed available. (The max sync would be lower if it was permanatly set at 12db.)

No, that's not right. The highest speed which can be achieved depends on the downstream attenuation as well as the noise margin. In your case the attenuation is a fairly low 33 dB, and a top speed connection is perfectly possible with the target noise margin set to 12 dB. I see that interleaving is enabled, which may slightly reduce the top connection speed - without interleaving you would probably get 8128 kbps, but the difference is so small that it's really not worth bothering about.

In time will the line managment temp change my setting to 9db so as to see if stability can still be obtained.

If yes after a period thenwill it perhaps step to 6db to see if stability can be obtained.(This time with my cable fixed I feel there is a good chance it will )

Maybe these things will happen, but the process doesn't seem to be well documented so I can't say with certainty that it will happen.

But as it won't make any noticeable difference to your connection speed there seems to be no advantage anyway. You have a stable connection at just about the highest available speed, so I would be tempted just to sit back and enjoy it.

[bb billy]

Thanks again,

                      I now have a slightly different angle of looking at the workings. As you state a lot of the workings are not well documented.

From my little experience with BB can I advise any reader who has a stability problem to check their cable from the point of entry to their NTE. If you can see it is in one piece OK, if your connection is not totally visable, do not assume it is all one piece with no joints.

Regards
Chris