Kitz Forum

Broadband Related => Broadband Hardware => Topic started by: Solstice on November 03, 2009, 02:20:04 PM

Title: How many errors are acceptable with a router
Post by: Solstice on November 03, 2009, 02:20:04 PM
These are the stats for my BT Voyager 2110 and I was just wondering should I be worried about the number of errors I'm getting?

I haven't noticed any problems while surfing/online games or corrupted downloads so are these errors within acceptable limits? (I don't really understand what they mean.)

I realize that they are because Ive forced a high sync speed with telnet and that in turn has given me a low downstream noise margin.

(https://forum.kitz.co.uk/proxy.php?request=http%3A%2F%2Fimg22.imageshack.us%2Fimg22%2F5521%2Fsnag001b.jpg&hash=76530e45c0956a12d133132c078c49bcda091258)

EDIT!

wow, after posting that picture I noticed that it says Trellis is switched off, shouldn't that be switched on? Im pretty sure it used to say "ON" but I haven't done anything to switch it off...

Should I try to switch it back on with the "adsl configure --trellis on" command in telnet
Title: Re: How many errors are acceptable with a router
Post by: waltergmw on November 03, 2009, 02:54:02 PM
Hi Solstice,

I don't think I would worry too much with those errors over a 13 hour period.

Here's a picture of a line I'm monitoring and the end user hasn't complained at all.

Kind regards,
Walter



[attachment deleted by admin]
Title: Re: How many errors are acceptable with a router
Post by: roseway on November 03, 2009, 03:07:08 PM
Quote
wow, after posting that picture I noticed that it says Trellis is switched off, shouldn't that be switched on? Im pretty sure it used to say "ON" but I haven't done anything to switch it off...

Should I try to switch it back on with the "adsl configure --trellis on" command in telnet

You could try, and it won't do any harm, but it may force your router to reconnect. There have been a few discussions on this subject recently, and it's not at all clear (to me at least) what the real situation is. It may be simply that the router isn't reporting the correct state of trellis coding. If it were really not enabled, I think your connection would probably be a lot less stable.
Title: Re: How many errors are acceptable with a router
Post by: roseway on November 03, 2009, 03:19:38 PM
As a postscript to the above, I just checked my own router (DG834GT with DGTeam firmware) and it also shows trellis as OFF. I tried the command adslctl configure --trellis on and it did force the router to drop the connection and reconnect, and after this trellis was still shown as OFF. My connection is currently very stable, so I tend to believe that the router isn't reporting the state of trellis coding correctly.
Title: Re: How many errors are acceptable with a router
Post by: Solstice on November 03, 2009, 03:40:36 PM
Ok :) thankyou walter & thanks again Roseway! you guys are awesome  :thumbs:
Title: Re: How many errors are acceptable with a router
Post by: kitz on November 03, 2009, 04:11:27 PM
If you have an interleaved line - which will have RS error correction switched on...  then trellis may not always be picked up by the router.

Quote Error Correction (http://www.kitz.co.uk/adsl/error_correction.htm#Error_Correction)
Quote
Convolutional coding is efficient at correcting random or white noise errors with little overhead, but doesn't fair well if a longer noise burst disrupts the sequence making the path impossible to recreate.
(See Trellis Coded Modulation (http://www.kitz.co.uk/adsl/error_correction.htm#Trellis))

Block coding is better suited for burst errors as it utilises more parity bits, but the downside of block coding is the redundancy increases bandwidth and delay. (See Reed Solomon encoding (http://www.kitz.co.uk/adsl/error_correction.htm#RS))

Both of these methods work independently but can be combined so that any burst errors resulting from convolutional coding may be caught by the block coding.
Concatenating these two different coding methods gives a high degree of correction. It's usual for the convolutional code such as TCM to be the "Inner code" whilst a block code such as RS is classed as the "Outer Code".


Also applying Interleaving to the block code, in order to scatter the errors from noise bursts, gives near optimum performance.


if both are applied/combined, because TCM is the inner coding..  the router may not necessarily be aware that TCM is actually in use and just picks up on the RS encoding.

Title: Re: How many errors are acceptable with a router
Post by: jeffbb on November 03, 2009, 10:40:46 PM
HI
My router DG834GT with Netgear firmware is showing Trellis as "on".
regards Jeff