Kitz Forum

Broadband Related => Broadband Technology => Topic started by: jid on October 31, 2008, 10:28:49 AM

Title: DMT Lpair Settings
Post by: jid on October 31, 2008, 10:28:49 AM

Hi All,

Could someone tell me what the Lpair settings do in DMT?

Also, what is Bitswap and should it be on or off?

Many Thanks

Jamie

Title: Re: DMT Lpair Settings
Post by: HPsauce on October 31, 2008, 11:12:38 AM

Thios is what my DGTeam firmware has to say:

Loop parity check
This option sets up the loop parity check. This is a way to test if errors have occurred during a data transmission.
The parity check can be inner (default) or outter.
--------------------------------------------------------------------------------
Bitswap
If supported, gives more reliability to ADSL line, trying to equalize noise margin on all frequencies.
Default setting is enabled.

Title: Re: DMT Lpair Settings
Post by: jid on October 31, 2008, 11:17:24 AM

Thanks for that HPSauce :D

I have switched Bitswap on now to see if it improves anything

Title: Re: DMT Lpair Settings
Post by: kitz on October 31, 2008, 11:41:09 PM

>> Bitswap and should it be on or off

Is this just in DMTtool you are talking about?

I could be wrong... but AFAIK all routers perform bitswapping by default as its part of the g.DMT standard (adsl1)
Very simply its a way of keeping the line more stable by constantly monitoring the frequency bins (carriers) in use and reusing them if possible. 
Theres a minimum amount of bits in a channel.. and if the bits fall too low (say if you had a quick noise burst at a certain frequency) then the router could mark that channel as unusable which may cause the line to loose connection. A carrier bin (or tone) needs a minimum of 2 bits = 6dB of SNR to be usuable.
With bitswapping the router can swap the bits around and redistribute the bits to other channels.

If you mean the "bitswap" tickbox under the graphs in DMTtool afaik that doesnt actually change any of the settings on the router.. its simply allows the graph to plot the bitswapping as it occurs

Title: Re: DMT Lpair Settings
Post by: broadstairs on November 01, 2008, 08:30:46 AM

At the risk of saying something dangerous, it is possible to set bitswap on or off if you telnet into some routers and issue the commands manually, the adsl command on the DSL-2740B certainly does allow this. In fact you can set just about everything with this command. However be very careful doing anything like this, only saving grace is that a reboot is likely to get you back to square one if you mess up.

Title: Re: DMT Lpair Settings
Post by: jid on November 01, 2008, 08:38:19 AM

Quote from: broadstairs on November 01, 2008, 08:30:46 AM

At the risk of saying something dangerous, it is possible to set bitswap on or off if you telnet into some routers and issue the commands manually, the adsl command on the DSL-2740B certainly does allow this. In fact you can set just about everything with this command. However be very careful doing anything like this, only saving grace is that a reboot is likely to get you back to square one if you mess up.

Yes, I worked out that so I have left well alone ;)

All I have changed is the Target SNR, bitswap was on by default as you said Kitz so there was need for me to check :)

Thanks guys

Jamie