Router that sets Sync Speed not Noise margin?

Does anyone have a pointer to either a piece of software, a model of
router or a router command line instruction, which allows the maximum
ADSL sync speed to be set rather than the target noise margin? (I know
DMT and Routerstats both allow the target SNR to be tweaked).

I have a fairly long (3.5km) reasonable quality line (Rx Attenuation
40db). The line is all overhead, and the noise levels vary by 4-5db
between day and night. I currently use an ex Sky DG834GT with the DGTeam
firmware which allows the Rx Noise target to be tweaked.
Currently the firmware is set up to re-establish connection in the event
of a loss at about 90% of the exchanges 6db target. That ensures it
resync's at 6300-6400 in the event of a dropout at night (to preserve
my 5500 BRAS profile).

Unfortunately if I get a dropout during the day when the line is at its
best (which happens occasionally - once per week?), the same setting
will resync at 7000+. This is OK during the day, but in the evening the
noise levels rise and the error rates make the line unusable ( it
doesn't drop out just has high retransmission rates (60 error seconds
per minute!!!) A manual resync drops the speeds to 6300-6400 and the
error rates go down to 1 or 2 per 15 minutes.

I would like to be able to tell the modem to resync at 6300-6400
regardless of the SNR at the time of the dropout. Any ideas how to do
this.
--
Peter R Cook

In message <(E-Mail Removed) >, Peter
Crosland <(E-Mail Removed)> writes
>
>> Does anyone have a pointer to either a piece of software, a model of
>> router or a router command line instruction, which allows the maximum ADSL
>> sync speed to be set rather than the target noise margin? (I know DMT and
>> Routerstats both allow the target SNR to be tweaked).
>>
>> I have a fairly long (3.5km) reasonable quality line (Rx Attenuation
>> 40db). The line is all overhead, and the noise levels vary by 4-5db
>> between day and night. I currently use an ex Sky DG834GT with the DGTeam
>> firmware which allows the Rx Noise target to be tweaked.
>> Currently the firmware is set up to re-establish connection in the event
>> of a loss at about 90% of the exchanges 6db target. That ensures it
>> resync's at 6300-6400 in the event of a dropout at night (to preserve my
>> 5500 BRAS profile).
>>
>> Unfortunately if I get a dropout during the day when the line is at its
>> best (which happens occasionally - once per week?), the same setting will
>> resync at 7000+. This is OK during the day, but in the evening the noise
>> levels rise and the error rates make the line unusable ( it doesn't drop
>> out just has high retransmission rates (60 error seconds per minute!!!) A
>> manual resync drops the speeds to 6300-6400 and the error rates go down to
>> 1 or 2 per 15 minutes.
>>
>> I would like to be able to tell the modem to resync at 6300-6400
>> regardless of the SNR at the time of the dropout. Any ideas how to do
>> this.
>
>
>Sounds like a classic case of RF interference caused by better medium wave
>propagation during darkness.What you need is a router/modem that can deal
>with high error rates without dropping the connection. It also seems that
>the exchange target SNR of 6dB is simply too high to give a reliable 24/7
>connection. Given the way the BT dynamic line management works what you are
>trying is unlikely to ever work successfully because you are forcing the
>equipment to work well outside the range at which it can function reliably.
>Having suffered a similar problem for many months and with much effort from
>BT the final solution was to use router modem designed for noisy and varying
>quality lines. Having used various Draytek, Netgear, Dlink and ZyXel I ended
>up using 2Wire 2700HGV. I since installed these at two other problem sites
>and they really are the dog's gonads. My line will not reliably support more
>than 2500 but the 2wire stays synced day after day at 3,500. You can pick
>one up on eBay for around £20 or so where you will find them badged as BT
>Business hubs. BT do have a prototype filter that reduces the effect of
>severe RF interference which is in the form of an ADSL filter faceplate for
>NTE5 sockets but I doubt you will get that installed on an unbundled Sky
>line!
>
>Peter Crosland
>
>
Thanks Peter for the input. I agree with your diagnosis that its Medium
Wave RF at night. It's not an unbundled Sky line, I simply use an ex-Sky
router bought from E-bay for £10 and reflashed with the DGTeam firmware.

The line is a BT line, and at 6300-6400 it is more than sufficiently
reliable for my needs. Once established at that speed it drops once or
possibly twice a week [usually as the result of a big noise spike which
I presume comes from one of the agricultural workshops dropping the arc
welder or something ].

Its just that when it does so I want it to reconnect at a speed that
gives 5 or 6dB at night. If the drop does occur at night then all is
well. Its when it happens during the day and I get a 7000+ (I have seen
as high as 7500ish running reliably at v low error rates during the day)
sync speed the router will hang on to the line very well at night, its
just that the error rates skyrocket and retransmission causes the real
throughput to go to hell in a handbasket.

I am actually very happy with 6300-6400 ( and a 5500 Bras profile) give
where I live. Its a fair bit higher than my neighbours get, and is the
result of taking some care with the internal wiring.

I will try for a 2700HGV and see whether that deals with the problem.

Thanks
--
Peter R Cook

Martin² wrote:
>>> Is there some software (like DMT) to set SNR for the 2700HGV ?
>>> Or the 1801HG ?
>
>> Not that I am aware of. In any case experience suggests that it is
>> counterproductive to do so.
>> Peter Crosland
>
> My line previously run at 2.8M/s at 6dB SNR, with random and fairly frequent
> disconnections. The 1801HG I use still worked at 1dB, so when it
> disconnected it was with good reason and higher SNR made no difference.
> Now BT got me stuck at 1.7M/s at 9dB and I STILL get the disconnections,
> 'cos at times there is noise on the line.
> I would like to be able to set the SNR at 7.5dB, or if that is not possible
> then 6dB, which was OK with me.
>
> What ADSL modem (router) can do that ?
> TIA
> Regards,
> Martin
>
>
My *guess* is that only a top end system like a Cisco might have a chance.

I hear what you are saying, and I have similar issues. MOSTLY I am
stable at 4Mbps, but sometimes a short burst of noise (typically the oil
boiler firing, or a room stat arcing: both produce heavy duty sparks)
knocks the thing off, then it will resync at a far higher rate, and go
unstable till it randomnly synchs again at a sensible rate.

The algorithms work well for sustained noise, but fall apart under burst
conditions. Ive got electrical noise here from the CH system, and it
makes use of it and broadband a less than ideal experience. One day I'll
put filters everywhere..