ADSL Stability

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Glynn

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Topic # 14625 12-Jul-2007 16:55

Hi,

I live in a semi-rural area, about 5 KM from the local exchange (so Telecom says). Ever since we have had Telecom Broadband installed (~3 years ago) it has varied greatly in stability. Some times, for months at a time, it will be fairly decent, other times, it can "disconnect" from the exchange as often as once/minute for days. On average it will disconnect 10 times a day. By disconnect I mean the "Status" and "ADSL Link/Act" lights will fade out completely. Sometimes it reconnects on its own after ~30 seconds, but mostly it will not and the only way to get it to reconnect is by dialing up.

We have been to Telecom several times about this in the past, and they have not been much help. We've checked filters, reset modems, filled out speed tests and other modem checks, and even had a Splitter installed for $150, but nothing has helped the problem.

I have to assume, now, the problem is in the lines themselves. I guess they're probably old and the distance from the exchange is what causes the disconnections. So, my questions are, if someone can help:

1) Do you think the problem is in all the lines, or personal house-only lines?
2) Is there some other checks/problems that can be investigated?
3) Can I ask something else of Telecom to improve it?
4) If all else fails, is there some sort of hardware component that will amplify or boost the reception from the exchange to make it more stable?

And, if not, will moving to another ISP help at all, or even make it worse?

I will appreciate any help as this really has me at the end of my wits.

Regards,
D. Glynn.

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Reply # 78054 14-Jul-2007 12:49

The standard ways of troubleshooting these faults are changing the pair between DSLAM (access multiplexor) and your demarcation point, changing the port on the DSLAM. Have Xtra/Telecom swap the router for one that they use for troubleshooting/logging faults, probably a Cisco.

You have to be very very persistent and deal with their level 2 fault people. Also ask any close neighbours about the reliability of their service.

Ross

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nakedmolerat

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Reply # 78070 14-Jul-2007 13:55

heya,sorry to hear about your problem.. I have 3 friend who experience similar problem. 1 in auckland,1 in wellington and 1 in dunedin. All 3 use telecom as their isp. For my friend in auckland,she rang telecom abt dis problem almost everyday. I told her to change the mode ADSL2+ to adsl and it works for her-no more connection drop. Same goes to my friend in wlgtn. Changin the mode seems to fix the disconnection problem. However,my friend in dunedin,changing the mode like others did,didnt fix the problem. He change to slingshot and experience similar problem. After one complaint to slingshot,problem solved! If you havent tried changing the mode from adsl2+ to adsl, you might want to try that first.

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Reply # 78076 14-Jul-2007 14:30

nakedmolerat: heya,sorry to hear about your problem.. I have 3 friend who experience similar problem. 1 in auckland,1 in wellington and 1 in dunedin. All 3 use telecom as their isp. For my friend in auckland,she rang telecom abt dis problem almost everyday. I told her to change the mode ADSL2+ to adsl and it works for her-no more connection drop.

Given most ADSL routers, including the Dlink ones don't allow one to switch between G992.5 (ADSL2+) and 992.1 (G.DMT) maybe you could provide more advice on configuring these routers. Using G.Lite (G992.2) had been rumored to solve this problem but many ADSL routers don't allow any choice. Only a handful of exchanges are even ADSL2+ enabled so the routers won't be using G992.5 anyway, http://www.telecom.co.nz/whstream/0,8768,205569-204216,00.html?link=rdt

Ross

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stuzzo

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Reply # 78097 14-Jul-2007 17:47

I live in a semi-rural area, about 5 KM from the local exchange (so Telecom says).

5km is probably getting to the the limits for ADSL so this is at least likely to be part of the problem. Most graphs disappear into the null at about 6-7km.

paradoxsm

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Reply # 78126 14-Jul-2007 22:56

funny question, can one make a dsl router connect at a slower, more reliable speed like at 1mb and get it to produce more consistent results?
Like the dial up modems of old works flawlessly when manually dropped to 28.8.

I'd go for a big read up but my nokia n95 is my current sole internet terminal.

stuzzo

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Reply # 78133 15-Jul-2007 04:04

paradoxsm: funny question, can one make a dsl router connect at a slower, more reliable speed like at 1mb and get it to produce more consistent results?

Like the dial up modems of old works flawlessly when manually dropped to 28.8.

I'd go for a big read up but my nokia n95 is my current sole internet terminal.

I'm not that clued up on the finer details of dsl modem operation but I believe they do test the line and attempt to operate within it's bandwidth limitations.

The basic problem is that twisted pair lines are not very well suited to high frequency communication. They are cheap to manufacture, easy to handle and have served their purpose well for basic phone cable but have several drawbacks, namely, wide variation in impedance (typically 10-15%) and high susceptibility to electromagnetic radiation and cable cross-talk. The boffins have developed sophisticated transceiver technology to get the most out of them but they are close to the limits.

It's interesting to note that co-axial cables are much more suited for running high frequency signals and it has been suggested that they would have been a better choice for the HDMI standard.

Niel

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Reply # 78148 15-Jul-2007 10:28

We need to clarify something here:

Twisted pair is used for Ethernet at speeds over 1Gbps. ADSL2+ goes up to 2.?MHz. It is not susceptible to far field EMI, because with every twist the induced noise cancels the noise in the previous twist (consider each twist as a small loop with opposite orientation, then you will understand). The twisted pair has an impedance of either 300 Ohm or 600 Ohm, can't remember exactly at this point. Coax has an impedance of 50 Ohm, and is much more susceptible to contact resistance in connectors. Maybe coax cable is more stable (due to mechanical stability), but is not practical for consumer use.

The development of ballanced line drivers/receivers is ancient. There is no new development in the drivers/receivers. The development is in the DSP processing of the signals, doing it faster and cheaper because old technology is actually more expensive than new technology. The designers are forced to redesign their products to reduce cost.

RS485 is an acynchronous ballanced communication interface standard that is older than any of us on this forum, and that is the basis for the ADSL interface.

You can never have enough Volvos!

stuzzo

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Reply # 78178 15-Jul-2007 13:53

Don't want to trash this thread with a technical discussion but I am right in what I said. Unshielded Twisted pair is at it's limits, it doesn't work well at high frequency. They have achieved Gbit (even 10 Gbit) speeds over ethernet (shorter distances than ADSL obviously) but that is by introducing shielding, sophisticated transceivers and software for error correction etc and using all of the pairs.The incentive is to maintain existing infrastructure and cabling.

At gigabit speeds coax and fibre are better mediums, fibre obviously for long distance.

Glynn

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Reply # 78332 16-Jul-2007 17:13

Spyware: The standard ways of troubleshooting these faults are changing the pair between DSLAM (access multiplexor) and your demarcation point, changing the port on the DSLAM. Have Xtra/Telecom swap the router for one that they use for troubleshooting/logging faults, probably a Cisco.

You have to be very very persistent and deal with their level 2 fault people. Also ask any close neighbours about the reliability of their service.

So I need to ring Xtra and ask them to provide a "troubleshoot router" to try and find line faults?

And I don't have ADSL2+ so that's not an issue.

Thanks for all the replies :)

inquisitor

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Reply # 79184 22-Jul-2007 11:44

You should ask your provider to switch your line to ADSL2+ if available.

ADSL2+ definitely lowers signal attenuation and so improves connection stability even on long lines like yours.

Three of my friends, who live 5-6 km away from their local exchange and so only got a downstream of 384 KBit/s to 1 MBit/s, today have 1 to 2 MBit/s with ADSL2+ plus connections are more stable. One of them had 59 dB downstream attenuation with ADSL, which improved to 48 dB after switching to ADSL2+.

The reason is that ADSL2+ uses double frequency spectrum and so compensates interferences better than regular ADSL. Recently I wrote an article about ADSL2+ in my blog, which may interest you.

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Niel

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Reply # 79201 22-Jul-2007 13:57

Also note that with ADSL2 and ADSL2+ the transmitting power of each frequency channel is dynamically controlled and lowered to the minimum required. This means that when your exchange is upgraded to ADSL2+ you will suddenly have less crosstalk when the neighbour's modems are rebooted and connect at ADSL2/ADSL2+.

I do not think your service provider is in control of switching you to ADSL2+, rather it will happen whenever Telecom has upgraded your exchange, done their trials, and then enabled the profile on all the lines (of that exchange). My ISP told me I'm already on ADSL2+, but it was only a week later that Telecom enabled it for everyone. When Telecom enabled it, they also made some adjustments and all of a sudden my line stays up all the time as opposed to 10 to 20 drops per day!

You can never have enough Volvos!

Glynn

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Reply # 80197 29-Jul-2007 12:14

ADSL2+ is not available in my area, and knowing Xtra, it won't be before I die...

If this helps to pinpoint an error, whenever it does disconnect, I have to dial up to get it reconnected. If it disconnects at night, it won't reconnect till I dial up next morning. I heard this could show filter errors?

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Reply # 80202 29-Jul-2007 12:23

If you have had a splitter installed you have a dedicated ADSL outlet to connect your router to, in which case you will NOT be using any filters on your phones. If you have installed a filter to allow a phone to be connected on the dedicated ADSL outlet then please remove it - at least to eliminate a fault.

Ross

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Glynn

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Reply # 80247 29-Jul-2007 18:13

Spyware: If you have had a splitter installed you have a dedicated ADSL outlet to connect your router to, in which case you will NOT be using any filters on your phones. If you have installed a filter to allow a phone to be connected on the dedicated ADSL outlet then please remove it - at least to eliminate a fault.

So remove all filters from my house? The splitter jack has one, but only a dialup and the modem lines connected. All other outlets still have filters, though.

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Reply # 80270 29-Jul-2007 20:45

Any additional filters connected to phones on the splitter's filtered output can be removed as they serve no purpose. As for the splitter's unfiltered output - if indeed the dialup modem initiates reconnection of ADSL then I would remove the filter on this outlet (Dick Smith sell RJ11 to BT adaptors if you need one to connect the ADSL router ONLY directly to the outlet) and test for several days. Post results.

Ross

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