ADSL sync and connectivity issues

[mongo66]

Hi folks,

It all began one evening... While viewing videos on YouTube, I experienced a loss of ADSL sync. After a several subsequent connection dropouts, sync-up could not be established. So I switched off the ADSL modem and unplugged the power adapter. After letting the device 'rest' for half an hour, I was back in business. However, connectivity issues persisted and got worse as time went by. I also tried plugging the modem directly into the wall socket, but to no avail. This 2-Mbit ADSL connection has served me well since day one. Good ADSL service is hard to come by in South East Asia. I've been using it for over a year without any problems.

I contacted my ISP, they told me everything on their end was "fine" and suggest I do a hard reset on the ADSL modem. I told them it didn't work as I had already reset the device beforehand... The technician then changed my connection profile to 1024/512. When I informed him there still was no sync, he asked me to leave the phone "off-hook" and try again. To my surprise, the phone off-hook trick worked on both connection profiles... The technician explained I might be experiencing a "high open" issue and suggested I contact my telephone company.

Now I'm thinking, what the hell is a "high open" ? After Googling, I came across this article. So without further delay, I proceeded to test NID the modem. With ADSL modem connected directly to the NID, 2048/512 sync was achieved in less than a minute. Next, I connected the splitter (modem > splitter > NID) also with positive results. But upon reconnecting the phone (to wall socket), I could hear "static" through the handset. I quickly came to the conclusion - faulty internal wiring. So I rewired my home over the weekend. It was long overdue, the old phone wiring in this house has been around since the mid-1990's. Rewiring got rid of the static. Connecting the modem to the new wiring I was able to achieve and maintain full ADSL connection with the phone on-hook. But after a while, dropouts started to occur and (re)sync took longer and longer. Reluctantly, I took the phone "off-hook", now the connection seems to be stable once again.

Some observations...

With phone "on-hook", I lose sync within a half hour. After connection dropout, ADSL (re)sync is VERY slow... sometimes it won't sync at all (ADSL light flashes continuously). When sync is achieved, the data rate varies from full speed (2048/512) to xxx/512. Downstream SNR margin is also very low -- anywhere from 5.0 to 8.0 db. However, if I powered off the ADSL modem and turn it back on, 2048/512 sync is achieved with downstream SNR margin of 13.0-13.5.

*** Typical line stats with phone "on-hook" ***

Mode: G.DMT / ANNEX A
SNR Margin (Down/Up): 13.0 / 18.0 db
Line Attentuation (Down/Up): 58.0-60.0 / 31.5 db

With phone "off-hook", it takes about 20 sec to 1 minute to achieve sync. Dropouts are at a minimum; connection is very stable (or so it seems). Downstream SNR is slightly better, ranging 14.5 to 16.5 db.

*** Typical line stats with phone "off-hook" ***

Mode: G.DMT / ANNEX A
SNR Margin (Down/Up): 15.0 / 20.0 db
Line Attentuation (Down/Up): 58.0-60.0 / 31.5 db

With my old ADSL modem, line attenuation (downstream) was in the 48-50 db range. Ever since I had the Billion 5210s router-modem, line attenuation reads 58-60 db... Yes, I do live pretty far from the exchange (4-5 km). Just wonder why there's a large discrepancy in attenuation readings between the two modems... I also notice a sharp increase in CRC and HEC errors while using the Billion 5210s as well. As of this posting, Billion 5210s performance stats are as follows:

near-end FEC error interleaved: 7941
near-end CRC error interleaved: 456
near-end HEC error interleaved: 2900

far-end FEC error interleaved: 49
far-end CRC error interleaved: 44
far-end HEC error interleaved: 61

Error second in 15min: 5
Error second in 24hr: 107
Error second after power-up: 107

ADSL uptime: 2:18:44

---------------

Data Rate: 2048/512
Mode: G.DMT / ANNEX A
SNR Margin (Down/Up): 15.0 / 20.0 db
Line Attentuation (Down/Up): 59.0 / 31.5 db

Phone is off-hook, btw. What really concerns me are the CRC and HEC errors. These numbers are extremely high. I've contacted the phone company and requested a line check...

What are your thoughts? Suggestions welcome.

Edited March 10, 2009 by mongo66

[Tripredacus]

My first thought is heat. I know my modem seems to get very warm for such a little thing.