India Broadband Forum

gtdaqua

I have researched quite a bit on the dropping ADSL connection in DG834x models. I have tried ALL combinations of
LLC/VC, ADSL2+/G.DMT, PPPoE/PPPoA.
I am using a DG384G on a PPPoE connection with repeated drops on the ADSL connection. I have isolated the telephone and not using a splitter.
The netgear statistic page reports the following values:

Downstream/Upstream
Line Attenuation 33 db 9.5 db
Noise Margin 30 db 10 db

Attenuation is good - lesser, better; noise value is inverse- higher, better; Minimum required noise margin value on today's DSL link is 12db.
Whenever the conneciton drops below 12 (my upstream is 10db as above), my internet connection will become unstable. It might drop anytime.

Surprisingly, when I use my ISP's beetel router/modem, I see different values:
Downstream Upstream
Attenuation (dB): 35.0 19.1
SNR Margin (dB): 23.3 12.9

Now the above meets minimum requirements and the link is perfectly stable - no drops, ever! So, why wud Netgear see the
noise margin as 10db (intermittent drops) while the ISP modem will see as 12.9? The cables are the same.

What could be wrong? NetGear or ADSL Link? Linksys WAG200G drops the connection too due to the same reason.

Bump. Anybody?

essbebe

explain please.
confirm:
Using telephone/s but not using an ADSL splitter anywhere.
para two ;
SNR ,SnrMargin, Noise, Noise margin, Attenuation
mean different things . Research.

gtdaqua

Not using the phone or ADSL splitter anywhere.

Netgear rotuer statistics page says:
Noise Margin 24 db 8 db (Downstream, Upstream).

As per Cisco, the measurement of Noise on the line is known as the Noise Margin which is also called as Signal to Noise Ratio or SNR. So, they are not different. So in my case SNR or Noise Margin (or Noise) is differing between two ADSL modems.

Thank you for your response. You are the only one who has replied.

essbebe

Being Airtel forum not many problems are reported, and users might have missed this post.
I have both Airtel and BSNL BB , and normally check both forums.

If you see the splitter diagram , the Data line goes directly to the modem.

http://i34.tinypic.com/s4c0me.jpg

At the same time a low pass filter for voice frequencies is incorporated, which effectively prevents data signal leaking into the phone ( also a High impedence path, to prevent loss of signals in telephone line)
Try the measurements with an ADSL splitter /telephone in circuit.

reference :
<--- Kitz - 404 ---> extract:

Another tweak is to select Mod mode.
ADSL2+, GDMT/, T413/, Glite etc seem to affect. SNR margin and Attn level .

For records:

gtdaqua

Thank you, that was very informative.

I tried ADSL2+ and G.DMT. ADSL2+ is the best I could get. I tried with the splitter too. Same results!

You have a good SNR margin 31.3 and 12. I have 31 and 8! 8 is too low. But the connection is stil stable. I don't know if disconnecitons would happen again.

One more thing, do electricity power affect ADSL links? Because, my adsl goes does down in the night when we see low voltage fluctuation - the modem is on through out and the LAN stays ON. But the ADSL drops, connects and repeats. This happens whenever there is low voltage.