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[huwwatkins]

Hi
When I moved to my current house I'd already decided i'd be installing a second phone line with ADSL and dividing my traffic across the two.

I am connecting with an HG612 as a modem on ADSL1

I've been here and month and the stats for the first original line look good considering its some 2km long:

                                        Downstream Upstream
Line rate (kbit/s)           8128    832
Attainable rate (kbit/s)   10328   1340
SNR margin (dB)           11.4           20
Line attenuation (dB)           28           16

Yesterday I had the second installed and the stats are way off the first one.

                                        Downstream Upstream
Line rate (kbit/s)           4416    448
Attainable rate (kbit/s)   4448    704
SNR margin (dB)           6.1           11
Line attenuation (dB)           32           19


Now, i'd expect some difference between lines but not almost 50%. Sync seems very low even for that attenuation. My lines are EO and im pretty sure they all go the same way back to the exchange.

Since I took those stats interleaving has kicked in on the second line and its now down to 3200Kbps.

Even though its syncing it wont establish a connection. I dont think the ISP has finished provisioning the line properly.

Even when thats don't think the line stats will change much.

Does anyone have an idea as to what could be wrong?

Thanks

Huw

[burakkucat]

Does anyone have an idea as to what could be wrong?

At the moment, with that very limited snapshot, there is really nothing that anyone could suggest.

[kitzuser87430]

Have you tried a swap around of the modems/routers?

Ian

[huwwatkins]

Hi
Sorry, wasn't much to go on. I've got HG612's on both lines and I've swapped them round.

I've got DSL stats running on the second line now. I've attached the bit loading chart for both. Theres quite a bit difference.

[burakkucat]

We can see that the bit-loading for the second circuit is approximately 3/4 of that for the first circuit.

How do the respective SNR, Hlog and QLN plots for the first and second circuits compare?

[huwwatkins]

Hi
Here are the stats for line 1 ( the one synced at 8128Kbps)

[huwwatkins]

and the same for the second line.

[Chunkers]

That's strange, I'll leave the technical stuff to the experts, but for what its worth I also have two lines, I am around 1.4 km from the cabinet and they are similar in overall performance.  I can't currently compare them easily because I have one on VDSL and one on ADSL but in general it has always looked similar to me based on the expected outcomes for the two different types of connections.

I'll risk stating the obvious but logic would suggest that if there is a significant difference its either to do with your hardware setup or some kind of fault on one of the lines. 

Hope you get it sorted

Chunks

[Weaver]

I have three lines and they are very similar in performance. The thing that strikes me is the poor SNR on the second line. Assuming that you have done all the necessary hardware swap-outs, got rid of phones micro filters and so on, this probably means getting the help of (a good) isp to investigate the matter.

[huwwatkins]

Thanks for confirming what I suspected - that is a fault. I'm at the mercy of my ISP to investigate then, seeing as I've just signed up with them (Origin Boradband) we'll see how it goes.

One thing of note - it does seem that I am on different hardware at the exchange for both lines. One is an Alcatel DSLAM and the other is a Infineon. I dont think that would make much difference though.

[ejs]

Which vendor for which line? I expect the Alcatel equipment is older and not as good, although I wouldn't have expected such a large difference.

[burakkucat]

Comparing circuit 1 with circuit 2, via the four plots from each, respectively, it is clear that something is not right with the health of circuit 2. 

Exactly what . . . ?

[NEXUS2345]

Looking at the Hlog, I don't see anything particular that would indicate a fault in the metallic pathway. However, I do notice a slightly raised noise floor on the second line. Is it possible that the engineer installed the second line from a different bundle which takes a longer route, or one which contains a larger volume of aluminium?

[burakkucat]

Looking at the Hlog, I don't see anything particular that would indicate a fault in the metallic pathway.

Agreed. I see nothing "wrong" in either Hlog plot.

[Digression]
View the two Hlog plots, side-by-side. If I was asked which was the "better" circuit (based purely on sight of the Hlog plots), my answer would be the first of the two.

Why? Although both plots have essentially the same shape, the curve of the first circuit is closer to 0 dB than the curve of the second circuit.

(Although we are familiar with seeing all four of the "snapshot" graphs, Bit Loading, SNR, QLN & Hlog, plotted in quadrant 1 both the QLN and Hlog graphs are actually quadrant 4, with the zero of the Y-axis along the top.)

To conclude this digression, I attach an extremely good Hlog plot. The only problem being that there was no exchange of the US data, from the CO end of the G.993.2 link to the CPE end of the link, hence the green segments are missing from the plot. So either use your imagination or some form of graphical editing software to install the three missing US segments!

Edit: With an application of a little magic, I have inserted an approximation of the three green US segments.
[/Digression]

[huwwatkins]

Line is now down to 3200Kbps. More interestingly - I've spoken to Origin Broadband's provisioning team who seem to think it's odd that I have sync seeing as even though it was a sim provide - the broadband order has not completed (makes sense as I still can't get a ppp session).

I wonder if the pair that they ultimately connected my phone line was an old one that was previously connected to a DSLAM in the exchange.