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[roseway]

So the text displayed in the relvant tabs will ALWAYS actually include data for all tones from 0 to 4095?

If the modem reports them, yes.

[rbel]

BE1

Here are the saved txt files for the period in question - they do have the complete data range - the previous missing stuff is down to my sloppy copy/pasting.

I will reboot the modem later and report the outcome.

[Bald_Eagle1]

Those files do now confirm that the last tone used for bitloading was tone 637, with 2 bits loaded.

VDSL2 does allow for only 1 bit to be loaded, subject to sufficient SNRM, thus making the most of whatever is available.



SNR ceased to be reported at tone 669.

The Medley Phase band plan reports that at least something from these tone bands would have been available when the connection synced:-

Medley Phase (Final) Band Plan
US: (0,95)
DS: (32,859) (1216,1959) 


The lack of bitloading & reporting of SNR is likely to be down to your current SNRM levels.
A reboot later on MAY improve matters, but there is a slight risk that it could actually reduce sync speeds (if target SNRM is then set at 6dB).



It appears that your HG612 is still using Asbokid's original unlocked firmware, which is likely to be remotely updated soon.
An update may bring some improvement.

If you wished to confirm your current firmware version & if DSLStats doesn't report it, you could telnet into the modem's Busybox & run this command:-

xdslcmd --version

The output should be something like this:-

xdslcmd version 1.0
DSL PHY: AnnexA version - A2pv6C030b.d22g
******* Pass *********

That is from Asbokid's firmware version.


This is how it would look with updated firmware:-

xdslcmd version 1.0
DSL PHY: AnnexA version - A2pv6C038m.d24j


If your current firmware does get remotely updated by BT, you will lose access to the modem's GUI, but the DSLStats & HG612 Modem Stats programs should still work.

If you wish to reinstate the modem's GUI following a firmware update, Wolfy's unlockedgui version will be fine.


It is unusual to see reduced performance when using a HG612 connected to an ECI DSLAM on a longer line as our remote monitoring definitely suggests the opposite is the case.

Do you know how long your line is?

[rbel]

BE1

I wonder if you could talk me through a couple of your notes:

]i)  I understand that the SNRM target is 6dB and that long lines can result in poor SNR, what tone value is it likely a 6dB SNR would be?

ii)  what is a "Medley Phase band plan"?

I will make time to have a look at the firmware update as soon as possible.

The reboot did increase the SNR levels from 3.1 down  and 4.9 up  to 3.8 and 5.0 initially, now settled to 3.7 and 5.5.  The sync speeds have dropped (see txt file).

Before swapping the ECI for the HG612 I was getting a stable 12+ Mbps down and 0.5 Mbps up, following the swap performance immediately dropped to 8.5 down and after the reboot to 8 down - up remained at around 0.5.

I watched an OR engineer calculate the line length using GSI kit on his laptop - not very accurate given the scale he was using, but better than guessing as previous engineers had done and he came up with 1418 metres from the cabinet to the box outside my place.  So allowing for another 40 metres from the box to the NTE5, 1458 metres in total.

[Bald_Eagle1]

I wonder if you could talk me through a couple of your notes:

I'll try to 

]i)  I understand that the SNRM target is 6dB and that long lines can result in poor SNR, what tone value is it likely a 6dB SNR would be?

SNR = Signal to Noise Ratio.

If you have a very quiet line, SNR will be high.

VDSL2 connections use a SNR(M)argin of 6dB to sufficiently allow for downward fluctuations (i.e. increase in Noise).
Otherwise, connections with quite low SNR could disconnect & resync regularly as SNRM drops into negative values (i.e. the Noise is Greater than the Signal).

As frequency increases, so does attenuation due to the physical properties of copper/aluminium cabling. i.e. there is more resistance as line length increases.

The effect is that Signal reduces as frequency increases.

If you look at a SNR graph & compare it against a Hlog graph, you will see SNR tail off as attenuation over frequency increases (attenuation is reported as negative values, so



Your SNR value at tone 669, after which point SNR values ceased to be reported was only 9.6875 (call it 9.7dB), compared to its peak at tone 224 of 31.7500dB.

SNR was 17.8125dB at tone 637, after which point bitloading ceased.


Attenuation at tone 669 was -63.2500 & at tone 637 it was slightly better at -60.6875

See the attached montage from a very short line length using a 40/10 service.
Bitloading per tone isn't at all high because it doesn't need to be to deliver the full 40/10.

QLN isn't fantastic, but there is hardly any attenuation as that user is only around 50m or so frm the cabinet, therefore there is very little weakening of the signal.

ii)  what is a "Medley Phase band plan"?

Discovery Phase determines the profile's DS & US band plan tones available from the particular cabinet's DSLAM.
There are slightly different tones available from Huawei & ECI DSLAMS.

Discovery Phase (Initial) Band Plan
               U0                   U1                  U2                          (U3 & now U4 from updated firmwares are not used for profile 17a)
US: (tones 0 to 95) (880 to 1195) (1984 to 2771)


               D1                   D2                  D3   
DS: (tones 32 to 859) (1216 to 1959) (2792 to 4083)



Medley Phase is supposedly the tones actually usable after the connection has trained up.
BT's & therefore Asbokid's original firmware listed the whole range of tones if anything could be used in a perticular band.

Also, DS & US 'shared' somet of the U0 & D1 tones, more often than not they were used for DS.


The updated firmware reports it like this (my connection):-

Discovery Phase (Initial) Band Plan
US: (7,32) (871,1205) (1972,2782)
DS: (33,859) (1216,1961) (2793,3970)

Medley Phase (Final) Band Plan
US: (7,32) (871,1200)
DS: (33,859) (1216,1932)

We can see that there is no longer any 'sharing' of tones between US & DS.

We can also see that after it has trained up, at Medley Phase, my connection can use:-

The whole of the U0 band's tones
The whole of the D1 band's tones
Almost all of the U1 band's tones
A fair amount of the d2 band's tones
None of the U2 band's tones
None of the D3 band's tones


Yours is worse at Medley Phase than mine:-

Medley Phase (Final) Band Plan
US: (0,95)
DS: (32,859) (1216,1959)

I'm not quite sure it suggests that you can use some of the D2 band's tones though, as attenuation is far too high at the starting point of tone 1216.

I will make time to have a look at the firmware update as soon as possible.

The reboot did increase the SNR levels from 3.1 down  and 4.9 up  to 3.8 and 5.0 initially, now settled to 3.7 and 5.5.  The sync speeds have dropped (see txt file).

Before swapping the ECI for the HG612 I was getting a stable 12+ Mbps down and 0.5 Mbps up, following the swap performance immediately dropped to 8.5 down and after the reboot to 8 down - up remained at around 0.5.

There are no guarantees, but the updated firmware does seem to make better use of the useable tones on longer lines.

You could always revert to the ECI modem, but unlocking it & reliably monitoring performance, changes in physical line conditions is nigh on impossible.

I watched an OR engineer calculate the line length using GSI kit on his laptop - not very accurate given the scale he was using, but better than guessing as previous engineers had done and he came up with 1418 metres from the cabinet to the box outside my place.  So allowing for another 40 metres from the box to the NTE5, 1458 metres in total.

Allowing for 'slack' & up & down poles etc. it's not too far off 1500m.
You can probably add a bit more for any 'detours' that the route migh take.
My connection measures around 840m on a map, but from the cabinet it initially runs away from my house to a road crossing, then past my house to a joint pit before doubling back to the pole mounted DP.

Actual line length of my connection is somewhere between 1000m & 1100m.
These are my attainable & actual sync speeds (DS Interleaving depth of 431):-

Max:   Upstream rate = 4977 Kbps, Downstream rate = 22812 Kbps
Bearer:   0, Upstream rate = 4999 Kbps, Downstream rate = 21987 Kbps

I could achieve almost 30Mbps / 7Mbps before new users being added increased crosstalk.





FWIW, we have recently been monitoring a HG612 on an ECI DSLAM connection of similar length as yours (if not longer) which now achieves around 13Mbps DS & around 0.5Mbps US.

US is hit particularly hard on VDSL2 connections with longer lines.

[rbel]

BE1,  many thanks for the explanations.

From comparing the example data you included I think it is clear that the bits per carrier spread across the higher frequencies is very constrained and that the SNR is truly abysmal.

SNR levels are now 3.6 down and 5.4 up.

As far as I am aware there is little I can do, without the intervention of ISP/BT, to improve on these current figures other than try the updated firmware or revert back to the ECI which will (hopefully) give me an increase back up to 12 Mbps?

As BT are due to contact me to run a remote TAP3 test early this week (inability to access the speedtest@speedtest_domain server) I think it would be wise to revert back to the 'official' modem until this has been completed.  It will also give me an opportunity to look at updating the firmware.

The line from the cabinet is underground all the way.  Today I carefully checked the same route measured from the cabinet by the OR engineer using MAGIC, a good GIS used by environmental bodies, and twice came up with a figure of 1200 metres, which makes the performance even stranger - perhaps I should try it with a measuring wheel!

[Bald_Eagle1]

Good luck with te engineer's visit.

If he says there is nothing wrong with the connection, you could always show him a graph or two