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[waltergmw]

Gentlefolk,

Can anybody tell me please whether the diagnostics data shown below has special "features" or whether the data is likely to be accurate.
In particular I'm interested to note that:-

1.  the Pilot tone 64 is shown with bits loaded

2.  the upload seems to have been chopped down to only 7 bits per tone where it might be expected to be substantially better.
(This data is the best I've ever seen in the jungle, but I know the line is shorter than many around here.)

The modem is synchronised but not authenticated on a standard BT G.DMT Annex A service.
Modem model No. BT2700HGV
Hardware version 2701-100589-005
Firmware version 6.1.1.48-enh.tm

Kind regards,
Walter



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[roseway]

I'm not using my 2700HGV at present, so I can't check, but I'm pretty certain that I noticed the apparent loading of tone 64 and was going to investigate further. I think that it must be misreporting by the router, because the pilot tone is part of the ADSL spec and can't just be taken over for use by the router.

As for the apparent clipping of the upstream section, I suppose that this could just be the result of bitloading optimisation by the router. The upstream speed is limited to 448 kbps, so it may be that the overall upstream noise margin is improved by using a more balanced spread of tones, rather than by squeezing the maximum out of the lower tones.

[waltergmw]

Thanks very much Eric,

Your idea re clipping seems quite logical as I've got other pictures where the upstream envelope is less well populated and then a few tones show 8 bits probably to make up the shortfall.
In this example there was obviously more capacity available and the table figures show an upstream max of 780 but a rate of 448.

I've also got a few v4 firmware pictures showing tone 64 is left blank.

Kiknd regards,
Walter