[adsl] ADSL2+ here and now?

[Simon Cobb]

So I'm in a very similar situation to Jared.  Same make and model of
modem (ADSL2+-capable D-Link G604T with latest V2 firmware) on an
ADSL2+-enabled exchange (Riccarton).  When I checked the status of my
modem I saw I'm getting 7659kb/s down 944kb/s up.  I asked my ISP
(Maxnet) to investigate why I wasn't seeing ADSL2+ performance.  They
were very helpful, replying thus:

Your line stats show that you are correct and ADSL2+ profiles have been
enabled on your ISAM. However I can see that your modem is not getting
the benefit that you should see.

Spectrum Profile:          HSI-ADSL2-AM
Service Profile:           HSI2-I-FSFS

parameter.actual.bitrate.ds             kb/s        7659.0      944.0
parameter.attainable.bitrate.ds         kb/s        16556.0     944.0

As you can see my attainable rate is 16556kb/s but I'm only getting
7659kb/s

They also noted that my SNR was 25db which is apparently too high and
they arranged for my line to be tweaked by Telecom to bring it within
the normal SNR range of 12-15db.  I was pretty dubious about this, but
not being a telecoms expert, I didn't argue.  This morning that tweak
seems to have happened because my SNR is now 13db.  Is there such a
thing as too high an SNR?

Anyway, while my SNR has reduced from 25db to 13db, my line performance
is basically identical (actually slightly worse this morning @7616kb/s
down 896kb/s up - I wonder if the reduction in SNR has caused that
slight reduction?)  Can anyone offer any advice as to how to get ADSL2+
performance, when everything at my end seems to be in place to get the
higher performance?

Regards,

Simon