Speed Degraded Over The Years!

[#1]

I just checked the estimates over on dslchecker.bt.com

ADSL Products	Downstream Line Rate(Mbps)		Upstream Line Rate(Mbps)		Downstream Range(Mbps)	Availability Date		Left in Jumper
WBC ADSL 2+	Up to 9.5		--		7.5 to 12	Available	--	--

Looks like you're currently in sync ever so slightly above 15Mbps currently.

I'm not entirely sure why it would be dropping over time to be honest. When I was on ADSL (20CN ADSL) my estimates were around 2-5Mbps, however it looks like they've actually increased to 3.5Mbps-7.5Mbps as 21CN ADSL2+ (4-8Mbps) and FTTC (33-50Mbps) have become available at that house over the past few years.

[#2]

Yes. 7.5 to 12Mbps? Jeez! So whatever happened to 'up to 21Mbps'?

As the router indicated line resistance has remained stable for donkey's years, I can only conclude it must be caused by increasing RF crosstalk due to the growth over the years of FTTC.

ADSL seems to be dying.

[#3]

“up-to 21mbps” is the product head line technical specification, the actual speed any individual sees is always a factor of their telephone line quality and length. Two users, one on a 200m line and another on a 4km line will experience markedly different speeds even though they are on the same “up to 21mbps” product.

[#4]

...We seem to be going around in circles here.

So why, in my case, has an up to 21Mbps line gone, over the years, to a Max 12Mbps specified line?

Unless, as I say, it is a side effect of the growth of FTTC.

Once again, I can vouch for that original 'up to 21Mbps', because I USED to always get ~18Mbps. 

Now, it's down with every reboot - despite the line sounding clear.  Destination 12Mbps?

Over that time the Download line loss remains constant, according to the router stats.

[#5]

Any news from the OP? I'd be interested to hear how it's going.

TIA

[#6]

I guess I'm the original OP.

With the noise margin reduced to 3db the router is now connecting at 16451 and the connection is stable. Overall speeds have improved a little too. I have not been there enough to do much testing, but overall seems better. 

[#7]

Good to hear things have improved.

From your attenuation stats. your line is pretty well the same as mine, maybe a bit shorter. But your original figure for upstream attenuation looked far too high to me given that for downstream. Here are my current figures:

Payload rate [Kbps]: 15154 1243
Attenuation [dB]: 29.0 15.0  (These figures are very stable over the years)
Margins [dB]: 6.1 6.4

Following an incident last year - when, coincidentally or not, a neighbour appeared to be being attached to fibre - I mysteriously and suddenly lost service, only reliably reestablised over the following days.

As I could find nothing wrong at the time with my line, for the first time I thought to look for REIN using Medium wave receivers. I have a 1970s vintage Grundig Party Boy (not seriously used since the 1970s!) and a 1980s vintage NAD Stereo AM/FM digital (sythesised) receiver. I was horrified at what I found on both receivers on MW; completely thrashed by interference and unusable. As I said at the time, I haven't used MW since the 1970s so didn't have any benchmark as to what is 'normal' there these days.

I have been repeating this exercise the last few days using the Grundig. It's a puzzle. Sometimes there is clearly bad interference on MW (during daylight hours), sometimes with a rythmic 'rotating' character. Other times MW is quite clear and useable. None of this seems to to be due to anything in my premises (provided I keep the laptop away from the receiver! And amusing to hear even a TV remote can be picked up on AM.) and none of it corresponds to anything obvious. There are no nearby commercial premises.