Fibre speed slowly falling

[#1]

Hi
Over the past two years my broadband speed has slowly dropped from 68Mbs to 56Mbs.
PlusNet have advised me that me expected speed is 74Mbs.
My current stats, from DSLStats,  are

				Downstream	Upstream
Line attenuation (dB):  	17.1		0.0
Signal attenuation (dB):	Not monitored		
Connection speed (kbps):	56038		19999
SNR margin (dB):        	6.5		7.5
Power (dBm):            	13.3		7.1
Interleave depth:       	4		1
INP:                    	52.00		0
G.INP:                  	Enabled		

I tried to escalate this today, but I am within 25% of the estimate, JUST, so until it falls more there is nothing PlusNet will do.
Is there any obvious reason why it my broadband speed is falling?

[#2]

One of the main reasons for speeds reducing over such a long period can simply be due to more update of the service from other customers on the same cabinet.
Please do shout up if the issue gets any worse though.

[#3]

Why have BT deployed G.INP (G.998.4) but not Vectoring (G.993.2)?
Most Telcos across Europe use both technologies, and it is simply a software change at the cabinets. BT Openreach's standards support Vectoring so why not deploy it?
This would improve my broadband signal considerably!

[#4]

Quote from: windsors

Why have BT deployed G.INP (G.998.4) but not Vectoring (G.993.2)?

Cost and simplicity. G.INP is a relatively simple technology. It pretty much only needed enabling on the line cards. It's almost better to ask why it wasn't there from the start. But vectoring is a whole other beast. It requires the DSLAM to continually perform a large number of calculations and process quite scarily large amounts of data. Back when I was looking at it a couple of years ago it seemed to me that more data would be generated and processed by the DSLAM itself than would actually pass through the cabinet. In both cases however they complicate the roll-out of FTTC so BT probably felt it was better to walk rather than run and keep things simple until it had a better idea of what was involved and what might be gained. Vectoring wasn't really ready for prime-time when BT started to roll-out FTTC and I think I'm right in saying that vectoring requires that line cards be replaced which makes it quite an expensive proposition.
Last I heard BT still intend to roll-out vectoring in a few areas where it will do the most good but they seem to have moved their focus onto G.FAST. That makes sense. G.FAST will take the local loop way beyond anything VDSL2 could offer so there's sense in saying that vectoring+VDSL2 is a dead-end best ignored.

[#5]

Quote from: windsors

Why have BT deployed G.INP (G.998.4) but not Vectoring (G.993.2)? Most Telcos across Europe use both technologies, and it is simply a software change at the cabinets. BT Openreach's standards support Vectoring so why not deploy it? This would improve my broadband signal considerably!

Vectoring aka G.Vector is defined under G.993.5. VDSL2 under G.993.2.
Andrue sums it up. I believe for the DSLAM's to support Vectoring they need to be updated with a 'Vectoring engine' of which deals with the additional processing.

[#6]

Thanks for the updates.
I wasn't aware that BT had to add Vectoring Engine hardware to each cabinet. This explains why the subject has gone quiet over the last eighteen month, and all the talk is about GFast.
Is there anything that can be done about interference and crosstalk? As high speed broadband becomes more popular, this will become more of an issue.

[#7]

I'm not completely sure what the situation is but this thread on Kitz discusses it and suggests that some DSLAMs at least would need upgrading:
http://forum.kitz.co.uk/index.php/topic,12591.msg237997.html#msg237997
That thread makes another good point. Digital technology is continually improving. If BT waited until every possible feature was implemented they'd never get anywhere. Same as an avid PC gamer would never own a PC if they kept waiting for the best graphics card or processor.
At some point BT had to draw the line. It had to decide what model of hardware and what version of firmware it was going to use. It could have tried to remain flexible but that complicates the roll-out because you'd end up with lots of different versions scattered across the network.