In reply to a post by adslmax:

In reply to a post by lee111s:

There are other factors aside from the SNR margin that affect the sync speed.

I'd like to see the documentation that shows an INCREASE in SNR margin leads to a higher sync rate. Not one example with no back up evidence. Actual documentation that explains this in detail and why it is so.

Here is my FTTC line stats but I don't know if my downstream SNR of 13.7dB are good or bad?

Downstream Upstream
Line Coding (Trellis) On On
SNR Margin (dB) 13.7 16.0
Attenuation (dB) 11.1 0.0
Output Power (dBm) 12.5 -0.9
Attainable Rate (Kbps) 106691 36183
Rate (Kbps) 79999 19999

As I explained above, it's because you're no where near your max attainable speed. There's still an extra potential 26meg available on your line should the cap be removed.

Because of that, your line has plenty of capability to be able to afford a higher noise margin to provide more protection to your line. As your line is capped at 80meg, there would be no point in DLM "risking" having your noise margin at 6db, there would be nothing to gain, only the potential to lose sync should a noise event occur.

I do remember Openreach engineer told me when he installed my first ever FTTC last February 2014 and say to me your FTTC max speed is 80Meg as you will never drop below that because your cabinet is only 200metre away from you.

You are incorrect. If you reduce the target SRNM, then that increases the potential bandwidth. That applies to all xDSL products. Indeed, it applies to any comparable modulation system. The target SRNM just provides the extra margin over the required SNR required to meet the target bit error rate (BER) for a given speed. Decrease the target margin and you increase the maximum speed. No arguments.

The downside is that a low SNRM can lead to an unstable line which is why, on some lines, the target SNRM has to be raised to 9db or even 12db thereby damaging the maximum achievable rate. Note that if the data rate is considerably below the maximum achievable rate the SNRM can, indeed, be higher than the target.

Edited by deleted (Fri 15-Apr-16 11:57:04)

In those circumstances, with a sync rate capped at 80mbps the target SNRM doesn't even come into play. The line will simply sync at either the capped rate or the highest it can reach without dropping below the margin, so DLM hasn't got a risk to take. Well, that's not quite true. Theoretically it could lower the transmission power, but I doubt that OR do that although it might (in principle) reduce the x-talk for other lines where they to do so.

Don't you just love BT, the customer's friend.
Currently I have Unlimited BT Infinity1 for £16-90 per month.6 months left on contract.I consistently get 36 Mbps.
On the BT website I am told I can upgrade to the 55Mbps service at £25 per month if I extend my contract. The estimated download speed is 43 - 56 Mbps. Here's the rub the guaranteed download speed is 35Mbps which is less than I get now.
Unless I misunderstand the situation I can spend more, for longer with my only guarantee being the speed I get now.
We may use BT out of necessity but are they really surprised that some of us loathe them.

In reply to a post by codsallandy:

Don't you just love BT, the customer's friend.
Currently I have Unlimited BT Infinity1 for £16-90 per month.6 months left on contract.I consistently get 36 Mbps.
On the BT website I am told I can upgrade to the 55Mbps service at £25 per month if I extend my contract. The estimated download speed is 43 - 56 Mbps. Here's the rub the guaranteed download speed is 35Mbps which is less than I get now.
Unless I misunderstand the situation I can spend more, for longer with my only guarantee being the speed I get now.
We may use BT out of necessity but are they really surprised that some of us loathe them.

It'll only be of benefit if your max attainable rate is greater than 40meg. Even then, if it was say 48meg, you'd need to make that decision as to whether it was worth it or not. What is the guaranteed download speed on the contract you're on at the moment? Probably around 28-30meg I'd imagine?

I don't understand why people think BT should be a charity and just give stuff a way for free. If you bought a BMW tomorrow that came with 140bhp, and next month, they released the same model with a tweaked engine that produced 150bhp, would you expect them to upgrade you for free? Probably not.

In the same vein, you were happy to pay the price for the service you were offered at the time you took out that service. Now a new service comes out you just want it for free? Life doesn't work that way.

Why use them out of a necessity. There are many other ISP's that you can use for FTTC connectivity. If you don't like BT, move supplier.

Thank you for your helpful advice. I was completely unaware that there are other FTTC providers and apparently I can I can move to one of them. I didn't know that.
My point was that whilst 36Mbps for £16-90 suits me at present BT's attitude to existing customers breeds no customer loyalty at all. Perhaps there are other forum users who feel that way too.

Its a new product and because a small 3-5% must have the latest shiny gadget things arrive at a premium price.

Once the offers kick back in you may be able to barter a better deal, customer retention is a barter game.

In reply to a post by codsallandy:

Thank you for your helpful advice. I was completely unaware that there are other FTTC providers and apparently I can I can move to one of them. I didn't know that.
My point was that whilst 36Mbps for £16-90 suits me at present BT's attitude to existing customers breeds no customer loyalty at all. Perhaps there are other forum users who feel that way too.

As far as I know BT are allowing existing customers access to the new speeds, all they need to do is re-contract. That's no different to new customers really, you're just agreeing that you'll pay for a service for a set amount of time.

With regards to loyalty, it's the same across the board I'm afraid. Almost all ISP's "reward" new customers with better offers. You no doubt got one when you became a BT customer.

Much like the insurance and mortgage markets, it really doesn't benefit you to remain brand loyal.

TalkTalk I believe has negotiated to use a lower level of support from Openreach if memory working correctly, to reduce price, so doubt they will suddenly upgrade entry level service two product price points.

SNRM behaves the same way, the physics are the same just people are getting confused by the way the DLM system can skew things with VDSL2.