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FTTC Range A (Clean) and FTTC Range B (Impacted)

Posted on: November 19, 2013, by Evolving Networks

BT have updated their Broadband Availability Checker along with the other internal checking systems available through the various BT portals we have access to.

What has noticeably appeared is a new separation of FTTC predicted speeds into two categories: Range A and Range B, or as they say in brackets Clean and Impacted.

Along with the normal (but important) caveats in writing underneath, such as explaining that factors outside of BT’s control (such as network congestion in an ISP, or even a customer’s local LAN) can affect speeds, is a new paragraph explaining these two new definitions.

It appears that clean is the term used to describe lines with no wiring issues or detectable copper line quality problems.  This is great, as if these things can be detected at this early stage, it will make it easier for us to set the correct expectations with customers.

Impacted has the clear definition of being the opposite of clean, so that FTTC Range B lines very much will suffer from problems with copper line conditions or things like Bridge Taps (which are a way of sharing and junctioning copper pairs further down the line to the exchange).

All sounds easy so far (even if you don’t really know or care what a Bridge Tap is, assume it will lower your speed and you’re on the right lines).

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Here’s the thing.  The speeds are now split into a High and Low figure for both downstream and upstream.  Ok, also doesn’t sound bad, except when those figures are identical…

Running one of our own FTTC services through the checker here we have not only got a lower speed estimate than in the past, but the high and low figures for both upload and download are identical to each other.  E.g. for Downstream Line Rate, 51.7 for High and Low, and for Upstream 13.2 for both High and Low.  There is no range of speeds any more, even though that column exists for ADSL2+ and ADSL Max.

So with this tight range (is it a range when the highest and lowest points are equal?) does that mean if my speed drops to 51.6 (ok an extreme example, but hey), will it be classed as a fault?

This is not as daft as it sounds.  It’s very difficult, certainly now that the speed figures bandied around are getting larger, to confidently predict the fault thresholds and also what is considered an acceptable reduction in speed at any given time.

This line was predicted more like 65mbps down and 20mbps up around 6 months ago.  If this was a customer of ours, we would have difficult resetting their expectations even though they may have seen at least a 20% drop in speed.

Reporting it to BT probably would result in them pointing at these new estimates and saying “sorry”.

Can I choose to order a clean line instead of an impacted line though?  We’ll have to wait and see.  So far all the checks we have done have also resulted in identical figures for both FTTC Range A and FTTC Range B.  Time will tell what impact all of this will actually have, and whether we are seeing the impact of the dreaded Crosstalk issue arising with the reducing speeds.

Nic Elliott – Technical Director

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