Stability Boost as Openreach Eye G.INP Fix for ECI “Fibre Broadband” Cabs

Last year Openreach (BT) was forced to stop a roll-out of Physical Retransmission ReTX (G.INP) technology, which can improve the performance of their FTTC “fibre broadband” lines, because of problems with their ECI based Street Cabinets. The good news is that a fix has been found.

Just to recap. G.INP (ITU G.998.4) is an error correction technology that is designed to help resolve spikes / bursts of Electromagnetic Interference (impulse noise), which can impact the stability and performance of VDSL2 lines (FTTC). Impulse noise generally comes in two main forms – intermittent and repetitive.

Noise that occurs as sporadic, unpredictable events are termed Single High Impulse Noise Events (SHINE) and these often originate from turning an appliance on or off. Meanwhile impulse noise that is consistent is known as Repetitive Electrical Impulse Noise (REIN), which can be caused by all sorts of things from faulty power adapters to household dimmers etc.

Suffice to say that G.INP can help to iron these problems out, which makes problematic lines more stable and less prone to errors. Improved line stability can also yield a small performance benefit for consumers. Some rival networks (e.g. Sky Broadband’s unbundled LLU platform) already support G.INP and in 2015 Openreach (BT) began a similar roll-out (here) but this didn’t go quite according to plan (here and here).

As usual the technology worked fine on Openreach’s Huawei based cabinets, although the same could not be said for those lines being served by their footprint of ECI cabinets and certain VDSL modems. Under certain conditions the ECI lines could suffer a loss of speed, higher latency and a few users also complained of connectivity problems.

Initially Openreach thought they had managed to develop a solution for this, although it soon became clear that there were still problems and the roll-out was ultimately suspended during early 2016.

The ECI Fix

The G.INP upgrade is an important enhancement and so Openreach has continued their efforts with ECI to find a proper solution. Recently ISPs have been told that a new fix has been developed and this is currently going through final testing before being piloted in the wild.

A Spokesperson for Openreach told ISPreview.co.uk:

“Openreach have been working very closely with our vendor to find a solution to the issues encountered last year during the rollout of G.INP on our ECI estate.

We have now identified and lab tested a solution that will manage the circumstances where a line was previously becoming unresponsive under a specific set of conditions.”

Openreach states that they expect to pilot the solution “later in the summer” and assuming all goes well then it will be deployed, which could begin as early as autumn 2017. However there is still a caveat for ECI kit, which has not been overcome.

Retransmission can operate in both downstream and upstream channels simultaneously, although ECI equipment (either modems or DSLAMS) still doesn’t fully support upstream retransmission. “Due to a hardware limitation G.INP will only be enabled in the downstream direction which is where we also see most benefit for customers,” said Openreach’s spokesperson.

Naturally we’ll be keeping an eye out for the first pilot and looking to see how it impacts line stability and connection latency.