BT Partly Suspends G.INP Roll-out to ECI Fibre Broadband Cabinets

Openreach (BT) recently began the roll-out of Physical Retransmission ReTX (G.INP) technology to their ECI based Street Cabinets, which can improve the performance of their 40-80Mbps Fibre-to-the-Cabinet (FTTC / VDSL) lines. But this has now been partly suspended after problems occurred on some lines.

The G.INP (ITU G.998.4) technology is an error correction solution that is designed to help resolve spikes / bursts of Electromagnetic Interference (impulse noise), which can affect the stability and performance of related lines. Impulse noise generally comes in two main forms – intermittent and repetitive, which we’ll briefly explain below.

Noise that occurs as sporadic, unpredictable events are called Single High Impulse Noise Events (SHINE) and these often originate from turning an appliance on or off. 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.

BTOpenreach completed the roll-out of G.INP to their Huawei based street cabinets (approx. 2.5 million lines) last year (here) and nearly all saw some benefit through fewer errors, greater line stability and even a small speed boost (sync rates).

Sadly Openreach could not begin the deployment to their footprint of ECI cabinets and certain VDSL modems / routers (e.g. those with older Lantiq chipsets) because they didn’t support upstream retransmission (here) and some related lines would thus suffer a loss of speed, higher latency and a few users also complained of connectivity problems.

Fast forward one year to early March 2016 and the first hints (via Kitz) began to emerge of Openreach rolling out G.INP to ECI cabinets, which was wonderful news and suggested that BTOR had found a viable solution to the earlier problems.

Unfortunately a small portion of people soon started to complain of problems similar to those that occurred on ECI kit last year and that was followed this month by rumours that Openreach had now partly suspended the G.INP ECI roll-out to problematic lines and removed the upgrade from those lines identified as likely to suffer from problems (these are then returned to the old method of Interleaving and RS Error Correction). Naturally we went on the hunt for a clarification.

An Openreach Spokesperson told ISPreview.co.uk:

“Openreach constantly monitors its fibre network and this identified some lines which would perform better without retransmission.

We’ve returned these lines to a pre-retransmission state, so that customers continue to receive the optimum speed. All other lines on the platform remain enabled with retransmission.

We’re investigating options to apply retransmission for all customers, and we’re working closely with equipment vendors. Openreach has communicated this position to all fibre CPs and we continue to provide regular updates to them.”

The above response specifically relates to the roll-out of G.INP on ECI cabinets / lines, which is something that we double checked before posting. We also asked Openreach whether they could say when or even if the roll-out to problematic ECI kit/lines would be restarted, although as alluded above there is currently no firm ETA, but they are investigating a solution.

It should be said that the ECI problems with G.INP aren’t always caused by issues on Openreach’s network and incompatible G.INP modem / router firmware can also be a big factor, which just goes to show that rolling out useful upgrades to existing infrastructure is rarely a simple walk in the park.