A few more details have leaked out today about Openreach’s (BT) new 330Mbps capable G.fast (ITU G.9700/9701) broadband technology, which among other things reveals that ISPs will be able to raise a fault if a customer’s line speed drops below a threshold of 100Mbps.
At present Openreach is currently expanding their G.fast pilot to cover 138,000 premises at up to 17 UK locations by the end of March 2017. You can find more details about this technology in our previous articles (examples here and here), although assuming all goes to plan then 10 million UK premises should be reached by 2020 and possibly many more by 2025, when the top speed might also be raised to 500Mbps.
However this pilot has also triggered the release of a lot more detail about the service and as a result it’s finally becoming easier to get answers to some of our longest held questions, not least of which is how Openreach plans to handle faults and at which point a line could be considered to be running too slowly (faulty).
The key selling point of a product that is being promoted as “ultrafast” is obviously its high speed and so it makes sense for Openreach to confirm that they’ve set the threshold at 100Mbps, which is the point at which many people consider the “ultrafast” definition to start (admittedly Ofcom prefer 300Mbps).
So here are the thresholds on which ISPs will be able to raise a fault (note: the line itself may not necessarily have a fault at this level but providers can flag it for investigation).
G.fast Fault Thresholds
* If the speed falls below 100Mbps.
* If the speed falls below the Point of Sale forecast by Openreach’s eMLC [Enhanced Managed Line Characteristics] system.
* If the speed drops by more than 30% from the line rate they received when it was installed.
We should remind readers that G.fast will initially come in two main product flavours: Download speeds of up to 330Mbps (50Mbps upload) and Download speeds of up to 160Mbps (30Mbps upload). During BT’s early G.fast trials we also recall that only 3% of lines delivered speeds of less than 100Mbps and 75% got more than 300Mbps, although their approach has changed a bit since then (it’s now more cabinet focused instead of FTTdp).
The latest engineering documentation from Openreach also says that G.fast, like similar DSL technologies, is generally being targeted at copper local loops of shorter than 500 metres, which makes sense because past this point the performance is much more akin to existing services (e.g. FTTC/VDSL2) and drops off much more quickly over distance. See our hybrid fibre technology page for a chart.
The update then notes that they have “performance targets” of 150Mbps for local loops shorter than 500 metres and it confirms how they’ve designated 350 metres or less for their highest G.fast speeds, which is something that has been known for awhile (here); even if they can’t quite yet deliver 300Mbps over 350 metres of copper (here).
Elsewhere Openreach confirms that the hybrid cable (fibre optic and power supply), which links their new 48 port G.fast pods (situated on the side of existing PCP street cabinets) to the nearby FTTC / DSLAM street cabinet, will have a reach of up to 100 metres. The cable itself contains 3 x 10mm2 conductors and a 12 fibre unit.
Speaking of pods, we’ve previously reported that Nokia / Huawei should eventually allow them to handle 96 ports and the latest update says to expect this “in future months“. Vectoring 96 ports is a huge challenge and it’s not yet ready for prime time, although initial G.fast uptake probably won’t be as high as it was for VDSL2 and that should offer some breathing room.