operational experiences of g.fast in the uk...tno ultrafast broadband seminar 2015 – slide 3...

Operational Experiences of G.fast in the UK

John MacDonald, BT TNO Ultrafast Broadband Seminar 2015 [email protected]

© British Telecommunications plc

TNO Ultrafast Broadband Seminar 2015 – slide 2

Presentation outline

� BT’s Ultrafast Vision

� BT’s G.fast Technology Trials

– Ipswich

– Hethersett

– St James

� Field Measurements

� Conclusions



BT’s ultrafast broadband vision� BT has been a believer in high speed

copper for over a decade and has been

working with industry to develop G.fast.

� On 30th January 2015, BT CEO Gavin

Patterson announced our Ultrafast

broadband vision and G.fast is at the

heart of that vision.

� Ten-year vision of 500Mbps available

across most of the UK.

� Premium 1Gbps fibre broadband

services for high-demand customers.



Superfast fibre speeds

� Currently around 75% of UK premises have been passed with the first generation of our

fibre technology, giving speeds of up to 80Mbps. BT is working with BDUK to reach ~95% of

UK premises.

� To do this, we have enabled over 60,000 of our 88,000 cabinet locations in the network with

power, fibre and equipment currently delivering superfast using VDSL2.

� The typical distance from a cabinet to the customer premises is ~350m.

350m typical



BT’s vision for G.fast deployment

G.fast from existing location G.fast from new location

� The original vision for G.fast was deployment at the Distribution Point. The typical

distance from the DP to the home in BT’s network is ~35m, making speeds of up to 1Gbps

achievable.

� However, our simulation work, lab measurements and technology trials showed that G.fast

has the potential to deliver several hundreds of megabits on longer loops.

� By extending the reach of G.fast towards 350m, this makes the existing PCP locations ideal

for reaching significant numbers of customers whilst leveraging our NGA investment.

� For customers out of reach, copper / network rearrangement will be required



Large-scale G.fast trials

� BT will run two large-scale trials of G.fast technology in

Huntingdon, Cambridgeshire, and Gosforth, Newcastle-upon-

Tyne, starting in the summer of 2015. Around 2000 premises

will be covered in each pilot area.

� BT will conduct a further trial of G.fast to Multiple Dwelling

Units (MDUs) and businesses in Swansea, South Wales.

� Trial participants will gain access to speeds of up to several

hundred megabits per second.

� The pilots will be run by Openreach, so the infrastructure will

be available to all Communications Providers on equal

terms; end-user customers will be offered the chance to

participate via their own service provider.

� We are currently running small-scale technical trials in

Suffolk and Norfolk, which will help inform our decisions for

the large-scale trials.

Gosforth

Huntingdon

Swansea

Hethersett

Ipswich



World’s first technical trial of G.fast, Ipswich, SuffolkFootway box

DPU� 3 customers connected to 1 DPU� Operational since October 2013

19m

47m66m

XGPON backhaulDPU


Ipswich G.fast trial topology

� The trial used existing duct structures and DP locations, but created a separate overlay to prevent interference to existing DSL services

G.fast is served via a diversecable infrastructure, and does not co-exist with existing DSLservices in any cable binder

or joint enclosure.



Ipswich G.fast trial performance results

� Chart shows aggregate data rates for shortest and longest trial lines for

different G.fast start frequencies and with vectoring enabled and disabled.

� Results showed that G.fast worked as expected.

� Vectoring critical in order to deliver the maximum bandwidth.



G.fast technology trial, Hethersett, Norfolk

DPU

Remote power

• 7 DPU’s, 23 customers, all u/g cables• Overlay network, 2nd lines installed



Spectrum compatibility between G.fast and VDSL2

� ITU-T G.9700 defines that G.fast can operate over the frequency spectrum

from 2MHz to 106MHz.

� As this overlaps with the VDSL2 spectrum (0.14 to 17.7MHz) it is essential to

preserve spectrum compatibility to avoid interference between VDSL2 and

G.fast signals operating in the same cable binders.

� For Hethersett, this was achieved by starting the G.fast spectrum at 23MHz,

well above the upper frequency of VDSL2.

VDSL2 G.fast

17.7 23 106 MHz

Guard Band

0.14



The results from our Hethersett G.fast technology trial

Overlay network, 23-106MHz operation� The Hethersett technology trial is using

G.9700/G.9701 compliant G.fast with a

start frequency of 23MHz.

� Good correlation observed between the

field results and lab measurements.

� The equipment is already delivering over

500Mbps aggregate at distances of

~120m.

� It is also delivering aggregate speeds in

excess of ~150Mbps at 300m.

� We expect this performance to continue

to improve as standards and

developments evolve.



Loop Characterisation

� As part of Hethersett trial we performed some loop characterisation

measurements on trial lines

� The following measurements were performed on each line:

- Insertion loss of the pair from DPU to NTE

- Ambient noise at DPU end of new pair

- Ambient noise at CPE end of new pair

- Ambient noise on existing line at CPE

- Calculation of Hlog (pre ITU-T G.997.2)

� Some examples shown on the following slides …


Example line #1

Est. length from TDR: 28 mEst. length from IL: 38 mEst. length from Hlog: 79 m

Note: IL and TDR estimates do not include umbilical and modem lead. Hlog is not calibrated.

VDSL crosstalk from existing line

FM RadioFM Radio


Example line #2



VDSL crosstalk from adjacent lines

FM RadioFM Radio

PLT

VDSL crosstalk


Example line #3



Much noisier line

FM Radio

VDSL crosstalk


Noise floor measurements� Network measurements analysed to calculate noise floor as a percentage of frequency

spectrum.

� Many lines have a measured noise floor below -150dBm/Hz.

� The lower noise floor gives a material boost to performance, especially on long lines.

At the DPU between 23MHz to 106MHz At the CPE between 23MHz to 106MHz

-140 < Noise

-145 < Noise < -140

-150 < Noise < -145

-155 < Noise < -150

-140 < Noise

-145 < Noise < -140

-150 < Noise < -145

-155 < Noise < -150


Planned G.fast technical trial, St James, Suffolk

� 20 DPU’s, ~60 customers, mainly o/h cables

� Overlay network, 2nd lines currently being installed

DPU

Customer



Conclusions

� BT has announced a vision for Ultrafast Broadband with G.fast

at its heart.

� Currently running several small scale technology trials of G.fast

to gain network experience of deploying G.fast and to provide

input into our plans for larger scale pilots.

� Results from the technology trials show good correlation

between laboratory and field measurements.

� G.fast can be successfully deployed to deliver Ultrafast

Broadband over 250m of cable.

� There are challenges to the Industry to further improve G.fast

performance.

operational experiences of g.fast in the uk...tno ultrafast broadband seminar 2015 – slide 3...

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