Broadband Access
in the BT Fixed Network
extract ofBCS Essex presentation, 20 March 2007
Dr Elspeth MacFadyen, Programme Director BT Group CTO
What I’ll be talking about
•
General context
•
Access network factors affecting DSL performance
•
DSL Max (“up to 8Mb/s”)
•
ADSL2+
•
Options for meeting future demand for bandwidth
Broadband UK: affordable, available and attractive
• Top of G8, better than mains water
• 99%+ commercially funded
• Infrastructure competition: LLU, cable and/or wireless in over 70% of the country
• Even wider set of technologies for broadcast applications (esp. TV)
• Hundreds of nationwide service providers with a number of wholesale providers
• E.g., IP TV, mobile over broadband, broadband on the move, IP telephony, hybrid platforms...
• Bundles and packages with wireless, landlines, software as a service
• 99.6% broadband
availability, over 12 million subscribers
• One of the lowest prices in the world
• Service and commercial
The access network – some numbers …
•
Around 30,000 people – all BT’s field operations
•
200,000 manholes
•
2 million km optical fibre
•
3.6 million customer visits per year
•
10.5 million broadband connections
•
14 million jobs a year
•
30 million customer lines
•
120 million km copper access
•
300 million calls a day
•
Around £8 billion assets
Business
Where is the last mile bandwidth an issue? What else
drives customer experience?
Example applications requiring different transmission rates & Quality of Service
Internet Access
Best Effort (e-mail, online gambling etc) On-line Gaming PC, Console P2P VoIP Communications (BE PC-PC, off-net PSTN quality) Video-Communications
(web-cab to TV, Video calls, Conference)
TV & Video
VoD download/streamed, SDTV, HDTV
Business applications
Software as a service, IP- Centrex, VPN
High u/s BW demand (Highest for VC) Gaming QoS Service level Best Effort Access (d/s) Bandwidth 100 kbps 1 Mbps 10 Mbps 10 kbps HDTV Video-on- demand VoIP Internet Access applications Video tel e phony Video Conferencing ???
… a picture…
Exchange Cabinet DP Equivalent to 3.25 km 0.5mm typical 420 m typical 25 m typical CustomerDSL performance – physics and its implications
•
The performance of DSL on any given line in the access
network is a function of the
signal to noise ratio
at the
end of that line:
– Signal is affected by the length, quality and dimensions of the copper cable,
and by the ANFP (Access Network Frequency Plan)
– Noise can come from
• network crosstalk (directly related to the “fill” level of the copper cables in use)
• sources in the home or premises (including home wiring)
• sources in the environment e.g. RFI
•
Geographic coverage achieved at any given speed also
depends on
– the topology of the access network
– the statistical distribution of line lengths
•
These factors are identical for anyone operating DSL on
BT’s access network
•
Service at 512kb/s offered nearly everywhere since Sept
2004 – but there remain some problem lines
Why line length is important
• Possible transmission rate decreases with increasing loop length
• Effect is more dramatic at higher frequencies
• Need to reserve and protect lowest frequencies for longest loops
possible
transmission rate
DSL Max
Line Rates
IPstream Downstream Upstream
Max 288 Kbps to 8128 Kbps 64 Kbps to 448 Kbps Max Premium 288 Kbps to 8128 Kbps 64 Kbps to 832 Kbps
Estimated DSL Max speed distribution
Based on line checker data and estimates only
Line rate
Percentage of PSTN lines
0.5Mb
98%
1Mb
96%
2Mb
93%
3Mb
89%
4Mb
78%
5Mb
63%
6Mb
42%
>or =6.5Mb
25%
Towards a market-led
strategy
Ample bandwidth for the vast majority today
• Bandwidth and price tend to dominate marketing messages – “simple” to understand and compare, or is it?
• Typical customer uses much less than ‘last mile’ capacity
– Average bandwidth usage <30 kbit/s
– Peak individual throughput much more constrained by ‘internet’ and servers, peak time of day also by backhaul and core networks
– Some intensive use(r)s: streaming SDTV throughput >200 MB/hour, peer-to-peer file transfer an effectively ‘unlimited’ consumer
• Current evidence shows that small segments (<10%) would consider to pay premium for bandwidth (£5/month) for bandwidth
• However BT aware of growing public debate and is keen to engage with end customers, Ofcom, CPs and other stakeholders e.g. BSG, content industry
© British Telecommunications plc
There are ‘unconstrained consumption’ scenarios where
bandwidth demand exceeds the current capabilities
Consumer - Couple with no children
Consumer - Family Corporate - Small Branch
Bandwidth Requirements
Upstream ~5 Mbit/s ~9 Mbit/s ~20 Mbit/s Downstream ~30 Mbit/s ~44 Mbit/s ~32 Mbit/s Key Drivers
Take-up of new real time
applications
• IP-HDTV – 4/3 concurrent sessions
• Video Calling • HD Video Conferencing • IP-CCTV • Video Calling Take-up of new computing architectures
• Adoption of thin client architectures
Unconstrained Consumption Scenario: Assumes that there are no constraints on bandwidth availability and bandwidth is available at no incremental cost to end-users
…but to date there is no identified mass market demand for a ‘paid for’ high speed service and alternative HDTV platforms are more cost-effective
HD: High Definition; IP-HDTV: Internet Protocol High Definition Television; IP-CCTV: Internet Protocol Closed-Circuit Television
© British Telecommunications plc
There are two main access fibre deployment options
ADSL
Copper from the exchange to the premises
FTTC: Fibre to the Cabinet; FTTP: Fibre to the Premises; ADSL: Asymmetric Digital Subscriber Line
Fibre Copper
FTTC
The fibre connection goes to a powered cabinet in the
street. The final connection to the premises is on copper
FTTP
The fibre connection goes all the way from the main
network to the premises
© British Telecommunications plc
Summary of technology options
Notes:
[1] Based on 25% cable fill. If cable fill increases then bandwidths decline [2] 2.4G sharable across 32 end users
[3] 1.2G sharable across 32 end users
Mbit/s: Mega bit per second; ADSL: Asymmetric Digital Subscriber Line; ADSL2+: Offers higher
downstream rate and upstream performance than ADSL and ADSL2; MSAN: Multi-Service Access Node; VDSL2: Very high speed Digital Subscriber Line 2, an enhancement to VDSL; FTTP: Fibre to the Premises
Bandwidth (Mbit/s)[1] DownStream (Headline) DownStream (Median) UpStream (Headline) Upstream (Median) Timeline
ADSL 8 4-6 0.8 0.75 Today’s technology ADSL2+ (MSAN) 18 6-10 0.9 0.75 21CN delivers this
ADSL2+ (Cabinet)
24 14-15 0.9 0.9 Future technology – may have use for reach extension
VDSL2 (Cabinet) c50 22-25 c24 9 Future technology - being considered by BT
FTTP/GPON c75 [2] N/A c37.5 [3] N/A Applicable to greenfield sites – end 2008
© British Telecommunications plc
What is happening elsewhere?
Supportive Regulatory & Government Environment
Other Specific factors
Netherlands FTTC •Sun setting exchange based LLU
• High broadband retail share • Capital release from sale of
exchange buildings France FTTP •Iliad - Cheap / free access
to duct
• Low cost deployment due to focus on multi-dwelling units
• Limited or no existing infrastructure
USA FTTP/
FTTC
•Regulatory forbearance
•Rural subsidy
• Step change in competitiveness vs. cable
• Long loop lengths
Germany FTTC •Regulatory holiday • Step change in competitiveness vs. single play cable
• High broadband retail share
Korea FTTB •National industrial policy • Low cost deployment - high housing density
• High payments for entertainment and social services
Japan FTTB •National industrial policy
•Tax incentives, cheap finance
• Low cost deployment- high housing density and overhead deployment • Capital investment in pre-provisioning
© British Telecommunications plc
There is no economic case for replacing the copper
access infrastructure with fibre solely on cost grounds
• Capex costs for greenfield sites are similar for fibre and
copper…and fibre offers scope for much lower maintenance costs. So it makes economic sense to use fibre (FTTP) for large greenfield sites
• But maintenance cost savings are insufficient to justify BT replacing existing copper with fibre.
• High definition television may be a future driver for higher bandwidths but hybrid technologies (satellite, freeview) are much more economic for broadcast.
• No revenue model has yet emerged for recovering the costs
© British Telecommunications plc
BT position on NGA strategy
• BT wants to respond to real demand in a commercially and technically innovative way that enables effective downstream competition everywhere.
• From 2008 BT will provide networks based on fibre to the premises (FTTP) for selected major greenfield housing developments, and businesses in such locations.
• Where BT builds fibre access networks for its own use it will make available equivalent wholesale services. BT does not seek a
regulatory “holiday”.
• Continued exploration of challenges and uncertainties – eg capex costs, demand, business models, applications, technology, public funding.
© British Telecommunications plc
Ebbsfleet Valley
“… a vibrant, cosmopolitan
development in the heart of Kent Thameside”
• Developed by Land Securities
• Over 1,000 acres
• the business core of up to 6 million sq ft will create
around 25,000 new jobs over the coming 20 years
• 3 million sq ft of retail, leisure and community facilities
• 9,600 new homes and 440 acres of new parks and open spaces and lakes.
• …will begin at Springhead, a joint venture residential scheme with Countryside Properties of up to 600 new homes with supporting community facilities including a school, parks and place of
worship