Contents of Presentation

1
(No Transcript)
2
(No Transcript)
3
Contents of Presentation

• What do we mean by Broadband?
• Some Broadband Myths
• Flavours of Broadband Communication
• Fibre to the Home
• DSL
• Wireless LAN
• Future Technologies
• Conclusions

4
What will I mean by Broadband?
A transmission facility having a bandwidth
sufficient to carry multiple voice, video or data
channels simultaneously. Each channel occupies
(is modulated to) a different frequency bandwidth
on the transmission medium and is demodulated to
its original frequency at the receiving end NB
used originally to describe a channel with more
bandwidth than a standard 48 KHz voice grade
channel.
5
What is commonly meant by Broadband?
At present, there is no internationally agreed
definition of broadband. In general, broadband
often refers to internet access service with
transmission speed from hundreds of kbps
(kilobits per second) to several Mbps (Megabits
per second) Note that 'dedicated bandwidth' or
'shared bandwidth' services advertised by ISPs
normally refers to the transmission speed of the
customer access circuit between the customer's
premise and the nearest exchange. The active
users still have to share the public network
resources outside the exchange, including local
and external transmission circuit.
6
Some Broadband Myths

• You can never have too much bandwidth.
• i.e. If you build it, they will come
• Internet traffic is doubling every three months.
• Everyone needs more bandwidth because of the new
  killer applications!

7
You can never have too much bandwidth

• If you build it, they will come.
• Q How quickly will they come?
• A Not as quickly as many had hoped.

8
Internet Traffic doubles every 3 months

• The reality.?
• Backbone traffic growth
• about 100 per year in 1990 through 1994
• about 1,000 per year in 1995 and 1996
• about 100 per year in 1997 through 2000
• Overall data traffic growth
• around 20 to 30 per year in the 1980s
• 30 to 40 per year in 1990 through 1998
• accelerating towards 100 per year

9
SWITCH traffic and capacity across the Atlantic
10
We need more bandwidth

• Traffic is not the same as bandwidth!
• Factors decreasing bandwidth demand
• Elimination of SONET rings, ATM cell tax, etc.
• VPNs over public network replacing private lines
• Factors increasing bandwidth demand
• Optical switching
• Demand for low transaction latency
• DWDM is doubling transmission capacity each year!
• However, magnetic storage is also doubling each
  year!
• So location matters

11
Some reasonable conclusions

• Transmission capacity is growing at about the
  same rate as traffic
• Magnetic storage is doubling each year
• Streaming media traffic is unlikely to be a
  dominant factor
• local store and replay will have a strong role

12
Flavours of Broadband Communications

• Fibre optics
• Fibre to the home?
• DSL/Cable Modems
• Data rates cost etc
• Wireless
• IEEE802.11
• Mobile
• 3G and beyond

13
What about Fibre to the Home?

• For 25 years researchers and telcos have been
  talking about delivering fibre to the home
• Currently connection costs to premises are 1500
  for fibre and 200 for copper DSL (assuming large
  scale deployments)!
• Fibre to the home is a long term goal but in the
  near and medium term DSL and developments thereof
  will be the main delivery mechanism for broadband
  services to the home.

14
What is Digital Subscriber Line?

• DSL is a generic name for a group of technologies
  which transport data at high rates over the
  access part of the network.
• DSLs are distinct from conventional modems in
  that the data is only transmitted as far as the
  local exchange.
• The signal bandwidth greatly exceeds 4kHz
• Based on secondary use of existing cables

15
DSLThe Access Network
Fibre optics is only In the core

• Construction and Topology
• Signal Degradation
• Noise and Interference

Switch
Overhead DP
Exchange to flexibility point 1-3km Flexibility
point to DP 0.5 to 1km DP to customers premises
50m
NTE
Street Cabinet or PCP
NTE
Underground DP
16
Flavours of DSL

• ADSL operates in 300kHz to 1.1MHz band
• 1.5Mbits/s to 6Mbits/s downstream, 640kbits/s
  downstream
• Always on (operates above baseband)
• G-HDSL (SHDSL)
• Single line 1Mb/s symmetric service
• VDSL potentially operates up to 30MHz
• 52Mbits/s_at_ 300m, 26Mbits/s_at_ 900m, 13Mbits/s_at_
  1.5km

17

• Both ADSL and VDSL use DMT modulation
  (Discrete Multi-Tone)

18
DSL Bit rates vs Reach
19
(No Transcript)
20
(No Transcript)
21
Future enhancements to DSL

• Problem of crosstalk in the network
• DSM Dynamic Spectrum Management
• Adapt transmit spectrum dynamically
• Reduce crosstalk (noise) for other users in the
  network.
• DMT is very suited to apply DSM (flexible
  spectrum allocation)

22
DSM principles
23
Wireless Technologies

• WLAN
• IEEE 802.11b and 802.11g standards transmit at
  2.4 GHz, while those that comply with the 802.11a
  standard transmit at 5 GHz offering data rates of
  11-54Mbits/s.
• Limited range of around 30m with discontinuous
  coverage.
• Frequency bands are unlicensed ?Interference!
• Mobile
• Operates between 1-2GHz in licensed bands
• Moderate data rates around 64kbits/s
• Extensive coverage and range

24
Wireless LAN and DSL

• Wireless routers with an inbuilt ADSL modem are
  available for around 70
• So wireless LAN avoids having to wire your house
  with CAT5 cable!

25
Wireless LANWhat is the underlying technology?

• Orthogonal frequency division multiplexing (OFDM)
  is a communications technique that divides a
  communications channel into a number of equally
  spaced frequency bands. A subcarrier carrying a
  portion of the user information is transmitted in
  each band. Each subcarrier is independent of each
  other.
• OFDM is the modulation technique for DSL,
  wireless LANs, Digital Audio Broadcast and
  Digital Video Broadcast systems and a candidate
  for future mobile systems.

26
The Future..

• So what does the future hold..?

27
The Drivers
28
B3G Design Challenges

• Although 3G is an important first step, several
  basic issues still need to be addressed for next
  generation wireless systems
• Fast/reliable broadband radios (PHY/MAC) with QoS
• 100 Kbps ?1-10 Mbps with adaptivity, link
  reliability QoS
• Scalable system capacity for mass-market services
  
• high service penetration implies Gbps/Sq-Km
• Integration of multiple radios into single IP
  network
• unified mobility architecture, open networks
  with
• modular services
• New networking modes, e.g. multicast, multihop
  peer-to-peer
• ...lower-cost infrastructure, networks that grow
  organically
• Truly useful mobile information services
• ...beyond web browsing on phones/PDAs,
• new portable devices

scaling capacity lower cost per bit
more flexible networks
adaptive services
29

• B3G systems can exploit Moores law advances in
  radio speed, but need to work with shorter
  range...

30

• Hierarchical, self-organizing network concept
  currently under consideration, based on
• 3 service tiers (cellular, WLAN, personal area)
• BSs, APs, FNs (forwarding radio nodes), user
  devices
• automatic discovery and power mgmt protocols
• hierarchical, ad-hoc multihop routing

31
Conclusions

• Present
• Moderate data rates across multiple
  non-interacting systems
• Near to medium term
• Increase in data rates
• Long term
• Truly broadband services with networks
  interworking

32
Thank You

• Any Questions?