Broadband Connections for the Last Mile

1
Broadband Connections for the Last Mile
2
Outline

• DSL
• Cable
• Some discussion questions
• What are the advantage and disadvantages of ADSL?
• What are the advantage and disadvantages of CATV
  network?
• Why not using T1 for the last mile?
• What are the services available at South Bend?
  Prices?

3
Last Mile Alternatives

• POTS (covered)
• ISDN (covered)
• DSL
• Cable
• Wireless (next class)

4
DSL

• DSL Digital Subscriber Line
• Different DSL solutions
• ADSL (asymmetric digital subscriber line)
• Most often deployed DSL technology
• VDSL (very high speed digital subscriber line)
• Provides up to 52 Mbps downstream and about 2
  Mbps upstream
• Major use video on demand
• SDSL (symmetric digital subscriber line)

5
ADSL

• Speed
• Within 18,000 ft from the carriers central
  office
• Upstream 150 kbps downstream 1.5 Mbps
• Within 12,000 ft
• Upstream 640 kbps downstream 6.0 Mbps
• Hardware
• Using existing phone lines
• ADSL units installed at both the customer sites
  and the central office
• ADSL modem for voice communication
• ADSL units provide an Ethernet 10Base-T interface
  to users PC

6
ADSL Architecture

• Using multiplexing
• allows multiple signals to be transmitted over a
  single link
• Frequency division multiplexing
• Definition Multiple input signals are modulated
  to different frequencies within the available
  output bandwidth, and are demodulated back into
  individual signals on the output end
• voice 0-4kHz
• upstream data 25 - 200 kHz
• downstream data 250 kHz - 1.1 Mhz

7
Cable TV Networks

• Cable companies have wired up approximately 60
  of homes.
• Could serve close to 90 with relatively minor
  additional infrastructure.
• Mechanism frequency division multiplexing

8
Development and Challenges

• Two major developments
• Utilize optical fiber to replace coax cables for
  long distance transmission
• Bi-directional networks
• Speed up to 10 Mbps
• Problems
• Shared connectivity
• Security