Graduate Journal Presentation

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Graduate Journal Presentation

• By
• Hemanth Ande
• May 3 2007

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Title

• A Receiver-based Vertical Handover Mechanism for
  TCP Congestion Control
• Yuci Gou, David A. J. Pearce, and Paul D.
  Mitchell, Member, IEEE

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This Presentation Contains

• Key definitions concepts
• Introduction Abstract
• Problem
• Solution
• Conclusion.

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Key definitions concepts

• WLAN linking of two or more computers without
  wires.
• Utilizes Spread spectrum or OFDM modulation
• Gives mobility to move around and still be
  connected to the network (typical reach is
  10-50m)
• limited area (only in Hotspots)
• Data rate (1-108Mbps)

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Key definitions concepts

• Handoff 2 types (apart from hard Soft
  handoff)
• Horizontal Vertical Handoff.
• Horizontal handoff similar systems or Network
  layer handover after a change of wireless access
  point (i.e. following completion of the data-link
  layer handover).
• Vertical handover where the handover is between
  two different systems (ex WLAN cellular
  network)
• network layer handover is typically decoupled
  from the data link layer Automatic failover from
  one technology to another in order to maintain
  communication.
• Example moving states (horizontal) Different
  countries (vertical)

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Key definitions concepts

• Bandwidth Delay Product (BDP) product of a data
  link's capacity (in bits per second) X its
  end-to-end delay (in seconds).
• or
• The number of bytes that have been transmitted
  but not yet received (in air).
• Example
• Customer on a DSL link, 1 Mbit/s, 200 ms one-way
  delay 200 kbit High-speed terrestrial network
  100 Mbit/s, 100 ms 10 Mbit

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Key definitions concepts

• Buffer Overflow

Data packets
Buffer
Spill over or wasted data
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Key definitions concepts

• Under utilization

Buffer
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Abstract

• Vertical Handoff Mechanism for TCP based on
  receiver BDP (WLANGPRS)
• Congestion Control using receiver Advertised
  window (awnd).
• Impact of abrupt change in link capacity
  Latency
• Buffer overflow under utilization.

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Introduction

• Objective for future
• Affordable
• High capacity wireless internet assess from any
  where on world
• Technology towards integrating 3G (GPRS) with
  WLAN

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Key Challenges

• Achieving seamless transition from one network to
  other.
• Integrating this in to present system hand hence
  receiver based handoff
• Direction in which handover takes place High BDP
  network-gtlow BDP Network
• low BDP Network-gt High BDP network

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Key Challenges

• High BDP network-gtlow BDP Network (WLAN)
  -gt(GPRS)
• Buffer overflow error

low BDP
High BDP
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Key Challenges

• low BDP Network-gt High BDP network (GPRS)
  -gt(WLAN)
• Under utilization problem

low BDP
High BDP
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Scenario
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Scenario

• Heterogeneous n/w
• MBB (soft) Vertical HO
• Correspondent node (CN) communicates to MN
  through internet
• MN uses care of address (CoA)
• TCP packets from the CN travel via the MNs Home
  Agent (HA)
• TCP packets destined for the MN are tunneled from
  the HA to the current FA, and returning
  acknowledgements (ACKs) from the MN are sent to
  the CN.
• MN roams between a WLAN and a GPRS network
  making vertical handoff.

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Solution
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Solution
Dont Jump now, wait for some time let level
decrease
High Capacity
Low capacity
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Solution
Now jump....123
Decreased High capacity Through awdn
Little bit increase in low capacity
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Result WLAN to GPRS handoff
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Result WLAN to GPRS handoff
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Result GPRS to WLAN handoff
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Conclusion

• Proposed Vertical handover mechanism with
  different link capacity.
• propose an algorithm for accurately measuring the
  maximum BDP supported by the networks
• Uses receiver-based congestion control at the
  mobile node to ensure smooth handover from one
  network to another by adapting the advertised
  window to suit the access network
  characteristics.

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• Questions ?