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Vertical Handoff

Vertical Handoff. Ling-Jyh Chen, Mario Gerla Computer Science Department, UCLA. Handoff Illustration. Horizontal Handoff Occurs when the user switches between different network access points of the same kind. Vertical Handoff

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Vertical Handoff

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  1. Vertical Handoff Ling-Jyh Chen, Mario Gerla Computer Science Department, UCLA

  2. Handoff Illustration • Horizontal Handoff • Occurs when the user switches between different network access points of the same kind. • Vertical Handoff • Involves two different network interfaces which usually represent different technologies.

  3. Seamless Handoff • Defined as a handoff scheme that maintains the connectivity of all applications on the mobile device when the handoff occurs. • Aims to provide continuous end-to-end data service in the face of any link outages or handoff events. • Design Goal: • low latency • Minimal packet loss

  4. The “ideal” solution – Mobile IP • The mobile users need a “practical” solution NOW!

  5. Universal Seamless Handoff Architecture (USHA) • A “simple” and “practical” handoff solution. NAT server NAT Server All packets are encapsulated and transmitted using UDP Applications are bound to the tunnel and transparent to the handoff.

  6. Detecting handoff events and performing service adaptation Transcoding according to available bandwidth and MH properties Smart Decision: decide the “best” time and target interface to handoff

  7. Smart Decision Model • With USHA, mobile hosts are able to select any network interface for its connection at any time. • However, still need a model that knows which interface to use based on various factors such as • Link Capacity, Available Bandwidth • Loss Rate, Delay • Power Consumption • Cost • Solution: Smart Decision Model

  8. HCC—Handoff Control Center Provides connection between network interfaces and the upper layer applications. Composed of DM (Device Monitor) SM (System Monitor) SD (Smart Decision) HE (Handoff Executor) Smart Decision Model

  9. Service Agility • Vertical handoff usually results in a dramatic change in the path capacity. • “Fast Rate Adaptation” forces TCP/TFRC to enter Slow Start when detecting a handoff from LOW to HIGH • “Agility” is triggered by • Explicit handoff notification • Implicit handoff notification

  10. Service Agility – TFRC Probe • TFRC Probe with “fast rate adaptation” • Vertical handoff from 1xRTT to 802.11b

  11. Service Agility – TCP Probe • TCP Probe with “fast rate adaptation” • Vertical handoff from 10Mbps to 100Mbps Unit: bps

  12. Summary • We proposed a practical vertical handoff solution, called USHA. • We proposed a Smart Decision Model to determine the “best” time and target interface to perform vertical handoff. • We evaluated Service Agility in vertical handoff scenarios.

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