Vertical Handoffs in Wireless Overlay Networks

1
Vertical Handoffs in Wireless Overlay Networks

• Mark Stemm Helen Wang Randy H. Katz
• Daedalus Wireless Research Group
• Department of EECS
• University of California, Berkeley
• July, 1998

2
Wireless Overlay Networks
3
Access is the Killer App

• Seamless connectivity anywhere anytime
• Single identity Mobile IP
• Horizontal handoffs within the same network
• Vertical handoffs across overlays
• Challenges latency, power, BW overhead, best
  BS, when to handoff

4
Basic System Overview
Home Agent
Source
Local Multicast Group
IR Base Station
RF Base Station
Wide Area Base Station
Beacon Packets
Data Packets
Mobile Host
5
Optimizations

• Fast Beaconing
• Send beacons faster than once per second
• Packet Doublecasting
• Send packets over both interfaces
• Like soft handoffs in IS-95
• Header Doublecasting
• Send packets over 1 interface and headers over
  other interface

6
Policy Enabling

• Emerging wireless WANs WCDMA, Info-Station,GPRS,
  Satellite
• Envisioning of a common cellular backbone with
  different service providers
• What is the best network? Tradeoffs cost,
  performance, power, connection duration.
• Policies allow user level involvement

7
Enabling Policies

• Separate policy from mechanism for a general and
  flexible vertical handoff system
• Mechanisms time/data accounting, network
  condition estimation, API for accessing system
  status and performing system operations
• Policies mechanism gluing

8
Conclusions

• Vertical handoffs enable seamless access to
  Internet
• Optimizations effective for reducing handoff
  latency (200-500ms, 1 overhead)
• Policy enabling brings flexibility, and improves
  deployability

9
Future Work

• Vertical handoff to wireless WANs
• Policy specification framework
• Experiment with interesting policies at testbed
  of DaimlerBenz internet car.