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

Vertical Handoff2 Wireless Overlay Networks

July, 1998Vertical Handoff3 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

July, 1998Vertical Handoff4 Basic System Overview Source Home Agent IR Base Station RF Base Station Wide Area Base Station Local Multicast Group Data Packets Beacon Packets Mobile Host

July, 1998Vertical Handoff5 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

July, 1998Vertical Handoff6 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

July, 1998Vertical Handoff7 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

July, 1998Vertical Handoff8 Conclusions Vertical handoffs enable seamless access to Internet Optimizations effective for reducing handoff latency ( ms, 1% overhead) Policy enabling brings flexibility, and improves deployability

July, 1998Vertical Handoff9 Future Work Vertical handoff to wireless WANs Policy specification framework Experiment with interesting policies at testbed of DaimlerBenz internet car.