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Announcements

Announcements. Did you hear about the Microsoft site crash yesterday? Compiling in Solaris (gemini) gcc <file.c> -lsocket –lnsl. Outline. The Anatomy of a Context-Aware Application – Andy Harter, Andy Hopper, Pete Steggles, Andy Ward and Paul Webster. AT&T Labs, Cambridge, UK (cont).

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Announcements

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  1. Announcements • Did you hear about the Microsoft site crash yesterday? • Compiling in Solaris (gemini) gcc <file.c> -lsocket –lnsl CSCI {4,6}900: Ubiquitous Computing

  2. Outline • The Anatomy of a Context-Aware Application – Andy Harter, Andy Hopper, Pete Steggles, Andy Ward and Paul Webster. AT&T Labs, Cambridge, UK (cont) CSCI {4,6}900: Ubiquitous Computing

  3. Bat Unit • Radio transceiver, ultrasonic transducer and control logic • Each bat has a GUID • Use the radio, ultrasonic transducer and the speed of sound in air (estimated from ambient temperature) to estimate location • Use multiple receivers to get 3D location using multilateration • Reflections of ultrasonic waves – statistical outlier elimination CSCI {4,6}900: Ubiquitous Computing

  4. Bat Unit (cont.) • It takes 20 ms between bat readings = 50 timeslots per base station per second • Location can be used to measure orientation • Attach many bats to the same object. Use the measurements to infer the orientation • Base station can provide Location Quality-of-service to allocate time slots to bats based on the expected update frequency • Bats carried by people – few times a second • Bats attached to workstation – once every few minutes CSCI {4,6}900: Ubiquitous Computing

  5. Bat Unit (cont.) • Bats perform handover when moving from one base station to another (similar to the cellular networks) • Hand off decisions can also be made based on the Bat location • Battery consumption is low, power consumed depends on the update frequency and power state • Bat is good enough to be used as a 3D mouse CSCI {4,6}900: Ubiquitous Computing

  6. Modeling the environment • Detailed model describing entities in the real world and their possible interactions • Use CORBA and databases to implement persistent distributed objects • Three classes of resource monitors: • Machine activity e.g. keyboard activity • Machine resource e.g. CPU usage, memory usage • Network point-to-point bandwidth and latency CSCI {4,6}900: Ubiquitous Computing

  7. Client level event filters • Update Frequency • The frequency at which items are monitored is based on how quickly the item tends to change • Relevancy • If a value has not changed significantly, it is not sent. This value depends on the data being monitored • Caching • Caching improves performance at the cost of consistency CSCI {4,6}900: Ubiquitous Computing

  8. API • Absolute and relative spatial facts • “Person is at (x,y,z) facing in direction ” .vs. “Person is standing in front of the monitor” • Geometric containment is used for relative spatial facts monitor person Contained(person, screenspace) CSCI {4,6}900: Ubiquitous Computing

  9. Scalability • With many devices, containment is complex • They use containment tree indexing system (a quad-tree based approach) CSCI {4,6}900: Ubiquitous Computing

  10. Implementation • BAT teleportation system • With their earlier active badge based teleportation system, they only knew that a user was in the room and so they had to cycle between multiple displays in a room • If a particular display was being use, they would still cycle that display because they did not monitor machines • If a machine is dead, their system would still wait because they did not monitor machines • With the BAT system, they have more accurate location information • Event driven programming style CSCI {4,6}900: Ubiquitous Computing

  11. Zones and Buttons • Action zone triggers teleportation • Within maintain zone, teleported desktops are maintained Action monitor Maintain CSCI {4,6}900: Ubiquitous Computing

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