Make computing context-aware
• Context: location, activity, preference, history
• A lot of progresses in location-aware services
Not enough …
• Need to use other signals
Do I like Italian restaurant?
Am I walking? Do I drive 10 miles to eat?
Is it lunch time or dinner time?
Alone with family?
Queue time ?
• How do we get them?
o Ask users to release more contextual information
o Rely on crowdsourcing
• Challenges to address:
o Energy: partially solved
o Privacy: mostly unsolved
• Many services require continuous sensing
• Acquiring context is expensive
• Many optimizations proposed
o Not sufficient for continuous sensing
o Phone will die in a few hours
• Challenge: continuous sensing for a day without
• Needs innovation: Efficient “Assisted” GPS
Low Power Assisted GPS
• Not regular GPS
Takes 1s to minutes
Same for ~150KM
Requires a few ms
• Mobile phone sends to server:
Cell tower ID
Computes mobile location
• Location-based services
(e.g. mobile search)
• Batched location
estimation (e.g. path
positioning (e.g. geotagging photos)
LEAP: A Low Energy Assisted GPS for Trajectory-Based Services, Ramos et al. Ubicomp 2011
Privacy: do we care?
• News: iPhone keeps record of everywhere you go
Do people care?
52% said they were "very or
extremely concerned" about loss of
privacy from using location-sharing
Are you worried about geolocation privacy?
48% seriously concerned, 32% little worried
Why is the stake high?
Apple fined 1M won ($932) by South Korea over iPhone tracking
The suit now counts 26,691 plaintiffs => $26 million
Lawmakers Demand Apple Clarify iPhone Tracking Capability
Facebook fights new California privacy bill
'Do Not Track Me Online' privacy bill introduced by California Rep.
Impossible to maximize all three
Trivial to maximize any two
Michaela Goetz and Suman Nath, Privacy-Aware Personalization for Mobile Advertising, no. MSR-TR-2011-92, August 2011
• My context-aware service knows what is relevant
• Without affecting my phone battery much
• Without me telling it much about my private
• Even if I release limited private information
o My privacy is preserved (even with strong adversaries)
o In future I can revoke my data
o (Only) I can decide how my data is used and shared