Smartphone Implementation

Nokia 6600

• Devices are nearly ubiquitous
• High degree of programmability
• Computational power of ~1994 PC (50-100 MIPS)
• Low-cost worldwide data communications
• Location aware ( GSM cell tower id, GPS)
• Extensible sensor network via bluetooth
• Nokia 6600 (Symbian OS, Series 60)

GSM Cell Towers

• Cells may be large (kilometers in diameter)
• Cells overlap
• Cells may be non-contiguous due to interference
• No one-to-one correspondence between physical location and cell

Available Phone Data

• Connected GSM cell tower ID
• Phone firmware does monitor other nearby cells to facilitate seamless transitions, but this data is not available from the phone operating system.
• Connected GSM cell tower AREA
• Rough correlation to physical area (city)
• International Mobile Subscriber Identity (IMSI) Number
• Nearby bluetooth devices
• Ambient noise, light, etc?
• User labeled timestamps/locations

Raw Data Format

GSM cells

 20050321T160550 area, cell, nw: 4001, 1693, T-Mobile
 20050321T160603 area, cell, nw: 4001, 1632, T-Mobile
 20050321T193514 area, cell, nw: 4001, 1632, T-Mobile
 20050321T202021 area, cell, nw: 4001, 1623, T-Mobile

• Cells are logged at transition events and at arbitrary, frequent times, allowing self-transitions.
• Ignore times of no reception

Bluetooth devices

 20050317T162726 devices: 000ad986c40e [T610,2:1:656] 000ad980e84a [T610,2:1:656]

• User defined scan interval (1-5 minutes typical)
• Log MAC, given name, and device type

Ongoing Work

• Improve of ContextLogger reliability, particularly bluetooth detection
• Modify ContextLogger bluetooth format. It is currently extremely fragile to parse, as user-defined names may match any regular expression.