System architecture:

The sensor network is organized as a 2-tier architecture: (a) more powerful Stargate2 nodes equipped with significant storage space and 802.11 network connectivity.(b) iMote2 nodes connected to each other via 802.15.4 radios and equipped with audio, video, and infrared sensors (mics, cameras, and PIR sensors). Mobile users carry tablets (e.g., Nokia N800 tablets) which connect wirelessly to stargate2 and imote2 nodes.

Hardware:

• 50 Crossbow iMote2 nodes
• 25 Crossbow Stargate2 nodvcess (3-7 imote2s per cluster)
• 15 tablets: Nokia N770s and N800s
• sensors boards: 30 basic sensorboards (3 axis accelerometer, humidity, temperature, and light), 30 cameraBoards (camera, microphone, PIR sensor)
• extension flash boards for extra storage

imote2 node	stargate2 node	Nokia N800 tabletPC

Software:

• iMote2 nodes run TinyOS-2.x operating system
• stargate2 nodes run debian linux
• tablets run debian linux

Graphical user interface (GUI) is implemented as web application framework. Mobile users interact with and configure stargate2 devices using a standard web browser. The requirements for such web application is that it must have small footprint (a few Mb), must have reasonable performance (1 sec to render a page), include a database to share data collected by sensors. We chose Lighttpd web server, SQLite database, and Clearsilver HTML template system.