1. Wireless Sensor Mote (TelosB) Ultra low-power wireless module –for sensor networks, monitoring app, rapid prototyping Key Features –2.4GHz 802.15.4 radio, 250kps –8MHz processor, 10k RAM, 48k Flash –Fast wakeup (6  s) –1MB external flash (16 segments, each 64kB) –Ultra low current consumption –TinyOS support

3. Some Useful Components of Mote/TOS Radio UART Timer (unique) Flash memory LEDs Sensor(s)

4. Some Research Area in WSN Wireless Communication Localization Calibration Time Synchronization Routing (Data-Centric Routing) Deployment, Lifetime optimization Signal Processing - compression, detection Storage (Data-Centric Storage) Mobility

5. Wireless Communication Ideal model Real model * [Ganesan TR ’02][ Marco Zuniga et al., USC]

6. Wireless Communication transitional connected disconnected distance (m) PRR Empirical: link behavior * – Three regions*: Connected Disconnected Transitional – Transitional region : Asymmetric links High variance space/time Large extent – Significant impact on some routing protocols** * [Zhao SenSys ’03] [Woo SenSys ’03] [Ganesan TR ’02] [Aguayo SIGCOMM’04] ** [Zhou MobiSys’03]

7. Routing ( Information Gradient-based Active Routing ) ( North Palm Springs earthquake of July 8, 1986 ) Isoseismal (intensity) maps ( North Palm Springs earthquake of July 8, 1986 ) Ref.: Southern California Earthquake Center. (http://www.scec.org)

8. Challenges - In real life, sensors are unable to detect or measure the event’s effect below certain threshold. So, diffusion curve has finite tail - Lack of sensitivity of sensor device(s) - Creates flat information region - Erroneous reading of the malfunctioning sensors - Due to calibration error or obstacle - Cause local maxima or minima - Environmental noise Routing ( Information Gradient-based Active Routing )

9. Brief Description of Routing Approaches Single-path Query forwarding with look-ahead, r = 1 Multiple-path Query forwarding 17.2 18.93.118.9 17.218.921.1 17.292.121.123.8 21.16.921.1 23.84.198.123.8 67.03.221.123.827.5 18.921.130.027.529.032.9 80.5 32.9 23.831.032.941.5 23.827.83.441.557.4 41.5 23.827.832.941.557.410057.441.5 57.441.5 57.4 41.5 Q 17.2 18.93.818.9 17.218.921.1 17.292.121.123.8 21.16.921.1 23.84.198.123.8 67.03.221.123.827.5 18.921.130.027.529.032.9 9.032.9 21.123.831.032.941.5 23.827.83.441.557.4 41.5 23.827.832.941.557.410057.441.5 57.441.5 57.4 41.5 Q SS Look-ahead = 1 Active Node Candidate Node Active Nodes 9

10. Still Have Limitations Q Q Q Multiple Events Flooding overhead is high for sparsely distributed events Flooding overhead is high for sparsely distributed events Unable to detect sparsely located events Unable to detect sparsely located events