1. Power Consumption Measurement and Clock Synchronization on Low-Power Wireless Sensor Networks Author : Yu-Ping Chen, Quincy Wu 1

2. Outline Introduction Application of Wireless Sensor Networks Low-Power WiFi Digital oscilloscope connection diagram. Power Consumption Measurement Low-Power WiFi ZigBee Clock Synchronization Conclusion and Future Work 2

3. Introduction Applications of Wireless Sensor Networks 3

4. Introduction cont. Low-Power WiFi system architecture 4

5. Introduction cont. Digital oscilloscope connection diagram. 5

6. Power Consumption Measurement Low-Power WiFi 6 --The electric current of beaconing status when the WiFi signaling strength is -32 dBm. --The electric current of beaconing status when the WiFi signaling strength is -79 dBm.

7. Power Consumption Measurement cont. 7 The start- up status of Low-Power WiFi. The start- up status of ZigBee.

8. Power Consumption Measurement cont. 8 The stand-by status of ZigBee.

9. Power Consumption Measurement cont. Average power consumption statistics. 9 Power StateZigBeeLow-Power WiFi Signaling strength -32 dBm-79 dBm Start-up0.0448 W0.0396 W Beaconing0.0957 W0.2145 W Stand-by0.0756 W0.0495 W

10. Clock Synchronization Clock synchronization of Low-Power WiFi devices by NTP. 10

11. Clock Synchronization cont. Clock synchronization flow chart with NTP. 11

12. Conclusion and Future work Compared with traditional WiFi equipment, the power consumption of Low-Power WiFi is reduced approximate 40%. The power consumption of Low-Power WiFi with start-up and stand-by status is lower than ZigBee. The power consumption of Low-Power WiFi device when it is receiving beacons from an AP, is twice of the power consumption at its stand- by status. 12

13. Conclusion and Future Work cont. The clock synchronization usually suffers from long latency problems in wireless sensor networks like ZigBee. We combines Low-power WiFi devices with NTP, it would be crucial to further investigate the efficiency and accuracy of NTP packet transmission. 13