1. LOW POWER SENSOR NODE DESIGN When A Node Is Joining ZigBee Network Yoon Mo Yeon RTLab. KNU

2. Contents  Discharge Test  Test Method  Test Result  New Issue  Poll Rate  Performance of a Node  Deciding Poll Rate

3. Discharge Test

4.  Test Method  Module ZPC2430 –Prochild  Parameters Channel : 23 (0x17) Poll Rate (Period) : 30ms  Battery Energizer AAA (1000mAh)

5. Discharge Test (cont.)  Test Result  Calculation Sleep : 4mA (with Power Amp.) Active : 220uA / poll Current Avg. : 9.7mA  Lifetime 1000mAh / 9.7mA = 4.3 days 9/4 17:30 ~ 9/7 ??:?? About 3 days

6. New Issue : Joining Power  Reason of Incorrect Lifetime Prediction  Assumption for battery capacity was wrong  A node consumes very much power when join network (about 500 times to one poll action)  Stable network environment is very important 100mA

7. Poll Rate

8. Performance Of A Node  Polling  ZigBee end-devices can receive a packet only by polling  Almost performance factors are influenced by poll rate Tx & Retransmission (Packet Error Rate) Delivery Time (Transmission Delay, Latency) (Number of hops * 15ms) + (poll rate)

9. Deciding Poll Rate  Usable Battery Power (AAx2, 2000mAh)  1 month : 2777uA  3 month : 925uA  6 month : 462 uA  12 month : 231 uA  Avg. current consumption of four sensors in ARTS FIPS : 110uA + α

10. Deciding Poll Rate (cont.)  Avg. current vs. poll rate (uA, s)

11. Conclusion & Future Works  Stable network environment is essential to low-power sensor network  Performance of ZigBee end device is influenced by its poll rate  Researches into performance factors and evaluation must be done

12. Q & A