1. Lichen Lee, Guixiz Kang, Xidong Zhang, Xiangyi Li, Longfeng Chen
An Interference Avoidance Strategy for Zigbee Based WeHealth Monitoring System
Lichen Lee, Guixiz Kang, Xidong Zhang, Xiangyi Li, Longfeng Chen
Dohwan Kim

2. Table of contents WeHealth Interference problem Experiment
Interference avoidance strategy
conclusion

3. What is WeHealth? Wireless electronic Healthcare Zigbee star topology
Interference from the other wireless equipment

4. WeHealth monitoring system
There are two mode for the sensors to transmit data, normal monitoring mode and emergency monitoring mode.

5. Interference problem Zigbee WiFi 2.4G ISM band, 16 channel(11 ~ 26)
3MHz bandwidth, 5MHz channel spacing
WiFi
2.4G ISM band, 22MHz bandwidth

6. Interference problem Collaborative approach Non-collaborative approach
Central controller can monitor the signal of zigbee and wifi.
They have good effect on in-system interference.
But they can do nothing to the out-system interference.
Non-collaborative approach
They base on the channel detection and performance measurements.
They consist of interference avoidance algorithm, transmission power control, and so on.

7. Experiment Zigbee chip of TI CC2530 The transmission power : 0dBm
The transmission rate : 10packets/s

8. Experiment
D1 : 3m, D2 : 5m, D3 : 3m
WiFi channel : 5

9. Experiment Zigbee channel : 16 the threshold for CCA : -77dBm
If D2 < 12m, the WiFi signal power is -75dBm
If D2 < 8m, the RSSI of zigbee is -55dBm and the WiFi signal power is -65dBm

10. Interference avoidance strategy

11. Interference avoidance strategy
Channel estimation algorithm
Zigbee interfered channel
The interference degree of zigbee channel

12. Result

13. Conclusion
By using proposed interference avoidance strategy, monitoring sensor can detected and estimated the interference.
The coordinator estimated the interfered degree of all the zigbee channels using the proposed algorithm.

14. Thank You