1. Operational Considerations in Simulation and Deployment of RFID Systems
Kin Seong Leong
Auto-ID Adelaide
School of Electrical & Electronic Engineering
University of Adelaide
Australia

2. Outline Introduction on RFID RFID EMC
Sources of Error in RFID Simulation
Others
Conclusion

3. Introduction on RFID
What is RFID?
RFID basic components:

4. Problems in RFID Regulations Large Scale Deployment Limited BW
Strict radiated power level
Large Scale Deployment
Collision problem
Interrogation zone

5. RFID EMC RFID EMC Frequency Hopping Spread Spectrum (FHSS)
Listen Before Talk (LBT)

6. FHSS Example: USA FCC Title 47 Part 15.277 902-928MHz
maximum total radiated power of 4 W EIRP
50 channels of 500 kHz

7. Listen Before Talk (1) Example: European ETSI 302 208 865-868 MHz
2 W ERP (approximately 3.2 W EIRP)
15 sub-bands, 200 kHz wide
Only 10 sub-bands at 2W ERP

8. Listen Before Talk (2)
Threshold Value for “Listen Before Talk”:

9. Current Situation

10. Sources of Simulation Error
Simulation Model
Reflection, Refraction, and Diffraction
Radiation Pattern of Antenna
Simulation Result Interpretation and Analysis

11. Simulation Model (1) A simple path loss model: (1)
n is the environment factor.

12. Simulation Model (2) Modification to (1): (2)
n increases as distance increases.

13. Simulation Model (3) Comparison of results:
(2) is accurate to a certain extend but cannot take in consideration of obstacles.

14. Simulation Model (4)

15. Simulation Model (5)

16. Reflection, Refraction and Diffraction
Suggested a hybrid path loss model
Using (2) together with ray tracing.
Not more than 5 rays.
Taking in consideration of obstacles encountered along path of rays.
Reduced error between computation and experimental results.
Infancy stage.

17. Radiation Pattern of Antenna
Measured in anechoic chamber.
Assumption:
Antennas of same model
have same radiation pattern.
Radiation pattern may
change due to surroundings.

18. Simulation Result Interpretation and Analysis
Consider: The LBT threshold limit for 2 W ERP with threshold value -126 dBW. If a signal with higher power is detected in a band of interest, this band of interest cannot be used for tag interrogation.
A sharp boundary in simulated results to represent the LBT threshold limit may not be appropriate. A boundary zone of 3dB (depending on the environment) is more suitable for interpreting simulated results.

19. Simulation Result Interpretation and Analysis
Boundary zone would be more appropriate than boundary line:

20. Sources of Simulation Error
Simulation Model
Reflection, Refraction, and Diffraction  
Radiation Pattern of Antenna
Simulation Result Interpretation and Analysis 

21. Simulation of frequency channelling.
Others
Simulation of frequency channelling.

22. Frequency Channelling
Transmit Mask for Dense-Interrogator Environments:
(extracted from EPCglobal C1G2)
This is the transmit mask fro dense interrogator environments when frequency channelling is used. In the simulation, an easy way to simulate frequency channelling is just to reduce the signal strength accordingly. For example, channel A and channel B are side by side. An antenna is operating at channel A. If we would like to know where we can deploy another antenna using channel B, we just need to run the simulation with signal strength in channel A reduced by 30 dB.

23. Multi Channel Simulation
Antennas operating
certain channels away
from channel of interest.

24. Conclusion
Identified common errors of RFID simulation and suggested ways of minimising some of these errors.
Some errors are unavoidable, but the extent estimated from empirical measurements can be shown to be not severe.

25. Question? Future Work A systematic way in determining n.
A user friendly simulator.
Question?