operational considerations in simulation and deployment of rfid systems kin seong leong auto-id lab...
TRANSCRIPT
Operational Considerations in Simulation and
Deployment of RFID Systems
Kin Seong Leong
Auto-ID Lab @ Adelaide
School of Electrical & Electronic Engineering
University of Adelaide
Australia
Outline
• Introduction on RFID
• RFID EMC
• Sources of Error in RFID Simulation
• Others
• Conclusion
Introduction on RFID
• What is RFID?• RFID basic components:
HO STCO M PUTER
RFID REA DER RA DIO W AV ES RFID TAG SO N O BJE CTS
RE ADERAN TEN NA
Problems in RFID
• Regulations– Limited BW– Strict radiated power level
• Large Scale Deployment– Collision problem– Interrogation zone
RFID EMC
Frequency Hopping Spread Spectrum (FHSS)
RFID EMC
Listen Before Talk (LBT)
FHSS
• Example: USA FCC Title 47 Part 15.277
• 902-928MHz • maximum total radiated power of 4
W EIRP• 50 channels of 500 kHz
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
Listen Before Talk (2)
• Threshold Value for “Listen Before Talk”:
Current Situation
Sources of Simulation ErrorSources of Simulation Error
Simulation Model
Reflection, Refraction, and Diffraction
Radiation Pattern of Antenna
Simulation Result Interpretation and Analysis
Simulation Model (1)
• A simple path loss model:
(1)
• n is the environment factor.
Simulation Model (2)
• Modification to (1):
(2)
• n increases as distance increases.
Simulation Model (3)• Comparison of results:
• (2) is accurate to a certain extend but cannot take in consideration of obstacles.
Simulation Model (4)
Simulation Model (5)
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.
Radiation Pattern of Antenna
• Measured in anechoic chamber.
• Assumption:– Antennas of same model
have same radiation pattern.– Radiation pattern may
change due to surroundings.
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.
Simulation Result Interpretation and Analysis
• Boundary zone would be more appropriate than boundary line:
Sources of Simulation ErrorSources of Simulation Error
Simulation Model
Reflection, Refraction, and Diffraction
Radiation Pattern of Antenna
Simulation Result Interpretation and Analysis
Others
Simulation of frequency channelling.
Frequency Channelling
• Transmit Mask for Dense-Interrogator Environments:(extracted from EPCglobal C1G2)
Multi Channel Simulation
• Antennas operating certain channels away from channel of interest.
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.
Future Work
– A systematic way in determining n.
– A user friendly simulator.
Question?