Operational Considerations in Simulation and Deployment of RFID Systems

1
Operational Considerations in Simulation and
Deployment of RFID Systems

• Kin Seong Leong
• Auto-ID Lab _at_ Adelaide
• School of Electrical Electronic Engineering
• University of Adelaide
• Australia
• kleong_at_eleceng.adelaide.edu.au

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Outline

• Introduction on RFID
• RFID EMC
• Sources of Error in RFID Simulation
• Others
• Conclusion

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Introduction on RFID

• What is RFID?
• RFID basic components

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Problems in RFID

• Regulations
• Limited BW
• Strict radiated power level
• Large Scale Deployment
• Collision problem
• Interrogation zone

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

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

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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

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Listen Before Talk (2)

• Threshold Value for Listen Before Talk

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Current Situation
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Sources of Simulation Error
Sources of Simulation Error
Simulation Model
Reflection, Refraction, and Diffraction
Radiation Pattern of Antenna
Simulation Result Interpretation and Analysis
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Simulation Model (1)

• A simple path loss model
• (1)
• n is the environment factor.

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Simulation Model (2)

• Modification to (1)
• (2)
• n increases as distance increases.

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Simulation Model (3)

• Comparison of results
• (2) is accurate to a certain extend but cannot
  take in consideration of obstacles.

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Simulation Model (4)
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Simulation Model (5)
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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.

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Radiation Pattern of Antenna

• Measured in anechoic chamber.
• Assumption
• Antennas of same model
• have same radiation pattern.
• Radiation pattern may
• change due to surroundings.

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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.

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Simulation Result Interpretation and Analysis

• Boundary zone would be more appropriate than
  boundary line

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

• Simulation of frequency channelling.

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Frequency Channelling

• Transmit Mask for Dense-Interrogator
  Environments
• (extracted from EPCglobal C1G2)

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Multi Channel Simulation

• Antennas operating
• certain channels away
• from channel of interest.

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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.

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Future Work

• A systematic way in determining n.
• A user friendly simulator.
• Question?