1. Positioning Analysis of Multiple Antennas in a Dense RFID Reader Environment Kin Seong Leong Auto-ID Lab, ADELAIDE

2. Objectives Investigate the art of antenna positioning. Minimise RFID collision problem by proper antenna positioning. Set up a convenient simulation environment in MATLAB. Provide a foundation for more advanced analysis.

3. Main Challenges in Simulation Simulation model Underlying assumptions

4. Simulation Model (The concept of free space path loss) The power transfer ratio for a pair of lossless antennas in free space with optimum orientation is given by: The factor is the free space path loss.

5. Simulation Model: 1

6. Simulation Model: 2 Based on results presented by Rappaport for in-building path loss model: The n is the environment factor and varies from place to place. On site measurement is required for the determination of n.

7. Experiment

8. Simulation Model n also changes as the distance increases. Hence: The boundary of d = 8 is based on the experiment results, also consistent with Rappaport’s results. However, it is an average and may change in some extreme environments.

9. Simulation Assumptions Negligible reflection, empirically justified. All Antennas deployed have similar gain pattern, orientations may vary

10. Simulation Concept The simulator accepts input data: a)Location of antenna b)Transmit power into the antenna c)Antenna gain pattern Output of the simulator: a)Signal strength at various locations when measured with a 0dBi gain antenna.

11. Simulation Concept Example output: One antenna located at (50,50) and both axes in unit of m.

12. Regulations “Listen Before Talk” – ETSI 302 208 The threshold values:

13. Results Interpretation Antenna radiating 2.0 W ERP at (50,50). The next antenna to be placed at the side must be 150 m away if the next antenna would want to radiate in the same channel. 350 m 150 m

14. Results Interpretation Antennas radiating 2.0 W ERPat (50,50) and (400,50).

15. Simulation Variation Antenna on ground: Antenna 2m above ground is very similar to antenna on the ground.

16. Results Interpretation Antenna radiating 2.0 W ERP at (50,50). Antenna on ground radiating 2.0 W ERP at (400,50). Reduced

17. Frequency Channelling So far, all the simulations are dealing with same channel radiation.

18. Frequency Channelling Transmit Mask for Dense-Interrogator Environments: (extracted from EPCglobal C1G2)

19. Frequency Channelling Both antennas operating 3 channels away from channel of interest. The black line indicates the boundary where a antenna can be positioned to operate in the channel of interest.

20. Summary of Results  Note that these results are only true when an isotropic 0dBi receiver antenna is used. When a directional antenna is used as the receiver, the results will be very different depending on the angle between the transmitting and receiving antenna.

21. Summary of Results  The results shown is very challenging for RFID deployment.  Luckily, various policies can be adopted to improve the situation. These include: a)Synchronization b)RF shielding c)Optimising reading time d)Optimising radiated power e)Sensor controlled readers

22. Future Work  A systematic way of determining n  Changes with different environments  A more user friendly simulator.

23.  Thank you Questions?