Using Passive UHF RFID to Create The Intelligent Airport

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2 Using Passive UHF RFID to Create Intelligent S. Sabesan, M. J. Crisp, R. V. Penty and I. H. White Photonics Communications Group Department of Engineering University of Cambridge 9 J J Thomson Avenue Cambridge CB3 0FA, UK ss740@cam.ac.uk Acknowledgements: UK EPSRC under the TINA project and Boeing Company for financial support.

3 Overview Background challenge Project aims & objectives Introduction to Radio over Fibre for Inbuilding DAS Progress Radio over fiber (RoF) distributed antenna system (DAS) RFID system RFID range enhancement with improved reliability RFID and communications overlay

4 Challenge Services to be supported in airport environment (mean data rates): 1,000 Fixed and 500 Mobile Video Cameras - 10 Gb/s 500 Displays - 10 Gb/s 500 Biometric Scanners - 10 Gb/s Private and Public Fixed and Wireless LAN - 20 Gb/s Cellular services - 10 Gb/s TETRA and private radio Gb/s Passive RFID Gb/s Active locatable RFID - 5 Gb/s Aggregate Mean Rate 65.7 Gb/s, assumed Aggregate Peak Rate 100 Gb/s And system must be upgradeable, scalable, resilient and secure

5 Current Installations Main Hub Hub Base Station Cellular/PCS/Pagers Tetra/PDAs/Private Radio Antenna Unit Antenna Unit Cellular Operator 2 Main Hub Hub Wireless Coverage Area Base Station Cellular/PCS/Pagers Tetra/PDAs/Private Radio X n IT Closet Ethernet switch Antenna Unit Access Point Antenna Unit Access Point < 100m Server WLAN IT Equipment Room(s) Fixed Ethernet

6 First Phase Network RfID Central Units Single Wired/ Wireless Infrastructure Antenna Unit Antenna Unit Cellular Operators WLAN, Antenna Cellular RFID Antenna Coverage Unit Unit Data Server Splitter/ Combiner Unit Splitter/ Combiner Unit WLAN, Cellular RFID Coverage IT Room

7 (TINA) Project Aims: To develop a next generation advanced wired and wireless network for future airport environments Design a passive UHF RFID system in a manner that is able to track a wide range of objects, including passengers & luggage. Project Objectives: To design a new form of wireless signal distribution network where multiservice antenna units cooperate, not only to provide communication, identification and location services, but also to provide network resilience.

8 (TINA) A Self-Organising, Wired/Wireless Converged Machine. Will manage a wide range of fixed and mobile equipment, including passenger information and entertainment services.

9 Why RFID over Fibre in s? Allows tagging of other items e.g. passengers Late passengers contribute to 10% of all delays in UK Extremely expensive for airline business models Different airlines would use passenger location information in different ways! Security Tagging of passenger, along with video, would reveal suspicious behaviour Monitoring of security areas

10 Technical Challenges in Passive UHF RFID Systems Conventional passive UHF RFID system: is limited in read range of up to 10m. has poor read efficiency of around 80%. has medium read rate/speed of up to 700tags/sec. limited in location accuracy of around 4m.

11 Progress RFID Service Operation Over a RoF DAS RoF DAS RFID system Demonstration of enhanced passive UHF RFID coverage with optically-fed distributed multi-antenna system (DAS) returned signal power is enhanced by 10dB. read accuracy of multiple tags is increased from 79% to 100%. Passive Demonstration of a feedback controlled harmonic suppression system to allow passive UHF RFID to be overlaid on a shared infrastructure with communications services.

12 Low link loss Optical fibre: <0.5dB/km for SMF, 0.5~2dB/km for MMF (1310/1550nm) Coax cable: 380dB/km at 2GHz (RG-214, 11mm diameter, 200kg/km) Link loss is almost independent on the fibre length simplified link design High bandwidth of optical fibre and components SMF: (for our purpose) unlimited bandwidth. MMF: ~500MHz km (1310nm) but can transmit narrowband signals at high carrier freq. Lasers and Photodetectors >10GHz Low-cost implementation RoF cheaper than coax for >100m Optical components getting cheaper Why Use RoF? Attenuation [db/km] Cable RG-142 Cable RG- 214 MMF RG-142 Fiber Frequency [MHz] RG-214

13 RoF DAS for Enhanced Coverage in s Unreliable coverage from outdoor cells Fewer RF transceivers needed compared to distributed radios Analogue links may be coax cable (<100m) or fibre (>100m) Wideband versions can carry all required baseband and radio services Aim to allow passive UHF RFID as well + 3G.11a.11b/g

14 A Schematic of a Typical Duplex Radio over Fiber (RoF) System RoF allows longer transmission distances. RoF also allows to distribute signals to a number of antennas and thus the field of view of the reader can be greatly expanded.

15 Comparison of RFID over Co-ax and RoF RFID Rx AU2 AU1 RFID Rx Atmel Tag Tag RFID network on a single RoF DAS system RFID RFID Rx Rx Tag Atmel Tag Conventional RFID network on co-axial cables

16 RFID Network on a Single RoF DAS Returned Power (dbm) Received Power Vs Distance for 868MHz Distance (cm) With out RoF With RoF Successful reads Rx An 868MHz continuous wave (CW) carrier is transmitted at 28dBm EIRP. Reflected side band power measured with spectrum analyser for both with RoF and direct coax connection. performance of optically fed AUs is comparable to that of co-axial fed AUs. Nulls 2m 2m Distance Atmel Tag 1.4m

17 Demonstration of RFID Tag Reading over AU a Three-Antenna DAS System RFID RFID Rx AU RoF Hub Zinwave Hub AU Rx AU1 RFID Reader Tag Holde r Rx AU1 AU2 Aim to show improvement in Floor RFID read rate / accuracy Grid and reduction in nulls Rx AU3 AU1 Atmel Tag Tag

18 Demonstration of RFID Tag Reading over a Three-Antenna DAS System 0 1 Rx AU1 (-1, 0) (1, 0) Three Antenna DAN Single Antenna DAN Y (m) (-1.30, 4.30) AU2 Rx (-1.30, 6.30) (2.60, 7.40) Rx AU3 9 (2.60, 9.40) X (m) Received Power (dbm) Distance (cm) Successful reads Nulls

19 Demonstration of RFID Tag Reading over a Three-Antenna DAS System Comparison between single and triple antenna DAS CDF Single Antenna DAS Triple Antenna DAS Received Power (dbm) EIRP on each downlink is reduced by 5dB to give a total combined output of +24dBm; the same power as a single antenna system. number of nulls is reduced from 63% to 28% in the three antenna DAS over a single antenna DAS. An average enhancement of around 10dB in returned signal strength is also achieved.

20 Demonstration of Error Free Operation of a Commercially Available RFID System Rx AU1 A U1 Motorola Reader Zinwave Hub Rx AU2 A U2 Alien Tag Tag Rx AU3 A U3 A Motorola Symbol UHF RFID reader and Alien tag is used in this experiment. reader is configured to transmit signals in the UK frequency band i.e. between to 866.7MHz with +31dBm EIRP power.

21 Demonstration of error free operation of a commercially available RFID system Y (m) Rx (-1, 0) AU1 (1, 0) (1.25, 9.75) AU2 RSSI (db) (m) 5 DAS system DAS system (m) Rx (1.25, 11.75) 18 Rx (-1, 19) (1, 19) AU X (m) experiment is carried out in a 19x2m area. +31dBm EIRP output power, UK frequency band RSSI (db) (m) (m)

22 Demonstration of error free operation of a commercially available RFID system CDF DAS system Triple antenna DAS Triple antenna DAS with optimization RSSI (db) RSSI value is obtained at the location where the ID of the tag is successfully read. number of read locations is increased from <80% to 100%, providing a >20% improvement in the current UHF RFID system.

23 Comparison of RFID and Communications Standards Standard Frequency Downlink services Power (10m Cell) 900 MHz 1800 MHz Mod Accuracy (EVM) Peak to Average Power RFID has requires ~20dB more power than communications GSM Communications services demand good SNR to meet modulation accuracy limits Bandwidth ~0 dbm 7 % 0 db 200 khz/ channel 3G Very large 2.2 dynamic GHz ~5 range dbm will be 12.5 key % to a <12 multi-service db 5 MHz RoF UL 5 MHz DL link. However, the bandwidth requirement at the high power (i.e. RFID) end of the dynamic range is small. TETRA 350 MHz 450 MHz 2.4 GHz 5.2 GHz ~ -5dBm 10 % 3.6 db 3 MHz UL 3 MHz DL WIFI 2 nd Harmonic of RFID ~5 dbm signal particularly 5.6 % bad 10 db it falls 11 inband MHz for wide-band DAS, and close to GSM1800 band. UHF RFID 900 MHz +30 dbm N/A 0 db < 200kHz

24 Problems of Combined RFID and Communications RoF Links Output Power RFID Signal Comms Output Required SNR Required Power Difference 2 nd Harmonic fundamental 2 nd Harmonic above permitted level Spurious emissions limit Noise Floor Input Power RoF links suffer from inherent slight nonlinearity as well as noise. high power RFID signal will cause harmonic generation Since the system is broadband this spurious signal will be transmitted and may interfere with other systems.

25 Wifi+RFID Overlay Feedback Harmonic Suppression System Sig Gen + 300mMMF Output 2f f Φ DAC DAC Φshift ADC ADC Φdet P det AD8302 BPF A, Φ Convert Integrator μcontroller IQ Convert

26 Combined RFID + WiFi 0-10 RFID Carrier No Suppression With Suppression Power (dbm) 200kHz Resolution BW nd Harmonic WIFI (3% EVM) Harmonic Suppression Frequency (Hz) x 10 9

27 Performance Improvement of Combined RoF link with Suppression Maximum RFID carrier to harmonic Ratio Fundamental output Power at max Ratio Max gain with <- 30dBm output spurious RFID Outpu t Power g at link output power for 15dBm output g EVM No 2 nd Harmonic Suppression 49dBc -18dBm 37dB 19dB m -22dBm 1.9% No Suppression Reduced Input Power 58dBc (calculated) -27dBm (interpolated) 55dB 28dB m -40dBm 9.5% With 2 nd Harmonic Suppression 58dBc -14dBm 42dB 28dB m -27dBm 3.12%

28 Intelligent System Tracking passengers Taken from HK sister project

29 Intelligent System Late Passenger Alert Taken from HK sister project

30 Other Possibilities Security / airport personnel location monitoring Co-ordination in case of emergency No doubt many other applications Privacy issues? Passenger evacuation Simulations location records would highlight pinch points etc Real emergencies would help locate injured passengers, stragglers etc

31 Conclusions Have demonstrated RFID operation over RoF link and have shown that performance of co-ax and fiber fed AUs for passive RFID are similar. Demonstrated error free tag reading using a commercial gen2 RFID reader at reduced output power over a 19mx2m area. Returned signal power is improved by an average of around 10dB in the current UHF RFID system. Demonstrated a feedback controlled harmonic suppression system to allow passive UHF RFID to be overlaid on a shared infrastructure with communications services.

32 Future Work Investigating techniques to achieve an average location accuracy of <1m in passive UHF RFID system Estimating the location of passive RFID tag is a major challenge due to the narrow bandwidth available. most common techniques are based on RSSI location algorithms. However, multi-path effects, fading and nulls result in the RSSI being only a weak function of range. Improving the passive RFID tag read rate/speed Need to read more than 1000 tags/sec in application. Currently limited to 700 tags/sec.

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