The INtelligentAirport
Multiservice RF Infrastructure with Passive Tag Location Capability
Richard Penty, S Sabesan, Michael Crisp, Ian WhiteCambridge University Engineering Department
The INtelligentAirport
• Unreliable coveragefrom outdoor cells
• Dedicated indoor capacity
• Fewer RF transceivers needed compared to distributed radios
• Analogue links may be coax cable (<100 m) or fibre (>100 m)
• Wideband versions can carry all required baseband and radio services
In-Building Coverage/Distributed Antenna System
The INtelligentAirport
Distributed Antenna Network Performance
3 Antennas
(m)
(m)
Single Antenna
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-5
0
5
10
(m)(m
)
3 Antennas
Thro
ughp
ut (M
bps)
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-5
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The INtelligentAirport
Adding Sensing to Communications DAS
• Passive UHF RFID allows very low cost tags to be used for object detection at ranges up to 10 m
• Increasing demands for mobile data bandwidth is driving down cell sizes, requiring closer antenna spacing.
Can RFID be added as an additional service on RoF DAS allowing a shared infrastructure?
Can RFID leverage similar power requirement reductions to we have shown with communications services?
The INtelligentAirport
Why RFID over Fibre in Airports?
• RFID is considered cheaper than bar code readers
• But <100% read rate reliability means critical reading for e.g. baggage is compromised
• Only two airports internationally implement RFID for baggage handling
• Within TINA we’ve tried to improve read success rate over a wider area
• Airport applications, particularly if security sensitive, really do need ~ 100% success rate
• Will allow 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
The INtelligentAirport
AU1
Tag
Rx Tx
AU3Rx Tx
AU2
TxRx
Zinwave H
ub
AU1
AU1
AU1
Tag
RFID Tx
RFID Rx
DA
S
Processing
Aim to show improvement in RFID read rate/accuracy
and reduction in nulls
Improved Tag Detection with DAS
The INtelligentAirport
Demonstration of Error Free Operation Usinga Commercial RFID System
-1 -0.5 0 0.5 1
0
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20
X (m)
Y (m
)
Rx (-1, 0)
Tx (1, 0)
(1.25, 9.75) Tx
Rx (1, 19)
Tx (-1, 19)
Rx(1.25, 11.75)
AU1
AU2
AU3
19 x 2 m area. +31 dBm EIRP output power, UK frequency band
The INtelligentAirport
Improving Read Rate and Accuracy - Intel R1000
Command-Begin Packet
Antenna-Begin Packet
Inventory-Cycle-Begin Packet
Inventory-Round-Begin Packet
Inventory-Response Packet
Inventory-Round-End Packet
Inventory-Cycle-End Packet
Antenna-End Packet
Command-End Packet
DAS Settings
Intel R1000 Firmware
Intel Transceiver R1000
Intel R1000
PC
Intel Transceiver Interface(executing on PC)
USB Interface
(executing on ARM7)
SSB Interface
Serial InterfaceARM7
Micro controller
DAS Settings
Intel R1000 supports host side applications (Intel Transceiver interface). The transceiver interface includes a C/C++ functional interface to talk to the firmware module using USB communication.
When an inventory is performed using the transceiver interface, it returns data from the Intel firmware in a sequential of packets.
Phase is varied when it returns the inventory-round-begin packet which indicates the beginning of a an inventory round on an antenna.
The INtelligentAirport
DAS RFID System
Tx
AU1
Tag
Rx Tx
AU3Rx Tx
AU2Rx
AU3
AU2
AU1
Alien Tag
Zinwave H
ub
Intel R1000 Firmware
Intel Transceiver R1000
Intel R1000
TagAlien TagTagAlien
TagTagAlien TagTagAlien
TagD
AS
Processing
The INtelligentAirport
Enhanced Read Rate/Accuracyusing R1000 Reader System
80 Alien Higgs2 tags are placed at a height of 2 m in a 50 cm grid interval over a 10 m x 4 m area.
AU3
AU1
AU2
The conventional RFID system takes 1.7s to read 62 tags out of 80 (77.5% accuracy) - read rate of 36 tags/sec.
The R1000 system takes 1.2s to read all tags (100% accuracy),- read rate of 67 tags/sec
The INtelligentAirport
Providing Location in optical DAS RFID system
Now we can read a tag (quickly) over a large area, we have lost the location accuracy of an RFID “portal” – can we somehow improve the accuracy
Estimating the location of passive UHF RFID tag is a major challenge due to the narrow bandwidth available.
The 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.
By using an optical DAS with multiple antennas, we can reduce the degree of fading in the field of view- and thus significantly improve the accuracy of RSSI location techniques.
The INtelligentAirport
Passive UHF RFID RTLS
Pillar
Location Algorithm• The area is first mapped by recording the
combined RSSI from all the AUs and the RSSI of each AU
• Measurements are repeated five times at each grid point and the AU with the highest number of successful reads is identified.
• Location is then estimated by finding the closest match of:
• the three antenna RSSI• the RSSI from the mostly likely
closest antenna • the probability that the antenna is
closest to the tag from the mapped data set.
• A maximum likelihood weighting is applied to the mapped data.
The INtelligentAirport
Demonstration of Enhanced Location Accuracy
Optimised DAS
Random Commercial RFID Reader
Mean error 1.9 m 4.6 m 4.1 mStandard deviation 1.0 m 3.6 m 2.1 m
Error Distribution
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15
20
25
30
0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5
Error (m)
Per
cent
age
(%)
Triple antenna DAS
Random
Commercial RFID Reader
The INtelligentAirport
Demonstration of Enhanced Location Accuracy
100% location estimations using the DAS has less than 4.2 m error compared to only 55% and 40% from the commercial RFID reader and the random algorithm respectively.
0 1 2 3 4 5 6 7 8 9 100
0.2
0.4
0.6
0.8
1
Error (m)
CD
F
Error distribution
Triple antenna DASRandomCommercial RFID Reader
The INtelligentAirport
Tracking/Location System GUI
We intend to use the current system as a test bed to develop new algorithms.
The INtelligentAirport
Application Software Integration with Hong Kong-TINA Project
Intel R1000
CambridgeSoftware
MySQLDatabase
HK-TINASoftware
The INtelligentAirport
Demonstrator
Passive RFID over DAS demonstrator exhibiting
• Large passive RFID field of view
• 100% read accuracy using DAS to reduce fading
• Enhanced read rate (67 tags/second)
• RSSI based location with 1.9 m mean error
• Integration with HK TINA software demonstrators