Towards Scalable Backscatter Sensor Networks Aggelos Bletsas & - - PowerPoint PPT Presentation
Towards Scalable Backscatter Sensor Networks Aggelos Bletsas & John N. Sahalos RadioCommunications Laboratory (RCL) Aristotle University of Thessaloniki, Greece Cost Assist Workshop April 2008, Cyprus Outline 1. Introduction to RFIDs:
Aggelos Bletsas & John N. Sahalos
RadioCommunications Laboratory (RCL) Aristotle University of Thessaloniki, Greece
April 2008 RCL, Cost Assist Workshop 2
Market Incentives, Technology & Business Challenges
April 2008 RCL, Cost Assist Workshop 3
RFID antenna + microchip, laminated,
printed or encapsulated, powered by battery or via magnetic, electric (NFC) or electromagnetic coupling. …part of automatic identification technologies (bar codes, magnetic stripes, twisted wires) 80’s: car parks, road tolls (vehicle) 90’s: smart cards (people, vehicle, animals) 00’s: large consumer goods (e.g. Gillette), supermarkets (e.g. Walmart)
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“An expensive technology with features no-
A PROBLEM”! “barcodes with an extensive network of readers can do the job” [R. Platts, “RFID-Panacea or Pain”, IEEE Engineering Management Review, vol. 35, no 2, 2007]
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Hospital employees spend ~25-33% of their time searching for
equipment and losing about 10% of their inventory annually (RTLS importance). RFID could save a 200-bed hospital 600 K$ annually, from less shrinkage, fewer rentals, procurement planning, staff productivity
[M. Glabman, “Room for tracking: RFID technology finds the way”, Materials Management in Health Care, May 2004]
USA FDA: ~500,000 deaths due to medical mistakes… … half of the drug errors are preventable … in paper-based environment errors approach 40% (39% at prescription, 12% at transcription, 11% dispensing )!!!
[M. McGee, “Health-Care I.T. has a new face”, Information Week 988:16, 2004], [A. M. Wicks, J. K. Visich, S. Li, “RFID Applications in Hospital Environments”, Hospital Topics, vol. 84, no. 3, 2006]
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Airport luggage handling: M$ market… [interestingly, combination of RFID/Barcodes!] Example Airports: Hong Kong, Stockholm, Brussels, Zurich, San Francisco
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Airport luggage handling: M$ market….(well-known)
…airport delayed check-in, security & boarding: multi-M€ cost for European Economy! (not well-known) …think of reducing the delay from 30 min =>1 min in terms of fuel flight value! Potential solution: RFID ticket(?)
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Just-in time inventory control: reconcile what you have with what you think you
have… [enormous business value] Intel example: 0.25 M units valued at 50M$, lesson learned: “100% read accuracy is needed only at selected stations, which helps products moving” Metro Group example: “highly satisfied customers from 34% => 54%”
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RFID: 0.05€ - 0.2€ (100billions/year) Passive RF Sensors: 0.1€ - 2€ (1 billion/year) Polymer (Printable) Sensors: < 0.01€ [source: Heikki Seppa, Functional Environment Seminar, VTT May 2004]
Emerging ideas: RFID + Sensors
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Improved Data Accuracy Increased Automation Real-time Inventory Tag/Reader Cost Obsolete Standards Limited Read Ranges 0 20 40 60 80 100 0 20 40 60 80 100
Technology Benefits Technology Risks
Tighter Partnerships Efficient Processes Labor Cost Reduction Lack of Standards No clear ROI Lack of Wide Industry Adoption 0 20 40 60 80 100 0 20 40 60 80 100
Business Benefits Business Risks
[ComputerWorld Magazine, 2004], [M.L. Chuang, W. H. Shaw, “RFID: Integration Stages in Supply Chain Management”, IEEE Engineering Management Review, vol. 35, no. 2, 2007]
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1. Read Range (frequency dependent) 2. Communication throughput (bps/sensor) 3. Scalability (number of RFID sensors) => anti-collision ability 4. Accuracy/Reading speed (number of sensors/sec): ~ 40 tags/sec current state of the art 5. Antenna size (as small as possible) 6. Packaging material & environment (affect reader/tag coupling) 7. Efficient tag manufacturing & programming 8. Tag/Reader Cost 9. Integration: addressing all (or most of) the above in an application!
Integrated, Application-Driven Approach is needed.
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Near Field Communication (Capacitive or Inductive Coupling) Backscatter Communication (Electromagnetic Coupling) Range increases… Throughput/sensor increases… Water/metal penetration increases…
ISM bands different across continents => need for flexible Readers… SDR a valid solution…
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Tag/Reader Cost Obsolete Standards Limited Read Ranges 0 20 40 60 80 100
Technology Risks RFID + Sensors => Sensor Networks via Backscatter = Backscatter Sensor Networks Cost => Commodity Hardware, Software-Defined Radio for Reader, Reader-less, ultra-low cost sensor ! Range => Semi-passive (battery assisted)… battery already present for sensor electronics (e.g. humidity/CO2 sensor)… however, communication is achieved via backscatter only… low-bit rate for environmental sensing (e.g. plant monitoring in agricultural fields ) Obsolete Standards => Software-defined reader!
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Ultra-low cost complexity tag/sensors
Unidirectional communication Ultra-fast fading (changes within same symbol) [Unique] Easy-to-debug, scalable implementation trading off bit-rate for all the above… (environmental sensing does not need large bandwidth/sensor)
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Main problem in sensor networks: battery life is limited…
Backscatter sensor nodes require battery for modulation purposes and not for transmission/reception!
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Networks", IEEE Transactions on Wireless Communications (TWC), in press.
Sensor Hub (Reader)
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1. Read Range (frequency dependent) 2. Communication throughput (bps/sensor) 3. Scalability (number of RFID sensors) => anti-collision ability 4. Reading speed (number of sensors/sec): ~ 40 tags/sec current state of the art 5. Antenna size (as small as possible) 6. Packaging material & environment (affect reader/tag coupling) 7. Efficient tag manufacturing & programming 8. Tag/Reader Cost 9. Integration: addressing all (or most of) the above in an application!
April 2008 RCL, Cost Assist Workshop 18
For agricultural fields, sensor density
is large (~1-1.5 sensor/m2)… Large number N of sensors is needed… Required bandwidth is proportional to N… Anti-collision performance depends
…tradeoff between anticollision performance and N (or bandwidth)
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Beamforming antenna: Tag Collision occurs when tags close in modulating frequency AND close in geographical space… => Larger number of sensors for given bandwidth (compared to omni)!
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Edge Collision probability is analytically derived as a function of reader antenna directivity
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Density: ~1.5 sensor/m2 Bandwidth Reduction (or Capacity Enhancement): ~2 Results apply to passive tags as well… Proposed Tag anti-collision assists alleviation of Reader Collision problem as well!
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Experimentation with meander-type antennas, proposed in the literature for passive tags… Battery-assisted tags: no need for power transfer => different problem…
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Design… Prototype… Radar Cross Section can be increased compared to passive case (perfect matching).
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Carrier transmitted… Tag modulating waveform… Received (backscattered)
waveform…
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Augment Reader Antenna with Diversity Reception Techniques… Experimental Testing indoors (many reflections) and outdoors…
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RFIDs present important technical challenges…
BSNs present important technical challenges… Scalability can be assisted by practical reader antenna designs… Theoretical and practical results could assist other relevant RFID technologies… RFID sensor technologies are emerging with significant financial and social potential… RFID & BSN Research should be holistic, application oriented with integration properties…
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Aggelos Bletsas & John N. Sahalos RadioCommunications Laboratory (RCL) Department of Physics, Aristotle University of Thessaloniki, Greece {sahalos,bletsas@auth.gr}
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Goals:
Maximize Range/Coverage Efficiency Maximize Energy Efficiency Maximize Security (not covered in this presentation) Minimize Complexity & Cost
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The backscattering properties of antennas are relevant but not necessarily the same as the radiation patterns, and as such, more fundamental research is needed to maximize antenna
and/or range. Special care should be given at the packaging material and the application- dependent antenna surroundings that significantly alter the EM properties.
The advantages of multi-antenna detection and reception techniques can be harnessed to further improve received SNR (or equivalently, increased range). In this category, falls multi- antenna non-coherent reception, beamforming or combinations therein. Moreover, emphasis should be given in computation-efficient algorithms able to extract information from hundreds or thousands RFID sensors simultaneously.
Materials and/or Metamaterials that could improve antenna properties, as well as manufacturing and packaging processes necessary for mass production, mass programming and scalable installation are the theme of this topic. Printed electronics is an example that could be of immediate help. The element of integration is crucial, given the interdisciplinary and applied character of research that requires a thorough, top-bottom approach.