RFID Sensor NetworksJoshua R. SmithAssociate ProfessorComputer Science & Engineering andElectrical EngineeringUniversity of Washington
FISC 2030
March 22, 2012
RFID Sensor NetworksJoshua R. SmithAssociate ProfessorComputer Science & Engineering andElectrical EngineeringUniversity of Washington
FISC 2030
March 22, 2012
WISP 3 axis x 10 bit accelerometer
First UHF RFID w/ accelerometer
RFID Sensor Networks with the Intel WISP Winner Best Demo, Sensys 08M. Buettner, B. Greenstein, R. Prasad, A. Sample, J.R. Smith, D. Yeager, D. Wetherall.
WISP: A Passively Powered UHF RFID Tag with Sensing and Computation, D.J. Yeager, A.P. Sample, J.R. Smith, in S.A. Ahson, M. Ilyas Eds. RFID Handbook: Applications, Technology, Security, and Privacy, CRC Press.
WISP: Wireless Identification and Sensing Platform
WISP & UHF RFIDUHF RFID: Much longer range than earlier generations of RFID (up to 30 feet)Uplink communication by “backscatter” (reflection)…very low powerBackscatter energy efficiency improves with Moore’s law, unlike conventional radio!!WISP has no battery…powered by “reader” deviceWISP: Programmable, software defined, sensor-extensible RFID tag
RFID readerant
Tag
TagPower & data (“downlink”)
Data (“uplink”)
WARP – Ambient RF HarvestingWARP: Wireless Ambient Radio Power
1 MW TV transmitter – 4.2 km distance
Harvests from environmental RF sources Television band GSM band
Onboard sensing and computation
Low-power radio uplink
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8am 4pm
“Wireless Ambient Radio Power,” A.P. Sample, A.N. Parks, S. Southwood, J.R. Smith inWirelessly Powered Sensor Networks and Computational RFID, Springer, 2012
WARP – Ambient RF Harvesting Battery-free environmental sensing
Weather statistics Toxic gas monitoring (e.g., CO)
Next Steps Extended range radio Optimized harvesting and storage GSM Harvesting
“Printed Low Power Amperometric Gas Sensors Employing RF Energy Harvesting”M. Carter, J. Stetter, J. Smith, A. Parks, Y. Zhao, M. Findlay, V. Patel, Proceedings221st ElectroChemical Society Meeting, May 2012
Key enabling trend
Range scaling of far field WPT
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1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020
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Microprocessor EfficiencyFriis Distance (Power Limited)Exponential FitExponential Fit
f
0.462 tc
Friis(Moore(t)) wireless power range scales exponentially (!) … …but with exponent that is ½ of EPI (IPuJ) scaling
Inst/Jdoubling time2 years
Rangedoubling time4 years
0.232 td
While Inst/J is continuing to scale, voltage scaling is ending. Thus techniques to efficiently harvest at low voltage are desirable.
Possible outcome if voltage scaling limits cannot be compensatedfor
from Mapping the space of wirelessly powered systemsin Wirelessly Powered Sensor Networks and Computational RFIDJoshua R. Smith Ed., Springer 2012
What does this scaling trend mean?
Capabilities that barely work today will become robust in the future
“Low end” devices like RFID tags will get increasing compute functionality, e.g. full-programmability
It will become possible to RF-power devices that seem too power-hungry today, e.g.
• microphones
• cameras
Research effort is needed to overcome the voltage scaling challenge
Bad news: the further away we are, the lower the voltage
Good news: voltage is not a conserved quantity…can be boosted!
8
Hybrid analog / digital backscatter sensing
The original Great Seal bug aka “The Thing”
Our idea:
WISPA digitally addressable passive backscatter micthat will be read by a SW Defined RFID reader
Combine benefits of analog (low power sensing)with digital (addressability, channel sharing, error correction, …)
Amazing that RFID reader can collect sound from a totally passive microphone! Theremin has come full circle.
Analog backscatter using SW Defined RFID Readers | Talla, Buettner, Wetherall, SmithIEEE RFID 2012
Digital / analog backscatter traces
4/11/201210
Default mode: Digital modeEPC Gen2 inventory followed by analog backscatter mode (1 second long)After 1 second in analog mode, switch to digital mode
Message exchanges between Reader and WISP
1 foot
5 feet
WREL Wireless power
“Analysis, Experimental Results, and Range Adaptation of Magnetically Coupled Resonators for Wireless Power Transfer,” A.P. Sample, D.T. Meyer, J.R. Smith, IEEE Transactions on Industrial Electronics, Feb. 2011, vol.58, no.2, pp.544-554
Powering a Ventricular Assist Device (VAD) with the Free-Range Resonant Electrical Energy Delivery (FREE-D) System, Benjamin H. Waters, Alanson P. Sample, PramodBonde, Joshua R. Smith, Proceedings of the IEEE , vol.100, no.1, pp.138-49, January 2012.
Future work:Extreme wirelessly powered sensor systems
Fully implantable, fully wireless, perpetual
• Heart pumps
• Neural implants
• Wirelessly powered telephones / listening devices
• RF-powered & read camera
• SMS-powered SMS messaging
Intel Science & Technology Center for Pervasive Computing5 year center funded by Intel
Acknowledgement
http://istc-pc.washington.edu
ECCS-0824265, "Realizing the internet of things with RFID sensor networks"
NSF EEC 1028725 “NSF Engineering Research Center for Sensorimotor Neural Engineering”
Faculty Research Award
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