15-446 Networked Systems Practicum Lecture 6 – RFID technology 1.
-
Upload
cody-bruce-blake -
Category
Documents
-
view
219 -
download
0
Transcript of 15-446 Networked Systems Practicum Lecture 6 – RFID technology 1.
15-446 Networked Systems Practicum
Lecture 6 – RFID technology
1
• Basic RFID
• NFC (RFID + Storage)
• Next Generation RFIDs (RFID + Computation + Storage)
2
RFID History
• First Bar code patents – 1930s• First use of RFID device – 2nd world war – Brittan used RFID-like
technology for Identify- Friend or Foe • Harry Stockman October 1948 Paper – Communication by means of
reflected power ( The proceedings of the Institute of Radio Engineers)• First RFID Patent - 1973• Auto-ID center founded at MIT – 1999
• Standardization effort taken over by EPC Global (Electronic Product Code)• Current thrust primarily driven by Wal-Mart and DoD
• Automate Distribution:• Reduce cost (man power, shipping mistakes)• Increase sales (keep shelves full)• DoD Total Asset Visibility Initiative
Basic Tag Operational Principles
NN
SS
TAG
Rea
der
Rea
der
TAG
BackscatterBackscatter
• Near field (LF, HF): inductive coupling of tag to magnetic field circulating around antenna (like a transformer)• Varying magnetic flux induces current in tag. Modulate tag load to communicate with reader• field energy decreases proportionally to 1/R3 (to first order)
• Far field (UHF, microwave): backscatter. • Modulate back scatter by changing antenna impedance• Field energy decreases proportionally to 1/R
• Boundry between near and far field: R = wavelength/2 pi so, once have reached far field, lower frequencies will have lost significantly more energy than high frequencies• Absorption by non-conductive materials significant problem for microwave frequencies
Inductive CouplingInductive Coupling
Tag DetailsLF HF UHF Microwave
Freq. Range
125 - 134KHz 13.56 MHz 866 - 915MHz 2.45 - 5.8 GHz
Read Range
10 cm 1M 2-7 M 1M
Market share
74% 17% 6% 3%
Coupling Magnetic Magnetic Electro magnetic
Electro magnetic
Existing standards
11784/85, 14223
18000-3.1, 15693,14443 A, B, and C
EPC C0, C1, C1G2, 18000-6
18000-4
Application
Smart Card, Ticketing, animal tagging,Access, Laundry
Small item management, supply chain,Anti-theft, library, transportation
Transportation vehicle ID, Access/Security, large item management, supply chain
Transportation vehicle ID (road toll), Access/Security, large item management, supply chain
Types of Tags
• Passive• Operational power scavenged
from reader radiated power
• Semi-passive• Operational power provided by battery
• Active• Operational power provided by battery -
transmitter built into tag
Real Tags
Real Tags
Real Tags
Electronic Product Code
Header - Tag version number EPC Manager - Manufacturer ID Object class - Manufacturer’s product ID Serial Number - Unit ID
With 96 bit code, 268 million companies can each categorize 16 million different products where each product category contains up to 687 billion individual units
Note: 64 bit versions also defined, 256 bit version under definition
Class 1 Gen 2 tags
• 900 Mhz
• 10m range
• Downlink = information + energy• 26.7 – 128kbps
• Uplink = energy sent down as continuous wave (CW) + modulate reflection coefficient of antenna
11
Multiple Tags?
• What happens when multiple tags are in range of the transceiver?
• All the tags will be excited at the same time.
• Makes it very difficult to distinguish between the tags.
Collision Avoidance
• Similar to network collision avoidance
• Probabilistic• Tags return at random times
• Deterministic• Reader searches for specific tags
CIG2 MAC
14
Traditional RFID Market Segments
Auto ImmobilizersAuto Immobilizers
Access ControlAccess ControlAnimal TrackingAnimal Tracking
Automated Vehicle IdAutomated Vehicle Id
• Isolated systemsIsolated systems• Simple readsSimple reads• Slow growthSlow growth
The New Mkt SegmentConsumer Pkg Goods Supply Chain
Wal-Mart•June ’03 announcement•Pallet/Case tagging
Top 100 suppliers Jan ’05Other 30K by end of ’06
•4 Billion tags/year•300k direct readers•18 Million indirect readers
• End to end systemsEnd to end systems• Complex readsComplex reads• Emerging marketEmerging market
++
RFID in the Supply-Chain
Today: Outside the Supply Chain
• Basic RFID
• NFC (RFID + Storage)
• Next Generation RFIDs (RFID + Computation + Storage)
19
NFC Phy
• 13.56MHz frequency, 14kHz band
• Range 4cm (max 20cm)
• Active (2 transmitters) and Passive (1 transmitter + load modulation) mode
• Data rate = 106, 212 or 424kbps
20
NFC Tag Types
• Type 1 and 2• 96 or 48 bytes, 106kbps• Read/write or read only • Expansion to 2kbyte
• Type 3• 2kbyte• 212kbps• Read-only
• Type 4• 32kbyte• 106-424 kbps• Read-only
21
• Basic RFID
• NFC (RFID + Storage)
• Next Generation RFIDs (RFID + Computation + Storage)
22
• Collection of small, battery-powered sensing devices (motes)
• Peer-to-peer communication (multi-hop network)• Range of monitoring applications:
• habitat monitoring, structural integrity of bridges• volcanic activity, forest fires, etc.
23
UHF RFID EPC Class Gen 2
• Powered reader infrastructure plus simple passive tags
• Direct reader to tag communication• 4W EIRP from readers, tags “backscatter,” range of up
to ~30ft • Applications around inventory / supply chain
management
24
25
• Combine the best of both: • Small / inexpensive passive tags that sense/compute
(WISPs) and communicate directly with apps in infrastructure (via readers)
• Key advantages:• Ubiquitous, long-lived instrumentation, business simplicity,
flexibility
26
Milk App
Cold chain monitoring: •Track many small items, e.g., bags of blood, items in fridge, with cheap and/or disposable tag •Use proximity of readers to sense temperature and vital statistics when refrigerated most of the time •Use stored energy (super-cap) to sense for brief periods when items are away from reader and exposed
27
Intermittent Power
• How do we run programs on WISPs with intermittent power?
• WISP power model: • Gathers energy from
readers, when in range (~15ft) at unpredictable times
• Has limited on board storage (capacitor << battery)
• Expends energy to sense/compute and communicate
• Slowly loses stored energy
28
• WISP API to expose power state to application code• “Enough power yet to complete this step?”
• Divide large computation into multiple small stages• Store state in non-volatile memory or on readers
• Coordinate to match reader power to WISP needs• Continue to provide for a sufficient interval
• Implications • Lower reliability due to unpredictable contacts, power
durations • Variable frequency of operation due to “pre-charge”
period
29