EPCglobal Class-1
Generation 2
UHF RFID
Todd Humes, CTO
Impinj, Inc.
501 N 34th Street, Suite 100 Seattle, WA 98103
todd.humes@impinj.com
An RFID Chip
More transistors than the
processor in a 1985 IBM PC-AT
Lower power consumption than
a honeybee’s brain
RFID Hardware Overview
Wafers
Tags
Reader
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RFID is Old, what’s New
• New standards at UHF (900 MHz) vs HF (13.56MHz)
• UHF - 10X range of HF RFID
• Faster data rates – up to 640kbps
• But, presents many new challenges:
• How to identify and read/write single tags from hundreds within
a reader field...
• Tag and reader RF interference...
• Security....
• Tag data processing...
• Solution - EPCglobal Gen2 standard
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RFID Systems
Network layer
RFID Reader
Air Interface
Tag
Tag
IP
RFID Reader
Tag
Network
Tag
RFID Reader
Example data exchange:
Forward
Link parameters
Link rates and encoding formats
Return
Tag inventory
Singulation parameters, tag identification
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Tag Identification
• Suppose…you are all tags
•
•
•
•
You
You
You
You
are all blindfolded
are nearly deaf
talk by whispering
can’t hear each other
• Suppose…I’m a reader
•
•
•
•
•
•
I’m blindfolded
I don’t know who is in the room
I need to yell so you can hear me
If two of you talk at once, I can’t understand you
I’m not allowed to say your name
I may hear many others like me screaming in the same room
• I need to identify everybody in the room
What do I do?
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Reader Environments
• Operating Environment
• A region within which a reader’s RF transmissions are attenuated
by less than 90dB (roughly a sphere with a 1km radius)
• Single-reader environment
• A single reader operating in the environment
• Multiple-reader environment
• # of simultaneously active readers < # of available channels
• Example: 10 readers operating in 50 channels
• Dense-reader environment
• # of simultaneously active readers  # of available channels
• Example: 50 readers operating in 50 channels
Readers require knowledge of operational deployment and the
ability to adjust their RF parameters for a given environment ie. One non-dense reader in a dense reader deployment will spoil
the whole frequency plan
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Air Interface Control
Gen2 features
Purpose
S/W Control
Tag selection and
identification
Singulation control and options
for faster inventories
Q-algorithm, Boolean
selection, truncated replies
Dense reader mode
Allows for a large number of
closely spaced readers with
minimal interference and
optimized data rate for high noise
or high speed comm
Forward link options – DSBASK, SSB-ASK, PR-ASK
Return link options –
Baseband or subcarrier
backscatter
Sessions
Multiple readers talk within same
tag population
Choice of four sessions
e.g. dock door reader + handheld
Variable data rates
Link closure in varied
environments
Configure forward link (Tari,
pulsewidth) and reverse link
(preamble type, data rate,
encoding - FMO or Miller)
Kill and access
password
Security
Password validation and
management
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