1. TECO
Protocol Optimizations
using anonymous EPC
Gen2 Inventories

2. Local Inventory Problem
How many products of a
certain type are in a
shelf ?
4-Apr-12 Copyright TecO 2007, Restricted Use 2

3. Conventional Solution
10000
 Use high level interfaces
.95
.99  Get IDs of all/selected
8000 tags
6000 Problem:
 Long readings
time (ms)
m
e
s
)
(
t
i
 Static environment
4000
 Still uncertainty
2000
0
Solution:
0 10 20 30 40 50 60 70 80
number of tags  Statistical approach
Source: Vogt, H. (2002). Efficient Object Identification with Passive RFID Tags.
4-Apr-12 Copyright TecO 2007, Restricted Use 3

4. Problem: Channel Arbitration
S ing le Tag Repl y
QueryRep or
Interrogato r Select CW Query CW Ack CW QueryRep QueryAdjust
if EPC is valid
NAK if EPC
NAK
is invalid
Ta g RN16 PC + EPC+ CRC16
T4 T1 T2 T1 T2
C ollided R eply No Repl y Invalid AC K
Inte rrogato r Query CW QueryR CW QueryRep CW Ack CW QueryRep
Collision No No
Detected Reply Reply
Ta g RN16 RN16
T1 T2 T1 T3 T1 T3
4-Apr-12 Copyright TecO 2007, Restricted Use 4

5. Idea 1: No IDs - just count
S ing le Tag Repl y
QueryRep or
Interrogato r Select CW Query CW Ack CW QueryRep QueryAdjust
if EPC is valid
NAK
NAK if EPC
is invalid
Ta g RN16 PC + EPC+ CRC16
T4 T1 T2 T1 T2
50% Speed up
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6. Idea 2: Count Collisions and
empty slots
C ollided R eply N o Re ply
Inte rrogato r Query CW Query CW
Collision No
Detecte d Reply
Tag RN16
T1 T2 T1 T3
Collision means 2 or more Tags
calculate: min # of tags
estimate: # tags
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7. Estimation of # Tags
in Slotted Aloha Frame
Lower bound
Estimation
Source: Vogt, H. (2002). Efficient Object Identification with Passive RFID Tags.
4-Apr-12 Copyright TecO 2007, Restricted Use 7

8. Algorithm
(1) Select Product (prefix in EPC memory)
(2) Start a new Round of 2Q slots
(3) Count Success, Empty and Collisions
(4) Calculate estimated and minimal
number of Tags
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9. Fully EPC Gen2 compatible
Query Power-up & ~killed
Slot NEW ROUND
QueryRep slot CMD: Query [mismatched
QueryAdjust Counter
inventoried or SL flags]
Reply: None
CMD: Select
Action: Return to ready
Ready
Reply: None. Note 1
CMD: Query NEW ROUND
Action: New round CMD: Query [slot > 0 & matching
Reply: Note 3 (inventoried & SL) flags]
CMD: All other Reply: None
Action: Remain in ready
Reply: None
CMD: QueryRep, QueryAdjust [slot <> 0]
Arbitrate Reply: None
NEW ROUND
CMD: QueryAdjust, QueryRep [slot=0] CMD: Query [slot = 0 & matching
Reply: New RN16 (inventoried & SL) flags]
CMD: Select Reply: New RN16
Action: Return to ready
Reply: None. Note 1
CMD: Query
Action: New round CMD: QueryAdjust [slot = 0]
Reply Reply: New RN16
Reply: Note 3
CMD: All other
Action: Return to arbitrate
Reply: None. CMD: ACK [valid RN16] CMD: ACK [valid RN16]
CMD: None within time T2 Reply: PC, EPC, CRC-16 Reply: PC, EPC, CRC-16
Action: Return to arbitrate CMD: Req_RN [invalid RN16]
Reply: None. Reply: None
Acknowledged
CMD: Req_RN [valid RN16] & {access password = 0}
Reply: Handle
CMD: Req_RN [valid RN16] &
{access password <> 0} CMD: ACK [valid han dle]
Reply: handle Reply: PC, EPC, CRC-1 6
CMD: Req_RN, Read, Write, Lock, BlockWrite, BlockErase
Reply: See state-transition tables
CMD: Select CMD: Kill [valid handle & kill password = 0]
Action: Return to ready Open
Reply: Error code
Reply: None. Note 1 CMD: Kill, Access [invalid handle]
CMD: Query Reply: None
Action: New round
Reply: Notes 2, 3 CMD: Access [valid handle & valid access password]
CMD: QueryRep, QueryAdjust Reply: handle when done
4-Apr-12 Action: Return to ready Copyright TecO 2007, Restricted Use 9

10. Tag Requirements
 EPC Gen2
 ...
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11. Reader Requirements
 Stage 1:
Get # of collisions
Get # of slots / frames
Select product group*
 Stage 2:
Set # of slots/frames
 Stage 3:
Raw Reader/No Firmware
Change Algorithm (i.e. No ACKs)
* product distribution could also be estimated
4-Apr-12 Copyright TecO 2007, Restricted Use 11