A PROTOCOL FOR DATA HANDLING IN RFID

1
A PROTOCOL FOR DATA HANDLINGIN RFID

• Ron Tillinger
• AIAG Program Manager
• Convenor of SC31 WG4 SG1 Data Syntax
• Oct 2000 ActionLINE Article

2
Developments Towards ISO/IEC 15962RFID for Item
Management - Data Syntax

• To date, RFID applications have been in closed
  systems
• where the mapping of the encoded data could
  be unique to
• the implementation (anything goes approach)
• To prevent chaos throughout the supply chain, we
  must
• move to open-ended systems where the data
  protocol
• data handling rules are done in a
  standardized prescribed
• way

3
DATA CARRIER TECHNOLOGYHow Does RFID Differ From
Bar Code?

• Features which bring benefits to users
• read/write
• no line-of-sight required
• anti-collision batch reading
• Features which are different
• data capacity
• - bar codes are fixed limited
• - RFID doubles in each new version
• - different capacity tags can be intermixed
• memory material

4
RFID TECHNICAL FEATURESRead / Write

• Overwrite some or all the data
• Append new data
• Selectively read some of the data
• All these mean that the data handling rules for
  RFID
• need to be different from the message-based
  structures of bar code
• RFID is better suited as a data carrier of data
  objects

5
RFID TECHNICAL FEATURESOthers

• No line-of-sight, so it is not possible to
  recognise that a tag is present,
• nor to recognise the format of the tag
• Air interface controlled by radio regulators,
  power emission is restricted -
• affects data transfer rates
• Differences between air interface protocols
  directly impact read / write
• rates
• Anti-collision, multiple tags in the field the
  more tags in the field, the
• shorter the time for tag to each transmit its
  data

6
READING A VARIETY OF RFID TAGS There Are No
Visual Clues to the Type of Tag Nor the Type of
Data It Encodes
Tag A
Tag
Tag C
Tag B
Tag A
Reader/Writer
7
ISO/IEC STANDARDISATIONSC 31 Structure
8
What WG4 SG1 Had to Consider

• SG1 was given its tasks before technology
  submissions were made to Air Interface group
  (SG3)
• SG1 had to work on the basis that there was no
  knowledge of
• how frequencies will be combined in applications
• which air interface protocols would be
  standardized
• tag architecture and functional capability
• One tag could offer the functions of a linear
  symbol, the next a complex 2-D symbol
• Therefore, the deliverable from SG1 had to be
  (generally)
• independent of technology features and constraints

9
THE CHALLENGE - Develop Data Handling to Address
the Technical Features

• RFID requires that data handling is treated
  differently to take
• advantage of attributes and respect radio
  regulations
• Opportunity to develop object orientated
  approach to AIDC
• data ( note still provide a hook for the
  legacy bar code data format)
• Requirement for data handling to be independent
  of
• technology differences in air interface
• RFID is a different data carrier technology

10
WG4 SG1s APPROACHCreative Thinking

• Used an Object Oriented approach where data
  handling
• encoding protocol makes use of object
  identifiers to
• uniquely identify data objects
• enable selective read and / or write in a
  reliable manner
• Used ISO specified ASN.1 as a tool to
  unambiguously
• compactly define objects to any level of
  granularity
• ASN.1 - Abstract Syntax (effectively a data
  definition language)
• has the power of high level programs but is
  independent of
• host application operating the system
• program language
• specific command structure between interrogator
  tag
• has a transfer syntax (set of Packed Encoding
  Rules)

11
WG4 SG1s APPROACHCreative Thinking

• Conceived logical memory map, (independent of
  tag architecture)
• Decided to support different data storage
  formats
• Decided to allow for Application Family
  Identifiers to
• support selective inventory /or addressing of
  groups of tag
• Developed specific data compaction schemes for
  all tag types
• Defined that commands could be specified as
  objects,
• separate from data objects

12
WG4 SG1s CREATIVE THINKINGLogical Memory Map

• Supports any size of tag
• Syntax is application-orientated so it ignores
  any tag architecture
• blocks size
• protection
• This is addressed by interrogation when tag type
  is identified
• Memory can have directory or no directory
  structure, identified by the storage format

13
WG4 SG1s CREATIVE THINKINGDirectory Structure

• Directory from first octet forward
• Data from last octet backwards
• Data elements are stacked
• n.3,2,1
• Data itself is byte 1 byte n
• Concept of dynamic boundary
• between directory and data
• Free memory can be used for either
• purpose, making best use of free
• memory space

Directory gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt
gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt
Free space to be used either for data or
directory
nth datagt gt gt gt
...3rd data gt
gt gt gt gt gt gt gt gt gt2nd datagt gt gt gt gt gt gt1st data gt
gt gt gt gt gt gt
14
WG4 SG1s CREATIVE THINKINGStorage Format

• Access method, for example
• no directory
• directory
• self-organising tag (future sophistication)
• Data format techniques
• For Auto Industry DIs (Data Identifiers)
• Other Peoples Data (UPU, IATA, UCC/EAN)
• Other features, e.g. making data secure
• Encoded as part of the Systems Information

15
RFID FOR ITEM MANAGEMENTData Compaction Schemes

• The processor looks, on a case by case basis, at
  the type of data to be written as a data object
  to the tag.
• It selects the most efficient encoding scheme
  from the following alternatives (the potentially
  most efficient scheme is at the top of this list)
  
• Integer encodes number as binary
• Numeric 4 bits per digit
• 5-bit uppercase alphabetic
• 6-bit uppercase alphabetic, numeric, etc
• 7-bit all ISO 646 (US ASCII)
• Octet unaltered 8-bit

16
Overview
APPLICATION
INTERROGATOR
RF TAG
COMMANDS by Tag Type
Command / Response Unit
COMMANDS
Physical Interrogator
ASN.1
WRITE DATA
WRITE DATA
Logical Memory Map
Formatter
Compactor
Encode
ASN.1
Application Data Format Converter
READ DATA
ASN.1
Decode
READ DATA
TAG DRIVER installed for a tag type
DATA PROTOCOL PROCESSOR for protocol features
ISO/IEC 15962 SG1 Work
ISO/IEC 18000 SG3 Work
17
ASN.1Object Identifier Names

• Data objects have to be unambiguous
• Achieved by a structure of integer arc values
  (like branches from a trunk of a tree)
• Examples
• 1 0 15434 ISO/IEC 15434
• 1 0 15434 01 ISO/IEC 15434 Format 01
• It is possible to split object ID into two parts
• Root Object Identifiers (common to all, like a
  tree trunk)
• Relative Object Identifier (specific to an
  object, like a branch)

18
ASN.1 OBJECT IDENTIFIERArc Structure
iso (1)
joint-iso-itu-t (2)
Itu-t (0)
standard (0)
reg auth (1)
member body (2)
15434
Format Identifier (05)
Application Identifier (01)SCC14
1 0 15434 05 01
19
ASN.1 FOR RFID FOR ITEM MANAGEMENTA Summary of
the Benefits

• Defines objects to any level of granularity -
  just need an
• object ID
• The object tree ensures uniqueness of objects
• Therefore, it is possible to encode different
  types, including
• closed system objects with no risk of
  corruption
• Extension techniques make the system totally
  expandable -
• not just for object IDs

20
SUPPORT FOR THE DATA PROTOCOLInterest From
Application Standards Bodies
Universal Postal Union
21
RFID DATA CAPTUREAchieving Open-Ended Systems (1)

• Enables a basic secure system to expand
• the WG4 standards support a single data element
  or a more
• complex data structure
• Provides efficient encoding
• using the appropriate data compaction rule
• Allows variable length data
• using the run length before each object
• Supports selective read and write
• using the directory structure to access any
  object

22
RFID DATA CAPTUREAchieving Open-Ended Systems (2)

• Allows different data combinations to be
  intermixed
• the object ID system allows any combination of
  objects
• Allows the data element list to expand
• new data elements can be added to the list at
  any time
• tags and interrogators do not need to be
  upgraded
• Accommodates different future technological and
  user
• developments
• tags of different capacity and capability can be
  intermixed
• data to other application standards can be added
  if needed

23
Thank you for your attention
Ron Tillinger