INTRODUCTION TO NUMBERING SYSTEMS FOR RAIN RFID TAGS

The coexistence of all RAIN RFID applications (including those considered as closed-loop ones) relies on the fact that every single RAIN RFID tag carries a globally unique identifier. Such unique identifier, called UII (Unique Item Identifier) or EPC (Electronic Product Code), is the cornerstone for successful and efficient inventory management. Without globally unique identifiers, RAIN RFID simply doesn’t work. Therefore, a fundamental question that must be addressed by all users of RAIN RFID technology is, “What should I encode to my tags/labels?”  Stated another way, “Which standard should I use to format the data in my tags/labels?”  This document is intended to serve as an introduction to this topic and to the more detailed information found in the AIM publication “GUIDANCE ON DATA CONTENT AND STRUCTURE IN PASSIVE RFID TAGS.” 

RAIN RFID tags can be thought of as a blank slate of memory, which can be encoded with data by the user.  This is both an opportunity and a danger.  It is an opportunity in the sense that encodings can be flexible, customizable, and targeted for specific use cases.  It is a danger however when encodings overlap with each other causing interference between applications and/or are not decodable by reading systems.  The terms “Tag Clutter” and “Tag Pollution” are used interchangeably to denote the problems that arise when tags are not encoded as per a standard (see below for more information)

To avoid the pitfalls and allow users to take full advantage of RAIN RFID, tags must be encoded in accordance with a standardized “Numbering System” (“encoding scheme” in GS1 terminology).  There are many different standardized Numbering Systems in existence today and more are being developed. 

In the context of RAIN RFID encodings, standardized Numbering Systems fall into two basic categories:

1. GS1 Electronic Product Code (EPC) encodings
2. ISO Application Family Identifier (AFI)-based encoding

Each of these categories is further defined by specific standards and specific encoding schemes.  

The GS1 identification system and its various encoding syntaxes (including, but not limited to, EPC encodings for use with RAIN RFID tags) have cross-sector applicability for multiple industries and applications.

In contrast, the ISO AFI-based numbering systems are generally targeted at specific use cases / applications / industries.

Both TDS and the respective ISO AFI encodings include normative specifications regarding: 

• Which characters are supported based on specific input character sets (e.g., numbers, alphabetical characters, hexadecimal characters, Asian language characters, etc.);
• Which character-to-bit conversions are required or supported (often confusingly referred to as “encodings”);
• Which data elements (e.g., company identifier, product identifier, serial number, date values, etc.) must be encoded;
• Which data elements may be optionally encoded;
• Required or allowable sequences of data elements in the encoding;
• Which tag memory bank(s) is (are) to be used for which purposes;
• And other more detailed aspects of the encoding.

Using either a TDS-based or an ISO AFI-based standardized Numbering System and corresponding encoding can optimize RAIN implementations and avoid multiple problems.  The use of a standardized Numbering System : 

• Eliminates Tag Clutter:  Tag Clutter is when either too many tags are in a read-zone for a reader to process in the allotted time, or when tags from another application are erroneously read.  Eliminating Tag Clutter allows for easy filtering of targeted tags from incidental, stray reads.
• Ensures uniqueness: Adherence to a standardized Numbering System and appropriate serialization management prevent different organizations from unknowingly encoding multiple tags with duplicate numbers. 
• Facilitates resolution: The use of Numbering Systems allows readers to quickly and efficiently resolve tag data to gain additional item information when desired.
• Supports interoperability: Uniformity of data structures supports supply chain partnerships.
• Efficiently uses memory space: RAIN RFID tags have limited memory, so data must be encoded efficiently.

Selecting the appropriate standardized Numbering System for a given RAIN RFID application is important.   If a specific Numbering System is already in use for a barcode (or other AIDC)–based application, the same numbering system should be used for the corresponding RAIN RFID deployment.  

Applications using a proprietary “numbering system” need to envelope their encodings in a standardized ‘wrapper,’ to avoid the risk of collisions.  In this case, AIM recommends the use of the RAIN Alliance ISO Numbering System as the wrapper for proprietary numbering systems.  

If you are not already using a standardized Numbering System, the RAIN RFID Alliance has created a guideline, including a decision tree, to help you select the best Numbering System for your application.  After deciding on the appropriate Numbering System for your needs,  the next step is to consult the relevant section for your selected Numbering System in AIM’s publication “GUIDANCE ON DATA CONTENT AND STRUCTURE IN PASSIVE RFID TAGS.”  That publication will also point you to further documentation that may be necessary to understand the technical details and intricacies for proper implementation. 

NOTE:  The RFID Experts Group is beginning an extensive review of the above guidance document.  If you would like to learn more on how to participate in this review contact AIM.