When you encode radio frequency identification (RFID) tags, what data should you encode to them? This is a common question from end users and resellers of RFID solutions. Many people have been influenced by the use of RFID in the retail space, and because GS1 standards are prevalent in retail, people often wrongly conclude that all encodings for all applications are GS1-based. This is not true.
Although we do not know what percentage of tags use GS1 encodings, a rough guess is 40 percent. What are people encoding to the other 60 percent of tags? Another rough guess is that about 30 percent of tags are encoded using an ISO-based encoding. These encodings include airline baggage tags, many vehicle identification tags and most automotive parts tags. This still leaves 30 percent of tags unaccounted for. We believe that the majority of these unaccounted-for tags are encoded with proprietary, rogue encodings.
RFID tags are basically a blank slate of memory, and because many people have no idea what to encode, they consequently devise their own encoding schema—their own data in their own format. This is what we refer to as a proprietary or rogue encoding schema. Devising a proprietary, rogue encoding schema that is not wrapped in a standard is absolutely not a good idea. Keep in mind that there are already billions of tagged items in the world and billions more are coming online every year.
Tags that are not encoded according to a data standard will eventually interfere with tags from other applications, also known as tag clutter. I often use the example of my suitcase being tagged at the airport for baggage tracking. But what if I am also lugging hundreds of tags for a tradeshow within my suitcase? Imagine if Delta Air Lines’ baggage-tracking system suddenly started reading some of the tags in my suitcase and confused these tags for baggage tags.
Let’s provide some background. There are two main families of tag-data encoding standards: GS1’s EPC Tag Data Standard (TDS) and various ISO-based standards. Most relevant ISO standards for RFID can be found at ISO.org, and the new RAIN Alliance ISO Numbering System can be found at RAINRFID.org.
GS1’s EPC Tag Data Standard is relatively straightforward and easy to understand. If you need help with your GS1 encodings, you can contact GS1 directly. If I am a supplier to a major retailer, I may be told by the retailer to encode my data as per TDS using an SGTIN-96 encoding scheme. I can work my way through the Tag Data Standard and figure out what to encode.
However, using an ISO-based encoding may make more sense if I am not facing a mandate to use GS1, and/or I am in an industry that generally uses ISO encodings, and/or I want to encode relatively complex data (power user) and/or I want to encode tags for my own closed application. In this case, it might be a good idea to consider an ISO-based encoding. Where do you start?
The common starting point for ISO-based encodings is the organization’s 1596x group of standards. Standard ISO/IEC 15961-2 and its associated Data Constructs Register provide a great overview. What is the Data Constructs Register? It is a registry of tag-data-encoding starting points and their associated standards and entities (organizations, industries and applications). In the first section of this document, you will see what ISO refers to as Application Family Identifiers (AFIs), shown as hexadecimal values. Assuming no one has told you to use a specific AFI, you can browse through the available AFIs and select an appropriate one for your industry and application (licensing and/or written permission to use a specific standard may be necessary in certain cases).
Let’s run through an example to help clarify the point. I am developing an application to identify vehicles for tolling or a similar tracking purpose. Looking through the AFIs, I would eventually find: 0xB0, 6C Toll Operators Coalition Monomorphic-UII using 8-bit (Octet) encoding in ISO/IEC 18000-63 tags. This means that the AFI to use is B0 in hexadecimal. Okay, I at least have my AFI now. What next? The description also mentions the associated entity of 6C Toll Operators Coalition. It would be nice if more information were in the notes section, but I am creative, so I Google “6C Toll Operators Coalition,” find the organization’s website and even find its detailed tag-data standard. Bingo! I now have the instructions for precisely what to encode to my tag, assuming I can work my way through the technical jargon of the standard.
Here are some commonly used AFIs for ISO-based encodings:
- 01 to 03: These are designed for closed applications for which only a closed group of users will use the tag data. All three AFIs serve the same purpose, but three are available, so that you can add an extra layer of filtering for your readers. You might have three separate closed-loop applications you want to implement. For the details of what you would encode to the tag following the AFI, you would reference ISO/IEC 15961-3 as shown in the “Additional Notes” section in the Data Constructs Register PDF document referenced above. Of important note with these AFIs is that they do not necessarily lead to encodings that are guaranteed to be unique. In other words, proceed with caution if you use them. They could lead to tag clutter and are consequently not an ideal choice (see “AE” below for our recommendation).
- A1, A2, A3, A5, AC: These are designed for encoding barcode content to RFID. Note that they all reference ISO’s 1736x set of standards. This set will soon be combined into one standard, 17360, to make things easier to understand and work with. The first four AFIs use 6 bits to encode each barcode alphanumeric character. This allows you to encode characters from ISO’s 6-bit character set, which can be found in the 1736x standards. Here it is:
Image courtesy of the RAIN Alliance
And here is an example encoding of barcode content to RFID using the AFI of A1 (note the T bit set to 1 to denote ISO):
Image courtesy of the RAIN Alliance
The last AFI in this series, AC, serves the same barcode-to-RFID purpose, but it uses 8 bits to encode each character. This allows users to encode characters from the UTF-8 character set (one variety of Unicode), so if you are, for example, a Japanese automotive manufacturer, you can encode your kanji characters.
- AD: This AFI also references 1736x and is generally used to encode barcode content, but it does not encode barcode characters to RFID using a fixed number of bits per character. Instead, it uses what ISO people call binary encoding—it’s all ultimately binary, so if you find this term confusing, you are not alone. This affords dynamic optimizations of the number of bits used per character. The objective is really to use less tag memory to encode more characters.
- 92: This AFI points you to the ISO/IEC 20248 standard. 20248 is a powerhouse standard, which is also targeted at encoding barcode content to RFID. Why yet another AFI and standard for barcode content? Because 20248 introduces some additional power features to your encodings, such as support for digital signatures and the use of JavaScript Object Notation (JSON) for data formatting. Digital signatures are rapidly gaining momentum in the RFID world as users are beginning to realize how vulnerable their data is. And JSON is basically a data format, which allows the data to be shared across systems extremely easily and efficiently, signifying, “My tag data can be sent to your system and understood by your system.”
- AE: Pay attention here, folks. This is a new AFI developed by the RAIN Alliance and ISO, designed for closed-loop applications. It is similar in purpose to 01, 02 and 03, but it guarantees unique encodings (assuming proper serialization practices) and is much easier to implement. This AFI is strongly recommended for closed-loop applications. Simply set your T bit to 1 (T bit of 1 = ISO encoding; T bit of 0 = GS1 encoding), encode the AFI of AE (hex), encode a RAIN Alliance-issued company identification number, and then you can encode whatever data you want. If you would like more information on using this new AFI, or to get a RAIN-issued company identification number, you can contact the RAIN Alliance at [email protected].
- C1: Here is our baggage-tagging AFI. I added this relatively easy one to the list to help you get your balance back after all the head-spinning material above. Scan your Delta Air Lines baggage tag, and you should see C1 amidst the data. Note that this AFI refers users to the International Air Transport Association (IATA)’s RP1740C standard for detailed data-formatting instructions.
This is quite a bit of information, but I hope you found it helpful to start properly encoding RFID tags using an ISO-based standard. For more information about RFID encoding, you can visit the RAIN Alliance’s website or contact Chris Brown here. Brown is an RFID subject-matter expert at TSC Printronix Auto ID. This article was written with contributions from Albertus Pretorius of Tönnjes and Carl Brown of SimplyRFID.