The State of Radio Frequency Identification (RFID): New EPC Gen2 RFID Standard Emerges

Publish Date: Mar 30, 2016 | 5 Ratings | 4.40 out of 5 | Print | 1 Customer Review | Submit your review


This tutorial discusses the emerging Electronic Product Code (EPC) Gen2 RFID Standard and is the second part of a six-part tutorial series. The tutorial series is based on the transcription of a presentation by Mark Roberti, Founder and Editor of RFID Journal, during the RF Summit at NIWeek 2005. The presentation is broken into six RFID topics, including successful real-world applications, industry trends, and areas of improvement.

1. Part 2: New EPC Gen2 RFID Standard Emerges

[Figure 1] is a typical passive ultra-high frequency (UHF) tag. Usually the tag is a dipole antenna, as opposed to a circular or loop antenna like you would see on a 13.56 MHz tag.

[One advantage of UHF—why is everyone so excited about UHF?] It’s because you get a longer read range. You’re going to get three feet at most with a 13.56 MHz tag, and that’s not good enough to read a pallet going through a dock door. If you can get 10 feet or eight feet, you can have a reader on both sides of a 10-foot dock door, and you can read the tag as it goes through, and that’s why companies are focused on UHF.

Figure 1. Example of a passive UHF tag

[Another advantage of UHF is that passive tags are low cost.] The idea is to make these things as simple and inexpensive as possible so that they can be thrown away with the packaging.

[The disadvantages of UHF—and there are several—include:] Signals are reflected by metal; Signals are absorbed by water at that frequency; There are null spots in the read field; The performance that people are getting is less than perfect.

With a 13.56 MHz tag you can control the read field very, very well, and you can isolate what you want to read. With UHF you send out a signal, it bounces all over the place, and you get lots of weird readings. Companies are figuring out, “If I’m putting tags on boxes and I’m trying to identify thirty products going down the conveyer, [but] I’m getting reads from a product that’s sitting on a shelf 20 feet away, how do I figure out what I really have moving on my conveyer?” These are some of the issues people are struggling with right now.

About three years ago when I started, there were two competing protocols. There was the ISO protocol 18000-6 and there was the EPC protocol, and they were at odds with eachother. EPC was founded by end users like Wal-Mart, Gillette, and PNG and they wanted a cheap tag, and they wanted a protocol that supported a cheap tag. “Make it as simple as possible so the chip could be as simple as possible, and the cost of the tag could be as little as possible.” ISO 18000-6 was supported by vendors, and they didn’t necessarily want a cheap tag, and they had this technology already developed. They wanted EPC to simply put their electronic product code on tags using this protocol.

What’s happening now is those two are merging. There is a new standard called EPCglobal Gen2, and it takes the best of 18000-6 and the best of EPC Gen1. It mixes in some new innovations and we’ve come up with what is the best, most advanced UHF protocol ever developed. [Table 1] explains some of the fundamentals of the different protocols that are out there.

Table 1. Comparison of RFID standards

The EPC Gen2 protocol is designed for optimal performance so [the designers] used two different ways of reflecting back the tag: New, or submask, and also FM zero. It’s designed to operate in a broadband of 860 to 930 MHz. This allows it to work around the world. It’s got a lot of special features built into it, such as special security that didn’t exist in the earlier versions of the standards. These are some of the things that are most important about the new standard.

Dense reader mode [allows 50 readers to work in one area]. What companies found out is that if you put three, four, five, or six readers on dock doors adjacent to one another, you’re going to have a hard time getting them to work. You had to either turn them on and off in sequence or you had to shield them from one another. Otherwise, they would interfere with one another because the UHF waves are interfering with each other.

Q algorithm [allows singulation of tags, even if they have the same ID]. One of the problems companies had was trying to identify unique tags. What happens when the reader tries to communicate with raw tags just manufactured with no serial number written to them? [With] the original protocol you couldn’t even communicate with the tags to write; you couldn’t singulate (to identify tags uniquely). You’d have to put one tag in the reader field and then put another in. Obviously that’s a very, very slow process. So they needed a way to singulate tags even when [the tags] didn’t have their own unique identifier. The reader needed to have a way of talking to one tag in a field of 50 so it can write a number to it. Q algorithm uses a system of having the tags generate unique IDs, and then the reader asks for this unique ID and then uses that to singulate.

[Gen2 also features “sessions,” which allows two readers to communicate with tags.] One of the problems companies ran into is counting a tag—counting tags on a shelf or on pallets. You’d be counting 50 tags and just as you got toward the fiftieth tag and you had about 10 more to go, someone would come with a handheld [reader] and start talking to those tags too. That would interrupt the first one because the tags would start responding to the [second] reader, and the first reader had to start all over again. So what they did is they came up with this thing called “sessions.” [Tags have] four sessions, so four readers could talk to the tag simultaneously without interfering with one another and without interrupting the count. [The tag] would just switch from one session to another.

This concludes the second part of a six-part tutorial series.

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2. Solution for Testing RFID Readers (Interrogators) and Tags

VI Services Network, a NI Alliance Member, currently offers a complete test system for testing RFID readers and tags.
The test system is based on the following NI products:








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Customer Reviews
1 Review | Submit your review

Need more information on singulation and writing to tags using Q algorithm - May 29, 2017

Would like to have more information on the specifics of writing to Gen2 tags, where multiple tags are in the field. Role of the TID is also to be understood. Also more information on the Gen2 v2 security standards.

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