In Range

Radio-frequency identification (RFID) originated in the logistics industry, but repeated attempts have been made in recent years to use the technology in asset tracking. One advantage of RFID tags is that the information they contain can be changed with most chip variants. Devices can record metadata such as purchase dates, asset IDs, or the last battery change date.

A complex topic like RFID is easier to understand if you start by looking at the hardware. The modules or cards, referred to as tags, are attached to individual assets and come in two variants: passive and active. Passive tags are available in the form of stickers, key rings, or HellermannTyton cable ties (Figure 1), whereas passive tags are larger, require maintenance, and need an energy source.

Tag Tech

The most important argument for passive tags is that they are generally maintenance free. Glued to the inside of a plastic housing, they become trackable "for life," because the energy comes from the reader.

Active tags differ from their passive counterparts first in that they are not maintenance free: They draw their energy from a (usually long-life) primary cell built into the tag, which inevitably leads to a larger design but is not necessarily a disadvantage. For example, mounted on metal, an active tag is superior to its passive counterpart in terms of range, with its greater radio power and physical size.

Passive tags operate in three frequency bands: low frequency, high frequency, and ultra high frequency. Low-frequency tags are the earliest version of RFID based on the Wiegand standard, and they operate in the lowest band at a frequency range of 125-134kHz. Their disadvantage is the maximum amount of data that can be stored: just a few bytes. On the other hand, the cards are very cheap. The achievable range depends strongly on the reader.

All low-frequency systems are short-range transmitters. Smaller readers can only read cards reliably if they are placed on the tag. Depending on the orientation angle between the card and the reader, larger cards support ranges of between 30 and 80cm. The high-frequency cards operating in the 13.56MHz frequency band – also known as near-field communication (NFC) – offer a longer range: between 1cm and 1m, depending on the reader. A classic application for NFC is passports, access doors, and exchanging data with smartphones.

Ultra-high frequency (UHF) cards are available in the 865-960MHz frequency range. These readers, which given sufficient quality and a correspondingly large antenna, can achieve ranges of 5m and even up to 30m in special cases. Whereas the high-frequency tags located in the 15MHz range can compete with low-frequency tags in terms of price, because of the sheer volumes on the market, UHF cards are comparatively expensive.

In the active tag field, the frequency band is either 433 or 915MHz. In general, 433MHz systems are considered to have a longer range, which makes them more popular. When it comes to the format of active tags, you are spoiled for choice. One interesting product (Figure 2) offers a group of buttons that can be used to send a message to the reader. In this case, the manufacturer also promises the tag will detect manipulation and send a warning to the reader.

Another interesting aspect of working with RFID tags is the possibility of burning "physical" information on a chip in addition to the electronic information. The classic method is to add a QR code, a barcode, or a serial number that uniquely identifies the individual asset. When selecting a supplier, you should therefore consider whether it can print the tags, so the physical information can be read and basic operations still can be performed without a reader.

Read Correctly

Although in theory you would want the reader to have as long a range as possible, in practice, this proves problematic: Imagine a server room in which several hundred or even thousands of computers are crammed together in tight spaces. If the range of the reader is too large, problems can arise, and the location information can be lost.

One interesting solution is a highly directional reader with an antenna that only scans in a certain area. You could then drive around with a cart carrying a group of scanners that automatically discover where the respective devices are located.

Far more interesting is the question of where the reader is placed. A mobile reader is not necessarily part of the solution. Behind the concept of the "choke point" hides the relatively simple idea that readers are placed at critical points. In a hospital, for example, readers can be placed inconspicuously in entrances and exits to prevent the loss of expensive medical equipment. The logical consequence is that such a reader ideally should not be visible, because a variety of different solutions now can prevent or complicate the detection of RFID tags.

When rolling out RFID systems, people often have the misconception that active RFID readers lead to problems with servers. This is not the case: Servers are designed for far higher electromagnetic compatibility (EMC) loads [1] than those caused by reading the average RFID tag.

Missing Standards

RFID tags, like any other wireless technology, depend on their environment. Tags with a low working frequency, especially, react badly when applied to metallic surfaces. To overcome this problem, you can procure special tags, but the price is off-putting. A guide online [2] suggests ways to place tags efficiently on different types of network hardware.

A number of problems can slow the adoption of RFID usage, including concerns about investment and operating costs, difficulty in exploiting the benefits, a lack of standardization, and, to some extent, data protection.

Integrating Additional Data

RFID tags are not intelligent technology: Unlike a smart card, they do not have real processors. The tag is a kind of electrically erasable PROM (EEPROM) that permanently stores several bytes of information. In practice, every provider uses this storage as they want: no standardization organization exists to keep them from storing their data in ancient Talmudic Aramaic or as Rumba dance step instructions. Although I exaggerate, in practical deployments, something like this type of behavior does occur: One of my customers stores serialized Java objects on tags.

Before considering frequently used methods, you need to take a look at general considerations. The information stored in tags can be divided into two groups: tags that only contain information about the element they describe or tags that store user data. The advantage of the first approach is that such a tag is comparatively inexpensive, requiring little memory; write once, read often works perfectly well. The disadvantage of such a tag, however, is that you need an Internet connection to evaluate the information, which increases costs.

The second and conceptually completely different approach of placing user data on the tags has the advantage that you can also interact with the tag offline. On the other hand, they are more complex, and not every tag reader is capable of writing such data.

In the Footsteps of Oracle

Of all the large IT companies, Oracle is the most active when it comes to RFID. Among other things, the company provides a whitepaper [3] in which various snippets of information on the structure of the company's own RFID solutions can be found. Of particular interest is a reference to the FSTC-compatible tags. The Financial Services Technology Consortium (FSTC) is a standardization organization, who defines various technology standards for the American banking market. The specification documents are difficult to find; however, you can find a list of the criteria that describe FSTC-compatible tags online [4]. These specifications include, among others, that:

• tags must be precoded and installed by the original equipment manufacturer (OEM),
• human-readable text on the tags is the same as the information encoded in them,
• each has a one- or two-dimensional barcode,
• tags must be able to survive minor collisions with other goods, and
• tags must be able to be attached to the server without penetrating the surface.

You can source such tags from Oracle, but they can also be found on some IBM power servers. The tags, also known as Gen 2 RFID tags, are estimated to cost between $20 and $30 per device. They come with at least 96 bytes but can have 1KB or more of total memory capacity.

Of particular interest is that the memory is divided into banks, much like older computers. Bank zero is the "reserved memory," an area in which, among other things, the "kill password" is hidden. This command permanently disables an FSTC tag and can be used, for example, to turn off a tag before the device is sold. The EPC and TID codes contain chip-specific information. TID is a code branded by the manufacturer that uniquely identifies the individual tag (Tag ID). Meanwhile, the EPC contains the electronic product code, known from other merchandise management systems.

Bottom Line

Companies need to keep track of their assets, and RFID can be a solution. In addition to making it easier to find goods, small tags ensure that casual theft is avoided. In addition to the not inconsiderable costs, however, the confusing market environment speaks against RFID-based asset tracking.

The best approach is therefore to contact a solution provider as the first step. The higher cost of the individual tags are – especially in the beginning – a good investment, because the really tricky part of an RFID system lies in the intelligence or software.