The Science of RFID and Inventory Asset Tracking

RFID tags

The science behind RFID solutions for inventory asset tracking

 

RFID (Radio Frequency Identification) technology solutions are widely used to track inventory assets in supply chains all over the world. But how exactly did RFID technology come about?

The origins of RFID technology can be traced back to the end of World War!!, when representatives of the Soviet Union presented the United States Ambassador with a heavy wooden ornament, later called ‘The Thing’, that contained an antenna with no batteries or power source (and therefore unable to be detected by officials looking for electronic bugs).

The listening device was activated by radio waves aimed at the US Embassy by the Soviets, which used the energy of the incoming signal to broadcast back. When the signal was switched off, The Thing remained silent. Taking pride of place in the Ambassador’s study, it went on to broadcast his private conversations for the next seven years.

Creating less geo-political controversy, RFID technology as we now know it as an asset tracking solution was officially invented in 1983, when the first patent with the word ‘RFID’ was filed. But it wasn’t until around 2002 that RFID technology started to gain traction in a variety of asset and inventory tracking applications. In the nearly 20 years since, the use of RFID technology has become ubiquitous as the technology has continually improved (while reducing in cost), and more applications have emerged across a range of industries.

The components of RFID technology solutions

RFID belongs to a group of technologies referred to as Automatic Identification and Data Capture (AIDC), used to automatically identify objects, collect data about them, and enter that data into computer systems with little to no human intervention, using radio waves to achieve this. 

There are three key components that come together to create effective RFID technology solutions:

  1. RFID tags, or smart labels, that has an integrated circuit and antenna that transmits data. Tags can be classified as passive or active, and we’ll look at how these differ a bit later.
  2. RFID readers, that receive data from tags, then covert that information into a more usable format.
  3. RFID software, that receives data from readers and stores that data for record-keeping and analysis.

We’ll take a look in more detail at each of these components later. For now, let’s consider the radio waves that are behind all RFID technology systems. 

What’s the frequency, Kenneth?

RFID tags are categorised according to the frequency at which they operate. There are four primary frequency ranges used for RFID tags, and these are allocated by governments and relevant authorities under a range of bands collectively known as Industrial, Scientific and Medical (ISM) radio bands.

The choice of frequency for an RFID tag and solution is critical, and which is best to use for a particular application largely comes down to the read-range, amount of data to be stored on the tags and the rate of data transfer between tags and readers. 

The four frequencies, their capabilities and relevant RFID applications are as follows:

Low frequency (LF): These tags have been in use the longest, and have the largest installed base around the world, with a variety of applications including access control, automotive control, healthcare and point of sale. They are passive tags (no battery, powered by readers) with the ability to store a small amount of data, a low data transfer rate and a very short read range (up to around 10cm). Importantly, they have limited ‘anti-collision’ capability, meaning it is nearly impossible to read multiple LF tags simultaneously. 

High frequency (HF): Like LF tags, HF tags are passive and are activated by an RFID reader. Compared to LF tags they can store more data, have a slightly faster data transfer rate and offer a read range of up to around a metre. They can also have anti-collision capability, so it is possible to read multiple tags at once (albeit at a very close proximity). Typical applications for HF tags include asset tracking, library books, airline luggage and smart cards. 

Ultra-high frequency (UHF): UHF tags offer far more utility than both LF and HF tags, including a read range of up to around seven metres, and anti-collision capability to allow multiple tags to be read simultaneously. The Gen 2 protocol for UHF tags is designed to read several hundred tags per second. UHF tags can be passive (like LF and HF tags) or active (meaning they have their own power source and don’t need to be activated by a reader). UHF tags are used in similar applications as LF and HF tags, but their characteristics enable, for example, pallet or case level tagging for inventory asset tracking, helping to speed up receiving, despatch and stock counts.  

Microwave frequency (microwave): Microwave tags can be passive or active, and the active tags offer a read range of around 100 metres. They are also better suited to work with tagged metallic objects. This type of tag is often used for long-range asset tracking and identification, such as in access control for vehicles, fleet identification and motorway tolling. 

All of these types of tags and frequencies can be utilised as part of an RFID inventory asset tracking solution, but the choice of frequency or tag type comes down to a range of factors including:

  • Read range required – close proximity is more manual, and LF/HF tags have limited ability for multiple tags to be read at once, whereas UHF tags work better in larger spaces and can read up to hundreds of tags simultaneously (useful for faster inventory stock takes). 
  • Cost of the tag – cost increases as capabilities such as read range, data storage and transfer rates increase, and active tags with power sources are more expensive than passive tags. 
  • Size and value of items being tracked – passive tags with less capabilities are smaller and can be disposed of as used (such as in retail apparel), while active tags with power sources are more appropriate for longer term use with higher value tagged items such as vehicles. 

A complete RFID technology solution

Whichever underlying frequency is part of an RFID asset tracking solution, the core components remain the same. Let’s look at each of them in detail:

RFID tags

While the term ‘RFID tags’ is widely used as a catch-all descriptor in the industry, the first thing to understand is that tags can take many forms including stickers, adhesive labels, hang tags and hard tags that suit any environment. 

Deciding on what tag will suit a particular application comes down to a range of factors that include:

  • The object being tagged, and where the tag needs to be placed for optimal reading.
  • The surface upon which the tag will be affixed (metal, plastic etc.) and if it is unusual or irregular.
  • The physical stress the tag may be subjected to, such as commercial linen or extreme weather conditions for objects in the field.
  • If the tag needs to be wearable by a person, such as on a wristband or fob.

As noted previously, there are two key types of tags, passive and active. Here’s how they differ:

  • Passive RFID tags do not have a battery or power source, and offer a shorter read range. Instead, they draw power from the RFID reader that sends out electromagnetic waves that create a current in the antenna of the tag. These tags lie dormant until they get a signal from a reader. Passive RFID tags are small, light and relatively cheap, and they are more readily disposable. They are suitable for fast moving retail items.

 

  • Active RFID tags have a transmitter and their own power source, such as a battery, and offer a longer read range. Power is provided to run the circuitry of the tag, and also to transmit or broadcast a signal to an RFID reader. This is similar to how a mobile phone sends a signal to a cell tower. Active tags are ‘always on’ and broadcasting their signal whether in range of a reader or not. These tags are bulkier and heavier (due to the power source) and are more costly than passive tags. They are suitable for larger and higher value assets, such as vehicles and equipment.

It should also be noted that specialised RFID printers that can simultaneously print and encode information on RFID tags and labels are often part of an overall RFID technology solution. In fast-moving retail environments, for example, an RFID printer provides flexibility and high-speed printing and encoding of RFID labels for inventory items. For businesses with operations or manufacturing in multiple countries around the world, RFID tag printing can be outsourced and off-shored via bureau partners with the assistance of your local RFID specialist

RFID readers

RFID readers can be mobile (handheld or App-based on a smartphone) or fixed (mounted) and pick up radio signals transmitted by RFID tags affixed to inventory items. Handheld readers are able to sweep a room and identify tagged items much faster, and more accurately, than manually reading each item from close proximity as with traditional barcode technology. 

Fixed RFID readers can be placed at strategic locations in warehouses, stock rooms and retail stores to track the movement of inventory in or out.

RFID readers provide the crucial link in an RFID technology solution between tagged objects and the software that records and displays locations (and other information) in real-time.

RFID software

RFID asset tracking and inventory management software captures data from fixed and mobile RFID readers to provide real-time asset and inventory visibility across your business or supply chain. 

An example of RFID software is RAMP’s locally-developed Loca.fi, a powerful, cloud-based platform designed to suit the requirements of a wide range of industries including manufacturers, retailers and transport and logistics providers, to name a few. 

RFID software not only captures and manages huge amounts of location data and other information, but it provides insights to help drive smarter, leaner processes and informed business decision-making. 

There are various options within each of the types of components that make up a customised RFID-based system that will be effective and efficient for particular use cases or applications. Talk to your RFID specialist about your specific needs to get a solution that best suits your requirements. 

Making RFID solutions simple

The science behind RFID technology is complex. But choosing the right combination of components for an RFID inventory asset tracking solution is made easy when you talk to Australia’s leading RFID specialist, RAMP

We’ve been working with Australian businesses for over a decade to design and implement customised RFID solutions for supply chain, inventory and vehicle tracking, retail and a range of other applications across many industries. 

RAMP can help you automate and streamline processes to improve efficiency, minimise losses and increase visibility with our locally-based consultants, engineers and software developers.