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How to Select a Real-Time Locating System

Real-time locating systems (RTLSs)—which employ RFID tags to automatically identify assets and individuals, as well as determine their locations in real or near-real time—have come of age. The benefits have been proven: RTLS technology improves visibility, which, in turn, enables companies and organizations to save money, manage assets, reduce labor, and boost safety and security. In addition, industry standards related to RTLSs have been ratified in recent years, enabling supply chain partners to share information.

Today, RTLSs are being employed in a wide range of industries, from defense to health care, logistics and manufacturing. The U.S. Department of Defense (DOD) alone is investing nearly $430 million in the technology, to track cargo and assets as they move around the world, including through war zones.

As RTLS technology matured, more RFID vendors entered the market (see the table below). The good news is that now there's a solution to meet your business needs. The problem is finding it among the many different options available. A wide range of RFID tags—from simple, low-cost, ultrahigh-frequency (UHF) passive RFID labels to sophisticated, high-cost active tags with embedded sensors—can be used as part of an RTLS. Some systems use ultra-wideband (UWB) technology, while some are based on the Wi-Fi standard and others employ proprietary protocols.



Click here to view a larger version of the table.

In this guide, we will explain what you need to know to choose an RTLS that's right for your company. The above table, listing several RTLS providers, can help you narrow your choices by technology, industry and application. But there is no one-size-fits-all solution, since every company has its own unique requirements and circumstances. In some cases, you might need a combination of hardware and software technologies.

Keep in mind that while you may be interested in an RTLS for a specific application, the solution can provide multiple benefits. For example, Genesis Health System, in Davenport, Iowa, deployed a Wi-Fi-based RTLS from AeroScout to track assets, such as infusion pumps, wheelchairs and stretchers. Now the firm is leveraging the system to respond more quickly to natural disasters or other emergencies (see Genesis Health System Uses RFID to Drill Deeper). Similarly, Transmed Foods, an exporter of olive products from growers in Morocco and Spain, deployed an RTLS to improve the visibility of its products in transit. The system saves labor and enables the company to optimize its inventory levels, while also deterring theft and counterfeiting (see GPRS-GPS Tags Help Shippers Fight Theft, Reduce Costs).
Step One: The Five Ws
The first step in narrowing your search among the many RTLS offerings is to begin with a journalistic approach, answering the questions, "who, what, where, when and why."

What? What are you interested in tracking? Metal assets, such as tools or heavy equipment, may require battery-powered active tags. Plastic items, such as reusable containers, can usually be tracked with less expensive passive (battery-free) RFID tags. So can many IT assets, such as servers or laptops, as long as the use case does not require constant, long-range monitoring.

Where and when? Here, you need to determine where within your facility—and how often—you want to track assets. Do you need to locate assets while they're in transit, or do you just need to know that your assets are, say, in a warehouse or on the third floor—or their exact location within inches? Do you need to inventory all tagged assets on a regular basis—such as once daily, or once per minute—no matter where they are located?


Caterpiller's Belgian hydraulic-valve plant deployed a real-time locating system to ensure that workers use the correct wrench and torque to install hoses.

Answer these questions in tandem with a site survey of the facilities in which you intend to use the RTLS. This will help identify any sources of radio frequency interference that may exist within your facilities that could hamper the performance of certain types of tags and interrogators.

Who? Will this be a closed-loop system? In other words, is your company the only party that will deploy the technology? Or do you require an open-loop system so other parties—suppliers, customers or partners—can also deploy the solution?

Why? What is the business objective? Do you want to improve asset utilization? Boost efficiencies? Improve safety? Or achieve a combination of these benefits?

Once you've answered these questions, the "how"—that is, the specific technology you should deploy—will be easier to select. Following these steps will also help you choose the most cost-efficient solution.
Step Two: Matching Needs With Capabilities
Which assets you need to track—as well as where and when (or how often) you need to track them—will determine which technologies are best suited for the task.

Active RTLS: Generally speaking, if assets are metal or contain liquid, if they need to be tracked to within a few feet or inches, and if the area in which they are to be identified and tracked is expansive, your best bet is an active RTLS. These solutions comprise active tags, interrogators (which transmit data to and collect information from the tags) and software that use algorithms to locate the tags in three dimensions. Tags' frequencies range from 433 MHz to 915 MHz, to roughly 6 Ghz. The higher a tag's frequency, the greater the distance over which it can be read.


At its Regensburg assembly plant, BMW is using an RFID-based real-time location system to identify cars and control the tools used to assemble them.

Solutions that use 2.4 GHz tags can incorporate the IEEE 802.11 (Wi-Fi) standard. These tags send data to Wi-Fi access points linked to a wireless local area network, where the tag and location data is collected. Employing a Wi-Fi system can lower infrastructure costs for end users whose facilities are already equipped with Wi-Fi access points, since they are used instead of standalone readers. But additional access points are sometimes required to meet specific use cases, or to increase the tracking system's accuracy.

Ultra-wideband technology operates across many frequencies, ranging from 3.1 GHz to 10.6 GHz. One advantage that UWB RTLS systems have over other active solutions is accuracy; UWB can determine location with accuracy to a few centimeters, whereas the accuracy of other systems is generally within feet.

Active RFID tags can be combined with sensors to monitor environmental conditions, such as temperature, light and movement. Monitoring products can help prevent damage during manufacture, storage and shipment.

Because active tags have a long read range and can be set to transmit their identities to the nearest reader on a periodic basis (say, every minute), they are best suited for applications in which assets must be tracked wherever they are located within your facility, and at any time—rather than just tracking them when they are moved through a defined read zone, or using mobile interrogators to move through an area where tagged assets are stored (a warehouse, for example) in order to find them. It's important to note that if you want to be able to locate all tagged assets at any given time, no matter where they are located within your facilities, then you must install a network of readers large enough to provide coverage throughout the facility.

The cost of an active RTLS solution depends on the base technology, as well as on the deployment's size and complexity. Active tags cost between $15 and $75 apiece. If you add environmental sensors or locking mechanisms, the cost can rise significantly. Keep in mind that the cost of a tag is amortized over its lifetime. An active tag's battery life can extend up to five or more years, but is dependent on how frequently it collects and transmits data, as well as on other factors, such as the number of sensors linked to that tag.
Passive RTLS: If you are tracking assets in an environment that posts no significant RF interference—and if those assets are going to be within 30 or 40 feet (9 or 12 meters) from read points whenever you want to track them—a system based on a low-cost passive tag containing a UHF ISO 18000-6c inlay should meet all of your needs. Assets composed mostly of metal or containing water are very difficult to track using basic ISO 18000-6c tags with an adhesive backing. But some tag manufacturers offer these passive tags in specialized housings designed to buffer the tags from RF interference, as well as boost the range from which they can be read. Some metal-mount tags can be read from up to 100 feet, and are used to track items largely made up of metal, such as IT assets or tools.

"There are some excellent [passive] metal-mount tags on the market," says Sujatha Bodapati, CEO of RFID systems integrator AssetPulse, "and we think they work well, as long as the business process is rigid," so that the assets move past a reader in a predictable manner. If metal-heavy assets are read in an ad hoc manner, at varying distances from read points, an active system is the best option.


The city council of Melbourne, Australia, estimated that once it fully deployed and integrated an RFID vehicle-tracking system with its employee ID system, it would reduce labor by at least 40 staff hours per month, resulting in an annual financial savings of up to $40,000.

Passive RTLS technology was previously only able to, at best, determine the direction in which tagged items were moving as they passed through a read zone. But now, Mojix and other vendors are starting to use combinations of signal-processing techniques and phased-array antenna technology to locate tagged assets in three dimensions. This breakthrough in both accuracy and read distance—up to 500 feet has been reported—is beginning to blur the line between what active and passive systems can achieve in an RTLS, says Toby Rush, president of Rush Tracking Systems (recently acquired by Pharos Capital Group), which provides RTLS solutions and integration services.

This breakthrough also means that a passive system could be used to locate tagged assets wherever they are located within your facility, and for tracking them at any time, instead of only when they are brought through a read zone, for example. As with active systems, you'll need a sufficient number of readers to create coverage throughout the facility. But if your site survey determines that your facility contains RF interference, an active RTLS is probably the better option.

If your assets are located outside and you do not require highly precise location data, the best route might be to employ a mobile passive RFID reader equipped with GPS functionality. This approach—sometimes dubbed the poor man's RTLS—enables you to associate the unique ID encoded to each tag read with the GPS coordinates collected at the same time, so you can track assets with little reader infrastructure and low-cost tags.

Passive tags are low-cost—ranging from 10 cents each for basic, adhesive tags (for very large bulk orders) to $1 apiece for tags in plastic housing. Metal-mount tags, designed for long read range, start as low as $3 or $4 per tag. And as a whole, passive RTLS solutions—which are less expensive than active systems—typically deliver a faster return on investment.
Step Three: Closed-Loop Versus Open-Loop
When they first emerged, most active and passive RTLS solutions employed proprietary technology that limited users to purchasing the necessary hardware and software from single vendors. That changed as passive tag standards emerged, around 2004, and in 2006, when Savi began licensing its active technology (based on 433 MHz tags and readers) to other hardware manufacturers. (Savi's technology is fundamental to the ISO 18000-7 air interface standard, which means all tags and readers based on that standard are interoperable.) As with most technologies, standardization may lead to price competition between vendors. That said, both Rush and Bodapati report that ISO 18000-7 systems are more widely deployed within the DOD (which specifies the technology in its active RFID purchasing contracts) than in the private sector.

If you plan to be the sole user of the RTLS—that is, if it will be a closed-loop system—then it is not as important to choose a solution based on standard or proprietary technology (though Rush notes that some companies—particularly large ones—prefer to use only open standards so they aren't locked into single vendors). But if your suppliers, customers or partners might also want to track or monitor assets—in other words, if it will be an open-loop system—then using a standardized solution offers significant advantages, both in terms of ease of use and from a cost perspective. With a standardized solution, all parties employ the same protocol to read the tags, process tag data and share information. This scenario also enables all parties to leverage the RTLS solution in other areas of their business. Your suppliers, for instance, will be more willing to participate if they can use the same system to tag and track assets for other customers.


Reyher utilizes passive 13.56 MHz tags to track the reusable containers it uses to ship nuts, bolts and other fasteners to companies all over the world.

Step Four: Determine the Business Case:
You've likely identified a number of business objectives that could be addressed by an RTLS. Evaluate and prioritize potential projects, identifying the biggest drivers for deploying the system in the first place. Multiple use cases will drive up the overall benefit of your RTLS investment—but they will also drive up its complexity and cost. Seek ways in which a single solution might address multiple problems—for example, a container-tracking system could improve the utilization of those containers, as well as increase product visibility or enable a work-in-process tracking system that can optimize the flow of raw materials for a manufacturing process.

At the same time, plan a long-term strategy. Once you have the RTLS infrastructure in place—and have achieved a return on your investment—you can use that money to expand the system and achieve benefits in other areas as well. We've provided examples below of companies that deployed an RTLS to solve one or two pressing problems, as well as how some firms leveraged their RTLS to deliver other business improvements.

You might find that in your long-term strategy, you will need an RTLS solution that uses both active and passive technologies. An RTLS systems integrator can help you design a back-end infrastructure that can support a mix of technologies and feed all data collected into a single software system enabling you to use the information to improve business processes. See Choosing the Right Systems Integrator for tips on how to find the company that can best help you get the most benefits from your RTLS.
Common RTLS Applications
From jewelry and casino chips to pipes and sewers, companies are tagging and tracking assets to improve visibility. Here are four of the more common RTLS applications, along with examples of how and why some companies are deploying these solutions to become more efficient.

Cargo or vehicles: In 2002, Land Rover deployed an active RTLS from WhereNet (now Zebra Enterprise Solutions) at its plant in Solihull, England, to improve parts replenishment. In 2007, the automaker leveraged its existing infrastructure, adding outdoor antennas to track newly assembled cars in its yard. One year later, the company achieved an ROI, indicating the RTLS is reducing the amount of labor needed to track vehicles in its yard, as well as ensuring vehicles are not shipped at the wrong times (see Land Rover Finds ROI in Tracking New Cars).

The city council of Melbourne, Australia, is tracking fleet vehicles in its corporate parking lot. The council estimates that once the RFID system is fully integrated and operational, it will improve efficiencies and deliver an ROI within the first couple of months (see Melbourne City Council Tracks Its Car Fleet).

If you need to determine the location of, say, a specific vehicle or asset within a large outdoor area, you will require an active RTLS. For logistics applications, active RFID tags are attached to cargo containers, or to the vehicles themselves, to improve the visibility of products in transit. The tags can also be embedded in locking cargo container seals, to improve security. What's more, the tags can be combined with GPS (Global Positioning System) and satellite and cellular services to monitor cargo before it is loaded onto a carrier, en route at sea, and after it arrives at its destination (see RFID-Enabled Electronic Seals).

Reusable containers and pallets: Reyher, a German supplier of screws, structural bolts, nuts and other fasteners and fastening technology, is employing passive RFID to manage the supply of empty containers the company uses to fulfill orders and ship hundreds of thousands of small parts to its customers (see German Screw Supplier Keeps Tabs on Product Bins via RFID).

Beverage manufacturer Ringnes is tracking containers of beer and other beverages with passive RFID, to keep tabs on its reusable containers as they are shipped, filled with products, to retailers, and then returned empty to its distribution center (see RFID Helps Ringnes Track Beverage Shipping Containers).

A low-cost, passive RTLS is also a good option for tracking pallets. Many pallet rental companies, including CHEP and Intelligent Global Pooling Systems (IGPS), offer RFID-enabled pallets, paired with RTLS managed services (see CHEP Announces New RFID-Enabled Container-Tracking Service and IGPS Rolls Out RFID-Enabled Plastic Pallets).
Tools: BMW is employing an RTLS from Ubisense at its assembly plant in Regensburg, Germany, to identify cars and control the tools used to assemble them (see BMW Finds the Right Tool). Similarly, Caterpillar is employing an RTLS at its heavy-equipment manufacturing plant in Belgium, to ensure its hydraulic valves and hoses are assembled properly (see RFID Tightens Up Caterpillar's Assembly Process).

Airbus has conducted several industrial tool-tracking pilots. As a result, the aircraft manufacturer has decided to commence RFID tool tracking at its manufacturing facility in Filton, England. The company wanted to reduce the time it takes workers to "book in" and "book out" the tools they need (see Airbus Issues RFID Requirements, Expands RFID Usage).

A passive RTLS is a good option for tool tracking if you have an open workspace that does not contain a lot of metal racks or storage bins—and if tests with passive tags designed for mounting on metal generate positive results. A passive system is also viable if you are tracking assets with a short shelf life, such as disposable blades or drill bits, because UHF tags are relatively cheap, making them more expendable. Tools can be accurately located anywhere from within 1 or 2 feet to several yards. If you have a Wi-Fi network, you could save money by opting for a Wi-Fi system; typically, this is good for tracking an asset to the room or floor level within a building, but it will not provide a highly precise location. If you need to locate tagged tools precisely—to within a few feet—consider a UWB system.

High-value assets: Brigham and Women's Hospital, in Boston, has deployed an RTLS from Radianse to track thousands of medical devices. The system improves patient care, streamlines patient flows and saves the hospital money (see Brigham and Women's Hospital Becomes Totally RTLS-enabled).

Bank of America is employing passive RFID to inventory its computer servers and other IT assets, and to record whenever any are removed from and returned to a data center, so that all equipment can be accounted for (see Bank of America Deploys RFID in Data Centers).

In a typical year, Mexico's Regiomontana University had been suffering approximately $15,000 in theft of its assets—primarily the projectors or laptops stationed in each of its classrooms. Since the university installed an RFID tracking system, the organization reports, no equipment has been stolen (see RFID Helps Mexican University Retain, Maintain Equipment).