If you’re looking for real-time location system (RTLS) technology, you know that this is a critical decision—and that not all RTLS technology is created equal. Every solution out there has different trade-offs. For instance, an Amazon warehouse isn’t going to use active Bluetooth-based RTLS, because it is only accurate to a room level. Instead, they’re more likely to use a highly accurate location solution like ultra wide-band. There are a number of trade-offs between the two, with the primary consideration being cost.

To give you a hand in finding the RTLS technology best suited for your application-level needs, take a look at this overview of five primary location systems.

Real-Time Location Systems: An Overview Of 5 Technologies

1. Infrared RTLS

Infrared works the same way as your television remote. An infrared tag (i.e., a remote) placed on an asset flashes a unique infrared ID at a fixed interval, which is picked up by a ceiling-mounted infrared reader (i.e., a TV). There needs to be a visual path between the tag and the reader—but much like your TV remote, they don’t have to be perfectly aligned to still register.

Benefits

  • It’s nearly impossible to get a false reading using infrared RTLS (unless someone attacks your system).

Considerations

  • Cost is the primary downside of infrared RTLS. It’s very expensive to install, because you have to put infrastructure in every room throughout the building. Because of the intensity of its infrastructure, it’s not ideal for retrofits—and is better suited for new construction.
  • Infrared tags transmit light signals, so battery life is a concern.
  • It’s harder to track items as they move through a building, as this would require readers in the hallways as well as in rooms. For this reason, infrared RTLS is best suited for capital assets and is not ideal for personnel tracking.

Technology To Consider

2. WiFi RTLS

WiFi RTLS technology uses tags that transmit a WiFi signal to multiple access points throughout the building. Using differential-time-of-arrival methods, the receivers are able to locate the tag.

Benefits

  • If you deploy WiFi-based RTLS, you can often use existing WiFi structure with firmware changes.
  • It is more accurate than proximity-based RTLS options because it uses time-of-flight measurements using a relatively wide bandwidth. Accuracy indoors is related to signal bandwidth, so if you’re doing 80 GhZ of 5-GhZ WiFi, you can get accurate location positioning within a few meters.

Considerations

  • WiFi-based RTLS tags are the most power-hungry, the largest in size, and the second most expensive of all RTLS technology. For example, an AeroScout tag costs about $60, so using it to track disposable or ad hoc assets isn’t financially realistic.
  • Installation can be difficult. For example, during deployment, you have to survey the building by walking around with devices to determine how to calibrate between the WiFi access points. And because WiFi-based RTLS rides on top of the IT structure, your IT team will have to be heavily involved with getting it up and running. Additionally, the access points to support a WiFi RTLS system are multithousand dollars a piece.
  • You often have to license the location software to feed into the location engine, which can increase the price.
  • While RTLS solutions don’t send much data and aren’t connecting to WiFi as much as pinging it, there are still security concerns about having unmanaged WiFi end nodes on your network.

Technology To Consider

3. Ultra Wide-Band RTLS

Ultra wide-band RTLS is the gold standard in terms of location precision. It uses small, low-powered tags that transmit an ultra wide-band signal using a spark-gap-style transmitter. This instantaneous burst of energy creates a very wide signal and transmits across gigahertz of spectrum.

Benefits

  • This is the most accurate of RTLS solutions. The RF chirps it sends out are barely detectable, but are able to be picked up by ultra wide-band receivers—which you place all over the building you’re monitoring in. And these chirps triangulate down to less than a meter.

Considerations

  • To ensure accuracy, you have to purchase a tremendous number of readers—and those readers are very expensive. In fact, every tag has to have 3-5 readers to get an accurate location.
  • This is the type of technology Amazon uses in its warehouse to track where every box and robot is—down to the centimeter. But an organization might not want or need such exact location positioning, which would make the expense unjustifiable.

Technology To Consider

4. Passive RFID

Passive RFID is the type of technology you’ve seen in libraries and retail stores and uses simple, battery-free tags and high-power readers. The readers send out a low-frequency radio signal that transmits so much energy over the air that the tag’s collector antenna picks up its radio waves with brute force. The tag then transmits back using a different frequency, which the reader receives.

Benefits

  • A passive RFID sticker tag is extremely inexpensive—as low as 10 cents.
  • These inexpensive tags last forever, which is a clear benefit.

Considerations

  • While the tags are inexpensive, the readers are expensive. And unless you’re using chokepoint RFID (which is what storefronts with large resonators use), you will need a lot of them for location tracking. In fact, you need to position these readers every 10-15 feet for them to work for RFID—which isn’t often realistic.
  • To work properly, passive RFID readers radiate a great deal of energy to pick up tag signals, which companies are typically wary of.

Technology To Consider

5. Active Bluetooth-Based RTLS

Active RTLS uses battery-powered sensors that connect to various access points throughout the building and transfer data to the cloud. These solutions use Bluetooth Low Energy (BLE) technology to reduce system and operational costs and enable asset tracking in emerging business areas that previously hadn’t been able to track assets.

Benefits

  • There’s no IT integration (depending on the solution).
  • This is the least expensive RTLS option.
  • You don’t have to cover the whole building. You can start in one area, or with one function, and create value before scaling. This “crawl, walk, run” approach with testing and deploying isn’t available with most integrative RTLS solutions.

Considerations

  • Location accuracy of active RFID is only as granular as the number of readers you have, so many readers are necessary for a high level of accuracy. Potential users must consider that there is a major cost trade-off between the pinpoint accuracy of ultra wide-band and the room-level accuracy of active RTLS.
  • Active RTLS can be prone to false positives. For instance, if you have a thin wall with a bed in front of it, the reader in the next room may be louder, making a particular item in room A appear to be in room B.

Technology To Consider

Questions?

We’re here to help you figure out which RTLS technology is best suited for your industry or application.

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Written by Brian Ray

Brian is the Founder and CTO of Link Labs. As the chief technical innovator and leader of the company, Brian has led the creation and deployment of a new type of ultra long-range, low-power wireless networking which is transforming the Internet of Things and M2M space.

Before starting Link Labs, Brian led a team at the Johns Hopkins University Applied Physics Lab that solved communications and geolocation problems for the national intelligence community. He was also the VP of Engineering at the network security company, Lookingglass, and served for eight years as a submarine officer in the U.S. Navy. He graduated from the U.S. Naval Academy and received his Master’s Degree from Oxford University.