What is a Real-Time Location System?
We talk a lot about RTLS in our office (because that’s what we do) and sometimes we forget that we may have terminology and techniques that are unfamiliar to our readers. Today, we are taking it back to the basics to really explain what we do and how we do it.
What is RTLS?
An RTLS, otherwise known as a real-time location system, is a technology that uses small transmitters (we call them tags) to determine the current location of people or objects. A person, for example, may wear a tag on a lanyard, while a forklift may use a tag mounted to the top of its cab. The tag transmits a signal that is heard by one or more radio receivers (“Readers”) that are placed throughout a building or venue. When a Reader hears a tag signal, this information is passed along to a software application that determines where the signal came from. Because the signal contains a unique identification code, we can distinguish the location of one person or object versus another. Once a tag has been located, we can keep track of where the person or object has been, where they are now, and (to a certain extent) where they are going.
How Accurate Is It?
One of the first things we determine for a new RTLS deployment is the type and accuracy of tracking that is needed to get the job done. This can range from proximity-level (it’s in this room somewhere, referred to as “0D tracking”), to a location in two-dimensional space (“2D tracking”, as in a top-down view of a flat map), to the precise location of an object traveling through three-dimensional space (“3D tracking”). When tracking in two or three dimensional space, we also have a choice of accuracy ranging from a few meters to centimeter level, based on the technology that we use.
As you might guess, higher accuracy systems come with a higher cost, so a thorough understanding of the goals of a given RTLS is important when designing the system. In some cases, mixed systems make a lot of sense – for example, tracking in 0D through the majority of a building, and outfitting certain areas for accurate 2D tracking only where needed. Next, we’ll discuss a couple of the technologies we use to enable various types of tracking.
RTLS Using Ultra-Wideband
Ultra-Wideband, also known as UWB, is a radio technology that uses precisely timed, short pulses of energy at a low power level. These short UWB pulses have a cleanly defined start time, which allows the UWB Readers to measure the exact time when a given tag is heard. This measurement, as you might imagine, is called the Time of Arrival, or “TOA”. When the same tag signal is heard by different Readers placed around the area, the slight differences in signal timing can be compared. This comparison is called Time Difference of Arrival, or “TDOA” – a term we use to classify, and describe this type of tracking. Note that other radio technologies don’t provide nice “clean” pulses that can be measured this way, and so tracking with other systems (such as WiFi or Bluetooth®) will generally use a different method such as signal strength measurement.
One more note on UWB transmissions- when a UWB tag transmits, it isn’t sending out a single pulse of energy. It’s actually sending out a series of pulses that make up a digital packet of information. The pulses are coded in such a way that a few key pieces of information are transmitted to the Readers, such as the tag’s unique identification code, remaining battery life of the tag, and sometimes a small payload of sensor data (temperature, acceleration, heart rate, etc.) as needed for a given use case.
RTLS Using Bluetooth®
PLUS also uses another short-distance wireless technology, Bluetooth® Low Energy (also known as BLE), which is a standard for connecting various wireless devices with other BLE enabled network devices. Our BLE tags, also called beacons, emit a BLE signal that is picked up by our BLE Readers. The same PLUS software used to process UWB signals analyzes the BLE signal strength and other characteristics to determine the approximate location of the tags relative to the BLE Readers.
BLE RTLS is mainly used for proximity-level accuracy, as the BLE technology does not allow for the type of precision tracking UWB technology provides. BLE is usually the lower-cost option for RTLS users wanting proximity-level accuracy of assets that move more slowly, such as automatically updating the inventory quantities and locations in an ERP system.
There are multiple use cases for how both UWB and BLE RTLS can benefit companies in multiple industries. Have questions about how RTLS could benefit your organization? Get in touch! We are looking forward to working together to solve your operational needs.
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