Real-Time Location Systems (RTLS) have enabled tracking of people and assets across various industries, improving safety, operational efficiency, and business visibility. RTLS provides real-time visibility and accurate location information across varying use cases.
RTLS Terminology: A Quick Primer
This RTLS glossary breaks down the key concepts and vocabulary behind Real-Time Location Systems, covering the components, technologies, and terms you’ll run into once you start evaluating or deploying a system.
For the full picture of what RTLS is and how it works, see our complete guide to RTLS. The rest of this page focuses on the vocabulary you’ll actually encounter once you’re evaluating or deploying an RTLS system, from positioning methods to tag types to coverage models.
Components of an RTLS System
An RTLS system consists of several key components that work together to enable location tracking and management. These components include tags, anchors, nodes, and a location engine.
Tags And Beacons
A crucial component of real-time locating systems is the tag or beacon. These small devices are attached to assets or people and emit signals at regular intervals. Beacons use Bluetooth Low Energy (BLE) or Ultra-Wideband (UWB) technology to communicate with the receiver nodes that are placed around the facility.
Tags have a longer battery life and can be rechargeable, while beacons require power from a source such as a wall outlet or battery. Depending on the vendor, you may see these devices referred to as RTLS tags or RTLS beacons, but the underlying function is the same.
Receivers
Receiver nodes, or anchors as they’re also called, capture the signals emitted by the tags/beacons and transmit them to the central server for processing. The nodes can be mounted on the walls, ceiling or placed on a stand for easy relocation. The number of receivers required depends on the size of the facility and the number of assets being tracked.
Large facilities may require hundreds of these location sensors deployed to provide full coverage, while small facilities may only need a few. In vendor documentation, receivers are also commonly called RTLS sensors.
Software
The software is the engine that powers the RTLS technology. It receives data from the receiver nodes and translates it into meaningful information that can be used for location-based services such as asset tracking, personnel tracking, or way-finding.
The software also provides a dashboard that displays the location and status of all assets in real time. The dashboard can be accessed from any internet-enabled device such as a laptop, tablet, or phone. Evaluating RTLS software separately from the hardware is worth doing, since the software layer is what turns raw signals into usable alerts, reports, and dashboards.
Network Infrastructure
The network infrastructure is another important component of RTLS technology. The receiver nodes communicate with the central server over an Ethernet or Wi-Fi connection. The software runs on a dedicated server or cloud-based service that can handle the volume of data generated by the tags and receivers.
The network must be designed and installed with redundancy and fault tolerance in mind to maximize uptime and reliability. Together with the receivers and tags, this network forms the RTLS hardware layer that the software depends on.
Location Engine
The location engine is the core component of the RTLS system responsible for processing the received data and calculating the real-time location of the tracked objects. The location engine software utilizes advanced algorithms and techniques to triangulate or trilaterate the signals received from the tags and determine their precise location within the RTLS environment.
Technologies Used In RTLS
RTLS can be implemented using various technologies, each with its advantages and limitations. Some of the commonly used technologies in RTLS include Ultra-Wideband (UWB), Radio-Frequency Identification (RFID), Wi-Fi, and Bluetooth Low Energy (BLE).
Ultra-Wideband (UWB)
Ultra-Wideband technology utilizes short-duration pulses to transmit and receive data. UWB-based RTLS technology provide highly accurate and precise location information, making them suitable for applications that require high granularity. UWB can achieve sub-meter accuracy and is particularly effective in complex indoor environments.
Radio-Frequency Identification (RFID)
Radio-frequency identification (RFID) technology-based RTLS systems rely on readers and antennas to detect and communicate with RFID tags. It employs electromagnetic fields that automatically track and identify tags attached to objects. RFID is widely adopted due to its cost-effectiveness, scalability, and compatibility with existing infrastructure.
Wi-Fi-Based RTLS
Wi-Fi-based RTLS leverages existing Wi-Fi access points and infrastructure to track the location of Wi-Fi-enabled devices. By analyzing the signal strength and time of arrival of Wi-Fi signals, the RTLS system can determine the approximate location of the tracked devices. Wi-Fi-based RTLS is convenient for organizations that already have Wi-Fi networks in place. Typical accuracy is 3 to 5 meters.
Bluetooth Low Energy (BLE)
Bluetooth Low Energy technology enables wireless communication between devices with low power consumption, such as mobile devices, computers, and such. BLE-based RTLS technology utilize Bluetooth beacons that transmit signals to nearby devices, allowing for proximity-based tracking. BLE is commonly used in applications such as asset tracking and indoor navigation. Typical accuracy is 1 to 3 meters. Learn how BLE tracking works in our guide to BLE indoor positioning and tracking.
Infrared RTLS
Infrared (IR) RTLS is ideal for businesses that require high-accuracy tracking of assets and people. IR RTLS uses sensors that detect infrared signals emitted by tags worn by employees or attached to assets. This option is highly reliable and accurate, but it requires a line of sight between sensors and tags and can be affected by ambient light.
GPS RTLS
GPS RTLS is ideal for businesses that require outdoor tracking of assets and people. GPS RTLS uses GPS satellites to determine location of people and assets within a given area. This option is highly accurate but has limited use indoors, where the GPS signal can be obstructed by walls and ceilings.
RTLS System Coverage
A well-implemented real-time location system enables businesses to efficiently track assets, reduce operational costs, and improve workflow efficiency. While the technology does offer numerous benefits, it’s only effective if implemented with the right coverage options.
Wide Area Coverage
One of the primary coverage options of an RTLS technology is wide area coverage. It enables organizations to monitor assets over a large area. This coverage option works using various technologies such as RFID, GPS, and Bluetooth beacons.
RFID technology is commonly used to achieve a wide range of wireless inventory tracking capabilities. It automatically detects assets within a specific range and provides instant alerts when they leave a predefined zone. Compared to GPS, RFID provides a more cost-effective solution for organizations that need to track valuable assets.
Local Area Coverage
Local area coverage is another coverage option, commonly used in localized settings. It helps organizations keep track of the movement and location of critical assets within a specific area.
For instance, local area coverage can be used to track high-value mobile equipment that needs to stay within a defined area. The system uses ultra-wideband to achieve more precise location information of assets. UWB provides increased accuracy by tracking objects to a few centimeters.
Choke Point Coverage
Choke points are another type of coverage option in RTLS systems. It utilizes the existing infrastructure in a building, such as doorways or gates, and enables real-time monitoring of assets that have to pass through them.
Choke point coverage can help monitor the movement of products from one area to the next and ensure compliance with safety measures and security. Additionally, this coverage option can be used to control access to sensitive areas and manage inventory records.
Positioning And Locating Methods in RTLS
RTLS technology employ various positioning methods to determine the location of tagged objects or people accurately. Some of the commonly used positioning methods include trilateration, dead reckoning, time difference of arrival, angle of arrival, and signal strength.
Trilateration
Trilateration is a positioning method that relies on the measurement of distances between the tagged object and multiple anchors. By calculating the intersection of the distance circles, the RTLS system can determine the precise location of the object. Trilateration is widely used in RTLS systems due to its simplicity and accuracy.
Triangulation
Triangulation locates an object from angles measured at two or more known points, while trilateration uses distances. In RTLS the words are often mixed: “RF triangulation” or “Wi-Fi triangulation” usually means trilateration from signal strength. True triangulation in indoor positioning uses angle of arrival.
Dead Reckoning
Dead reckoning is a technique used in RTLS systems to estimate the position of a moving object based on its previously known position, direction, and speed. Dead reckoning can be combined with other positioning methods to improve accuracy, especially in environments where line-of-sight or signal coverage is limited.
Time Of Arrival Method (TOA)
TOA is a popular location indicator that determines the location of a device by calculating the time taken for a signal to reach the device from a known location. The time taken for the signal to travel from the known location to the device is used to determine the distance between the two. This method is typically used in applications that require high precision, such as navigation systems.
Time Difference Of Arrival (TDOA)
Time difference of arrival (TDoA) is a positioning method that locates a tag by comparing when its signal reaches several fixed receivers. The tag sends one short signal, called a blink. Because the receivers share a synchronized clock, the system can measure the tiny differences in arrival time and calculate where the tag must be.
TDoA needs at least 3 receivers for a 2D position and 4 for a 3D position. The tag only transmits and never waits for a reply, which saves battery and lets one system track thousands of tags. That is why TDoA is the most common method in industrial UWB RTLS. Its main requirement is precise clock synchronization between receivers, usually over cable or a wireless timing signal.
Two related methods use the same idea: frequency difference of arrival (FDOA) compares Doppler frequency shifts instead of arrival times, and is often combined with TDoA to locate moving transmitters. Observed time difference of arrival (OTDOA) is a TDoA-based method used for positioning in LTE mobile networks. Read how TDoA works with UWB in What Is UWB?
Two-Way Ranging (TWR)
Two-way ranging (TWR) measures distance by timing a message exchange between a tag and an anchor. Single-sided TWR uses two messages; double-sided TWR adds a third so both devices can correct for clock differences. TWR needs no synchronized receivers, but the tag must listen and reply, which uses more battery than TDoA. Phones, digital car keys and smart locks use TWR.
Angle Of Arrival (AoA)
AoA is a positioning method that determines the direction of signals emitted by the tagged object relative to the anchors. By analyzing the angle of arrival of signals, the RTLS system can calculate the object’s location. AoA is commonly used in systems that utilize directional antennas or beamforming techniques.
Phase Difference of Arrival (PDoA)
Phase difference of arrival (PDoA) estimates the angle a signal arrives from by comparing its phase at two or more antennas on the same receiver. It is the usual way UWB and Bluetooth devices measure angle of arrival, and combined with distance it can locate a tag from a single receiver.
Time Of Flight Method (TOF)
TOF is another popular location indicator that determines the distance between a device and a known location by calculating the time taken for a signal to travel from the known location to the device and back. This method is commonly used in applications that require high precision, such as long-range radar systems.
Received Signal Strength Indicator (RSSI) Method
This method works by measuring the strength of the signal received by a device. The signal strength is used to determine the distance between the device and the known location. This method is commonly used in applications that require low-cost positioning, such as asset tracking systems. Used by Wi-Fi and BLE systems, RSSI is low cost but less accurate than time-based methods such as TDoA and TWR.
Types Of RTLS Tags
RTLS tags come in different forms and functionalities, depending on the specific requirements of the application. The three main types of RTLS tags are active tags, passive tags, and semi-passive tags.
Active RFID Tags
Active tags are battery-powered tags that continuously transmit their unique identifier signal. These tags have their power source, allowing for longer-range communication and real-time tracking. Active tags are commonly used in applications that require long-range tracking.
Passive RFID Tags
Passive tags do not have their power source and rely on the energy emitted by the RTLS system’s infrastructure to operate. These tags are cost-effective and have a longer lifespan compared to active tags. Passive tags are commonly used in applications that require proximity-based tracking, such as access control and inventory management.
Semi-Passive RFID Tags
Semi-passive tags, also known as battery-assisted passive (BAP) tags, contain a small battery that powers certain functionalities, such as transmitting the unique identifier signal. The battery in semi-passive tags extends the tag’s read range and enables real-time tracking capabilities. Semi-passive tags are commonly used in applications that require a balance between battery life and performance.
Additional RTLS Terms & Jargon
Ranging
The process of measuring the distance between a tag and an anchor using signal timing or strength. Ranging is the raw input that positioning methods like TDOA and trilateration convert into an actual location.
Line of Sight (LOS) and Non-Line of Sight (NLOS)
LOS describes a clear, unobstructed path between a tag and an anchor, which produces the most accurate readings. NLOS occurs when a wall, piece of equipment, or person blocks that path, adding error that positioning algorithms need to correct for.
Update Rate (Ping Rate)
How frequently a tag reports its position, typically measured in updates per second. A higher update rate gives smoother, more real-time tracking, but shortens battery life on battery-powered tags.
Latency
The delay between an asset’s actual movement and when that movement appears on the RTLS dashboard. Lower latency matters most in safety-critical use cases, such as collision avoidance.
Real-Time vs. Near Real-Time
Real-time data is available almost as soon as an event happens, within milliseconds to about a second. Near real-time (NRT) data arrives with a short but noticeable delay, from a few seconds to a few minutes, because it is collected and processed in batches. The opposite of real-time is batch or offline processing, where data is analyzed hours or days later.
In RTLS, safety functions such as collision warning and duress alerts need true real-time updates. Reporting, dashboards and utilization analytics usually work well with near real-time data.
Accuracy vs. Precision
Accuracy is how close a reported location is to the asset’s true position. Precision is how consistent repeated readings are with each other. A system can be precise without being accurate if it consistently reports the wrong location.
Zone
A defined area within a facility, such as a loading dock or a restricted room, used to trigger alerts or reports when a tagged asset enters or exits it. Zones are the building blocks behind geofencing rules.
Dwell Time
Dwell time is how long a tracked asset, vehicle or person stays in a zone. Individual dwell time measures this per tag, for example how long one patient waited in triage or one pallet sat in a staging area. Dwell time reveals bottlenecks, idle equipment and process delays.
Mesh Network
A network topology where anchors relay data to each other rather than each connecting directly to a central server, improving coverage and resilience in large or complex facilities.
Middleware
Software that sits between the RTLS hardware and business applications, translating raw location data into a format that ERPs, WMS, or other systems can use.
Anchor Density
The number of anchors installed per unit of area. Higher anchor density generally improves accuracy but increases hardware and installation cost, making it a key tradeoff in system design.
Calibration
The process of fine-tuning an RTLS system after installation, adjusting for environmental factors like wall material or signal reflection, to bring reported locations closer to actual positions.
Sensor Fusion
Combining data from multiple positioning methods or technologies, such as UWB and inertial sensors, to improve accuracy beyond what any single method could achieve alone.
Situational Awareness
Situational awareness is a live understanding of who and what is where, and what is happening around them. In the workplace, RTLS supports situational awareness by showing staff, vehicles and assets on one map, with alerts for unsafe proximity, restricted zones or emergencies. Situational awareness software combines this location data with sensor data and alarms.
Challenges and Limitations of RTLS
While RTLS technology offers numerous benefits, there are some challenges and limitations that need to be addressed for successful implementation.
RF Propagation
RF propagation describes how radio signals travel through an environment: how they weaken with distance (path loss), bounce off surfaces (multipath), and are blocked or absorbed by walls, metal, water and people. Understanding RF propagation is the basis of every RTLS site survey, because it decides where receivers go and how many are needed. RF propagation delay, the time a signal takes to travel, is what time-based methods such as TDoA and TWR measure.
Multipath
Multipath refers to the phenomenon where signals take multiple paths to reach the receiver due to reflection, diffraction, or scattering. Multipath can cause signal interference and impact the accuracy of reporting the exact tag location. Mitigation techniques, such as signal filtering and antenna placement optimization, are employed to minimize the impact of multipath. RF multipath is one of the main reasons signal-strength methods lose accuracy indoors.
Interference
Interference from other wireless devices or environmental factors can disrupt the signals transmitted and received by RTLS systems. Interference can result in inaccurate location information and reduced system performance. Advanced interference mitigation techniques, including frequency hopping and signal modulation, are employed to overcome this challenge.
Path Loss
Path loss refers to the attenuation or weakening of signals as they travel through space. The strength of the received signal decreases with distance, resulting in reduced accuracy and range in RTLS technology. Careful positioning of anchors, signal amplification, and power optimization techniques can help mitigate the effects of path loss.
RSSI Fingerprinting
RSSI fingerprinting is a technique used in signal strength-based positioning to create a database of signal strength measurements at known locations. However, RSSI fingerprinting is susceptible to environmental changes, signal interference, and other factors that can impact the accuracy of the system. Regular calibration and updating of the RSSI fingerprint database are necessary to maintain accurate positioning.
Advancements In RTLS
RTLS technology is constantly evolving, with advancements in hardware, software, and algorithms enabling more accurate and efficient tracking solutions.
Telemetry
Telemetry refers to the collection and transmission of real-time data from remote devices to a central system. In the context of RTLS, telemetry capabilities enhance the tracking and monitoring of assets by providing additional information such as temperature, humidity, or motion. Telemetry-enabled RTLS technology enable businesses to gather valuable insights and make data-driven decisions.
Zigbee
Zigbee is a wireless communication protocol that provides low-power, low-data-rate connectivity. Zigbee-based RTLS technology offer energy-efficient and cost-effective solutions for tracking and monitoring assets. Zigbee’s mesh networking capabilities allow for reliable communication, even in complex environments.
Chirp Spread Spectrum (CSS)
Chirp spread spectrum (CSS) is a radio technique that spreads a signal across a wide band using chirps: pulses whose frequency rises or falls steadily over time. Chirps are resistant to interference and multipath and work at low power over long range. LoRa uses a form of CSS, and the IEEE 802.15.4a standard defined a CSS physical layer that some RTLS products use for ranging. CSS typically gives meter-level accuracy, while UWB reaches 10 to 30 centimeters.
Final Thoughts on RTLS Technology Jargon
Real-Time Location Systems (RTLS) have transformed the way businesses track and manage their assets, people, and objects. RTLS offers real-time visibility and accurate location information.
By understanding the components, technologies, and applications of RTLS, businesses can leverage this technology to optimize operations, enhance security, and improve efficiency. As RTLS continues to advance, we can expect even more innovative solutions that will revolutionize various industries.
And speaking of innovation, Litum offers the best in class real-time location tracking systems and software so you can grow your business efficiently and sustainably. At Litum, we take pride in being a globally recognized indoor tracking and real-time location systems & software provider.
To suit your specific tracking needs, we offer static RFID, zonal BLE, and real-time UWB RTLS tracking options, reducing costs and boosting performance. As an end-to-end solution provider, we offer a full line of sensors, tags, system design, and software.
Backed by a strong partner network across 50 countries, we are confident in our ability to help you give your customers a better experience and ensure sustainable business solutions. So, drop us a line and let us know how we can help you get started.
Frequently Asked Questions About RTLS Terms
What is TDoA?
TDoA (time difference of arrival) is a positioning method that locates a tag by comparing when its signal reaches several synchronized receivers. It needs at least 3 receivers for a 2D position and 4 for 3D, and because tags only transmit, it supports long battery life and thousands of tags.
What is the difference between TDoA and TWR?
TDoA locates a tag from the differences in arrival time of one signal at several synchronized receivers. TWR (two-way ranging) measures the distance between a tag and one anchor by timing a message exchange. TDoA scales better and saves tag battery, while TWR needs no receiver synchronization.
What does near real-time mean?
Near real-time means data arrives with a short delay, from a few seconds to a few minutes, rather than instantly. In RTLS, safety alerts need real-time updates, while reports and analytics usually work well with near real-time data.
What is chirp spread spectrum?
Chirp spread spectrum (CSS) is a radio technique that spreads a signal across a wide band using pulses whose frequency rises or falls over time. It resists interference and works at low power over long range, and it is used in LoRa and in some RTLS products.
What is dwell time in RTLS?
Dwell time is how long a tracked asset, vehicle or person stays in a zone. RTLS measures it automatically for each tag, which helps reveal bottlenecks, idle equipment and long waiting times.
