UWB and RTLS glossary

A

Accelerometer (motion sensor): An accelerometer is a motion sensor that detects movement, tilt and impacts. RTLS tags use it to sleep when they are not moving, which saves battery and radio capacity. Read more
Accuracy: Accuracy is how close a measured position is to the true position, while precision is how closely repeated measurements agree with each other. In RTLS an accuracy figure should always come with conditions, such as line of sight, movement and the share of positions within the figure, for example 95 %. Read more
Active RFID: Active RFID uses battery-powered tags that transmit on their own, giving longer read ranges than passive RFID. Most active RFID systems locate tags to a zone rather than a precise position. Read more
AGV and AMR (automated guided vehicle, autonomous mobile robot): An automated guided vehicle (AGV) follows fixed routes, while an autonomous mobile robot (AMR) plans its own path around obstacles. Both move materials in factories and warehouses and can be tracked with indoor positioning. Read more
Airtime: Airtime is the time the radio channel is occupied by transmissions. Because tags in the same area share the channel, the airtime each position costs limits how many tags an area can serve at a given update rate. Read more
Aliro: Aliro is an access-control standard from the Connectivity Standards Alliance that lets phones and wearables open doors. Version 1.0, released in February 2026, uses NFC, Bluetooth LE and, for hands-free entry, Bluetooth LE plus UWB. Read more
Andon (digital andon): Andon is a lean-manufacturing signal that tells others a workstation needs help, materials or attention. A digital andon sends the call to a system, and with an RTLS the call carries its location. Read more
Andon Button: The Andon Button is Noccela’s wireless, location-aware call button for andon calls, assistance requests and evacuation activation. Because it knows where it is, it can be moved to another workstation without reconfiguration. Read more
Angle of arrival (AoA) (AoA): Angle of arrival (AoA) is a positioning method that finds the direction a signal comes from by comparing its phase at two or more antennas. Combined with a distance, or with angles measured elsewhere, it gives a position. Read more
Angle of departure (AoD) (AoD): Angle of departure (AoD) is the Bluetooth direction-finding method in which the transmitter has the antenna array and the receiver, often a phone, calculates the angle. Read more
Antenna delay: Antenna delay is the small, fixed time a signal spends inside a device’s antenna and circuitry before it is transmitted or timestamped. UWB devices are calibrated for it, because 1 ns of error is about 30 cm of distance. Read more
API (application programming interface): An application programming interface (API) is a defined way for software to request data from, or send commands to, another system. RTLS APIs deliver positions, zones and events to other applications. Read more
Asset tracking: Asset tracking is following the location and status of physical items such as tools, carts, containers, equipment and pallets. With an RTLS it shows where each item is now and where it has been. Read more
Automatic calibration (self-calibration, auto-positioning): Automatic calibration is a process in which base stations measure the distances between each other to work out their own positions, instead of every position being surveyed by hand. In Noccela’s system, two base stations are measured and the rest locate themselves. Read more

B

Base station (UWB anchor, anchor, locator): A base station is a fixed radio unit at a known position that measures signals from tags so that their positions can be calculated. In UWB systems it is also called a UWB anchor; Noccela’s base stations calibrate their own positions after installation. Read more
Beacon 3: Beacon 3 is Noccela’s compact indoor base station (UWB anchor), powered over Ethernet and mounted like a security camera. It covers up to 500 m² and calibrates its own position after installation. Read more
BLE beacon (Bluetooth beacon): A BLE beacon is a small Bluetooth Low Energy transmitter that repeatedly broadcasts its identity. Receivers estimate how near it is from signal strength, which typically gives room-level location. Read more
Blink: A blink is a short one-way message that a tag transmits without waiting for a reply. TDoA systems locate a tag from the arrival times of a single blink at several base stations. Read more
Bluetooth Channel Sounding (Channel Sounding): Bluetooth Channel Sounding is a ranging feature, added in Bluetooth Core 6.0 in 2024, that measures the distance between two devices from phase differences across many channels, with round-trip time as a cross-check. The Bluetooth SIG reports about ±20 cm in early implementations. Read more
Bluetooth direction finding (Bluetooth AoA, Bluetooth AoD): Bluetooth direction finding, added in Bluetooth 5.1 in 2019, measures the angle of a signal using an antenna array at the receiver (angle of arrival) or at the transmitter (angle of departure). Read more
Bluetooth Low Energy (BLE) (BLE, Bluetooth LE): Bluetooth Low Energy (BLE) is the low-power version of Bluetooth used by beacons, wearables and sensors in the 2.4 GHz band. It can locate devices by signal strength, by direction finding or, since Bluetooth 6.0, by Channel Sounding. Read more

C

CCC Digital Key (Digital Key): CCC Digital Key is the Car Connectivity Consortium’s standard for using a phone as a car key. Release 3.0 uses Bluetooth LE and UWB so that a car can unlock hands-free and check that the key is really nearby. Read more
Channel 5 (UWB channel 5): Channel 5 is the UWB channel centred at 6489.6 MHz with about 500 MHz of bandwidth, used by many UWB products, including Noccela’s. It overlaps the 6 GHz band used by Wi-Fi 6E and Wi-Fi 7. Read more
Channel 9 (UWB channel 9): Channel 9 is the UWB channel centred at 7987.2 MHz with about 500 MHz of bandwidth. It is the only mandatory channel in the FiRa Consortium’s specifications and lies above the 6 GHz Wi-Fi band. Read more
Clock drift (clock offset): Clock drift is the small difference in speed between two devices’ crystal oscillators, measured in parts per million (ppm). In two-way ranging it causes distance errors unless it is cancelled, for example with double-sided ranging. Read more
Clock synchronisation: Clock synchronisation keeps the clocks of several base stations aligned so that their timestamps can be compared. TDoA positioning needs synchronisation to a fraction of a nanosecond, using cables or wireless reference messages. Read more
Collision avoidance: Collision avoidance is an umbrella term for measures that reduce the risk of vehicles hitting people, other vehicles or structures. An RTLS contributes proximity warnings and awareness; slowing or stopping a machine is done by safety-rated functions supplied by the machine builder or integrator. Read more
Coverage: Coverage is the area in which a positioning system can locate tags to its stated accuracy. It is often given per base station; Noccela’s figure is up to 500 m² per base station. Read more

D

Dead reckoning: Dead reckoning estimates position from a known starting point using measured speed, direction and time, typically from accelerometers and gyroscopes. Its error grows over time, so it is combined with radio positioning. Read more
Digital twin: A digital twin is a live digital model of a physical site, process or object that is kept up to date with real data. Location data from an RTLS adds where people, vehicles and materials are right now. Read more
Dilution of precision (DOP) (GDOP, geometric dilution of precision): Dilution of precision (DOP) is a number that describes how the geometry of base stations or satellites magnifies measurement errors into position errors. Base stations that surround the tracked area give low DOP; base stations in a line give high DOP. Read more
Double-sided two-way ranging (DS-TWR) (DS-TWR): Double-sided two-way ranging (DS-TWR) is a ranging method that uses three messages so that both devices measure a round trip and a reply time, which cancels most of the error caused by clock drift. Read more
Downlink TDoA (DL-TDoA) (DL-TDoA, reverse TDoA): Downlink TDoA (DL-TDoA) is a positioning method in which synchronised base stations transmit and each device calculates its own position from the differences in arrival time, like a GPS receiver. It supports any number of devices, and the infrastructure does not know where they are. Read more
Dwell time: Dwell time is how long a tag stays in a zone or at a location. It is used to measure waiting, queueing, process times and idle equipment. Read more

E

EIRP (effective isotropic radiated power, e.i.r.p.): Effective isotropic radiated power (EIRP) is the power a transmitter would need to radiate equally in all directions to produce the signal strength it actually produces in its strongest direction. UWB emission limits are expressed as average EIRP per MHz. Read more
Enterprise resource planning (ERP) (ERP): An enterprise resource planning (ERP) system manages a company’s core business data, such as orders, inventory, purchasing and finance. Location events from an RTLS can update ERP records automatically. Read more

F

FIFO (first in, first out): First in, first out (FIFO) is the rule that the oldest stock or work is used or shipped first. Location data can show whether FIFO is really being followed in a warehouse or production buffer. Read more
Fingerprinting: Fingerprinting is an indoor positioning method that compares live signal-strength readings with a map of readings recorded in advance at known points. It improves on plain signal strength but must be re-recorded when the layout changes. Read more
FiRa Consortium (FiRa): The FiRa Consortium is an industry group, founded in 2019, that writes specifications and runs certification so that UWB devices from different makers work together. Its specifications cover two-way ranging, downlink and uplink TDoA, and angle of arrival. Read more
First path (first-path detection): The first path is the earliest-arriving copy of a radio signal, normally the one that travelled the direct route. UWB receivers pick it out from later reflections to measure distance accurately. Read more
Fractional bandwidth: Fractional bandwidth is a signal’s bandwidth divided by its centre frequency. Under US rules a signal is ultra-wideband if its fractional bandwidth is at least 20 % or its bandwidth is at least 500 MHz. Read more

G

Geofence (virtual fence): A geofence is a virtual boundary drawn on a map, such as a room, an aisle or a danger area. When a tag enters, leaves or stays inside it, the system raises an event. Read more
GNSS (GPS, global navigation satellite system): A global navigation satellite system (GNSS) is a satellite positioning system such as GPS, Galileo, GLONASS or BeiDou. It works well outdoors, but its signals are too weak for reliable positioning inside most buildings. Read more

H

Heatmap: A heatmap is a map coloured by how often or how long tags were at each place. It shows busy aisles, congestion points and unused space at a glance. Read more
High-Performance Ranging (HPR) (HPR): High-Performance Ranging (HPR) is Noccela’s proprietary UWB positioning protocol. It is a hybrid designed to give two-way-ranging accuracy and coverage with an airtime per tag closer to TDoA, and it keeps a two-way link to every tag. Read more

I

ID Badge: The ID Badge is Noccela’s wearable personnel tag with a call button, LED and buzzer. It is rechargeable, sealed to IP67 and updated over the air. Read more
IEEE 802.15.4: IEEE 802.15.4 is the IEEE standard for low-rate wireless networks that defines the UWB physical layer used for ranging, as well as the radio used by Zigbee and Thread. The current revision is IEEE 802.15.4-2024. Read more
IEEE 802.15.4a: IEEE 802.15.4a is the 2007 amendment to IEEE 802.15.4 that added an impulse-radio UWB physical layer designed for precise ranging. Read more
IEEE 802.15.4ab: IEEE 802.15.4ab is the next amendment to the UWB standard and was still a draft in October 2026. It adds narrowband-assisted operation, longer range through multi-millisecond ranging, sensing and higher data rates. Read more
IEEE 802.15.4z: IEEE 802.15.4z is the 2020 amendment that improved the integrity and accuracy of UWB ranging and added the scrambled timestamp sequence (STS) for secure ranging. Its content is now part of IEEE 802.15.4-2024. Read more
Indoor positioning system (IPS) (IPS, indoor GPS): An indoor positioning system (IPS) is a system that locates people or objects inside buildings, where satellite positioning is unavailable. When it reports positions continuously as they change, it is also called a real-time location system. Read more
Industrial Tag: The Industrial Tag is Noccela’s IP65-rated tag for vehicles, machines and harsh conditions. Read more
ISO/IEC 24730: ISO/IEC 24730 is the international standard family for real-time locating systems, covering an application programming interface and several radio air interfaces. Read more

K

Kalman filter: A Kalman filter is an algorithm that combines a stream of noisy measurements with a model of how an object moves to produce smoother and more reliable estimates. Positioning engines commonly use it, or a similar filter, to track moving tags. Read more

L

Latency: Latency is the delay between a tag being at a place and that position being available to an application. It includes radio, calculation and network delays, and matters most for safety warnings. Read more
Line of sight (LOS) (LOS): Line of sight (LOS) means there is an unobstructed straight path between a transmitter and a receiver. UWB positioning is most accurate in line of sight. Read more
Local positioning system (LPS) (LPS): A local positioning system (LPS) is a positioning system with its own infrastructure covering a limited area, such as a sports pitch or arena. In sport, the term distinguishes UWB-based tracking from GPS vests. Read more
Location Intelligence Platform (Noccela Location Intelligence Platform): The Noccela Location Intelligence Platform is Noccela’s software for turning tag positions into maps, dashboards, alerts, workflows and data for other systems. It runs in the cloud or on an on-premise server. Read more
Lone worker: A lone worker is someone who works without close or direct supervision, for example at night or in a remote part of a site. Lone-worker systems raise an alarm from a button press or when a person stops moving, and show where help is needed. Read more

M

Manufacturing execution system (MES) (MES): A manufacturing execution system (MES) tracks and controls production on the shop floor, such as orders, operations and work in progress. RTLS events can confirm automatically where each order or batch is. Read more
Mobile Anchor with Flash: The Mobile Anchor with Flash is Noccela’s portable kit that combines a base station, a signalling flash, a battery and an LTE router in one rugged case. It creates a temporary warning zone wherever it is placed. Read more
MQTT: MQTT is a lightweight publish-and-subscribe messaging protocol, standardised by OASIS, that is widely used to move IoT data between devices, brokers and applications.
Multilateration: Multilateration is calculating a position from differences in distance, or in arrival time, to several known points; each difference places the object on a hyperbola. TDoA systems use it. Read more
Multipath: Multipath is the effect of a radio signal reaching the receiver by several routes: directly and via reflections from walls, metal and floors. It distorts signal strength and timing; UWB’s short pulses help separate the direct path from reflections. Read more
Mustering (muster point, evacuation headcount): Mustering is gathering people at assembly points during an emergency and confirming that everyone is accounted for. With RTLS badges, the system lists who has reached a muster point and where missing people were last located. Read more

N

Non-line of sight (NLOS) (NLOS): Non-line of sight (NLOS) means the direct path between transmitter and receiver is blocked, so the signal arrives weakened, delayed or only by reflection. NLOS adds errors to UWB ranging, which good systems detect and reduce. Read more

O

OAuth 2.0 (OAuth): OAuth 2.0 is the IETF authorisation framework (RFC 6749) that lets an application obtain an access token to call an API. Noccela’s APIs use the client-credentials flow, in which a server application authenticates with its own ID and secret. Read more
omlox: omlox is an open standard for locating systems managed by PROFIBUS & PROFINET International (PI). It defines a hub API that brings location data from different technologies into one interface, and a UWB air interface, the core zone, for interoperable tags and base stations.
On-premise RTLS (on-prem): An on-premise RTLS runs its positioning engine and software on servers inside the customer’s own network. It keeps location data on site and keeps working without an internet connection. Read more
On-Premise Server: The Noccela On-Premise Server runs the positioning engine and the Location Intelligence Platform inside the customer’s own network instead of in the cloud. Read more
OPC UA (OPC Unified Architecture): OPC UA (OPC Unified Architecture) is an industrial standard, published as IEC 62541, for secure, platform-independent data exchange between machines, control systems and software.
Over-the-air update (OTA) (OTA, firmware update over the air): An over-the-air (OTA) update installs new firmware or settings on a device by radio, without anyone handling it. It needs a two-way link to the device. Read more

P

Passive RFID (UHF RFID, RFID): Passive RFID uses battery-free tags that are powered by a reader’s radio field and reply with their identity. It shows that a tag was near a reader, typically within a few metres, rather than where it is between readers. Read more
Phase difference of arrival (PDoA) (PDoA): Phase difference of arrival (PDoA) is the difference in phase between copies of one signal received at two antennas. UWB chips use it to calculate the angle of arrival. Read more
Position uncertainty: Position uncertainty is an estimate, often a radius in metres, of how far a reported position may be from the true one. Applications use it to ignore positions that are not reliable enough for a decision. Read more
Positioning engine (location engine): A positioning engine is the software that turns raw radio measurements from base stations into tag coordinates, filters them and estimates how certain they are. It runs in the cloud or on a local server. Read more
Power over Ethernet (PoE) (PoE): Power over Ethernet (PoE) delivers electrical power and data over one Ethernet cable, as standardised in IEEE 802.3. Base stations powered over Ethernet need no separate power socket. Read more
Power spectral density limit (-41.3 dBm/MHz, UWB emission limit): The UWB power spectral density limit is −41.3 dBm/MHz, the maximum average power that UWB devices may radiate per megahertz in the main UWB bands in the US and the EU. Over a 500 MHz channel it adds up to about 0.04 mW. Read more
Proximity warning: A proximity warning alerts people when two tracked objects, such as a pedestrian and a forklift, come closer than a set distance. It complements physical separation, training and the machine’s own safety functions. Read more
Pseudonymisation: Pseudonymisation replaces names or IDs with codes so that data cannot be linked to a person without separately kept information. In people-tracking systems it allows analytics without revealing who was where. Read more
Push API (webhook): A push API sends data to a receiving system as soon as an event happens, instead of waiting to be asked; webhooks are the most common form. Noccela’s Push API sends events such as a tag entering or leaving a zone. Read more

R

Ranging: Ranging is measuring the distance between two devices. UWB ranging measures the time a radio signal takes to travel between them. Read more
Real-time location system (RTLS) (RTLS, real-time locating system): A real-time location system (RTLS) is a system that continuously finds the position of tagged people, vehicles and objects inside a defined area and passes those positions to software as they change. Read more
Received signal strength indicator (RSSI) (RSSI, signal strength): The received signal strength indicator (RSSI) is a measure of how strong a received radio signal is. Positioning based on RSSI estimates distance from it, which typically gives room-level or metre-level accuracy because bodies and objects change signal strength. Read more

S

Scrambled timestamp sequence (STS) (STS): The scrambled timestamp sequence (STS) is a cryptographically generated pulse pattern, added in IEEE 802.15.4z, that makes UWB timestamps hard to fake. It protects distance measurements against relay and spoofing attacks. Read more
SDK (software development kit): A software development kit (SDK) is a set of libraries, examples and documentation that makes it easier to build software for a platform. Noccela publishes a JavaScript and TypeScript SDK for its real-time API. Read more
Secure ranging: Secure ranging is distance measurement designed so that an attacker cannot make two devices appear closer than they are. In UWB it relies on the scrambled timestamp sequence and is essential for car keys and door access. Read more
Signalling Flash: The Signalling Flash is Noccela’s location-triggered light and tone unit for zone warnings and andon status. Read more
Single-sided two-way ranging (SS-TWR) (SS-TWR): Single-sided two-way ranging (SS-TWR) is a ranging method in which one device sends a poll and measures the round trip to the reply, minus the known reply delay. It needs only two messages but is sensitive to clock drift. Read more
Site survey: A site survey is an inspection of a site before installation that checks the layout, mounting points, cabling routes, metal structures and radio conditions. It is the basis of the base-station plan. Read more
Smart Tag: The Smart Tag is Noccela’s small asset tag for tools, carts, pallets and equipment. Read more
Spaghetti diagram: A spaghetti diagram is a lean tool that traces the path a person, vehicle or item takes through a process on a floor plan. Drawn automatically from location data, it reveals wasted walking and driving. Read more
Sports Beacon: The Sports Beacon is Noccela’s rugged base station for sports fields, outdoor areas and harsh industrial sites, mounted on fences, poles or tripods. Read more

T

Tag (RTLS tag, badge): A tag is a small radio device attached to, or worn by, the person or object being tracked. RTLS tags include badges, asset tags and call buttons, and are usually battery powered. Read more
Tag battery life (battery life): Tag battery life is how long a tag runs before its battery must be replaced or recharged. It depends mostly on the update rate, how much the tag moves and the positioning method; Noccela’s tags typically last several years, depending on utilisation and update rate. Read more
Tag capacity (capacity): Tag capacity is the number of tags a positioning system can locate at a given update rate within one radio area. For Noccela it is 1,000 active tags at 1 Hz within radio range; tags that are not moving sleep, thanks to the accelerometer, and do not use capacity. Read more
Time difference of arrival (TDoA) (TDoA, TDOA): Time difference of arrival (TDoA) is a positioning method that locates a transmitter from the differences between the times its signal reaches several synchronised receivers. It needs only one transmission per position. Read more
Time of flight (ToF) (ToF): Time of flight (ToF) is the time a signal takes to travel from transmitter to receiver. Multiplied by the speed of light, about 30 cm per nanosecond, it gives the distance. Read more
Triangulation: Triangulation is calculating a position from angles measured at two or more known points. Angle-of-arrival systems use it, although the word is often used loosely for trilateration too. Read more
Trilateration: Trilateration is calculating a position from distances to three or more known points, where the circles or spheres around them intersect. Two-way ranging systems use it. Read more
Two-way ranging (TWR) (TWR): Two-way ranging (TWR) is a way of measuring distance in which two devices exchange messages and each measures time only on its own clock, so no clock synchronisation is needed. It costs two or three messages per base station for each position. Read more

U

Ultra-wideband (UWB) (UWB, IR-UWB): Ultra-wideband (UWB) is a short-range radio technology that sends very short pulses across a band at least 500 MHz wide, so that devices can measure distance to within centimetres by timing them. It is used for indoor positioning, digital car keys, item finding and secure access. Read more
Update rate (refresh rate, blink rate): The update rate is how often a tag’s position is calculated, given in hertz (Hz): 1 Hz is once a second and 0.1 Hz once every 10 seconds. Higher rates follow fast movement better but use more battery and radio capacity. Read more
Uplink TDoA (UL-TDoA) (UL-TDoA): Uplink TDoA (UL-TDoA) is a positioning method in which a tag sends a single blink and synchronised base stations calculate its position from the differences in arrival time. It gives long tag battery life and high tag capacity. Read more

W

Warehouse management system (WMS) (WMS): A warehouse management system (WMS) controls storage locations, stock movements, picking and shipping in a warehouse. RTLS data can confirm put-aways and picks automatically from forklift and pallet positions. Read more
WebSocket: WebSocket is a web protocol (IETF RFC 6455) that keeps a two-way connection open between a client and a server, so that data such as live tag positions can be streamed without repeated requests. Read more
Wi-Fi RTT (FTM, fine timing measurement, 802.11mc): Wi-Fi round-trip time (RTT) is a Wi-Fi ranging method that measures the distance to access points from signal travel time, defined as fine timing measurement in IEEE 802.11mc and extended in 802.11az. It typically gives 1–2 m accuracy. Read more
Work in progress (WIP) (WIP): Work in progress (WIP) is production that has started but is not finished, such as parts, batches or assemblies between operations. Tracking WIP with an RTLS shows where each order is and how long it waits. Read more

Z

Zone: A zone is a named area on a site map, such as a workstation, storage bay or danger area, used to turn positions into events and statistics. Zones are a kind of geofence. Read more

Glossary of UWB, RTLS and indoor-positioning terms

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Questions the glossary does not answer?