Indoor location: which technology for which purpose?

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We are all familiar with outdoor geolocation technologies such as satellite positioning (GPS…), but today, companies are looking for indoor positioning solutions that provide an accurate position of objects or people. However, the radio signals emitted by satellites are difficult to pass through walls and obstacles.

To meet this growing demand and its specific requirements, manufacturers in the IIoT (Industrial Internet of Things) market are tending to offer ever more efficient indoor positioning systems (IPS: Indoor Positioning System). Many of these solutions are based on already existing technologies, but the addition of innovative software bricks makes it possible to offer increasingly precise indoor positioning systems.

IPSs use positioning approaches that vary widely in terms of accuracy, cost, scalability, robustness, and security. To help you choose the most suitable solution for your needs, here are some relevant criteria related to indoor positioning systems: location accuracy, coverage and resolution, position refresh time, infrastructure costs, or errors inherent in the type of technology used.

In order to better understand the difference between these indoor localization technologies, we suggest you start by studying the different physical principles involved.

The physical principles of positioning classified into 5 categories

To calculate the location of an object or a person, the algorithms extract position data from radio signals travelling between reference nodes (fixed and known position), serving as a benchmark for locating mobile nodes. However, not all use the same physical principles. We can classify them into 5 main categories:

  • Time of Arrival (TOA)
  • Angle of arrival (AOA)
  • Time Difference of Arrival (TDOA)
  • Received signal strength (RSSI)
  • Hybrid systems (mix of several measurements related to different physical principles)

Now that you know what are the criteria to take into account and that you have in mind the different physical principles of localization, we propose you to discover in more detail 4 indoor localization technologies.

Active RFID for a localization by zones

Active RFID technology was not originally developed for location-based applications. Nevertheless, the standard ISO 18000-7 (Dash7), defined an Active RFID technology operating on two frequency bands (high and low) allowing to realize a localization by zone or more precisely by crossing points.

The active RFID system consists of transponders (also called tags) and one or more interrogators. When a person or an object equipped with a tag passes in the zone of an interrogator, this one activates the tag in question via low frequency signals. This triggers a radio transmission containing the identifiers of the interrogator and the tag. The UHF transmission is picked up and read by a reader provided for this purpose.

En savoir plus sur la différence entre RFID active et passive.

For indoor location, active RFID can be very effective. Indeed, by emitting low-frequency signals (125 kHz), this technology makes it possible to locate indoors during a passage in the zone covered by the interrogator and this, in spite of the presence of obstacles.

This indoor positioning system, which is suitable for locating people and objects at short range, is used in many industrial applications such as the safety of isolated workers, vehicle access control or the location of logistics equipment in a warehouse.

Pros

  • Better accuracy compared to UHF (Ultra High Frequency) technologies
  • Reliable when facing obstacles
  • Single Application Scenario
  • Energy efficiency allowing a very high tag lifetime
  • Easy to install without the need for heavy infrastructure

Cons

  • Short operational range (5 to 15m)
  • Need to have fixed supports to place readers and antennas
  • The refinement of the network depends on the environment

Localization based on the intensity of the received signals (RSSI) in Mesh network

A Mesh network is designed to network a large number of connected devices based on a very simple infrastructure that does not require a central controller. In order to transmit information, the devices communicate data to each other over several bounces. Data, which is collected on a gateway, which in turn feeds back the raw information to a server.

Some solution providers, such as Wirepas, have developed innovative software bricks to optimize the management of the network of connected devices. This brings intelligence to local decision making, ensuring that operations are always optimized, as well as unparalleled adaptability to changes in the environment and network.

For indoor localization, Wirepas Mesh technology relies on a mesh network of fixed and mobile beacons/tags. The former, also called anchors or fixed nodes, are installed at regular intervals (25 meters) over the entire site to be covered and provide reference points for the calculation of the location. The second, mobile, are positioned directly on the people and industrial equipment to be located.

fonctionnement-technologie-mesh-wirepas
Operating diagram of Wirepas Mesh technology

As mentioned above, the beacons will communicate with each other by bouncing and feeding raw information back to a gateway/gateway, thus avoiding data congestion.

The Wirepas Positioning Engine tool will then transform the raw data into GPS coordinates (latitude and longitude) based on the intensity of the signals received by the different anchors. Thus, facilitating the visualization of the position and movements of each person or object equipped with a mobile beacon (mobile node). All this with an accuracy of 5 to 10 meters.

Ces données pouvant être lues sur toutes les plateformes IoT du marché, ainsi que sur des applications web métiers propriétaires, cette technologie répond à de nombreux cas d’usages, tels que la sécurité des travailleurs isolés, l’optimisation de parcs d’équipements industriels et logistiques , la gestion du parcours des patients dans les centres hospitaliers ou encore, le monitoring de bâtiment.

Thanks to its infrastructure of battery-powered autonomous objects, the deployment of this indoor positioning system is very simple. Indeed, the installation is limited to placing anchors and equipping people or objects with mobile beacons. This indoor positioning solution does not require any cabling, its total acquisition cost is therefore one of the most competitive on the market.

Pros

  • Allows hundreds of devices to be connected without interference
  • Network size is scalable
  • Total network coverage is unlimited
  • Messages are protected and cannot be modified
  • The client holds the data and has access to it at all times.
  • Ultra simple installation and low infrastructure cost

Cons

  • Average autonomy of the beacons in particular when the position is refreshed in a sustained way.

Discover our range of Wirepas Mesh products dedicated to indoor localization.

Time of Flight (TOA) calculation in Ultra Wideband Positioning, for ultra-precise localization

Ultra Wideband (UWB) technology allows high bandwidth communication at short range, and was originally used for radar imaging. Today, Ultra Wideband’s ability to achieve data rates of up to 100 megabits per second (Mbps) and its extremely short pulse shapes make it one of the most accurate localization solutions on the market. Indeed, the UWB pulse frequency, together with its Time of Flight Information Triangulation (TOA) system, allows the signal to easily pass over obstacles such as walls and objects. This greatly improves positioning accuracy by up to a few centimeters.

In addition, this technology, invented by the U.S. military, has the capacity, thanks to the width of its frequency spectrum, not to interfere with other radio communications, thus ensuring maximum compatibility with third-party devices and technologies.

Pros

  • Localization accuracy
  • No direct line of sight needed
  • Technology very little affected by other communication devices or by external noise

Cons

  • Significant acquisition cost
  • Significant installation cost

The Angle of Arrival Principle (AOA), for real-time localization with low energy consumption

Angle-of-arrival positioning technology calculates the angles formed between an antenna and a beacon in a 3D reference frame. The beacon sends a radio signal to the antenna which will calculate its exact position according to the angle of elevation of the tag in relation to the vertical axis of the antenna, but also according to the point of intersection between the vertical axis of the beacon and the horizontal axis of the antenna.

Some RTLS (Real Time Locating System) solution providers, such as QUUPPA, offer a technological mix, based on the combination of the physical principle linked to RSSI, the Bluetooth Low Energy (2.4 GHZ ISM) protocol and the signal angle of arrival (AOA) detection. This unique concept makes it possible to obtain a positioning accuracy superior to other technologies based on signal strength (RSSI), down to less than one meter.

En savoir plus sur le Bluetooth Low Energy.

fonctionnement-technologie-quuppa-aoa
Schéma fonctionnel du protocole de communication par angle d’arrivée

In addition, the use of the standard BLE protocol not only optimizes beacon energy consumption and maintenance costs, but also facilitates the use of this technology. Nevertheless, it is important to keep in mind that the addition of the QUUPPA software brick requires more integration and knowledge than a simple Bluetooth connection.

Cette technologie est aujourd’hui déployée dans de nombreux secteurs, comme les sports collectifs pour calculer la position exacte des joueurs ou encore dans l’univers médical, pour suivre les déplacements des équipements. Découvrez quelques uses case RTLS par angle d’arrivée.

Pros

  • Positioning accuracy
  • Real-time update (information processed in less than 100 ms)
  • Long battery life
  • Adaptable according to the size of the project (from a few tags to several hundred thousand)

Cons

  • Relatively large infrastructure (antennas, cabling, server, etc.)
  • Higher installation costs compared to other localization technologies

Things to remember

As you will have understood, indoor positioning is today a major issue whether in industry, hospitals or sports. In a permanent search for performance optimization, various localization technologies are being developed offering many possibilities.

It should be noted that the choice of technology must be made according to the use and business needs. All the parameters must then be taken into account, and in particular those of the acquisition and installation costs in relation to the expected positioning accuracy. Indeed, if you want to locate large equipment, you will not necessarily need to have a location accurate to within 30 centimeters. In this case, it will be preferable to go for a plug and play solution, easy to install and less expensive, rather than a solution requiring heavy investments in infrastructure.

Below is a comparative table of the few technologies mentioned in this article.

tableau-comparatif-technologies-localisation-indoor

*Costs increase according to the degree of precision desired.

 

 

Pierre BONZOM
BONZOM Pierre
CEO
A graduate in Applied Physics and holder of a PhD in Robotics, Pierre BONZOM founded the company ELA Innovation in 2000 with the values of innovation, responsibility and quality. In 19 years of experience, he has been able to surround himself with collaborators having the same objective and the same vision as him to make ELA Innovation a major player on the European market of radio frequency identification.
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