Indoor localization: which technology for each use?

Published on 01 sept. 2019 In: Techno

  • Reading time10 min.
  • LevelMEDIUM

Indoor localization nowadays has become a major focus in any kind of industry. From collective sports to healthcare and manufacturing, all are looking for positioning systems allowing to optimize their core business and maximize their performance. Therefore, new software components further develop to meet these requirements and enhance the existing range of indoor localization technologies.

Indoor localization: which technology for each use?

While most of us are all familiar with outdoor geolocation technologies such as satellite tracking (GPS...), companies nowadays are looking for indoor tracking devices providing an accurate geolocalisation of objects or people. However, satellite radio signals can hardly cross walls and other obstacles.

In response to this growing demand and its specific requirements, manufacturers of the Industrial Internet of Things (IIoT) sector tend to develop more effective indoor positioning systems (IPS). Most of these applications rely on existing technologies, but by adding innovative software layers, indoor location systems are getting more and more accurate.

IPSs use a great variety of different localisation systems in terms of accuracy, cost, scalability, reliability and security. In order to help you finding out which solution suits your specific needs, please consider the following criteria: localization accuracy, coverage and resolution, location refreshing period, infrastructure costs or even possible errors related to the type of technology to use.

In order to better understand the difference between these indoor localization technologies, we highly recommend you to first consider the different types of physical principles of such technologies.

 

Physical principles of localization might be divided into 5 different categories

 

In order to determine the precise location of an object or person, the algorithms extrapolate location-related data from radio signals that circulate between the reference nodes (fixed and known location), used as a reference for the location of mobile nodes. However, all of them do not rely on the same physical principles. They can be divided into 5 main categories:

  • Time of arrival (TOA)
  • Angle of arrival (AOA)
  • Arrival time delay (TDOA)
  • Received signal strength (RSSI)
  • Hybrid systems (mix of different physical principles related metrics)

 

Since you are now familiar with the various criteria to consider and have a clear understanding of the different physical localization principles, you may now want to discover 4 indoor localization technologies more in depth.

 

Active RFID for an area-based localization

 

Active RFID technology has not initially been developed for localization applications. Nevertheless, according to ISO 18000-7 (Dash7) standard, Active RFID technology is available in two different frequency bands (high and low), allowing a localization by areas, or rather by crossing points.

An active RFID system consists of transponders (also known as tags) and one or more interrogators. Every time a person or object equipped with a tag enters an interrogator's area, the interrogator activates the corresponding tag by means of low-frequency signals. This process triggers a radio transmission that contains both the interrogator and tag identifiers. A dedicated reader enables to receive and read such UHF broadcast.

 

Please click >>here<<< to find out more about the difference between active and passive RFID technologies.

 

In terms of indoor location, active RFID can prove to be very effective. Indeed, by emitting low frequency signals (125 kHz), this technology allows a great indoor localization throughout the area covered by the interrogator, even in case of obstacles.

This cost-effective short-range indoor localization system designed both for people and objects can be used in many industrial applications such as remote worker safety, vehicle access control or locating logistics equipment within a warehouse.

 

highlights

  • Improved accuracy with respect to UHF (Ultra High Frequency) technologies
  • Reliable also in case of obstacles
  • Single application scenario
  • Energy efficiency allowing a very long tag lifespan
  • Easy to install with no need for any major infrastructure

Lowlights

  • Limited operative scope (5 up to 15m)
  • Need for fixed brackets to install readers and antennas
  • Network performance depends on the surrounding environment

To find out more about indoor localization related active RFID technologies, please click >>here<< .

 

Received signal strength (RSSI) in Mesh network localization

 

A mesh network is designed to connect a great number of interconnected objects by means of a very simple infrastructure that does not require any central controller. The different devices transmit data to each other over a range of bounces in order to transmit data. Data is collected on a gateway, which uploads the raw information to a server.

Some software providers, such as Wirepas, have developed innovative software packages to optimize the network management of connected objects. This way, local decision-making gets smarter, which provides an optimized performance at any time, as well as an increased adaptability to environmental and network variations.

In the area of indoor localization, Wirepas Mesh technology relies on a mesh network of fixed and mobile beacons/tags. Fixed beacons, also known as anchors or fixed nodes, shall be deployed at regular intervals of distance (25 metres) over the entire coverage area, and shall include reference points to calculate the localization. On the contrary, mobile tags shall be placed directly on individuals and industrial equipment to be tracked.

 

Wirepas Mesh Technological operation

 

As described previously, beacons are communicating with each other by bouncing and uploading raw data to a gateway, thereby avoiding data congestion.

The Wirepas Positioning Engine device then converts raw data into GPS coordinates (latitude and longitude) based on the intensity of the signals received by the different anchors. This makes it easier to visualize the position and movements of each individual or object equipped with a mobile beacon (mobile node). All of this with an accuracy ranging from 5 up to 10 metres.

Given that such data may be read on all IoT platforms currently available on the market, as well as on business-specific web applications, this technology can be used in many different kinds of applications, such as remote worker safety, optimization of industrial and logistics equipment fleets or patient-tracking management in hospitals.

With its infrastructure of stand-alone battery-operated devices, this indoor positioning system can be deployed very easily. The installation indeed only requires the deployment of anchors, as well as the use of mobile beacons for individuals or objects. This indoor localization system is cable-free, and therefore is one of the most cost-effective solutions available on the market.

highlights

  • Enables to connect hundreds of devices without any interference
  • Scalable network size
  • Unlimited overall network coverage
  • Encrypted e-mails that cannot be modified
  • Customer owns the data and might access it anytime.
  • Very easy to install with a low infrastructure cost

Lowlights

  • Average lifespan of the beacons, especially when refreshing the position on a regular basis

Please click >>here<< to discover our range of indoor localization-specific Wirepas Mesh solutions.

 

Flight time calculation (TOA) using the Ultra Wideband Positioning technology, for an ultra-accurate localization

 

Ultra Wideband (UWB) technology provides both high bandwidth and short-range data transfer, which was used primarily for radar imaging. Ultra Wideband technology nowadays can reach speeds of up to 100 megabits per second (Mbps), and provides the highest pulse shaping rates, that is the reason why such technology is one of the most accurate localization applications available on the market. UWB pulse frequency and its Flight Time Triangulation Information (TOA) device indeed enables the signal to easily cross obstacles such as walls and objects. This process significantly improves the localization accuracy, up to a few centimetres.

In addition, this high frequency spectrum technology, developed by the US military, has the ability not to interfere with other radio transmissions, thereby ensuring a full interoperability with further devices and technologies.

 

highlights

  • Localisation accuracy <1m
  • No need for a direct sight connection
  • Very low sensitivity to other communication devices or other external disturbances.

Lowlights

  • Major acquisition cost
  • Significant installation cost

Angle of Arrival (AOA) principle, for real-time and energy-efficient localization

 

Angle of Arrival position technology calculates the angles formed between an antenna and a beacon from a 3-D repository. The beacon sends a radio signal to the antenna that calculates its exact location according to the elevation angle of the tag with respect to the antenna's vertical axis, but also depends on the intersection point between the beacon's vertical axis and the antenna's horizontal axis.

Some RTLS (Real Time Locating System) providers, such as QUUPPA, provide a technological mix based on the combination of the RSSI related physical principle, the Low Energy Bluetooth protocol (2.4 GHZ ISM) and the Detection by Angle of Arrival (AOA) of the signal. This unique concept offers an enhanced accuracy of positioning compared to other signal strength-based technologies (RSSI), up to less than one meter.

 

AOA QUUPPA technical operation

 

In addition, a standard BLE protocol enables not only the optimization of beacon energy consumption and maintenance costs, but also the easing of its use. Nevertheless, please note that adding a QUUPPA software layer requires a more sophisticated integration and an increased knowledge than a simple Bluetooth connection.

This technology is nowadays being used in many industries, such as: collective sports in order to calculate the exact position of players, or healthcare to trace equipment moves. Read our article about RTLS use cases here.

highlights

  • Positioning accuracy < 50 cm
  • Real-time update (information processed in less than 100 meters)
  • Long battery lifespan
  • Customizable according to project scope (from a few tags to several hundred thousand of them)

Lowlights

  • Significant infrastructure (antennas, cabling, server, etc.)
  • Increased installation costs compared to other localization technologies

Key concepts to keep in mind

As explained, indoor localization has become a major challenge in various business sectors such as industry, healthcare and sport. As part of a constant effort to optimize performance, various localization technologies are being developed, offering a great number of various options.

Please remember to choose your technology according to your specific use and needs. Do take all relevant parameters into account, including acquisition and installation costs with respect to the expected positioning accuracy. In fact, to be able to track large equipment, you do not necessarily need a 30 cm accuracy localization. In such case, we rather recommend using a plug and play solution, which is easy to install and less expensive, instead of a solution that requires major investments in terms of infrastructure.

Please find below a comparative table of some of the above-mentioned technologies.

 

* Costs increase depending on the degree of accuracy desired.

 









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