Wireless Indoor Localization

Established GPS systems are opening up vast opportunities in the area of localization, particularly in relation to the ever-increasing prevalence of mobile end devices. Use of these devices in car navigation or in vehicle tracking for goods transport is now an everyday occurrence. However, there are still environments known as “GPS-denied areas” in which GPS-based localization does not work, for example inside buildings or street canyons. This is why many sectors today are experiencing an increasing need for seamless localization in both indoor and outdoor areas – for large infrastructures such as airports and company premises, for example. The use and continued development of wireless communication technologies have allowed the emergence of various Wi-Fi-based indoor localization solutions that close these gaps in localization coverage, thus generating new opportunities and added value across all levels of the value chain.

Cross-Sector Applications of Indoor Localization Systems

Indoor localization solutions are employed whenever traditional GPS-based systems cannot be used due to signal blockage and reflection within buildings and large infrastructures. For indoor applications, different technologies come into play, such as Wi-Fi, optical sensors, and motion sensors. The diverse fields of application of Wi-Fi-based indoor localization systems cover the entire value chain in the following sectors: sports, security, production, logistics, automotive, healthcare, and entertainment.

In the context of Industry 4.0, for example, new opportunities are emerging thanks to the integrated capturing and networking of infrastructures, processes, and products via indoor localization systems across all levels of the value chain. The Internet of Things is an essential prerequisite for Industry 4.0. It will allow new potential benefits to be reaped in optimizing processes, speeding up work processes, and increasing industrial and corporate safety.

Indoor localization in the manufacturing sector will enable the application of concepts such as geofencing, which makes it possible to check whether people or vehicles are located in specific areas, such as near machines. You can also verify whether people in a specific area are authorized to be there. This is particularly useful in terms of ensuring transparency and safety for work processes.

Another application of indoor localization systems is the optimization of logistics processes, as it allows the automatic location of pallets, products, forklifts, and even people in real time. This makes it possible to speed up, connect, and improve logistics processes as well as make them more secure, both at a single location and across several locations. Finally, a complete localization solution paves the way for new services.

Indoor localization systems also support coordination and operational safety in large infrastructures like airports. Critical situations such as near collisions can be recorded centrally using collected location data in combination with camera monitoring to prevent accidents and hazardous situations. An additional application scenario is the localization of passengers and employees in airports or employees and visitors on company premises.

In the sporting field – for example in football – indoor localization systems are used to analyze games and process the data collected. By linking sporting performance with athletes’ vital data, training strategies and games can be objectively assessed and optimized. For instance, technical aids based on indoor localization technology can provide visually impaired people with support in their training programs and their day-to-day mobility and accessibility. The Fraunhofer Institute for Integrated Circuits IIS is developing a positioning system that uses a sensor belt worn by the visually impaired person to transmit tactile and acoustic warning signals and instructions whenever the person leaves a predefined path.

In the context of ambient assisted living (AAL), indoor localization solutions are being developed to support elderly people, people with disabilities, and people in need of care, while also ensuring full localization coverage by means of Wi-Fi and Bluetooth, for instance. In this field of application, experts are creating intelligent environments and seamlessly integrating different components and solutions. This will enable medical condition monitoring and geofencing. Specific incidents such as a fall can thus be detected and carers notified. Different radiolocation technologies can be used for a wide variety of assistance systems, allowing people to lead independent lives to the greatest possible extent and to improve their health and overall quality of life. Researchers at Fraunhofer IIS have demonstrated that systems for monitoring vital body functions can help to locate people quickly in the event of emergencies.

In the area of public transport, an intelligent combination of satellite positioning (GPS), Wi-Fi positioning, and motion sensors via sensor fusion can facilitate door-to-door navigation. In particular, this makes it easier for passengers to find their bearings when changing buses, trams, trains, and subway systems.

Diverse Requirements of Indoor Localization Solutions

Because they have such a wide range of applications, the various indoor localization solutions have to fulfill different requirements in each field of application to ensure reliability and user-friendliness. Accuracy and availability are particularly important for these systems, which are employed whenever traditional GPS-based solutions do not work. The different levels of availability range from the basic feasibility of identifying a given position, to the degree of accuracy to which this can be determined across all areas. Availability is paramount for both individuals and companies in areas such as logistics, production, or AAL. In addition, a technical distinction is made in terms of infrastructure function. One option is for the infrastructure to enable a device to locate itself (self-positioning), as seen in museum navigation systems based on Wi-Fi networks, for example. Alternatively, the infrastructure can locate the device (remote positioning), whereby data is captured and processed centrally. Size and the physical attributes of an area play an important role in large infrastructures, logistics, and manufacturing, as both line of sight and radio-wave transmission are frequently interrupted by obstacles (such as machines) or thick walls. Likewise, specific indoor localization solutions can be defined based on the number and speed of the objects to be located, or depending on whether it is objects and/or people that are to be located. The incorporation of sensor technology in localization systems is particularly beneficial for sports and AAL systems that assist individuals in need of support, for example to monitor vital data or detect a fall. In this context, transmission speed and frequency for additional sensor data, such as temperature data for medical supplies, can be defined according to specific users’ needs. It may also be necessary to use a real-time analysis system that responds appropriately to specific events – by triggering an alarm in the event of an emergency, for instance. Other critical issues include battery life as well as transmitter form and weight, as these properties are subject to different considerations depending on the application. Indeed, in a variety of situations, transmitter operation is crucial for the effective deployment of an indoor localization system. In addition, the update rate must be optimized for the relevant application, as both positioning speed and frequency can be varied depending on the application. While the goal is to achieve the best possible design for indoor localization solutions that are tailored to customer requirements, both cost issues and the availability of the required system must be factored in for implementation. To meet the considerable demands placed on indoor localization systems, Fraunhofer IIS is working to combine these diverse technologies and develop them further.


Technical Foundation

The indoor localization technologies discussed above use different techniques to determine the position of objects or people. The following provides an overview of the most important indoor localization techniques and the possibilities these techniques offer.


Field intensity measurement – which works inside buildings such as museums using existing infrastructure like Wi-Fi or Bluetooth networks – measures field intensity distribution and compares it with a field intensity map stored in a database in order to calculate a position. These systems, which have an accuracy of several meters, can be used for guidance and information systems in museums or shopping malls, for instance, or to ensure the safety of rescue workers in crisis situations. The beacon solution also enables positioning by using short-range radio systems such as Bluetooth low energy (BLE) or RFID (Radio-Frequency Identification) to determine the area in which a person or a device is located. This is useful for theft prevention or navigation in shopping malls.

For angle measurement techniques, the position of the transmitter is calculated to an accuracy of one meter based on the angle of incidence of a radio signal on an antenna array. This system can be used to locate rescue forces, or for security applications in airports, for example.

Travel-time-based radiolocation enables a position to be determined by measuring the time it takes a radio signal to travel between the transmitter and the receiver. This positioning solution, which offers centimeter-scale accuracy, is used in sports and in satellite navigation (GNSS) for vehicles.

Sensor networks use proximity relationships to measure the relationships or distances between sensor nodes, and then calculate their own position on the basis of nodes whose positions are known.


The different localization technologies can be combined, which means they can be supported by other technologies and techniques such as inertial sensor technology and event detection. Combining the systems ensures higher accuracy, reliability, and availability. Environment models also incorporate a position’s environs, which is useful for applications such as route planning. Depending on the technique, positioning data comprises both the position at which something is located as well as its destination and the speed at which it is moving there. Depending on the sensor technology used, people’s vital functions or device functionality can also be conveyed.

The Future of Wi-Fi-Based Indoor Localization

Overall, the entire field of indoor localization is a major up-and-coming trend that is now set to conquer internal spaces. In addition to basic indoor availability, one of the primary concerns is improving performance, in particular accuracy. One major goal here is to achieve localization using as little infrastructure as possible, or even without any infrastructure at all. This would allow the seamless, reliable location of objects both indoors and outdoors. Due to the widespread availability of smartphones and the resulting development of new markets, such as direct marketing, we can expect seamless indoor/outdoor localization and navigation to become available in the next few years. In terms of integration, a central role is played by the availability of increasingly high-quality sensors on the one hand, and the large quantities of these sensors on the other. Another promising approach concerns the use of “pseudolites.” These “pseudo-satellites” are transmitters that amplify satellite signals inside buildings, thus enabling indoor localization via normal GPS receivers. In addition, we anticipate that an increasing number of miniaturized, localization-enabled components will be integrated within devices, infrastructures, and vehicles as standard, enabling them to communicate with each other. This will give rise to new standards, protocols, and interfaces. Increasing standardization, integration, and networking will improve technology performance and enable new applications and services – in the area of Industry 4.0, for example, or by connecting cars together (Car2Car) or with infrastructures such as parking garages or machinery (Car2X).

We would like to thank Dr. Stephan Otto from Fraunhofer IIS for his contribution of this chapter on Wireless Indoor Localization.

Case Study: KLM

KLM Royal Dutch Airlines, in cooperation with indoo.rs, enhanced their KLM app with an indoor positioning and navigation prototype functionality to be used by its transit passengers at Amsterdam Airport Schiphol. The application, running on iOS and Android, shows the position of the user as a dot on the map and the route from their current position to the next gate. The application also calculates the time needed to walk there.

The primary aim of the project was to improve gate closing times and decrease transfer times by providing additional services to their customers. Also, by providing the airline’s customers with map directions, the journey from their arrival gate to their connecting flight should be much easier.

In order to enable accurate positioning within the transit area, iBeacons were installed at KLM kiosks. When a customer who has the KLM app installed on their phone passes an iBeacon, a push notification is sent to their smartphone if route information is available. If the user decides that they would like this information, the app then opens and displays the route to next gate starting from their current position.

The navigation service is available in the newest release of the KLM app, which can be downloaded from the Apple and Android app stores.

Project Management Perspective

The project-specific challenges can be summarized as follows:

  • The solution put in place at Schiphol Airport requires BLE beacons to be installed in the transit area and reception of these signals by users’ smartphones. Historically, Bluetooth has been known for being battery draining. Thus, KLM feared that app users wouldn’t turn on Bluetooth 4.0 (Bluetooth Low Energy/BLE) to use the navigation feature. Also, not all users own smartphones that support BLE as standard.
  • The latter constraint will become irrelevant over time as newer generations of smartphones support BLE as standard. It is common that new and upcoming technologies would encounter some compatibility issues with older devices. Compared to earlier Bluetooth versions, Bluetooth 4.0 is characterized by very low power consumption (iBeacons can run for up to 4 years off a single coin cell, for example). Having Bluetooth connections enabled on newer smartphones accounts for only a small fraction of total battery consumption compared with earlier Bluetooth versions. Explanation of the core benefits of BLE helped to overcome the opposition to a Bluetooth-based solution.
  • Small iBeacons have been installed at the KLM kiosks in the transit area. Interestingly, the beacons attracted the curiosity of people passing by these kiosks and were sometimes removed or taken away. The installation of iBeacons at the airport is subject to several restrictions for a variety of reasons due to the fact that the project is partnered with the airline and not the airport. Thus, beacons could not be installed anywhere but at KLM kiosks (in higher places, for example). The small iBeacon devices have been firmly mounted with adhesives to prevent loss.

Learning and Best-Practice

Several stakeholders are involved in an airport’s business operating environment (airport operator, airlines, retail operators, for example). Successful indoor navigation systems in airports require the cooperation of various players: a technology company, building facility management, passenger services.

Every building has unique characteristics and these need to be taken into consideration for the installation of BLE beacons. Airports can be considered a building site 365 days a year: appearance and arrangement of airport areas are subject to ongoing changes (temporary promotions, additional stands, etc.). Bluetooth signals are affected by objects with insulation and absorption properties. Hence, beacons should be installed in places that guarantee high visibility so that the impact caused by an ever-changing environment can be minimized.

The high degree of innovation involved means that IoT projects and initiatives require users in the market to be educated about the potential of such technologies. Only then can the value to both operators and users be fully realized.

We would like to thank Bernd Gruber, COO of indoo.rs, for his support with this case study.