Bluetooth AoD as the Technology of Choice for Indoor Positioning Systems (IPS)

This article discusses how GPS and Location Based Services became so ubiquitous that we expect access everywhere we go and explores how and why Bluetooth AoD has become a frontrunner technology for bringing these GPS-style positioning solutions to the indoors.


People have posed the questions “Where am I?” (location) and “How do I get to where I need to go?” (navigation) since the early human migrations. These questions have driven us to explore our environment and to develop various measurement tools for observing the world around us. For example, the celestial navigation tools that have been developed and refined over the centuries allowed explorers to evaluate location based on the stars.

Even today, we look to the sky for location information. However, today the stars have for the most part been replaced with satellite-based navigation systems jointly called the Global Navigation Satellite System (GNSS), probably the most well-known of which is the Global Positioning System (GPS) together with GLONASS and the recent Galileo. Originally developed for the military, GPS has, over the past 25+ years, expanded into commercial applications as well. The value of GNSS has proven to be disruptive in a variety of vertical markets and created a host of new applications across industries. Over the years, GPS has become an integral part of our lives. Something that we use across devices and applications and has come to expect. We use GPS, either directly or indirectly, multiple times each day. We leverage GPS when navigating to work in the morning and when we exercise in the evening. We simply turn on the device and expect access to location-based content such as the optimal route to our destination, the distance we ran today, the location of the nearest branch of our favourite shop, or even information about when the next bus will arrive at the stop where we are waiting. GPS has become so widely adopted that it is now almost synonymous with the word “location”.

Key Ingredients of Successful GPS

So how was GPS so successful in making location-based services (LBS) ubiquitous? The key lies in its architecture. GPS is a network of satellites that orbit Earth and transmit radio signals carrying their position data to a variety of receiver devices (e.g. mobile phones and other handheld GPS units). Applications on these devices can then use the positioning data from multiple satellites to calculate their own relative position.

The reason this type of architecture is so powerful is that it enables a connectionless and device-centric approach to positioning. With the device itself calculating its own position, GPS-based positioning solutions provide effectively unlimited scalability as centralised system capacity is not needed for the positioning calculations. In addition, this architecture provides much higher privacy for users, as they can choose whether or not to share the positioning data calculated by their own device with others. These benefits, made possible by the system architecture, have enabled GPS to disrupt the location market.

Bringing GPS Indoors

GPS is an enabling technology that has unlocked the door for LBS and revolutionised the way we as consumers interact with location. However, the technology itself has its limitations. GPS is designed and leveraged as an effective location technology for the outdoors. That being said, the value of location and positioning has innumerable uses indoors.

Statistics show that people spend as much as 90 % of their time indoors (in buildings, transit hubs, shopping malls, sports facilities, homes etc) where GPS signals cannot reliably reach and unlock the value of location services.
Despite the technical limitations of GPS, interest in finding ways to bring the well established outdoor LBS to the indoors has grown dramatically. According to a MarketsandMarkets study, the indoor location market is expected to grow to 41 billion USD by 2022 at a compounded annual growth rate (CAGR) of 42% between 2017 and 2022. The first significant wave of demand comes from industry, businesses and professional work spaces. Developers of consumer applications have also already recognised the potential benefits of location based technologies in their verticals.Bluetooth® and Indoor Positioning

With GPS as we know it limited to outdoor environments, it is up to other technology solutions to bring the GPS-style location architecture to the indoors. One technology taking significant strides in this arena is Bluetooth.

Bluetooth Direction Finding using the mobile-centric Angle-of-Departure (AoD) methodology can recreate many of the advantages of the GPS architecture on a smaller scale for the indoor positioning market to leverage. Bluetooth-based positioning solutions have come a long way from conventional Bluetooth proximity beacon technologies. Today, they can truly offer accurate and reliable positioning in indoor environments.

The AoD methodology and IPS

AoD-based systems have mobile-centric architectures, where the positioning intelligence is in the device e.g. a mobile phone. In these cases the network transmits signals to the device and the device calculates its own position based on the data received from the network. This model is typical for indoor positioning systems (IPS).For example, a visitor at a museum could use their own mobile phone to navigate through the exhibition by using the data transmitted by the network to calculate their own position relative to the museum’s floor plan. Similarly, a robot or an automatic guided vehicle (AGV) at an industrial site could use an AoD Positioning Engine to compute its own location in real-time to navigate around the site.

In AoD-based systems, the majority of the power consumption is in the device rather than the network and so these types of solutions are optimal for devices such as mobile phones and tablets that are charged regularly anyway. This architecture option proved to be the best choice for the consumer market with GPS, and is the most effective solution for consumer IPS also. It means that there are a limited number of active devices providing the aid location signal (i.e. the Locators) and an unlimited number of devices receiving and independently computing their own locations. This allows the user to gain full control of their own location information, as data is only transferred to the central network if the user opts in.

With the Bluetooth Direction Finding feature, the standardised approach for radio direction finding will in time be integrated into new Bluetooth chips and stacks, making it possible for any Bluetooth device with these new chips to determine its own location by computing the direction of a Bluetooth signal. Effectively, this means that these new Bluetooth devices, entering the market soon, will be capable of Bluetooth AoD positioning without any need for customisation (e.g. adding new antennas or hardware components). A positioning engine can be activated on the device with a simple software update. This will allow consumers to take advantage of any applications and services built on the AoD method, unlocking the door to vast market opportunity for IPS.

The Key Benefits of AoD

The fast growing IPS market aspires to do for indoor positioning what GPS did for outdoor positioning: make LBS accessible everywhere and for everyone. So far, the full expansion of IPS services has been limited by factors such as technology performance, ecosystem maturity and consumer market readiness. The Bluetooth Direction Finding feature is the next step in the evolution of Bluetooth technologies. It takes the concept of location to a completely new level, from proximity positioning to continuous and accurate positioning. It removes the technical barriers to growth for IPS.

What makes AoD the technology of choice for IPS?

  • AoD is the only truly scalable technology on the market today. When the positioning calculations are run on mobile devices, rather than in the network, the number of simultaneous users becomes unlimited as network capacity limitations are no longer an issue. This is not possible with technologies that compute the round trip time (RTT) and require two-way communication.
  • AoD enables complete data privacy. With AoD, the central system only transmits positioning data to the end users device. The device itself then calculates its position based on this data. This means that the end users location information is only available to the end user, except if they actively chose to share it with others. This is similar to how GPS-based location services work.
  • Bluetooth AoD is a standardised technology that requires no additional hardware. Soon, Bluetooth Direction finding will become available in all new Bluetooth-enabled devices. This makes it a cost-effective solution for both industries and consumers as new hardware components are not needed for existing devices and the need to invest in any new custom devices for accessing IPS solutions is removed. It is also a global technology solution that operates on the standard 2.4GHz ISM band.
  • AoD is an efficient solution for integrators as the system has limited infrastructure needs and is easy to both deploy and maintain. The system also consumes very little power as the positioning calculations are done on the individual devices rather than by the network.

The wider availability of technology that can make use of AoD suddenly makes it possible to implement innovative IPS solutions across market verticals. Retail & hospitality, manufacturing, logistics & warehousing, healthcare, sports, exhibition & museums, transportation and smart buildings to name just a few. The possibilities are endless, now it is up to the innovators and developers in these sectors to figure out what all can be done using this technology base.

As location technology is at the core of many of the trends revolutionising industries at the moment (e.g. digital transformations, Internet of Things, industry 4.0, smart buildings, digital twins and location-based services), the Bluetooth Direction Finding based on the AoD methodology is a significant step towards a future where indoor positioning is available everywhere and for everyone.


Location services have become an integral part of our daily lives and they will continue to shape our lives as technology develops and indoor applications and services become more prevalent. Bluetooth Direction Finding based on the AoD methodology paves the way for new and exciting applications that are truly scalable and provide better data privacy while still being easy to deploy. The new enabled opportunities will make Bluetooth AoD the technology of choice for indoor location and IPS.

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