What’s Inside Counts: How 6G Can Enable Ubiquitous, Reliable Indoor Location Services

March 16, 2022

Written by Subhankar Pal

By Subhankar Pal, Global Research & Innovation Leader for Future of Networks, Capgemini Engineering.

How much time do you spend indoors? If you’re British, for example, you spend about 90% of each day inside. In fact, that’s also been the case for most other Europeans for the past 20 years, according to the European Commission.

Now think about how often you’re in a building that’s sprawling, unfamiliar or both, such as a stadium, hospital, convention centre or airport that you’ve never flown into. How much time did you waste trying to find your way around?

Or maybe you work in one of those large buildings, such as a medical centre complex. How long would it take for you to find a high-value piece of portable equipment, such as patient-monitoring system?

All of these questions highlight a paradox: The vast majority of our working, living and playing occurs inside a building, yet the majority of location-based services (LBSs) focus on outdoor spaces. Isn’t it time to give more attention to indoor LBS to make it just as ubiquitous?

But achieving indoor location coverage is not a straightforward extrapolation of existing systems used for outdoor like GPS, and therefore other methods need to be explored for indoor.

Why GNSS, Wi-Fi and Other Incumbent Technologies Fall Short

Most of today’s LBSs rely on satellites to pinpoint the location of a device, such as a smartphone or an IoT tracker. Unfortunately, GPS and other GNSS systems don’t work well — or even at all — inside buildings, where concrete, steel and tinted window glass attenuate or completely block satellite signals. Very few buildings have a network of GNSS repeaters to provide an indoor signal.

Without a reliable signal, GNSS-based LBSs also struggle to pinpoint a device’s location in multi-story buildings. For example, they can’t tell first responders that a 999 (or 911 in the US) caller’s smartphone is located on the 5th floor or the 50th. In the case of a heart attack, the delay that results could mean the difference between life and death.

These are just a few of the shortcomings that highlight the need for an indoor positioning system (IPS) that can accurately locate people and objects inside any type of building. This IPS also must be ubiquitous, which is not the case with current IPS technologies. For example, some IPSs require each building to have an extensive, expensive network of dedicated hardware, such as RFID readers or Bluetooth beacons. Many building owners and tenants can’t justify that expense.

To get around that barrier, other IPSs leverage a building’s existing Wi-Fi network. But they still require fingerprinting — manually mapping signal strengths at different indoor locations — which takes a lot of time and labour and thus money.

The ideal, next-generation IPS would leverage cellular to avoid the limitations that come with GNSS and specialised systems. One reason is ubiquity: Cellular has far more indoor coverage than Wi-Fi, RFID and Bluetooth.

For decades, building owners and mobile operators have invested in small cells and distributed antenna systems to ensure reliable, ubiquitous voice and data services — most recently for IoT applications such as building automation. A cellular-based IPS can leverage that infrastructure instead of requiring bespoke equipment.

Another reason is that cellular is getting more granular with each generation. 2G supported location accuracy in the hundreds of metres. 5G has improved it to tens of centimetres thanks to its use of millimetre wave (mmWave) spectrum and antenna technologies such as beamforming. With 6G standards development just beginning, now is the ideal time to ensure that it can support the kind of robust, ubiquitous IPS that the world needs.

6G’s Advantages 

5G New Radio (NR) has several features and capabilities that benefit location applications, such as centimetre level accuracy and 1 millisecond latency. 6G will raise the bar with:

  • Radar-like technology that enables positioning accuracy below 1 cm. 6G can calculate the velocity of the measured object by measuring the doppler shift in the received echo compared to the transmitted signal. It also can work in complete darkness and “see” in rain or fog, albeit with somewhat degraded performance.

  • Terahertz spectrum enables sensing capabilities. As a result, 6G is an opportunity to provide communications, positioning and sensing over a single network.

  • Support for additional use cases like positioning using unlicensed spectrum (e.g., NR-U-based positioning), very-low-cost and low-complexity positioning to enable asset tracking, sidelink and V2X positioning for autonomous vehicles in subways etc.

  • Native support for machine learning, which enables more flexible and accurate approaches to 6G localisation and sensing based on state-of-the-art deep learning and probabilistic methods.

6G IPS also can complement, or act as an alternative, to GNSS-based positioning, such as where satellite signals are too weak or unavailable. 6G IPS could be combined with GNSS positioning to improve accuracy and to provide a ubiquitous indoor positioning technique.

The figure below shows the expected accuracy level of 6G localization vis-à-vis other localisation methods available today for indoor, outdoor urban, and rural scenarios.

Figure 1 – Expected horizontal accuracy of 6G vis-à-vis other localisation methods for indoor, outdoor urban and rural scenarios.

Source: Whitepaper “Survey of Cellular Mobile Radio Localisation Methods: from 1G to 5G”.

Enabling New Use Cases

To understand these capabilities and benefits, consider the example of Industry 4.0 factory automation. 6G-based IPS could precisely determine where a robot arm is located and if there are any interfering objects, such as a human, inside its intended space of motion. The position estimation of objects that a robot should grip, or of objects that the robot has released, would also be a useful feature.

Retail is another use case. In a big-box store, 6G IPS could guide shoppers around the shop to find their desired products while also providing valuable information such as promotions. For example, when they pass by digital signage, it could alert them about a discount on the item they’re looking for.

Much work needs to be done to achieve these benefits and use cases, which highlights why it’s not too early to start brainstorming how 6G can support IPS. For example, mobile operators and their vendors need to prepare for base station densities far higher than 5G and 4G, which affects CAPEX and OPEX such as backhaul. Terahertz spectrum will require advanced power amplifier designs to ensure reliable transmission and reception. The industry also will need to develop methodologies and solutions for identifying and mitigating propagation variables such as walls and even people.

None of these challenges is insurmountable. That’s good news for the people and businesses who will benefit from 6G IPS — a future that could arrive by the end of this decade.

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