Technologies to Address the Indoor Vertical Location Challenge

In 2015, the Federal Communications Commission (FCC) launched new location accuracy metrics (horizontal and vertical) for callers contacting the E911 emergency line through a wireless phone, particularly in indoor environments. Motivated by the requirements imposed by the FCC on Mobile Network Operators (MNOs), The 3rd Generation Partnership Project (3GPP) Release 13 conducted a study (TR 37.857 V13.1.0) to assess the performance and accuracy of the positioning mechanisms available in Long Term Evolution (LTE). As a result of the study, 3GPP concluded that existing positioning mechanisms (prior to 3GPP Release 13) can satisfy the 80% positioning accuracy requirement of 50 Meters (m) in the horizontal axis. However, new positioning methods were required to target the indoor positioning needs (TS 36.305 v13.0.0), namely Wireless Local Area Network (WLAN), Terrestrial Beacon System, Bluetooth, and Barometric sensor methods.

The FCC requested that, by April 2021, MNOs should not only provide tighter metrics in the horizontal axis (50 m accuracy for 80% of the calls), but also provide a dispatchable location or z-axis technology in each of the top 25 cellular market areas, which is to be extended to the top 50 cellular markets by 2023. The technology should deliver 3 m accuracy above or below the handset for 80% of the wireless E911 calls covering 80% of the population and 80% of the buildings that exceed three stories. To date, no evidence was found that describes the strategy adopted by the different MNOs to comply with the requirements of the FCC to deliver vertical location for wireless E911 callers. Instead, there have been different events that signal additional setbacks for E911 location accuracy:

• MNOs asked the FCC to change the original requirements in the vertical axis to meet 3 m accuracy for 50% of calls, rather than 80%, and to move the 2023 deadline to 2025. These requirements were rejected by the FCC in January 2021.
• In early 2020, the wireless industry signed out of the National Emergency Address Database (NEAD) that was created to deliver a dispatchable location for E911 calls made indoors, providing a secure database to associate Wi-Fi access points and Bluetooth beacon reference points with validated civic addresses. However, the performance of the NEAD depends, in part, on the cooperation of multiple entities, such as businesses possessing information on Wi-Fi access points, perhaps not giving enough flexibility and assurance to MNOs to deliver 3 m accuracy in the vertical axis for 80% of the calls.

However, there are promising technologies from NextNav and Polaris Wireless that could enable Three-Dimensional (3D) geolocation accuracy, meeting the requirements of the FCC. ABI Research provides a brief description of the mechanisms of the solutions provided by both companies:

• NextNav has developed Pinnacle, which relies on three main pillars: barometric sensors (already available in various devices, such as smartphones and tablets), altitude stations, and cloud services. The altitude stations take samples of different environmental variables, delivering the collected data to the cloud service platform through an LTE connection. Similarly, the barometric sensor in the phone sends environmental measurements to the cloud platform where the information is synthetized and combined. Then, the cloud platform compares the device data with local conditions to provide a very precise altitude measurements to applications that integrate their software.
• Polaris Wireless has developed a similar solution that relies on barometric sensors in end devices, weather reference networks, and cloud-based location platforms to deliver vertical location accuracy.

In fact, in a report by the FCC in January 2021, it is noted that both technologies have been tested and both have the potential to meet the z-axis requirements. The report states that the NextNav solution showed a vertical location accuracy in a rage of 1.8 m in 80% of the test calls and 3 m for 94% of the test calls. On the other hand, Polaris Wireless’ solution can achieve 2.8 m for 80% of the test calls by using additional available location data to recalibrate and refine the z-axis metric accuracy.

Following the requirements of the FCC and the availability of enabling technologies, ABI Research expects that hybrid positioning mechanisms consisting of Assisted Global Navigation Satellite System (A-GNSS), Enhanced Cell ID (E-CID), or Observed Time Difference Of Arrival (OTDOA), among others, with complementary technologies, such as Pinnacle and Polaris Wireless’ solution, will enable MNOs to deliver the 3D location accuracy required to pinpoint the exact location when a user calls E911. However, cellular coverage should be sufficient so that the mobile wireless user can place an emergency call. Without cellular coverage, the user will not be able to contact E911 and none of the aforementioned mechanisms will be able to deliver the required information to the Public Safety Answering Point (PSAP).

Furthermore, ABI Research expects that as users start to migrate to 5G, the positioning mechanisms standardized in 3GPP Release 16 will start to be leveraged, because it introduces dedicated 5G positioning signals, measurements, and procedures with enhanced parameters for positioning accuracy compared with previous cellular generations. Particularly, time (multi-cell Round Trip Time (RTT)), and angle-based positioning methods (Angle of Departure (AoD) and Angle of Arrival (AoA)), which are enabled mainly due to beamforming, massive Multiple Input, Multiple Output (MIMO) technologies, and the use of high-frequency bands.

In addition, ABI Research expects that angle-based positioning solutions will benefit emergency callers in indoor and dense urban areas, mainly because the user equipment will have more base stations in view, which are more likely to be operating in the high-frequency bands; using beamforming and massive MIMO technologies will concentrate the RF energy in a beam in the direction of the user equipment. Therefore, 5G positioning mechanisms have the potential to support MNOs with addressing the positioning accuracy requirements of an E911 wireless caller with less dependency on privately owned infrastructure. However, these mechanisms have to be tested in order to confirm their effectiveness and accuracy in indoor environments.