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Z-Axis - 9-1-1 Location Test Bed Finalizes Google’s ELS Tests

But, Report Marked Confidential

Monday, May 18, 2020 

"CTIA officials discussed generally the most recent 9-1-1 Location Technologies Test Bed testing of 9-1-1 vertical (Z-axis) location technologies, Stage Za, in an FCC filing, but the full report is unavailable to the public.Stage Za reviewed a single emergency location solution, Google’s Android-based Emergency Location Service (ELS), which is commercially available on about 99% of active Android devices. The Stage Za tests demonstrated that device-based solutions offer promise to meet the goal of providing accurate Z-axis location information with indoor wireless 9-1-1 calls beyond the top 25 to 50 cellular market areas (CMAs), CTIA said. The participants also said the results demonstrate that Google’s ELS has the potential to produce Z-axis location information across a diverse range of devices with different capabilities, including devices that do not have barometric sensors. However, the report was marked confidential and is not publicly available. The Boulder (Colorado) Emergency Telephone Service Authority (BRETSA) opposed CTIA’s confidentiality request and said Google’s statements don’t support CTIA’s assertions that the report should be withheld from the public.

Handset-based emergency location technologies such as ELS and Advanced Mobile Location (AML) have found success in Europe and other countries but have yet to gain a foothold in the United States. However, last year RapidSOS partnered with Google to deliver 9-1-1 caller location information to public-safety agencies nationwide.

In addition, CTIA representatives said that to date, no commercial Z-axis solutions have been validated to achieve ± 3 meters for 80% of wireless calls across all of the test regions and morphologies in the test bed. In Stage Za, Google’s ELS achieved ± 3 meter accuracy for more than half of calls in the test bed, and exceeded the 80th percentile metric in one morphology. Notably, solutions tested in Stage Z and Stage Za showed variations by morphology, the CTIA filing said.

In November, the FCC adopted rules that will help first responders locate people who call 9-1-1 from wireless phones in multistory buildings. Specifically, the order adopted a vertical, or Z-axis, location accuracy metric of ±3 meters relative to the handset for 80% of indoor wireless 9-1-1 calls.

The test bed plans to test Z-axis solutions in Stage Zb, which is scheduled to begin later this year subject to challenges encountered because of the COVID-19 response. In their own filing, AT&T Services and NextNav provided a list of the 105 CMAs where the vertical location (Z axis) network will be available for use to support the First Responder Network Authority (FirstNet) and potentially E9-1-1 services.

AT&T said the network is designed to provide vertical location accuracy of within 3 meters to at least 80% of all commercial buildings that are three or more floors in height within the 105 CMAs. The network is scheduled to be completed within these 105 CMAs in advance of the commission’s April 2021 deadline for the initial provision of vertical location services to support public safety.

Verizon executives met with FCC officials in late April and responded to questions concerning the future use of dispatchable location (DL) solutions and delivery of floor level accuracy to public-safety answering points (PSAPs) that were consistent with its February comments in the proceeding.

“We described the products and methods used to deliver DL information to PSAPs on a limited scale today and explained that our z-axis focus today is meeting the ± 3-meter metric through commercially available technology given the upcoming April 2021 date,” the filing said.

Verizon said it is continuing to evaluate different vendors’ solutions, both through the CTIA Test Bed process and on its own. Verizon agreed with CTIA’s assessment of Stage Za testing of Google’s ELS technology.

“Verizon hopes that an OEM-approved solution for iOS-equipped handsets can be assessed in the Stage Zb testing scheduled for later this year (provided building access can be obtained) and provide more visibility into its performance,” the carrier said. “… Verizon already can deliver a Z coordinate for a 9-1-1 call from a capable device to a capable PSAP.” Verizon said that all Z-axis solutions under consideration remain dependent on support from handset manufacturers and, to some degree, on use of the device’s barometric pressure sensor. Verizon’s Z-axis compliance plan requires a preloaded solution native to the device that works without further action by the user.

“Any solution that is dependent on a consumer download or opt-in consent — to the extent an OEM allows such a solution on its device in the first place — would compromise service providers’ ability to meet the commission’s and public safety’s objectives for this proceeding,” Verizon’s filing said.

For its part, T-Mobile discussed its proposed alternative path for Z-axis compliance that it said will lead to more 9-1-1 calls receiving a ±3 meter Z-axis location estimate than under the current rules. T-Mobile’s proposed alternative compliance plan relies on mobile operating system (OS) provider Z-axis location solutions and is compatible with the vast majority of devices in use.

Under T-Mobile’s proposal, the percentage of calls meeting ±3 meter accuracy would increase in three steps. The proposal would require 50% of calls in the test bed to meet ±3 meter accuracy nationwide by April 2021, 70% to meet ±3 meter accuracy nationwide by April 2023; and 80% of calls in the test bed to meet ±3 meter accuracy nationwide by April 2025.

The carrier said that even at the initial benchmark, its approach will provide ±3 meter accuracy to more 9-1-1 calls than under the current rules, which limit compliance obligations to the top 25 CMAs and for which the purpose-built solutions will only enable a comparatively small number of devices.

In a May 15 filing, the International Association of Firefighters (IAFF) said it is disappointing to see proposals submitted in response to the FCC’s fifth notice of proposed rulemaking in the wireless location accuracy proceeding “that instead seek to weaken the accuracy requirements agreed upon only a few months ago.”

IAFF said the new proposals largely revisit accuracy metrics rejected as inadequate in 2018 by both public safety and the FCC.

“It appears from recent filings that some carriers have begun taking important steps to provide public safety with vertical location capabilities in a timely manner, but we would hope that others, as well as handset and operating system providers, will also take the needed actions to comply with the requirements the commission established in its carefully constructed order,” the IAFF filing said.

All the filings in the proceeding are here."

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