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21st Century Mobile E911 Now One Step Closer to Reality


Emergency lights on a first responder vehicle
Image: chatchaiphoto -
I have written previously about the woeful state of mobile E911, so I am happy to report that a workable technology for at least one piece of that puzzle — FirstNet, the national broadband public safety network operated by AT&T — has hit the market. Using technology from NextNav, Intrepid Networks now offers a smartphone app that will allow FirstNet responders on its Intrepid Response platform to locate users accurately (i.e., within three meters) both in terms of horizontal (x- and y- axes) as well as vertical (z-axis) location.
This capability is only available to first responders on FirstNet using this specific Intrepid Networks product, but the SDK is available to others. Importantly, it is not yet available in the public network. However, the FCC’s sixth and most recent Report and Order on Wireless E911 Location Accuracy Requirements (PS Docket No. 07-114) requires the mobile operators to provide “dispatchable location” (e.g., street address) with z-axis location within three meters on 80% of calls in the top 25 markets by this April, and the top 50 markets by April 2023. National carriers must provide nationwide coverage by April 2025.
The deficiencies in the current location accuracy for mobile calls to 911 centers is an embarrassment to our industry, given the superiority of location technologies available in smartphones and incorporated in hundreds of commercially available applications. I recognize the challenges involved in upgrading the 6,000 or so public safety answering points (PSAPs) in the U.S., but our last century mechanism for locating mobile 911 callers is a glaring vulnerability with the percentage of 911 calls originating from cell phones now estimated at 80%.
While the big news will be the nationwide availability of a mobile 911 location capability that can potentially save thousands of lives a year, having a working z-axis solution available shows that we are indeed making real progress towards that goal.
What Is NextNav?
While the initial z-axis location capability is available only to FirstNet subscribers using Intrepid Networks’s Intrepid Response platform, the secret sauce that makes this work is found in NextNav’s Pinnacle, a vertical — or z-axis — positioning service. Besides the Pinnacle z-axis service, this 10-year-old geolocation startup makes a resilient GPS augmentation system.
Current cellular location technologies primarily use assisted GPS (AGPS). If a GPS station can hear signals from three of its GPS satellites, it can establish vertical and horizontal location; with signals from a fourth, it can determine altitude. However, GPS satellites are 12,550 miles above the earth, and because they must punch through roofing materials in determining indoor locations, accuracy performance, as specified by the FCC, is notoriously unreliable.
Newer location technologies that augment GPS with known Wi-Fi access point (AP) or Bluetooth beacon locations can provide z-axis or floor location (i.e., if we know you’re near the AP on the sixth floor, we can guess you’re on the sixth floor). One of the advantages to the NextNav approach (and why it’s popular with first responders) is that it operates without having to rely on Wi-Fi, which might be out of service if power is cut during a fire.
The key to NextNav’s solution is that today’s smartphones incorporate a fairly accurate sensor for estimating altitude (i.e., height above terrain, or HAT) based on barometric pressure. Unfortunately, a sealed building’s environmental control and HVAC systems can wreak havoc on a smartphone barometer’s accuracy. This is where NextNav comes in. It provides a stable reference to improve that accuracy by gathering precise barometric data from sensors located throughout the coverage area, Christian Gates, NextNav’s SVP for strategy and development, described.
A smartphone needing to determine its altitude will send its barometric pressure reading over the cellular data channel (or Wi-Fi if available) to the NextNav Cloud, where the z-axis technology makes adjustments based on the prevailing conditions and returns a precise altitude reading to the user. AGPS, triangulation, or other augmented techniques can then establish the user’s vertical and horizontal coordinates.
In testing z-axis solutions, the FCC found the NextNav technology was able to meet the plus-minus three-meter accuracy requirement for 94% of calls. That level of accuracy is significantly above the FCC’s 80% requirement.
The company has installed its infrastructure in 105 metropolitan areas, enabling it to provide the service in over 90% of all three-story or higher buildings in the country, Gates said.
Intrepid Response Platform
With Intrepid Networks’s Intrepid Response situational awareness platform, the NextNav technology is available for first responders today. Along with push-to-talk and other situation management capabilities, the platform provides a 2D location map of all tracked personnel (i.e., everyone with a device running the Intrepid Response software). NextNav now augments that 2D location with floor information.
We should note, first responders currently must calibrate their devices on ground level at the location, a process that takes about 30 seconds but ensures them accurate floor reading when they enter the building. However, NextNav said it will introduce automatic calibration capability, which it said it has already developed, on FirstNet in the near future. That capability is key if this technology is going to power public mobile E911 service.
While this FirstNet first responder use case does not translate directly into the requirements of a public 911 service, it can provide a real-world test of the technology’s capabilities and limitations. First responders make an excellent test case, because they are often entering environments most of us would be wise to stay clear of. And, since FirstNet operates over AT&T’s public radio access network, it stands to reason that if AT&T can provide a vertical location capability with this accuracy to FirstNet users, it should be able to deliver it to the rest of its customers as well.
While we’re not there yet, the type of mobile E911 capability we should have had 10 years ago finally seems within reach. More importantly, technologies like those from NextNav are demonstrating that the industry can come up with creative solutions that meet or exceed the FCC requirements while capitalizing on device capabilities (i.e., barometers) in conjunction with a cloud-based solution to deliver the required accuracy.
This example also demonstrates one of the benefits we foresaw for FirstNet, that being to serve as a testbed for new cellular capabilities that can then be extended to the network at large.
Whether or not NextNav’s technology becomes part of the carriers’ implementation to meet the FCC location accuracy requirements will be up to the carriers. Wisely, the FCC doesn’t tell the carriers what location technology to deploy, but rather it specifies expected results and leaves the carriers to figure out how to get it done.
Improving mobile E911 requires more work, including the ability to add text and video capabilities and to tap into all of the other environmental and body sensors in the smartphone to give 911 operators a better picture of the situation with which they are dealing. Emergencies come in many forms, from fires to car wrecks, hurricanes, floods, and the list goes on. While each brings with it a specific set of challenges, if we’re looking for the one capability with the potential to save the greatest number of lives, that would be the ability to locate people who need help.

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This post is written on behalf of BCStrategies, an industry resource for enterprises, vendors, system integrators, and anyone interested in the growing business communications arena. A supplier of objective information on business communications, BCStrategies is supported by an alliance of leading communication industry advisors, analysts, and consultants who have worked in the various segments of the dynamic business communications market.