Aruba’s Self-Locating AP Technology is Truly Remarkable

At Aruba Atmosphere 22, Aruba announced their new Self-Locating AP technology. Using an integrated GPS receiver on the 6xx series Access Points, the APs can locate themselves and and automatically be positioned on a floor plan.

I was very skeptical when I first heard about this technology. I thought, how is a GPS going to work indoors? Why do I even need the network to automatically place the APs on a map? How will the APs determine which floor they are on? I was also a bit put-off by the term “Indoor GPS” being used to describe the technology. However, the more I learned about it, the more sense it made, and the more I could envision some real benefits as a result of it. Hopefully I can explain some aspects of the solution so that you can have the same realization.

First, it is not expected that every AP will be able to receive a GPS signal indoors. APs near the edge of the building will receive a GPS lock and act as “anchors” for the rest of the APs that can’t receive a GPS signal. The location of the anchor APs will refine itself over time, as the GPS satellites travel through the visible sky from the AP’s perspective. The anchor APs will receive a lock almost immediately, but it is expected that the location will be refined over the next 24-48 hours as this process runs its course.

You’re probably asking yourself, how will the rest of the APs will auto-locate themselves if they can’t receive a GPS signal? There are two location mechanisms in use for this process: GPS and FTM. The network of APs will determine their own relative locations by way of Fine Time Measurement (FTM) ranging. This process uses very accurate measurement of the time it takes for a signal to travel the distance between each AP. This is similar to how a GPS receiver uses time-of-flight measurements to locate itself via the signals coming from the GPS satellites, except this part of the process doesn’t require satellites or GPS. Once the ranging process establishes relative locations for each of the APs, it is then anchored to latitude/longitude coordinates by way of the APs that were able to receive a GPS lock. This is all done completely irrespective of any floor plan that is in place. It is strictly based on latitude and longitude. You could have nearly perfectly-located APs in “space” without any floor plan loaded at all, if you wanted to.

FTM is measuring the time of flight of Wi-Fi frames. It doesn’t have its own dedicated radio in the AP. What that means is that the network is going to need to coordinate APs briefly going off-channel to perform this process. Distance measurements of nearby APs will have to be performed on a common channel, as well. I’m interested to see if this adds any noticeable overhead to the already noticeable (in some situations) off-channel scanning that occurs for automatic channel selection, and rogue scanning. I wonder if it will become a best practice to perform the auto-locate process once, and then once the location has been determined and refined, turn the process off until changes are made. There are many intricacies to this process that I’m excited to be able to see and optimize in a real production environment.

Another great aspect of this solution is that the FTM ranging is compatible with the previous generation Wi-Fi 6 (AP5xx) APs! While they don’t have the integrated GPS receiver, they are fully capable of participating in the FTM ranging process. Maps of 5xx series-only APs could be manually anchored to position it on a floor plan, but the relative position between the APs will benefit from the same high level of accuracy as the 6xx series APs.

The part that I am most interested in seeing how well it works in the real world is the elevation measurement. If these APs are going to automatically place themselves on floor plans, they will need to be able to accurately determine which floor of a building they are on. GPS is notoriously inaccurate when it comes to measuring elevation, due to the fact that the satellites required to accurately determine elevation are on the other side of the earth from the receiver. However, Aruba thought of this, and has come up with what seems to be a reasonable solution to the problem. The anchor APs will determine their elevation from GPS, and while the actual elevation from sea level may not be very accurate, the relative elevation of each AP should be. The network will be able to determine which APs are at the lowest elevation, and then see the relative elevation difference between the APs on the next floor. Over time, the FTM ranging process will allow the process to “correct” for any inaccuracies in the GPS elevation, to help assign them to the proper floor.

I also wonder if since the APs will be receiving the precise time measurement from the GPS network, can this be used as an NTP source? I know customers that have spent a lot of money to provide their network with their own GPS-based NTP source. If this could provide NTP functionality, it would certainly differentiate it from competing solutions. Aruba has also said that the location information could be used to improve AP neighbor reports in the future.

I didn’t really understand the importance of self-locating APs at first. I’ve always been one that spends the necessary time to properly locate APs on floor plans in the management platform, and once you get into a rhythm, it really doesn’t take that long. However, when you consider how easy it is to place those APs on a map upwards of 15-30′ from where they are actually located, you can imagine what a significant impact that would have on indoor asset location accuracy. That’s the real reason this solution is necessary. If it can correct the location of every AP in your environment, imagine how much more accurate it will be able to report the location of client devices within your environment.

Another exciting aspect of this technology is its ability to share location information via Open Locate. Open Locate is a movement intended to provide a method to share and utilize the location information with other devices in the network. Some Android and Windows operating systems already support client-side FTM, which could allow them to take advantage of the location information. What this means is your mobile device may be able to use this information to position itself in space, while indoors in an environment where GPS is not available. Ideally, the operating system would provide this location to applications just like it does today for GPS location. This could be a huge advancement for indoor location applications. However, I estimate that there will be particular challenges with the speed of client-side FTM for moving clients. This is yet another piece of this puzzle that I am excited to experience in the real world.

Aruba also announced their partnership with Tile. If you are unfamiliar, Tile is a product that uses BLE to locate small devices that can be attached to your personal belongings. Until now, the Tile network has relied on other Tile users to anonymously report locations of any Tile devices nearby. The location of the devices comes from the device that the Tile mobile app was running on. Aruba’s partnership with Tile allows Aruba wireless networks to provide location reports for Tile devices without the need for a Tile user/device/app. I suspect this is the first of many partnerships like this that we will see from the benefits of this technology.

I am really excited to see the benefits of Self-Locating APs in the real world. I’m very impressed with the amount of R&D that has clearly gone into this. I was fortunate enough to be able to hear Aruba’s experts speak about their Self-Locating APs in-person at Tech Field Day’s portion of Aruba Atmosphere 22, and it really made the conference for me. It’s not often I go from “what’s the point of this” to “where has this been all my life” in the matter of an hour presentation. The formatting and verbiage in this article may be a bit rough, but I am excited about the technology and wanted to write about it as soon as I could. I plan to refine it a bit when I have more time. I’m interested to hear your thoughts on this, as well!

If you are interested in learning more about Aruba’s Self-Locating APs, I encourage you to watch this recording of the Tech Field Day session at Aruba Atmosphere: https://www.youtube.com/watch?v=kVdFNR0R3EE

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