Interview with an Engineer: What is XLE, and How Does XLE Work?

Most companies searching for an asset tracking system are looking for one that is sustainable, specifically regarding battery life. Our products' sustainability is what gives Link Labs an advantage over competitors. Our AirFinder Xtreme Low Energy is a groundbreaking technology that extends the battery life of Bluetooth Low Energy IoT tracking devices by up to three years and improves accuracy in asset location to within a meter. We have conducted an internal interview with our engineering team to explain more about XLE, and why XLE has the ability to revolutionize the IoT industry. Here is how they answered our questions!

The Interview

What is XLE?

XLE, which stands for ‘Xtreme Low Energy,’ is Link Labs' proprietary 2.4GHz radio protocol. It has two key components: an ultra low-power communications protocol and a phase-based positioning system.

Currently, XLE uses phase ranging to determine location… I know that we want to add TDoA and location capability for XLE… What is the difference between phase ranging and TDoA?

The phase-based positioning technique used in XLE now is a type of two-way Time-of-Flight (ToF) ranging–except we measure time indirectly via phase.  This technique involves a tag and beacon forming a 20ms connection to make a series of phase measurements, from which the tag can estimate the distance between it and the beacon. When range measurements to sufficient beacons are collected, the tag can use them to calculate its position. 

A Time Difference of Arrival (or TDoA) system works slightly differently. Rather than measure ranges to individual beacons, the tag measures the difference in ranges to pairs of beacons; for example, instead of ‘I believe I am 5m from beacon A’ the tag determines ‘I think I am 2m closer to beacon A than I am to beacon B.’  It’s a little nuanced, but this approach has a very significant benefit: these range differences can be measured without the tag and beacons forming any connection, i.e., it is entirely a one-way transaction from beacons to tag. In practical terms, thousands of tags in the same area can simultaneously determine their location without interfering with each other. This technique also enables high-speed, low-power positioning because the tag acquires enough information for a fix in one shot; we estimate that a single TDoA fix is approximately 1/10th the energy of a ToF fix.

What would the accuracy potential be if XLE used TDoA? 

This is a good time to mention that the TDoA version of XLE is still very much in the R&D phase; we have a fair amount of work to do before it is ready to be included in the release version of XLE. So, given that, it’s a little too early to say for sure how it will compare in accuracy to ToF XLE, but I suspect it will be slightly poorer: instead of the 1-2m accuracy we get with ToF, it may be on the order of 2-3m. However, given the significantly lower energy consumption of TDoA, we may be able to make up for some of the difference by averaging more TDoA fixes.

Would XLE completely walk away from phase ranging or would we continue to use both location technologies?

I suspect ToF will remain the primary mode of operation for XLE, with TDoA supporting applications with extremely high tag densities (e.g., pallets full of tagged assets moving simultaneously) or very low power budgets (such as tags with ultra-small batteries or perhaps those using energy harvesting techniques). However, our ultimate goal is to enable ‘mixed-mode’ sites that feature both modes of operation, with tags that can sense their environment and seamlessly switch between technologies.

What are some of the top use cases that XLE is being used for right now?

Manufacturing / WIP: Link Labs Real-Time Location System (RTLS) — with no WiFi or IT dependency — tells employees where equipment, parts, and products are. Knowing the location has dramatically reduced bottlenecks and wasted time. It enables staff to improve customer satisfaction and enhances profitability. Increasing efficiency rates within a manufacturing plant is a huge boost to companies in the sector by saving time and increasing throughput.

Warehousing: Quickly and easily locate assets throughout a warehouse, such as pallets, ladders, machinery, and more. Productivity is greatly enhanced in warehouse environments when users know where materials are located at all times. Whether you are responsible for managing the inventory in your retail backroom or a manufacturing distribution center, having visibility of all your assets is necessary for a productive and compliant warehouse. 

Equipment/ Tool Tracking: Are you tired of misplacing equipment and tools? With Bluetooth LE technology, you can visualize the location of equipment as accurately as you need to. With Link Labs’ AirFinder, companies can reduce or eliminate wasted costs and production downtime by tracking equipment and tools in real-time.

I know that AF2 is using BLE for communication and location right now and that AF3 is using XLE for communication and location… Will there ever be a day that AF2 will use XLE for communication and location?

This is another active R&D effort.  The goal would be to include AF2’s signal strength-based positioning in the XLE umbrella.

Why would we want to make that addition to AF2? 

The significantly lower energy consumption of XLE is the primary reason.  We’d also like to enable XLE installations to leverage signal strength positioning for areas that don’t need the accuracy of ToF.

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Sustainability of Xtreme Low Energy

Xtreme Low Energy serves campus-based environments enabling companies to track, manage, and monitor assets. XLE is the ideal option for an indoor commercial setting. Here are a few reasons why XLE is the most sustainable option for companies needing asset tracking.

• Powerful Battery Life

Link Labs has pioneered XLE to last up to 7 years, resulting in cost savings on both the purchase of replacement batteries and the labor required to change batteries.

• Precise Asset Location

Using phase-ranging technology, our users can determine asset location within a meter or less

• Enhanced Infrastructure

XLE can cover a larger open indoor area with fewer beacons than traditional IoT Bluetooth LE asset tracking systems.

• Patented Phase-ranging Technology

Link Labs asset tags and beacons communicate through our patented phase-ranging technology that uses the triangulation of x/y/z coordinates.

Closing Thoughts

XLE is a big topic with many layers to it! However, it is not the only asset tracking technology that we use. We also use Bluetooth Low Energy for indoor tracking, GPS, Wi-Fi sniffing, and Cellular for outdoor tracking. If any of our products pique your interest or you just want to learn more about AirFinder, visit our website or book a demo today.