Fathom Bluetooth RTLS Webinar – Questions and Answers

Randy Asset Tracking, Beacons, IoT, Press

Our recent webinar, High Accuracy Indoor Location Using Bluetooth – When Proximity Isn’t Good Enough, was a huge success with over 1600 people registering for the event. As expected, we received many interesting questions during the webinar, so here’s a list of all the questions along with the answers. If you have any additional questions, please feel free to contact us!

Q: How important is the placement and density of the Fathom Hubs in detecting the position of a BLE tag?

The placement and density is very important. Hubs are typically deployed 10 to 15m apart for each other to collectively form an umbrella of coverage over the desired venue. Tighter arrangements may be used for improved accuracies or to account for venue specific characteristics. The Hubs are affected by their surroundings so their placement near walls and obstructions is carefully calculated using our Hub placement planning tool.

Q: How can you enable Angle of Arrival (AoA)? Do you need to use a specific chipset or special antennas?

Fathom Hubs contain six Bluetooth antennas arranged in a hexagon pattern – so Fathom Control (residing in the Cloud) can detect the Angle of Arrival in 60 degrees increments. Then our estimation algorithm further refines the angle of arrival using statistical signal processing techniques. We use off the shelf silicon from Nordic Semi. Our antennas are custom designed to be high-gain and directional.

Q: I understood that we can get proximity to a Hub. But how would you determine the geo location of the Tag based on Hubs?

Our Fathom Hubs are “anchored” in the real world with a known Latitude and Longitude. In a single Hub setup, our patent pending algorithms derive the position of a BLE device by analyzing angle of arrivals and signal strengths from the Hub’s six antennas and compute the BLE devices’ geodetic coordinates via Fathom Control, our Cloud-based service which includes the Location Engine.

In a multi Fathom Hub context, AoA and RSSI observations from all Hubs are integrated in the position calculations in Easting Northing reference frame, which is then transformed to geodetic coordinates using Hubs’ coordinates, yielding more accurate positions for the BLE device.

Q: How long does it take to resolve to an accurate location?

Location determination timing depends in part on the beaconing rate of the BLE device. In a typical configuration where a device beacons at a few hertz, Fathom Control can compute an initial position within 4 seconds (i.e. when a device is first seen by the system), and maintain an update rate of 1Hz thereafter.

Q: For doing positioning, do you need a specific BLE IC with special hardware bloc?

Fathom Hubs are engineered with off-the-shelf components from various silicon vendors and can position any third party BLE beacon.

Q: What is the effect of and can you compensate for shadowing from human body model or physical objects in movement between Hubs and Tags?

Multipath and fading are typical factors one must take into consideration. With a distributed architecture, signals from a given device are picked up concurrently from multiple Hubs and multiple antennas from each Hub. In aggregate processing, this diversity of inputs helps offset and mitigate typical signal degradations and yield more robust position calculations, both from an RSSI-based ranging and Angle of Arrival perspective.

For BLE devices that can also emit dynamic information, such as Fathom’s own industrial-grade Tag equipped with an onboard accelerometer, motion detection can further enhance position determination.

Q: Do you need the long-range feature of BLE 5.0?

No, not really. The Fathom Hubs are equipped with high gain directional antennas to collect multiple views of a device in order to determine a device’s Angle of Arrival with respect to any given Hub. These antennas have a 5.6dBi gain and a beam of about 60 degrees, enabling devices as far as 70- 100m to be detected. While BLE 5 improved signal range is most helpful for data collection, from a positioning accuracy perspective, Hub placement density is more important.

Q: Is multipath an effect to consider? Any performance degradation on AoA estimation?

Multipath and fading are typical factors one must take into consideration. With a distributed architecture, signals from a given device are picked up concurrently from multiple Hubs and multiple antennas from each Hub. In aggregate processing, this diversity of inputs helps offset and mitigate typical signal degradations and yield more robust position calculations, both from an RSSI-based ranging and Angle of Arrival perspective. For BLE devices that can also emit dynamic information, such as Fathom’s own industrial-grade Tag equipped with onboard accelerometer, motion detection can further enhance position determination.

Q: Are the Hubs battery powered?

The Fathom Hubs consume ~6W at 8V and can be powered in a few different ways depending on the application. In a permanent setting, they are usually powered via their AC/DC wall adaptor, or alternatively, using Power over Ethernet (PoE) adaptors. In some temporary installations, such as for a trade show or short-duration uses, they can be battery powered. A typical 10,000mAh Li-Ion battery pack can feed a Hub for more than a day.

Q: For the calibration process, is there any calibration needed on the mobile device?

No. This is one of the reasons Fathom can position any third party BLE beacon.

Q: Which device performs the rendering? The Fathom Hub, sensor or central server?

Our network of Hubs collects signal observations from all of the directional antennas; this is relayed in real-time to our cloud based positioning engine, through which applications can query or consume various positioning data streams over standard APIs.

Q: What is the accuracy to reach at distances like 100m (using long range BLE -modulation or 20dBm)?

Fathom relies on receiving BLE observations from a particular BLE beacon at multiple Hubs. This is necessary for providing the claimed accuracy irrespective of the environmental factors. 100m is too much of a distance and will cause accuracy degradations no matter how strong the signals are. Correlated measurement information is important for our estimators and with Hubs so far apart, there would be almost no correlation between multiple measurements from different Hubs.

Q: Is AoA reliable in non-line of sight or multipath conditions? If not, is there a way to find that out through some means so that AoA can be discarded for such situations to avoid false positives?

Multipath and fading are typical factors one must take into consideration. With a distributed architecture, signals from a given device are picked up concurrently from multiple Hubs and multiple antennas from each Hub. In aggregate processing, this diversity of inputs helps offset and mitigate typical signal degradations and yield more robust position calculations, both from an RSSI-based ranging and Angle of Arrival perspective. For BLE devices that can also emit dynamic information, such as Fathom’s own industrial-grade Tag equipped with onboard accelerometer, motion detection can further enhance position determination.

Q: How do you solve the problem of multipaths?

Multipath and fading are typical factors one must take into consideration. With a distributed architecture, signals from a given device are picked up concurrently from multiple Hubs and multiple antennas from each Hub. In aggregate processing, this diversity of inputs helps offset and mitigate typical signal degradations and yield more robust position calculations, both from an RSSI-based ranging and Angle of Arrival perspective. For BLE devices that can also emit dynamic information, such as Fathom’s own industrial-grade Tag equipped with onboard accelerometer, motion detection can further enhance position determination.

Q: What are the backhaul options for sending data from the “hub” to the “control” in the cloud?

Our Hubs can backhaul the data via Wi-Fi (2.4GHz or 5GHz) or wired Ethernet.

Q: What is the latency in the position estimation?

Fathom Control computes tag positions every second with an initial latency of ~4 seconds when a device is first seen or when movement is detected.

Q: Is Angle of Arrival (AoA) part of the standard Bluetooth protocol?

Because Fathom has been working on this technology for the past three years, it had to implement its own AoA data collection strategy within its Hub devices. There are efforts underway to standardize AoA information collection and transfer within the Bluetooth protocol. Should these eventually be ratified and implemented, Fathom’s cloud positioning service can align and take advantage of a potentially broader base of hub-like gateways from multiple vendors.

Q: How do you handle beacons that are not in line-of-sight with one or more of the hubs?

Fathom Control can position BLE tags from any vendor and through walls and other structures as long as the BLE signal can be received. Our estimators rely on correlated measurements to mitigate the effects of NLOS.

Q: Is this device able to capture and store in different formats in cloud?

Fathom Control runs on AWS and our streaming API of positions can be further transformed in the Cloud to any format of your choosing using Fathom Control API extensions.

Q: What is the Bluetooth advertising interval of the Fathom Tag for 5 years life of the battery?

One second at 0dBm.

Q: Do you already use the coming CTE within the standard?

The only information we use from Radio side is the estimated RSSI. All other information is generated by Fathom, which includes AoA, range estimation, static/dynamic conditions.

Q: What are the dimensions of the Fathom Hub?

Hubs are hexagonal in shape, about 15cm wide and 8cm high.

Q: How do you handle reflections/multipath of the signals? Do you use mathematical super-resolution methods like MUSIC?

Fathom’s position estimators take advantage of correlated measurements from various viewpoints (Hubs). These measurements along with estimated AoA and temporal correlation of RSSI based ranging allows for mitigation of multipath effects in the form of outlier detection and removal.

Q: What about the use case to work with Mobile phone in the market, instead of both gateway and tag from Fathom.

If your question is about using phones instead of dedicated gateways to collect location information of nearby BLE asset tags, the webinar slide 12 touched on this. This can be a valid use case in some applications, provided one knows the position of the phone while it is collecting data. For instance, some applications are just focused on retrieving logged sensor data, not really positioning, so using a phone in that context may be just fine.

If your question is about how to position the phone itself indoors without solutions like Fathom Hubs and Tags, as mentioned in the webinar, a smartphone has more onboard capabilities to estimate its own position than say, a low-cost simple asset tag. However, the smartphone can only really achieve this if it has access to some reference information, such as the position of nearby BLE beacons. If those reference BLE beacons are not present, or improperly geocoded, the quality of position calculated by the phone will be affected.

Systems like Fathom can provide a monitoring service to ensure the reference BLE beacons are indeed active and where are supposed to be. So, while Fathom may not be used to position the smartphone (though it can), it can ensure the integrity of the beacons the smartphone relies on for its own onboard positioning.

Q: What algorithm is used for positioning the Tag?

Our patent pending algorithms are proprietary. They take the measured angle of arrival and signal strengths and triangulate with neighboring Hubs to compute the beacon’s latitude and longitude.

Q: What have you found the time range for channel coherence to be? That is, the time where you can reliably compute positions, without parameter updates? Numbers from 20 ms to 200 ms are typically cited.

100 ms is what we have found to be the optimal coherence time for RTLS. For applications where users can wait for 10-30 minutes for a position update, we can use beacons that advertise @ 0.1 Hz. In such cases, the coherence time is of the order of minutes. It all boils down to measurement correlation time. We have performed detailed Allan variance analysis to properly model the system.

Q: Are Fathom Hubs connected to the network via LAN cables?

Our Hubs can backhaul the data via Wi-Fi or wired Ethernet.

Q: The application on buses are similar to what my teams working on, how many sensors did they use? Did they have one every 20m?

Two Fathom Tags are placed on each bus. The Hubs are located at 15-20m intervals.

Q: While using Fathom’s system for dynamic positioning or movement detection, what is the max refresh rate achievable? In other words, how much time does it take to refresh and update to the newer position?

In the GPS world, this is a round 2-3 seconds. Fathom Control computes tag positions every second with an initial latency of ~4 seconds when a device is first seen or when movement is detected. This is for beacons advertising @ 10 Hz, which is what we recommend. Slower beacons have different update rates ranging from seconds to minutes (0.1 Hz beacons)

Q: External companies are hesitant in letting 3rd parties on their network. Do you also include dedicated network solution since different sites may have different networking policies and requirements?

Fathom Hubs require a pathway up to the Fathom cloud service (either wired or Wi-Fi 2.4GHz or 5GHz) but how this is ultimately setup is a function of a customer’s requirements. If a dedicated Wi-Fi or wired network is required, we would expect this to be part of the site preparation prior to commissioning the Fathom system itself.

Q: Do you have a motion sensor in the Fathom Tag to detect movement?

Yes, our Fathom Tags contain an accelerometer which is used to detect motion. This is incorporated in our proprietary positioning algorithm to optimally render updates in dynamic scenarios, reduce jitter in static scenarios and optionally extend battery life.

Q: What is your business model?

Fathom is a subscription-based LaaS (Location as a Service) model, with onetime costs for the necessary Fathom Hub hardware and integration support for site provisioning if needed. While Fathom can position any 3rd party beacons, we also offer an industrial grade, IP67 rated beacon called the Fathom Tag which can yield better positioning and can be remotely managed and configured. In 2018, 3rd party beacons will become available with built-in Fathom firmware that will enable better positioning and remote management capabilities currently available on Fathom’s own Fathom Tag. The recurring subscription model is typically a function of the number of devices and site coverage characteristics.

Q: What is the end to end positioning latency of your product?

From the moment of movement to viewing it on the UI, Fathom Control computes tag positions every second with an initial latency of ~4 seconds when a device is first seen or when movement is detected.

Q: Would this approach work in a smaller, more constrained space, for example to find out in which room of a house beacon is in?

When Fathom is deployed to cover a venue and its various rooms, the position data can be used to determine room level presence. Fathom is also working on a dedicated room level detection system optimized for use cases that may not need full (x,y) positioning across a venue but rather, for example, in/out transit detection through a doorway across different rooms. If this is of interest, we’d be happy to discuss this in more detail with you.

Q: Will Bluetooth 5.0 affect the Fathom systems accuracy?

No, not really. The Fathom Hubs are equipped with high gain directional antennas to collect multiple views of a device in order to determine a device’s Angle of Arrival with respect to any given Hub. These antennas have a 5.6dBi gain and a beam of about 60 degrees, enabling devices as far as 70- 100m to be detected. While BLE 5 improved signal range is most helpful for data collection, from a positioning accuracy perspective, Hub placement density is more important.

Q: Do you know if Apple or Google are working to add that functionality (beacon) in their OS?

We can’t really speak to what smartphone OS vendors have in plans. However, smartphone OS and device vendors already have deeply integrated beacon detection capabilities to optimally trigger events for the benefit of user apps (e.g. when entering a proximity zone of interest). Many apps can also effectively turn a smartphone to appear just like a beacon. In such a case, Fathom can then easily position that device.

Q: Is AoA accuracy (in a particular direction), a function of the number of antennas?

Our Hubs contain six Bluetooth antennas arranged in a hexagon pattern – so we can detect the angle of arrival in 60 degrees increments which is then refined to a few degrees accuracy using state of the art estimation and statistical signal processing techniques. We came up with current Fathom Hub design after 1.5 years of detailed research and development.

Q: Is AoA available to your system even for BLE-4.0?

Yes, we work with any BLE device.

Q: Can your solution be used for 3D?

Fathom Hubs are equipped with pressure sensors. If a beacon has an onboard pressure sensor that it reports in advertisements, we can use this information to perform z/ vertical axis estimation.

Q: Do you have any advice about where we should place the beacons? In the middle of the wall or in corners? Does the material influence the RSSI (concrete, metal, glass)?

Your question is about placement of beacons. In a Fathom system, consideration is on the placement and density of the Fathom Hubs, i.e. our beacon detection network. For effective detection and positioning of any BLE device that comes in range of the Fathom Hubs, the Hubs must be typically set 10-15m from each other. Tighter densities (e.g. 8m) may be required depending on the venue characteristics. We provide a planning tool to help ensure the optimal deployment of Hubs.

Q: Is there any z-axis positioning?

Fathom Hubs are equipped with pressure sensors. If a beacon has an onboard pressure sensor that it reports in advertisements, we can use this information to perform z/ vertical axis estimation.

Q: What are the real-time / mobile accuracy / battery life trade-offs in a crowded RF environment?

Fathom can position any BLE beacon. However, the real-time positioning of a beacon depends in part on the beacon’s own beaconing rate configuration. When beaconing at multiple Hz, Fathom can typically detect a device within about 4 secs and maintain a position update rate every second.

If on the other hand the asset tag was configured to beacon at a much lower rate, say once every 10 seconds (to save battery), Fathom will still detect and position the device, but not in real-time. Such scenarios are more typical of devices or equipment that are generally static in nature (such as the cannabis compliance scenario discussed in the webinar).

Finally, Fathom Hubs constantly scan and relay their observations to the Fathom cloud. The scans can contain several hundred observations per second, enabling detection of large numbers of devices even in crowded RF environments.

Q: Is there any improvement with BLE 5.1?

No, since we do not rely very deeply on BLE protocol in general. Our focus is to provide positioning capabilities without too much reliance on the radio packets. So, our system would work with BLE 4 or BLE 5 seamlessly.

Q: How you are planning to achieve battery-less operation?

Fathom itself does not produce battery-less devices. Fathom partners with device vendors for optimal detection and management of their devices. Some of these partners are working on battery-less sensors. From Fathom’s perspective, they appear as normal BLE beacons and will be detected and positioned as such.

Q: Are you one of the main contributors to CTEs in BLE 5.1?

No, we are not part of any such contribution groups. We don’t want to mold the radio technology in our favor. We focus on how to reliably and accurately position BLE beacons whether they are BLE 4 or BLE 5 based.

Q: What are the power consumption of Fathom Tags and Hubs?

Our Fathom Tag is designed for a 5-year battery life using a field-replaceable CR123 battery. Our Fathom Hubs are normally powered by an AC/DC adaptor or via a third party Power Over Ethernet (PoE) adaptor; since they consume 6 watts, they can alternatively be powered by a battery pack in certain temporary site setup scenarios. A typical 10,000mAh Li-Ion pack can feed a Hub for more than a day.