In UWB literature, there is a notion of tag devices being mobile, lightweight, energy constrained UWB devices that typically users or robots would carry. Anchors on the other hand are UWB devices that are fixed in predetermined locations and serve as reference points to perform relative localization. Research at my lab has explored many relationships between tags and anchors and has challenged the notions of what is "fixed" and what is moving. In this blog, I will run over some of these configurations and point you to papers from my research as examples.
Multiple fixed anchors, infinite number of tags, privacy preserving:
If you are looking for an infinitely scalable indoor localization solution, you should read the PnPLoc paper. The paper also describes how to create a natural organically expanding anchor system that is easy to deploy and easy to maintain. The tags use a new TDoA formulation with clock drift mitigation, which is a key innovation in this paper. A big plus is that the infrastructure does not know your location. #indoor_localization, #scalable_localization
Two fixed anchors, single fast-moving tag:
Sometimes, a particular object is so important that localization of that one object is all that we desire. In a constrained cricket field setting, we show how to track a cricket ball using the wickets as anchors. We use a very fast active-passive ranging scheme to locate the ball. The physics of the ball in free fall is useful as well to derive the trajectory. The iBall paper is worth a look if you are exploring something similar. #sports_analytics, #tracking_fast_movements
One moving anchor, multiple moving tags:
A moving anchor is a bit odd. However, systems like this exist if the anchor is on a drone or a car, for example. It becomes particularly helpful if the trajectory of the moving anchor is known. We built a system for tracking firefighters inside a building using a drone flying outside. Read the TrackIO paper if you want to try something similar. #firefighters, #firstresponders, #drone
Moving Anchors and Moving Tags
An adhoc formed geometry on a sports field for example treats tags and anchors interchangeably. The P2PLoc system is a good example. This paper uses a cascaded pipelined TWR protocol. #sports, #players, #topologies
Spoofing detection system
In a setting where the clients have incentive in cheating about their location, we have developed an unspoofable ranging protocol. Read the UnSpoof paper for insights about such a system. #trustworthy_localization, #uwb_spoofing
Inter-node distance measurement
Sometimes, just peer to peer distance measurement is desired, and not so much location. ViSig identifies body signals such as those used by law-enforcement officials, sports umpires and referees, aircraft marshallers, construction workers, etc. Sometimes, the number of devices is very large but you care about only the few that are nearby. That needs rethinking the link-layer protocol: 6-Fit-A-Part is a system to keep a certain distance between patrons, during the Covid-19 pandemic, and is useful for grocery stores, hospitals, tourist spots, etc. #UWB_distance, #Covid-19, #body_signals
Fine-grained location
A pen's movements over a whiteboard are tracked in this fine-grained localization paper. It is called ITrackU. A small work for drone landing also used similar idea and was shown as a poster: home-coming. #education, #precise_motion_tracking
UWB as a Wireless Sensor
If you only want a sensing based system, where signal reflections or signal refractions are captured, you might want to read the LiquID paper which identifies liquids using UWB signals. UWB reflections can be used to create art! Read the Travelogue paper. This idea was exhibited at Georgia Tech's library. #uwb_sensor, #wireless_sensing
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