Downlink Reverse-TDoA architecture: autonomous beacons broadcast, the receiver inside the helmet listens.
Satellite navigation stops at the building perimeter. Bluetooth and Wi-Fi only indicate which room a worker is in — far too coarse for dangerous industrial zones. A person standing safely near a barrier and a person stepping inside an exclusion zone are fundamentally different operational events. Beyond a certain accuracy threshold, coordinates transform from simple map markers into verified events: zone entry, dwell time, and exact transit trajectories.
UWB has offered high-precision tracking for over a decade, but broad industrial adoption has stalled due to commercial realities rather than technical limitations. In conventional uplink-TDoA systems, fixed anchors must receive packets from every tag, maintain sub-nanosecond wired time synchronization, and backhaul measurements over Ethernet. Industry benchmarks show that roughly 85% of total deployment costs stem from cabling infrastructure alone: conduit runs, PoE switches, industrial lifts, and certified electrical labor.
Capacity is the second fatal bottleneck. Marketed tag counts are often theoretical arithmetic: with random ALOHA channel access at just 18% load, roughly a third of transmissions collide. The highest data-rate radio profiles marketed for capacity are the least resilient to structural steel and multipath reflections. In industrial safety, a dropped packet is an unmonitored worker.
Technical report TR-XENOM-2025-01, static testing on the DW1000 platform with four beacons.
Fixed beacons transmit UWB packets every 300 ms; the receiver in the helmet only listens and sends timestamps to the server over the ordinary telemetry channel. The beacons receive nothing and share no time reference with each other — not over cable, not over radio, not over GPS. Every other advantage of the system follows directly from this architecture.
No timing lines, no PoE switches, no cable routes to the mounting points. In the DW1000 configuration at a 300 ms period, a beacon runs for about six days on a 10,000 mAh battery. Mounting points are chosen from the radio geometry of the building, not from where the power sockets are.
Beacons, rovers and RF paths need no bench alignment and no correction tables before installation. Deployment requires no costly calibration equipment and comes down to basic radio planning: mounting at the designed points, recording their coordinates and running an acceptance check.
The helmets work in RX mode — receive only. Adding even 10,000 workers to a site creates 0 bytes of additional UWB traffic and no channel collisions (ALOHA). Infrastructure scales with the area to be covered, never with the size of the shift.
The UWB rover is built into the safety helmet — mandatory protective equipment. That removes the purchase and upkeep of third-party trackers, the fuss with charging cabinets, and the human factor of tags forgotten or lost.
We deliberately chose a long preamble and the lowest packet data rate. That gives the maximum radio link budget and resilience to multipath reflections off metal, instead of chasing a nominal throughput figure.
The figures come from a furnished room, not an empty laboratory: sustained non-line-of-sight, radio paths crossing two plasterboard walls, two of the four beacons standing beside resin printers with metal post-curing chambers, and a mirror directly opposite a third. No Kalman filter, moving average or trajectory smoothing of any kind was applied.
Testing used four beacons and a stationary receiver on the DW1000 platform. The architecture is also implemented on DW3000, but these quantitative results do not transfer to it — nor to an industrial site at scale with moving personnel — without a separate measurement campaign.
A deliberately unfavorable stress series is part of the published data: coordinate availability fell to 15.79% and P95 radial error rose to 93.93 cm. Removing wired synchronization simplifies installation. It does not remove the need for coverage engineering and an acceptance test.
Presence in a hazardous zone, detected at the moment of entry
Time spent in work, hazard, service and waiting zones
Automatic radio channel switching by area
Access control for specific rooms
Personnel location during evacuation
Route and incident analysis, and event generation for the control room
The same architecture would suit indoor navigation on consumer phones — a passive listener computing its own position, with beacons that by design do not know who is listening. That is precisely the scenario FiRa calls Untracked Indoor Navigation. Apple introduced a DL-TDoA API in iOS 26 and Google added FiRa 4.0 support in Android 17, but our packet format is proprietary and phone system APIs do not understand it. Switching the beacons to standard FiRa mode would mean returning to a network of anchors that must constantly coordinate — losing the independence the architecture was built for. The direct path requires Apple and Android manufacturers to open developer access to received UWB frames and their hardware timestamps. Until that happens this is a research direction, not a shipped feature, and we keep the distinction deliberately.