Channel Surroundings RTLS

[mfguney]

Hello Nordic Team,

I am currently investigating the feasibility of building an RTLS (Real-Time Location System) based on trilateration using the new Bluetooth Channel Sounding (CS) feature with the nRF54L15 series.

Our target environment requires deploying around 15 fixed Anchors (acting as CS Initiators) to track the precise X-Y locations of 100+ mobile Tags (acting as CS Reflectors).

I understand that according to the Bluetooth 6.0 specification, Channel Sounding is strictly connection-oriented, requiring an active, paired, and encrypted connection between the Initiator and the Reflector. Given this requirement, I have concerns about the scalability and latency of trilaterating 100+ moving tags.

Could you please share your insights on the following points:

1. Feasibility: Is it practically feasible to manage 100+ Reflectors with 15 Initiators purely using Channel Sounding for trilateration?

2. Architecture Approach: What would be the recommended connection topology for this scale?

   • Should a single tag maintain simultaneous connections with at least 3 Anchors to perform trilateration?

   • Or should the system rely on a "round-robin" approach where a tag connects, measures, disconnects, and hops to the next Anchor?

3. Latency for Moving Tags: If we use a round-robin approach, how would the connection/pairing overhead affect the latency? Would the measurement delay cause significant accuracy drops for tags that are in motion?

4. Alternative/Hybrid Solutions: Considering the connection bottleneck, would you recommend relying solely on CS for this scale, or would a hybrid approach (e.g., combining connectionless AoA for general tracking and CS for specific high-security proximity checks) be more suitable?

Any guidance, reference architectures, or performance estimations you could provide regarding nRF54L15's capabilities in such a high-density scenario would be highly appreciated.

Thank you in advance for your support.

Best regards,

[Maria Gilje]

Hello, 

The system you are describing and, more critically, the scale of it, is something we have not tested for. I'm aware of one project where measurements were done with 6 initiators and one reflector with consistent connections and the total measurement time was about 5 seconds in that case. Please note that these are just numbers from one project and not a benchmark on what to expect. 

Since your system has a much larger scale, maintaining a large amount of concurrent connections is not feasible, so as you suggest you would likely need to do the connect-measure-disconnect approach. We don't have indicator numbers for a case like this, but you should be able to measure this with three nRF54L15 boards configured as two initiators and one reflector. 

You also mention a hybrid solution, and my initial thought is that this is more feasible than a pure CS solution. Are you also in contact with one of our regional sales managers? They are very good at evaluating if Nordic has a solution offering which satisfies your requirements. Let me know if you are not in contact with one, and I'll make sure that you are contacted. 

Best regards,

Maria