BLE mesh LPN localization questions / suggestions

[jacek_tig]

Dear Nordic Crew,

I have got 5 adafruit feathers based on NRF52832 and nRF52833-DK so far.
I would like to implement indoor localization based on BLE mesh and RSSI.

As far as I understand, to gather RSSI in your NRF5-SDK-for-mesh, I can use your great RSSI model (RSSI model)...
and the question is, is it possible to use RSSI model in LPN, to make "RSSI multilateration" of LPN or it can talk only with its friend node?

If measuring RSSI by LPN is not possible:
    option 1. assuming, that my LPN have battery, is rechargeable and power consumption issue is important but not critical, can I implement it as regular mesh node, turn radio on - gather RSSIs - publish some data for subscriber - turn radio off to save battery?
    option 2. can LPN work simultaneously as BLE beacon (similar to SDK_coexist) and can mesh nodes gather BLE advertisement and parse advertising from LPN using RX callback (a chapter in beaconing)?

Additional question, do you recommend NRF5-SDK-for-mesh or NCS/Zephyr for BLE mesh? In my opinion, option 1 can be made on Zephyr if I create RSSI model, but what about option 2?

I will appreciate any other idea or suggestion.

Best regards,
Jacek

[tesc]

Hi,

Our recommendation for new projects is to use nRF Connect SDK (i.e. the new SDK which is based on Zephyr OS.) This is where new development and new features will happen, whereas the nRF5 SDK is now in maintenance mode and will only receive security patches and other bugfixes.

Regarding LPNs, they can only receive messages via the Friend, and they also send messages to the Friend in order to poll for new messages. However, when they send messages on the mesh network, they use the same approach as any other node on the network. This means any protocol relying on the node sending messages, will work exactly the same as for any non-LPN node. It is only messages being received by the LPN that are different (as they always come from the Friend.)

Please note that RSSI is not an accurate measurement of distance. The measure is simply an indication of the power level received around the given channel, and the accuracy may vary depending on the surroundings. There will be situations where the signal strength is weaker due to loss of line-of-sight (e.g. people in the way,) or because the signal received is reflected off a surface (e.g. wall, ceiling.) You can get multi-path issues with constructive and destructive interference (direct signal mixes with signal bouncing off one or several surfaces.) You can get interference from other RF sources, and you will experience other effects such as antennas not sending and receiving uniformly (all antennas have better gain in some directions than in others.)

Regards,
Terje