Hi @hoonppark, good questions.
- It is still TDOA. Using the 1st generation Semtech reference design works as well, but is less accurate. In any case, it requires GPS indeed. Not necessarily for the location, because as you say you can put this in config, but for time synchronization.
Note that Semtech’s 2nd generation reference design works with encrypted timestamps. You’d need a license from Semtech to be able to decrypt it.
It would be in the Handler, after deduplication and before putting it in a nice packet on MQTT. Currently there’s a chain; look for ConvertLoRaWAN and ConvertFields.
Well, you have the metadata from the different gateways in the Handler, so with that it’s not difficult. @Thomas has a model
WiFi-based geolocation is not meant as the holy grail; as with any localization everywhere, it’s good to implement and combine different technologies: LoRa triangulation using TDOA, using signal strengths, using WiFi BSSIDs and signal strengths, using GPS.