Knowledge Base

Which LoRa module?

Hi everybody,
I have a project in Germany where I want to connect up to 100 client devices in a larger area (a big building complex or a free field with a radius of roundabout 2km).
Those devices should be connected to one base station which runs the app.
Each client device needs to send 16 bytes each 5 seconds. Because of our law, the frequency I would like to use is 868.4-869.3 Mhz. That's because in this area I am allowed to use the duty cycle without restrictions as long as the transmission power is less than 10mw.

The client devices run on an ESP32 while the base station is running on a RaspberryPI.

Now I need to know whether LoRa is a suitable solution for my project and if that's the case which module I should use for the clients and the base station.
In case anybody has a better solution I would like to hear them as I am still in the early phase of planning.

Thanks in advance:
- Rimaito

At such frequencies you can use SX1261 chips or modules.
Thanks for your reply,
but I still have some questions:

How can I ensure that this module won't send a signal stronger than 10 mw?
And the other thing is, is this module capable of acting as the base station? (It should be able to handle multiple connections at once)
Regarding the maximum transmission power you can select the output power of the chips, but it will also dependent on your board and antenna, so you will have to tune it.

The chips are able to TX at one frequency/SF at a time, so you have to ensure that you have successive TX with no collision. Depending on the amount of data you have to send you might want to have a look to SX1301/SX1308 which is able to demodulate several channel in parallel.
Thank you very much for your help!
It is really confusing with all those different modules when you are completely new in this field.

- Rimaito
Are there any SX1261 modules, in the style of RFM98 etc ?