How to fully utilize the high sensitivity of RAK831 gateway?

Issue: Hardware/Software

Setup: RAK831 Gateway (AS923) + Ai-Thinker Ra-01H sx1276 end devices

Server: A PC running MQTT to get packets from the ChirpStack Gateway Bridge running within RAK831

Details:

I saw on the RAK’s website saying that the sensitivity of RAK831 can be -139 dBm (@ 293bps) (https://store.rakwireless.com/collections/lpwan-gateways-concentrators/products/rak831-gateway-module?variant=22375114801252 ).

I’d like to know that the stated “293bps” refers to which part of the system, and how do we tune the system to achieve that data rate?

In general, what are some good practice to tune LoRa parameters to maximize communication range? Our application operates at < 1kb/s and we want to maximize the coverage. After reading Semtech’s document (http://wiki.lahoud.fr/lib/exe/fetch.php?media=an1200.22.pdf) and this online resource (https://revspace.nl/DecodingLora), it seems that we should use

  1. a higher coding rate, and
  2. a higher SF value

and what else? Please correct me. Also, would decreasing/increasing SPI speed help? I don’t know if the reading/writing rate would affect the performance in this case.

Best regards,

Chao