As Krishna Easwaran said in video Gateway Demo: LoRa Basics Station - Krishna Easwaran (Things Industries) & Anton Beitler (Semtech) - YouTube (at time 17.20) choosing relevant gateway depends on RSSI, SNR and other factors. Theorethically I agree, but in practice is different picture.
We have some nodes, covered by three gateways at least. Gateways are on different locations, so their RSSI&SNR are on different levels. Some nodes are really close to particular gateway. As far as I have noticed, closer nodes are rarely connecting to closest gateway. By the rule, the closest gateway has far the best RSSI&SNR.
The explanation, which I couldn’t find is how gateway server choose which gateway which will process particular packet. In our case there are nodes on different areas which are connecting to gateways with weaker signals in nearly 30 % cases at least (in case of one gateway even in more than 80%).
Thank You for any idea.