I noticed a strange interaction between some Dragino LSE01- nodes and Dragino gateways. At a hilly field site (about 1km²) 60 LoRa nodes are installed. Forty nodes are buried at a depth of 35 cm to allow normal agricultural use of the area and 20 nodes are from Dragino (LSE01) for mobile measurements of upper soil moisture. To pick up all signals especially in periods with high soil moisture and/or canopy height two Dragino gateways (DLOS8) in a distance of about 500m were installed.
For unknown reasons some of the LSE01 stopped transmitting after months and we are unable to join them again. They did not stop at the same time. There are days to weeks in between. There is another Gateway (LG308) about 8km (linear distance) away, which sometimes receives also some Lora frames from the site. However, if we bring the LSE01 near to this gateway, no join is received either.
We sent the activated (but not re-joined?) nodes to the office (180km away) by mail. The strange thing is that they start sending within an hour of arrival, with no user intervention. The Gateway in the office is a Dragino Pico Station. We are using Webhooks to receive the uplink messages from TTN and can see, if the nodes send regular or not.
I suppose the problem is somehow related to the gateways, since the nodes are working with the office gateway (the nodes were never connected to the office gateway before).
Does a LoRa gateway do more than just transmit data frames between the nodes and the application server (TTN) and vice versa?
What could be the reason for this behavior (we observed that for five nodes until now)?
Could it have something to do with the frequencies (we use EU686-nodes, selected in the gateway as well) - maybe the join request is not received on the right frequence?
I am grateful for any advice!