Class A downlinks not being transmitted

[LanceBeasley]

I have captured and analyzed a failure we are seeing where a Class A' (see below) packet fails to transmit, with no indication of failure in the Laird RG191 gateway log or in the SX1301 SPI data. This happens about 10% of the time. Since there are already mechanisms in place to prevent (and respond with an error) to improperly scheduled packets, we can rule out errors in our code that generates the transmission command.

In the attached file I have an analysis of a successfully transmitted packet, followed by a failing packet (both are Class A'). And the only indication there was a failure is that the lora device didn't receive a packet and the spectrum analyzer didn't see any RF. I tried to be as detailed as possible in my analysis, but there is a lot going on, so please reply with any questions.

Class A' details I refer to the transmission that failed is a Class A' (A prime). The reason is, we have found a way to track the gateway tmst time and use that to schedule downlinks in a way similar to Class B.

I appreciate the help! Missed Packet 08-14-2020 16-17-59.pdf