Trouble getting stable OTAA on SF12 with a RN2483 module

[arjanvanb (Arjan)]

@mogul

I see no reason why lower data rates you require longer delay

The delay is just a result of using either RX1 or RX2. And using RX1 or RX2 is just a choice of the server.

For regular uplinks, when using RX1 then the downlink uses the same SF as the uplink. The higher the SF, the longer the transmission time. But for RX2, the frequency and SF are fixed, at least for EU868. And for RX2, TTN uses SF9 in EU868 (for the regular downlinks; not for the OTAA Join Accept).

Now:

• Any regular uplink that uses a low (fast) SF, like SF7 or SF8, would also use that low (fast) SF in RX1, but would use the slower SF9 in RX2. So, TTN prefers RX1 then.

• For an uplink using a high (slow) SF, like SF11 or SF12, RX1 would also need to use that high (slow) SF, while for RX2 it would again use SF9, which then is faster compared to RX1.

Or, like Hylke wrote:

@htdvisser

We try to avoid RX2 if possible. For RX1 we have 8 channels available, while RX2 is fixed on 1 channel and a very inefficient data rate. Therefore, expect most downlink messages to be sent after 1 second.

I guess the same reasoning applies for a Join Accept.