LoRaWAN MACs calculate a start time for starting the receiver.
It looks like SF12 is wrong for the LMIC -- too late. I found this with EU RX testing. Here are the times in ms.
Code SF12 SF11 SF10 SF9 SF8 SF7 LMIC 41 8 -8 -16 -20 -22 Semtech reference code 33 17 5 -2 -8 -9 mbed 88 39 14 2 -4 -7(Semtech reference: RegionCommon.c RegionCommonComputeRxWindowParameters()).
It's OK if you start early, but not OK if you start late, as you can miss the start of the packet.
In fact, the current LMIC only shows problems at SF12.
Part of the problem is that both use a specific number of symbols as "min syms". But LMIC uses 5 whereas Semtech uses 6. If LMIC uses 6, the table becomes:
Code SF12 SF11 SF10 SF9 SF8 SF7 LMIC 41 8 -8 -16 -20 -22 Semtech reference code 33 17 5 -2 -8 -9 mbed 88 39 14 2 -4 -7 LMIC with min RxSym = 6 29 -3 -19 -27 -32 -34We'll test tightening this up, but also will test just changing RxSym to 6.
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