How to sense the channel using SX1276 LoRa IC

End Devices (Nodes) Hardware
1

In LoRa you can send 6 packets in the same channel at the same time with high probability of success.
I want to know if two things are possible using a SX1276 IC.

1. Sense a particular channel for ANY ongoing LoRa transmissions using the SX1276 IC
2. Sense a particular channel for a particular SF using the SX1276 IC

I want to do 1 and 2 prior to transmission to avoid possible collisions. I am merely interested to know at least if this is possible or know if I am going along an impossible path. I am conformable with register level programming of the SX IC.

Note: I want to sense using the SX1276 IC itself without using further RF equipment. I.e. I have an Arduino MCU and an SC1276 IC.

2

LoRa CAD detects the preamble, so if you switch channels and the preamble has passed, the transmission will not be detected.

The preamble is specific to the SF, so presumably if your receiver is set to SF7, you will not detect a SF12 pre-amble, not tried it though.

3

Check these sources.
From the blurb:

(emphasis mine)

4

To answer that specific question, then if the pre-amble has passed and the packet is in progress, then you cannot detect it as ‘LoRa’.

You could read the RSSI and use that to assume there is a LoRa packet in progress, but that method of detection would only be reliable if the signals were fairly strong.