Why is there co-channel interference in the LORA module? How?

In recent years, LoRa technology development trend is more and more extensive, in all walks of life have been widely used. With the continuous development of LoRa technology, the interference events of various LoRa modules are increasing day by day, of which the co-frequency interference is the most serious, and the interference harm is also the biggest, so what is the co-frequency interference?

The carrier frequency of the useless signal is the same as the carrier frequency of the useful signal, and the interference to the receiver which receives the useful signal of the same channel is called co-frequency interference. This can happen with multiple LoRa modules communicating on the same frequency. Here's how to solve the problem of on-screen interference:

1、Host polling

Host polling is the way the host one by one polling call number, the principle is very simple, through the way of roll call response. If the host is sent to slave 1, only slave 1 can respond to the host because the slave has address settings. After receiving the host's command from Machine 1, upload the data to the host. The host then polls the other slave data in the same way. This is the host polling approach. The advantage of polling is that there is no conflict between devices and the network is stable, but the disadvantage is that it takes a long time.

2、From the machine timing upload mode

The principle of timing uploading is that the host broadcasts information to the slave computer, and the slave computer receives the host information, and then synchronizes the time, and then uploads the information according to the time we set for the slave computer, and sets the time for uploading the information from the slave computer, avoiding data uploading at the same time, so as to avoid co-frequency interference.

3、Active upload mode from computer

The Lora module with RSSI function is a relatively reliable active upload mode. This is done by detecting the strength of the RSSI signal in the environment when the slave machine needs to upload the data. If the RSSI strength in the current environment is high, then waiting for the RSSI value to decrease before uploading. If the upload is successful, the host will feed back to the slave and decide if it needs to be re-uploaded. But this method is not suitable for Lora module without RSSI function, because the more frequent the upload from the machine, the higher the probability of communication failure, that is, we say the same frequency interference.