With the continuous development and application of LoRa technology, the incidents of CCI between LoRa modules are increasing, and the harm of interference is becoming more and more prominent. You may ask what is CCI.
CCI(Co-channel Interference): The carrier frequency of the unwanted signal is the same as that of the useful signal, causing interference to the receiver which receives the useful signal. As long as we use multiple LoRa modules to communicate in one frequency, co-channel interference will exist.
In order to solve the problem, we have three solutions to it.
Method 1: Host Polling
Host polling mode is the way that the master polls and calls the salves one by one. The principle is very simple. For example, the master sends to slave1, since the slaves have address settings, only slave1 can respond to the master. After the slave1 receives the command from the master, it uploads the data to the master. The master then polls other slaves for data in the same way.
Method 2: Slave Scheduled Upload
For this method, the master broadcasts and sends information to the slave. After the slave receives the information from the master, it synchronizes the time, and then uploads regularly according to the time we set, avoiding simultaneous uploading of data, so as to avoid CCI.
Method 3: Slave Active Upload
The slave machine actively uploads, and the networking mode of the LoRa module itself with RSSI function is a relatively reliable active upload mode. This transmission method is to detect the RSSI signal strength in the environment when the slave needs to upload data. If the RSSI strength in the current environment is relatively high, wait for the RSSI value to become smaller before actively uploading. Whether the upload is successful, the master will give feedback to the slave to decide whether to re-upload.
