Mi Max 3 ENG QCN
What is QCN file and its function in android device? QCN means qualcomm calibration network file.Basically QCN file built in all Samsung Galaxy smart phone and latest android mobile phone. QCN is the main and sensitive file of network, hidden in the deepest core of mobile phone internal memory file system (in efs folder, where all information of imei and baseband are saved).
What are QCN/EFS on Qualcomm Devices
QCN and EFS files contain cellphone manufacturer utility program which is used to edit many features of a modern smartphone. These files are hidden deep inside a phone firmware and are pretty hard to access or update them. However, these files hold special information such as IMEI numbers, wifi address and Bluetooth address keys. So in case you need to restore your device from any invalid or null IMEI problems, then you need to back up these files.