This is not a language question, it is a technical one. User association is a fundamental and quite deep feature of cellular communications networks; if you don't know what it is already, either you don't need to, or you are a telecommumications engineering student and should ask one of your lecturers.

It stands for "Internet of Things", which are any devices or home appliances that have electronics that allow them to exchange data with computers.

How about Internet of Things?