A method of determining a network parameter in a telecommunication system is disclosed. The system has a coverage area including at least two sub-areas, and also includes a User Equipment (UE) being in idle mode and being registered in at least two of these sub-areas. According to the present disclosure, a network node in the system receives from the UE a time information relating to the time periods the UE has been present in each of the at least two sub-areas it is registered in, respectively, and then this time information is utilized to determine a network parameter in the system.