Abstract: A method includes collecting data related to a key performance indicator (KPI) for a cell in a mobile network. The method includes aggregating the collected data for the KPI into a plurality of groups, wherein a first group of the plurality of groups comprises values of the KPI during a time period in a first day, a second group of the plurality of groups comprises values of the KPI during the time period in a second day preceding the first day, and a third group of the plurality of groups comprises values of the KPI during the time period in a third day preceding the second day. The method includes determining whether the cell is a sleeping cell based on a comparison of the first, second and third groups. The method includes labelling the cell as sleeping in response to a determination that the cell is sleeping.