A computer implemented method for analyzing operation of a cell of a communications network includes collecting data with measurement samples of signal level performance indicators from multiple cells of the communications network; calculating a characteristic value for a signal level performance indicator for a first cell type based on the collected data, wherein a part of the best measurement samples of the signal level performance indicator of the first cell type are taken into account in the calculation of the characteristic value; calculating a difference between the calculated characteristic value and a measurement sample of signal level performance indicator of a first cell of the first cell type; and providing output information indicating that an antenna system of the first cell is operating incorrectly in response to detecting that the calculated difference is greater than a preset threshold.