A base station in a cellular radio network and user equipment assigned to a cell are linked by an air interface for communication on a respective communication channel in a communication band. The same communication band is common to at least one of the cells and to the user equipment on the respective communication channel of a cell. A jamming transmitter is detected by decoding a cell, by way of successful reading of control information of the cell, detecting a wideband power parameter representative of the communication band, and detecting a channel power parameter representative for a part of the communication band that is a communication channel. A narrowband jamming transmitter is indicated in the case that decoding of the cell failed, the wideband power parameter is not above a first threshold, and the channel power parameter is above a second threshold.