A user equipment (UE) without service in a communication system measures the radio-frequency (RF) power in a bandwidth received by the UE on the possible downlink carriers in a frequency band that is supported by the UE. The bandwidth is typically the bandwidth of communication channels in the communication system. If the UE supports more than one frequency band, the UE may scan more than one of those frequency bands. The UE processes the measurement results with a noise-reducing enhancement technique, such as a median filter, and then examines the processed results for a particular spectral shape, e.g., a shape that corresponds to a cell signal.