An example device comprising: a monitor to detect cellular signals; and a processor to: calculate frequencies of interferences produced due to the detected cellular signals; estimate energy levels of the interferences at the calculated frequencies; and determine available frequencies based on the calculated frequencies and the estimated energy levels to avoid transmissions on a plurality of frequency bands associated with a second order harmonic distortion, a third order harmonic distortion, a second order inter-modulation distortion (IMD 2), or a third order inter-modulation distortion (IMD 3).