Spectrum sensing of TETRA systems through timefrequency analysis

In a cognitive radio system where the primary user is a TDMA based system, spectrum sensing must be able to identify the occupation of both a frequency band and a time slot. Whereas this can be done by scanning each narrowband frequency channel in turns, we can also perform a wideband sampling of the transmitted signal, and identify simultaneously the occupied frequency bands and time slots by means of a time-frequency analysis. In this paper we propose the use of this approach, using a spectrogram, in order to sense the spectrum and determine the occupied channels of a TETRA system.