Flexible filter bank based spectrum sensing and waveform processing for mission critical communications

In this paper we consider the broadband-narrowband coexistence scenario where the unused spectral gaps in the professional mobile radio (PMR) frequency band are used for broadband data communications. Spectrally confined filter bank based multicarrier (FBMC) waveform is applied for broadband transmission in order to minimize the interference leakage between the new broadband system and the legacy narrowband system. Fast convolution filter banks (FC-FBs) are used for flexible waveform processing both on the transmitter and the receiver sides. Furthermore, subband energy detection based methods utilizing FC-FBs are proposed for robust spectrum sensing of the legacy PMR signals of the terrestrial trunked radio (TETRA) family. The main idea in this study is to observe the spectral variability due to primary transmissions by dividing the sensing frequency band into relatively narrow subbands and then comparing the subband energies. The flexibility of FC-FB makes it possible to optimize the broadband waveform processing and spectrum sensing filter characteristics independently. Our proposed maximum and minimum subband energy based approach shows improved robustness to the uncertainty of noise, considering also the interference due to power leakage effects.