New multiple‐input multiple‐output‐based filter bank multicarrier structure for cognitive radio networks

Cognitive radio (CR) has been proposed for spectral efficiency improvement while avoiding interference with licensed users. The offset quadrature amplitude modulation‐based filter bank multicarrier (OQAM‐FBMC) modulation is a promising candidate for CR‐based systems. Although it behaves better in many aspects than orthogonal frequency division multiplexing (OFDM), the application of some techniques with FBMC becomes more challenging due to the imaginary interference, as in the case of multiple‐input multiple‐output (MIMO) technique. Here, the authors first propose a new MIMO‐based FBMC transceiver structure for CR systems. The proposed structure is based on QAM transmission to handle the interference presented in conventional OQAM‐FBMC systems. The authors also introduce two different methods to satisfy the orthogonality conditions and cancel the residual interference in QAM‐FBMC systems. Both methods are based on discrete cosine transform (DCT) to achieve superior spectrum confinement and hence better spectral efficiency. Moreover, the authors present a resource allocation algorithm for the proposed structure. Simulation results demonstrate that the proposed structure outperforms the conventional FBMC‐based MIMO techniques in terms of bit error rate (BER) and computational complexity. The results also show that the spectral efficiency of the proposed structure could be further improved by applying the proposed resource allocation algorithm.