OFDM-based overlay cognitive radios with improved spectral leakage suppression for future generation communications

Dynamic spectrum sharing with minimum spectrum leakage is actively considered to meet the requirements of future generation networks which are expected to support huge amount of data traffic beyond 2020 with limited spectrum. In this paper, we propose a spectral leakage suppression technique for orthogonal frequency division multiplexing (OFDM)-based overlay cognitive radio (CR). We apply the Bohman window-based pulse shaping, which has a high sidelobe fall rate and low highest sidelobe power, to the edge subcarriers rather than the entire waveform of the secondary users (SUs) utilized spectrum. We allocate antipodal symbol pairs to the Bohman-windowed subcarriers to overcome the problem of a slightly large 3-dB bandwidth of the Bohman window. The power spectral density (PSD) of the proposed scheme rolls off asymptotically as of f^-8, as compared to the current state-of-the-art where the sidelobe rolls off asymptotically as of f^-4. Simulation results show improved bit-error-rate (BER) performances of the primary user (PU) and the SU in the proposed scheme due to improved spectral leakage suppression. The practicality of the proposed scheme is validated by field programmable gate array (FPGA) prototyping.