Ripple Window OFDM (RW-OFDM) System for Improvement of Spectrum Resource Utilization

Recently, various windowing techniques for reducing the high out-of-band (OOB) power of orthogonal frequency division multiplexing (OFDM) system have been actively studied. Spectrum resources can be used more efficiently when OOB power is reduced. In this paper, a ripple window OFDM (RW-OFDM) is proposed. This RW-OFDM uses a window with overshoot and ripple characteristics. This window can reduce the higher OOB power within a given window length. Simulation results show that this ripple window OFDM (RW-OFDM) system has similar peak-to-average power ratio (PAPR) characteristics and OOB power is very low compared with CP-OFDM system using conventional window. In additive white Gaussian noise (AWGN) environment, the performance of RW-OFDM is similar to that of conventional OFDM with cyclic prefix (CP-OFDM) system. In Rayleigh fading channel, RW-OFDM system using 4-ary quadrature amplitude modulation (4QAM) modulation has a performance difference of less than 1dB from CP-OFDM system at bit error rate (BER) of 10^−4. If a compensation for the ripple window is made in multipath channel environment, this performance degradation will be resolved.