Waveform Design and Performance Analysis of DFT-Spread WR-OCDM System for PAPR and OOBE Reduction

Recently, orthogonal chirp division multiplexing (OCDM) system has been proposed as an alternative waveform contender for next-generation wireless communication systems. OCDM is a spread spectrum (SS) technique that uses a set of orthogonal chirps as carriers for maximizing the spectral efficiency (SE). However, like OFDM, the OCDM system suffers due to its high out-of-band emissions (OOBE) and high peak-to-average power ratio (PAPR). These lead to adjacent channel interference (ACI) and signal degradation in transmissions. To solve these serious issues, we proposed an advanced OCDM system for reducing OOBE and PAPR without degrading communication quality. The proposed scheme combines discrete Fourier transform (DFT) precoding and time-domain windowing techniques along with the OCDM system. By DFT operation, the energy of each chirp of the OCDM system spreads over all the chirps. Hence, PAPR of the OCDM system is reduced. On the other hand, to reduce the OOBE of OCDM system, time-domain windowing is applied at the transmitter side. Simulation results verify that the proposed scheme reduces PAPR at the CCDF level of 1 × 10–
³
by 2.43 dB compared to the conventional OFDM, OCDM, and windowing and restructuring (WR)-OCDM systems. In addition, the proposed scheme reduces OOBE by a maximum of 67 dB compared to the OFDM and OCDM systems. Moreover, the bit error rate (BER) performance is evaluated for different modulation formats, such as 4-QAM, 16-QAM, and 64-QAM over the AWGN channel. Our proposed system shows similar BER performance to the conventional multicarrier systems.