DFT-Spread WR-OCDM Communication System for the Reductions of OOB and PAPR

Abstract

Orthogonal chirp division multiplexing (OCDM) system has been considered as one candidate for the nextgeneration 6G cellular system that will support many new services and applications but will suffer from the sub-THz frequency band. It is anticipated that this will significantly harm the waveform orthogonality of conventional systems and lead to obnoxious intercarrier interference (ICI) and a very high propagation loss on information signals by introducing peak-to-average power ratio (PAPR). As a result, PAPR reduction is the most important aspect of 6G wireless communication system than 4G long-term evolution (LTE), 5G new radio (NR) schemes because it will use the Sub-THz frequency band which has a very high tendency toward propagation loss component. Therefore, spread spectrum technology termed as orthogonal chirp division multiplexing (OCDM) takes into account for the orthogonality of cyclically shifted quadratic chirp signals in order to increase spectral efficiency and reducing PAPR. The OCDM system, however, emits considerable out-of-band (OOB) power. To solve this problem, we suggest a new discrete Fourier transform (DFT)Spread Windowing and Restructuring (WR)-OCDM (DFT-Spread WR-OCDM) method for a suitably acceptable PAPR and OOB power emission reduction. In the system, the OOB power emissions are successfully reduced at the transmitter using time-domain windowing, and relatively shorter in window length is sufficient to satisfy the standard spectral mask. Comparing the proposed scheme to previous OFDM and OCDM systems, simulation findings show that this technique greatly reduces PAPR by about 2 dB and OOB power emission approximately by 64 dB and 70 dB. Additionally, we examine the bit error ratio (BER) performance using AWGN channel. This DFT-Spread WROCDM scheme performs almost similar results as compared to the conventional OFDM, OCDM, and WR-OCDM systems.