Spectral Encapsulation to Block the Out-of-Band Emission of OFDM Signals for Future Communications

Abstract

The next 6th generation (6G) mobile communication technologies should solve the out-of-band emission problem of cyclic prefix (CP) orthogonal frequency division multiplexing (OFDM) that the 4th generation technology did not solve in order to use frequency resources efficiently. In this study, we propose the spectral encapsulation (SE) that shapes the spectrum of OFDM signals. We also derive the orthogonalizing matrix and thoroughly analyze its characteristic. Since vector (v) SE-OFDM is a spectral shaping technique based on zero insertion without using any long filter, it can be applied to even short OFDM symbols. We build the precoder with the accurate orthogonal matrix and show that it has perfect blocking at the frequency bandwidth boundaries. Since the information transmission part of the proposed vSE-OFDM is the same as the CP-OFDM, it maintains the bit error rate (BER) performance of CP-OFDM as it is, and the complexity can be significantly improved because it can be implemented using IFFT.