Out-of-band emission suppression techniques based on a generalized OFDM framework

Abstract

Orthogonal frequency division multiplexing (OFDM)-based cognitive radio (CR) systems suffer from the large out-of-band emission (OOBE) that may interfere with other users. Since most existing OFDM OOBE suppression schemes are derived on the base of an original OFDM system without any other scheme, we first propose a generalized OFDM framework that is capable of describing these schemes no matter whether any one or more of the schemes is applied. Then, according to the place where these schemes are implemented in our framework, they are classified into three groups, namely symbol mapping techniques, precoding techniques, and time-domain techniques. Finally, based on the proposed framework, we propose three new schemes by combining a precoding scheme named singular value decomposition (SVD) precoding with three other schemes from the three groups, namely spectral precoding, N-continuous symbol mapping, and filtering. Numerical results show the power spectral density (PSD), peak-to-average power ratio (PAPR), and bit error rate (BER) performances of the three proposed schemes. Since the individual schemes have complementary characteristics, the three proposed combined schemes are constructed to maintain the merits and avoid the drawbacks of the individual schemes involved. Thus, it is demonstrated that the proposed framework can be employed to develop other new combined OOBE suppression schemes tailoring to some specific practical needs.

Spectrally encapsulated OFDM: Vectorized structure with minimal complexity

“…In Figure 6, when r = 2, that is, when the length of the filter is 3, the additional calculation amount is 10% (0.1) or less regardless of the IFFT length N , indicating that OoBE can be completely blocked. In the case of [29], which is a combination of existing methods, it can be seen that the proposed method is better the method that requires more than 200% of the computational amount compared to the original method.…”

Enhanced OFDM for fragmented spectrum use in 5G systems

“…However, the normalisation factor T u has to be replaced by T s to model the time extension. Figure 1 depicts the reference block diagram of enhanced OFDM schemes [27]. Therefore, it will be used to illustrate the suppression techniques in the next section.…”

“…Figure depicts the reference block diagram of enhanced OFDM schemes . Therefore, it will be used to illustrate the suppression techniques in the next section.…”

Characterization of GFDM Signal with Timing Offset, CFO, Non-Linearity, and PN

“…Therefore, the use of OFDM for 5G needs to be reconsidered. [4,5] Generalized frequency division multiplexing (GFDM) [6] is a promising candidate waveform for 5G. In this paper, we consider the GFDM waveform, which is based on the modulation of independent blocks and offers a highly flexible time-frequency structure.…”