# A Hybrid PAPR Reduction Method Based on SLM and Multi-Data Block PTS for FBMC/OQAM Systems
## 1 Introduction  
Multicarrier technology is now widely used in various wireless communication systems [1; 2; 3]. Recently, many researchers have given a great deal of attention to the filter bank multicarrier (FBMC) employing the offset quadrature amplitude modulation (OQAM) technique [4; 5; 6], since it is considered as a potential alternative to the best-known orthogonal frequency division multiplexing (OFDM) scheme for 5G wireless communication systems [7; 8; 9; 10]. FBMC/OQAM, without inserting cyclic prefix, can overcome the drawbacks of OFDM. The FBMC/OQAM utilizes an inverse fast fourier transform/fast fourier transform (IFFT/FFT)-based filter bank for time-frequency-localized (TFL) pulse shaping, and interleaves OQAM symbols on subcarriers [11]. Although FBMC/OQAM is more complex than cyclic prefix (CP)-OFDM, it can provide higher robustness against carrier frequency offsets, significantly reduce out-of-band emissions, and have better spectrum in bandwidth-sensitive systems [12]. However, since FBMC/OQAM is a multi-carrier transmission technology, it has high peak-to-average power ratio (PAPR). In order to make use of FBMC/OQAM technical characteristics, it is very necessary to conduct the study of how to reduce the PAPR of FBMC/OQAM systems. In the past decade, the researchers have proposed a number of PAPR reduction methods of OFDM signals, such as the selective mapping (SLM) [13], partial transmit sequence (PTS) [14], tone reservation (TR) scheme [15], active constellation extension (ACE) [16] and so on. Considering that there is a certain similarity between the OFDM technology and FBMC/OQAM technology, it is natural for researchers to study how to use the PAPR reduction methods of OFDM signals to reduce the PAPR of FBMC/OQAM signals. However, there is a difference between these two signals, that is, the signals in the OFDM system are independent, while the FBMC/OQAM signals overlap with the adjacent data block signal. Hence, the conventional methods for OFDM cannot be effectively employed for FBMC/OQAM. Recently, many researchers have conducted the effective PAPR reduction studies for FBMC/OQAM systems. Some modified schemes have been proposed in [17; 18; 19; 20; 21; 22; 23; 24]. In [17; 18; 19], the authors proposed some modified SLM-based PAPR reduction schemes. [PERSON] et al. [17] proposed a multi block SLM method. [PERSON] et al. [18] proposed a low-latency trellis-based SLM method. [PERSON] et al. [19] proposed a half complexity of trellis-based SLM method. These SLM-based methods all consider the nature of overlapped FBMC/OQAM symbols, and have better performances than conventional SLM-based methods. In [20], an alternative signal (AS) generation scheme for PAPR reduction was proposed to reduce the PAPR of FBMC/OQAM signals, and the method considered the overlapped data blocks to obtain the optimal phase rotation sequence. Besides, two segmental-based PTS methods have been proposed in [21; 22]. [PERSON] et al. [21] proposed a segmental PTS (S-PTS), where the overlapped FBMC/OQAM signals were divided into several segments. [PERSON] et al. [22] presented a segment-based optimization scheme. In the optimized S-PTS scheme, the PAPR of each data block is first minimized. Then, each segment is optimized based on the previous results. The simulations demonstrated that both the two modified PTS-based methods can reduce the PAPR of FBMC/OQAM signals effectively. [PERSON] et al. [23] proposed a multi block tone reservation (MB-TR) scheme. The proposed scheme considered the adjacent data blocks to obtain the optimal clipping noise. In [24], the authors proposed a new type of FBMC/OQAM to achieve a low PAPR without the use of any PAPR reduction process. Moreover, some hybrid PAPR reduction schemes have also been proposed [25; 26; 27; 28]. [PERSON] et al. [25] proposed a hybrid scheme based on SLM and TR methods. In [26], the authors combined TR and companding techniques to reduce the PAPR. The hybrid methods can give better PAPR reduction performance than single method.