## 1 Introduction  
Filter bank multicarrier with offset quadrature amplitude modulation (FBMC/OQAM) has attracted attention as a strong competitor of orthogonal frequency division multiplexing (OFDM) in 5G technologies [1]. Although OFDM systems are very efficient, their spectral efficiency deteriorates with the addition of a cyclic prefix (CP) and a high out-of-band emission caused by rectangular filtering [2]. However, FBMC/OQAM achieves better side-lobe suppression than some existing suppression methods in OFDM signals, with a moderate increase in complexity [3]. OFDM requires perfect carrier synchronization between different users to avoid interference in the uplink. However, FBMC separates different signal frequencies using pulse-shaping filters, which makes time synchronization unnecessary [1, 2]. Although FBMC has attractive merits, it also experiences a high peak-to-average power ratio (PAPR) caused by the inverse discrete Fourier transform (IDFT) at the transmitter.  
Conventional PAPR reduction schemes, such as discrete Fourier transform (DFT) spreading, clipping and filtering, partial transmit sequence (PTS), tone reservation (TR), and selective mapping (SLM), effectively reduce the PAPR but at the expense of high computational complexity, degraded spectral efficiency, and an increase in bit-error rate (BER) [4].  
Conventional methods reduce the peaks of each symbol block separately; however, in FBMC/OQAM, the symbol blocks overlap. Consequently, the PAPR reduction is marginal compared to OFDM. The authors in [5] proposed a tone reservation technique with sliding windows, where the sliding windows are overlapped to prevent out-of-window peak regrowth. PTS has been intensively studied [6; 7; 8; 9; 10; 11]; the authors in [6] combined PTS and TR techniques to reduce the peaks of FBMC signal segments. In [11], the authors proposed a method based on PTS, referred to as multi-block joint optimization with a dynamic programming algorithm.  
DFT spreading has gained popularity as a very efficient PAPR reduction scheme in OFDM systems, especially for uplink applications that require less power consumption. Unfortunately, this method does not achieve desirable results in FBMC signals. Earlier studies focused on exploiting the DFT spreading effect to improve PAPR reduction in FBMC by employing diverse techniques such as the identically time-shifted multicarrier (ITSM) condition, generalized DFT spreading (GDFT), pruned DFT, and pre-coding technique [12; 13; 14]. In [14], the authors proposed a method based on pruned DFT spreading that effectively reduced the PAPR, sacrificing the system's computational complexity.  
In this study, we propose a novel method for reducing PAPR in FBMC/OQAM by combining DFT spreading, satisfying the ITSM condition of the phase factors, and a modified PTS method that complies with the structure of FBMC/OQAM. In the modified PTS method, partitioning and searching for the candidate with the least PAPR are performed at the real and imaginary parts of the FBMC/OQAM, respectively. Furthermore, the overlapping of the previous symbol parts is considered while calculating the candidates' PAPR at each part.  
The remainder of this paper is organized as follows. Section 2 introduces the FBMC/OQAM signal structure with a concrete definition of PAPR. In Section 3, the proposed method is explained in detail. Finally, the simulation results and conclusion are presented in Sections 4 and 5, respectively.