# Palm Date Leaf Clipping: A New Method to Reduce PAPR in OFDM Systems
## 1 Introduction  
Orthogonal frequency division multiplexing (OFDM) is the fundamental technology employed in Wi-Fi, Worldwide Interoperability for Microwave Access (WiMAX), and 4G wireless communication systems such as Long-Term Evolution (LTE), Long-Term Evolution Advanced (LTE-A), and 5G [1; 2; 3]. However, its main deficiency is its relatively high peak-to-average power ratio (PAPR) [4; 5]. Several methods have been proposed to reduce the high PAPR of OFDM systems. For example, the Selective Mapping Technique (SLM) [6] is a promising technique to reduce the PAPR. Its principle consists of generating U alternative sequences and choosing the one that has the minimum PAPR value [7; 8]. Several improvements and variants of the SLM method have been proposed to reduce its complexity [8] by avoiding side information [9; 10]. Another technique called Partial Transmit Sequences (PTS) was proposed in [11]. The basic idea of PTS is to divide the original OFDM signal into some sub-blocks. Each sub-block is weighted by a given value to obtain many candidate signals with a lower PAPR value [12; 13; 14]. It is known that PTS is a popular method used to reduce PAPR in OFDM systems. Several variants of PTS have been proposed, such as Hybrid Genetic Algorithm Partial Transmit Sequences (HGA-PTS) [15], Particle Swarm Optimization Partial Transmit Sequences (PSO-PTS) [16], and Genetic Algorithm Partial Transmit Sequences (GA-PTS) [17]. In [18], Tone Injection (TI) is used to reduce PAPR with the insertion of a tone. However, it requires a certain amount of computational complexity to find the right tone to inject into the signal in order to reduce its PAPR. Tone Reservation (TR), which was proposed in [19], reverses a small number ofsubcarriers to create a signal that can cancel the high peaks in the original signal on the transmitter side. However, the effectiveness of this method on PAPR reduction depends on the number of reserved tones and their positions. Therefore, it requires a high computational complexity to find the reserved positions. In addition, TR requires additional information, also called side information, which reduces the data rate. The channel coding-based technique is not only used for correcting the received errors, but also to reduce the PAPR values of OFDM systems. The main idea behind this is to select a code word that produces a good PAPR reduction [20; 21]. However, this method has high computational complexity when finding the best code word to reduce PAPR values and allow the received errors to be corrected. Companding (compressor/expander) techniques are generally used in wave domains. They are also used to reduce PAPR values by compressing the OFDM signal at the transmitter end; the receiver expands the signal. The main inconvenience of this technique is the signal degradation quality, which increases the Bit Error Rate. Mu-law and A-law are the most common companding techniques used to reduce PAPR, and often these methods are combined with other methods such as coding [22; 23] or SLM [24] in order to improve signal quality. Clipping is the most basic method used to reduce the PAPR value. The main idea is to truncate the peak of the OFDM signal below a threshold level [25]. Thanks to its simplicity, many clipping techniques are used to reduce the PAPR, including Classical Clipping (CC) [26], Smooth Clipping (SC) [27], Heavyside Clipping (HC) [28], and Deep Clipping (DC) [29]. Recently, hybrid techniques have become the most commonly used methods. They are based on a combination of two or three techniques used to obtain good results in terms of PAPR, Bit Error Rate (BER), complexity, and transmission rate [30; 31; 32; 33; 34; 35]. In this paper, we present a new Palm date leaf Clipping (PC) method based on the hyperbolic cosine function to reduce the PAPR in OFDM systems. The PC method is inspired by the shape of palm date leaves on a massive stem. Their form allows them to resist both interference from other leaves and twisting that can be caused by the wind.