## 1 Introduction
By using channel measuring rather than previously collected data, it can alleviate the drawback of key extraction. In [8], the RSA Algorithm and Constellation Encryption Design Based on Chaotic Sequence are introduced. The main goal of this technique is to construct a large number of highly secure encrypted sequences by efficiently combining chaotic sequences and RSA. The precise procedure is to communicate system parameters using the asymmetric RSA algorithm, create a secret sequence using the chaotic sequence's initial value sensitivity, and then encrypt the original sequence using the secret sequence. There are many physical layer encryption (PLE) schemes applied to the IoT networks. The key idea of PLE is to exploit the randomness of channels to degrade the received signal quality at the eavesdropper. Three new PLE techniques complement IoT features well and have a lot of promise for use in the future [9]. The noise aggregation and self-encryption [10; 11], fountain-coding based secure transmission [12; 13; 14; 15; 16; 17; 18] and Self-Encryption via constellation rotation [19; 20; 21; 22; 23; 24; 25; 26; 27; 28] are different examples of the PLE used in the IoT. OFDM, which has a high spectral efficiency and easy implementation, is used as a self-encryption via the constellation rotation principal. It has been incorporated into different protocols including IEEE 802.11 a/g/n, IEEE 802.16 WiMAX, the frequency domain [29; 30; 31], data scrambling in the time domain [32], rotation of the modulation symbols [33], and noise-enhanced constellation rotation [34; 35] for many of these reasons. Research has looked at using PLE, such as constellation scrambling, to increase the security level of OFDM. The majority of IEEE 802.11 Wi-Fi amendments, including 802.11 a, 802.11 g, 802.11 ac, 802.11 n, 802.11 ax, and 802.11 p (the protocol used in vehicle networks) [36; 37; 38], have embraced OFDM. High-speed Wi-Fi has recently emerged as a viable option for IoT devices due to its compatibility with existing networks. As a result, IEEE 802.11 ah [39] has been proposed as a new Wi-Fi standard for IoT systems. The basic physical layer structure of the transceiver adheres to the conventional design to maintain backward compatibility with access points and clients that support the OFDM physical layer structure despite the fact that this standard offers a number of new and enhanced features to improve power and spectral efficiency [39]. IoT applications can be categorized into two groups: low data rate applications like smart meters and high data rate applications like multimedia IoT. A number of IoT communication protocols, including NB-IoT and 802.11 ah, rely on OFDM as an effective multiple access approach to support the successful operation of high data rate IoT applications [40]. One key feature of IoT systems is their ability to support a variety of legacy and emerging communication protocols, including SigFox, cellular technology, 6 LoWPAN (IPv6 Low-power Wireless Personal Area Networks (LoWPAN)), BLE (Bluetooth low energy), ZigBee, RFID (radio frequency identification), NFC (near-field communication), Z-Wave, NB-IoT (Narrow Band IoT), LoRaWAN (long-range wide area network), and Wi-SUN (wireless smart utility network) [41]. There are currently eight major categories of PLS schemes that concentrate on data confidentiality for OFDM systems: channel-based encryption [42], phase encryption [43], permutation [44; 45], artificial noise (AN) and artificial fast fading (AFF) [46; 47], preamble modulation [48] (Figure 1), power allocation [49], Peak-to-Average Power Reduction (PAPR) encryption [50], the frequency domain [51] and the time domain [52] are two other areas in which these techniques can be used. Chaos-based physical layer encryption is used in OFDM-based IoT systems to achieve the phase randomization and constellation rotation in the transmitted image in both spatial and transformation domains. An investigation of the Fractional Fourier Transform (FrFT) domains is introduced in [48].