## 1 Introduction
Another significant advantage of the model is the reduction in complexity involved in classical channel modelling by halving the required number of real random variables [17]. The method has also been used to optimize PD gain with dual-polarized antennas [18]. However, the model has not been used to evaluate the performance of M2M communication. Rotating Polarization Wave (RPW) is a newly emerging LPWAN that provides highly reliable M2M communication. Since RPW is a nascent technology, it has not been widely discussed in literature. A prototype was developed, and its performance was experimentally evaluated [19]. However, there is no commercial module available. Providing deterministic communication in a highly disruptive environment is the hallmark of the RPW communication. When transmitters and receivers are fixed as in a typical industrial environment, the power of regular reflected waves is significantly higher than the irregular reflected waves even if there is no Line-of-Sight (LoS) available between the transmitter and the receiver. These waves can be handled as a single direct wave in classical mobile radio environment [20]. The received signal polarization can be adaptively controlled by slowly rotating the polarization of transmitted signal, such that the message can be received at an arbitrary number of polarization angles. Theoretically, the received RPW signal is 10 dB stronger compared to the uni-polarized signal. The field tests in industrial environment conducted by [PERSON] [20] have demonstrated higher received signal strength (RSS) and improved error performance. The existing method of RPW employs BPSK modulation that offers high reliability with a limited available bandwidth. Because of simple demodulation and minimum channel estimation requirement, its performance is superior to other modulation schemes in real-time applications. Since RPW is a PD technique, compact and power efficient base stations and mobile stations capable of RPW communication can be realized. Therefore, RPW communication is an attractive unification of efficient modulation and diversity techniques. Another useful feature of RPW is combining the strengths of PD and circular polarized (CP) systems. PD systems are often adopted in multipath environment because of their simple transmit and receive antenna structures. CP systems perform better than linear-polarized (LP) systems in cluttered propagation environment [13]. Such environments are formed by several flat surfaces like buildings, internal walls, and metallic structures. Another advantage of CP is a low delay-spread, that can mitigate jitter or delay variation in the received signal. RPW signal physically resembles the LP signal at carrier frequency, \(\omega_{c}\); however, this LP signal is rotated at an angular frequency \(\omega_{r}\) that is much lower than \(\omega_{c}\). In fact, RPW is generated by transmitting two baseband signals of frequency \(\omega_{r}\) having a phase difference of \(\pi/2\) through a dual linear polarized antenna operating on ISM carrier frequency \(\omega_{c}\). Hence RPW combines the spatial characteristics of CP and PD to offer an increased link reliability for a highly reliable M2M communication. Figure 1 shows a comparison between RPW and other forms of polarization at carrier frequency. For illustrative purpose, \(\omega_{c}=40\pi\) rad/s, while \(\omega_{r}\) for RPW is taken to be as low as \(2\pi\) rad/s. The horizontal and vertical polarizations are denoted by \(E_{x}\) and \(E_{y}\) with amplitudes \(E_{ox}\) and \(E_{oy}\) respectively. Existing prototype of RPW transceiver operates on Sub-Gigahertz ISM band and offers a data rate of 125 kbps using RP-BPSK modulation [20] which is comparable to NB-IoT and more than double the data rate of LoRa. However, this data rate is much lower that the data rate of Wi-Fi HaLow mentioned above. RPW can overcome this data rate limitation if  
Figure 1: Comparison of RPW with conventional forms of polarization. higher order modulations are being used.