## 1 Introduction  
The demand for novel wireless communication techniques is at an all-time high to meet capacity targets and envision a new era for 5G and beyond technologies. In this regard, some promising fifth generation (5G) techniques have been acknowledged, such as non-orthogonal multiple access (NOMA) [1, 2, 3], interleave division multiple access (IDMA) [4, 5], sparse code multiple access (SCMA) [6], low-density spreading multiple access (LDSMA) [7], pattern division multiple access (PDMA) [8], massive multiple input and multiple output (massive MIMO) [9], cooperative communication [10], and so on. Each of the above 5G techniques is unique in its own right and is classified based on a diverse range of quality of service, user fairness, spectral efficiency, low latency, and a diverse degree of freedom. The power domain NOMA (PD-NOMA) is a 5G wireless technique that incorporates all of the above properties into a single package. In PD-NOMA [11], users around the 5G base-station (gNodeB) are served at the same frequency and time but with varying powers. Considering the downlink PD-NOMA, the superposition coding (SC) is performed at the gNodeB and SIC schemes on the serving user's side. After decoding an undesirable user's signal, the SIC technique [12, 13] is used to eliminate its effect by subtracting it from the received signal. The PD-NOMA system has been broadly investigated for a maximum of two users in [14; 15]. To achieve the capacity goals in congested NOMA networks, some recent work has been proposed in [16; 17] that effectively addresses the multi-user PD-NOMA systems. The overall performance of PD-NOMA is thoroughly dependent on power allocation (PA) and user clustering techniques. The PA is established through a distance-based power allocation algorithm (DBPA) in [16; 18], whereby the near-user is allocated a lower power and the far-user a higher power. User clustering techniques (Best with Best and Best with Poor models) were proposed by [PERSON] et al. in [19; 20]. In the Best with Best model, users having the same channel conditions are grouped into the same cluster, while the Best with Poor model has users in descending order of their channel gains. Orthogonal and non-orthogonal spreading codes such as(Pseudo-Noise (PN) and Walsh codes are used to distinguish equidistant users from the gNodeB in multi-cluster PD-NOMA [18]. As a result, the inter-cluster interference is overcome with the help of spreading codes and intra-cluster interference over the SIC technique. Consider the practical 5G micro-cells with foliage or vegetation close to the gNodeB, which operates using millimeter wave (mmWave) communication at gigahertz (GHz) frequencies. At such higher frequencies, the mmWave signals are obstructed by small particles. As a result, the signal is attenuated more, which leads to substantial path losses. For the sake of simplicity, we include the foliage part in our simulation because it weakens the signal but does not totally block it, as do buildings wall and other barriers. To address such path loss issues, multiple advanced techniques have been introduced, such as unmanned-aerial-vehicle (UAV) assisted communication [21], re-configurable intelligent surfaces (RIS) or meta-surfaces [22; 23] and cooperative communication [24]. UAVs mostly help in providing a direct line-of-sight (DLOS) path between transmitter and receiver where chances of signal blockage and attenuation are reduced effectively. The RIS is installed on the surfaces of building walls to direct the phase-shifted and amplified version of the incident signal with negligible attenuation [25]. To shift the trend in mmWave communication from using probabilistic radio channels to deterministic channel modeling, an efficient radio technique called Ray-tracing [26] is being used nowadays. Ray tracing was first introduced in the 1990s [27] but is currently attracting the attention of most researchers due to its reliability in high-frequency communication.