## 1 Introduction
Each element in the RIS can be programmedto configure its reflection and transmission properties based on the desired application requirements or network conditions [7; 13; 14; 15]. The RIS-aided MIMO system presents many advantages compared to conventional MIMO systems that do not integrate RIS. RIS significantly enhances EE by leveraging passive elements without requiring active radio frequency (RF) chains. Unlike traditional MIMO systems, which are limited to performing beamforming at the transmitter, the RIS-aided MIMO system supports joint beamforming at both the transmitter and the RIS. This capability improves signal quality and allows for the dynamic reconfiguration of the communication environment. Furthermore, while conventional MIMO systems can suffer from blockage and exhibit poor performance in non-line-of-sight (NLoS) conditions, the RIS-aided MIMO system excels in these challenging scenarios. Additionally, conventional MIMO systems rely on fully active antenna arrays, which can lead to increased hardware costs and complexity. In contrast, the integration of RIS streamlines these aspects, offering a more cost-effective and efficient solution for B5G. RIS offers a myriad of advantages that address critical challenges faced by next-generation systems. By intelligently controlling the phase shifts of the reflected waves, RIS can steer, focus, amplify, or attenuate the signals, enabling it to shape the wireless propagation environment effectively. RIS can reshape electromagnetic wavefronts, effectively mitigating path loss and shadowing and improving signal coverage in challenging environments. RIS can selectively reflect and cancel interfering signals, reducing overall interference levels. RIS can adapt its real-time configuration, responding to variations in the wireless channel and user locations. Because RIS is a passive technology, passive RIS elements consume negligible power compared to active radio transmitters and amplifiers, resulting in a more energy-efficient and environmentally friendly alternative for future 6G networks. Leveraging mmWave for unmanned aerial vehicle (UAV) communications can meet the data rate requirements of future networks; however, obstacles like tall buildings and trees often block line-of-sight (LoS) connections. RIS can assist in improving the quality of UAV-integrated mmWave communication [16]. RIS technology finds utility in high-speed trains (HST), where mmWave waves are pivotal in delivering a superior experience for highly mobile passengers [17]. RIS complements other advanced technologies such as M-MIMO [18; 19], mmWave frequency communications [20; 21], NOMA [22; 23], and integrated sensing and communication [24] to achieve unprecedented levels of performance to support a diverse range of applications envisioned for the B5G and 6G era. One of the significant research challenges in integrating RIS with potential technologies such as M-MIMO and mmWave frequency communications is channel modeling. Few studies have discussed RIS channel modeling for mmWave M-MIMO systems. In [25; 26], the authors introduced the SimRIS simulation tool, which provides a system and channel model for RIS according to 3 GPP 5G standards. These works emphasize channel modeling but fail to include practical performance assessments like ABER. Ref. [27] conducted an ABER analysis and quantified performance comparisons between 28 GHz and 73 GHz frequencies in RIS-assisted MIMO configurations for both InH and UMi models. However, it did not adequately examine the influence of the size of the RIS array on system performance at mmWave frequencies. Studies conducted thus far have not investigated the effects of discrete versus continuous phase resolution of RIS on ABER performance. Ref. [27] also did not examine multi-user MIMO setups. Table 1 outlines the differences between our proposed framework and prior SimRIS implementations [25; 26; 27; 28]. Here, the proposed framework and previous works indicate included factors with a tick mark and excluded factors with a cross.