In the ever-evolving landscape of wireless communication, the deployment of millimeter-wave (mmWave) technology has emerged as a game-changer for indoor environments. As the demand for high-speed, low-latency connectivity continues to surge, especially in densely populated areas, mmWave access point deployment has gained prominence due to its ability to deliver unprecedented data rates thanks to the available wide bandwidths. However, mmWave signals are more prone to blockage by objects and their coverage area is small. Therefore the deployment of mmWave technology is preferred for the cases where a high number of users require high data rates in an environment free of blockages. Indoor dense spaces (IDSs) refer to compact indoor environments with many objects and users within. The main examples of IDS are airplane cabins and high-speed train wagons. On the one hand, due to the dense user existence, IDSs can benefit from mmWave connectivity. On the other hand, the dense blockage in the environment due to the seats and humans would cause significant propagation losses.  

In this thesis, we investigate the potential of mmWave communications in IDSs. As a first step, we investigate the mmWave signal propagation in IDSs by using ray-tracing (RT) simulations. We provide large-scale fading and spatio-temporal fading characteristics considering the 28, 39, and 60 GHz bands. The results demonstrate that the dielectric characteristics of the environment provide considerable differences in signal propagation, while the geometry and the user denseness are not influential. Furthermore, the coverage area of the IDS is half of the coverage area of the indoor office, demonstrating the severe attenuation in IDS. After analyzing the signal propagation, we investigate the optimal AP deployment for IDSs by minimizing the number of deployed APs while guaranteeing the data rate requirements of the users in the environment. The proposed algorithm jointly allocates time and power resources and selects the optimal locations of the APs considering different levels of AP cooperation. This study shows that R-ZF with C-JT outperforms MRT and NC-JT, providing higher data rates to UEs and reducing the total number of deployed APs. By using 10 times higher bandwidth in the mmWave band compared to sub-6GHz, we can guarantee 9 times higher data rates for users. Later, we investigate the potential of reconfigurable intelligent surfaces (RISs) in extending the coverage of a single mmWave access point. The results of this study show that the coverage area of a single AP can be extended four times by optimally placing the RISs.