The introductory chapter leads the way towards the main steps of the present master’s thesis, and its scope is to theoretically address the aim of this thesis, which is to deal with the problems of huge propagation loss and the quite expected laws of attenuation and absorption. In addition, it encircles the study over the THz signaling as well as the communication systems, their foundations, and not only their linear and optics theory but also their utilization in nowadays. The second chapter examines the literature concerning the capacity of MIMO systems. Apart from that, it provides information about MIMO channel systems and their efficiency, in order to justify its usage in this particular thesis. The third chapter is concerned about the system channel models and attenuation. Besides that, it introduces the basic physical variable, which is the K-factor, helping with the modeling of these channels, among other ones. The end of this chapter reveals how the atmospheric factors, such as attenuation, re-radiation, spreading, climate, govern telecommunications. The fourth chapter presents the results of a MIMO experimental simulation, created in the MATLAB environment. Furthermore, it compares the beamforming and multiplexing MIMO capacity of two distinct models: the Hosseini’s and the Simplified one. Finally, it outlines state-of-the-art developments relevant to THz communications.