## 1 Introduction  
Wireless communication systems have offered outstanding achievements and opportunities for applications and services in information and communication technologies. In the upcoming 5G era, the future cellular networks should be envisioned to support efficient and flexible resource management and provide customized services to meet the service-specific high performance requirements in a variety of use cases. New higher frequency bands are also allocated for employment in future cellular networks and in order to support the new challenging demands of the users that generally need more bandwidth. The propagation channel plays one of the most crucial roles in order to provide reliable communications, high availability systems and also determine efficiently the system dimensioning (number of antennas, relays, base stations, gateways etc.). The future cellular architectures are becoming more complex and the performance of different types of links in multiuser, multi-cells, small cells, and relaying scenarios that are changing topology very frequently should be evaluated. Moreover,the upcoming 5G communication systems are planned to accommodate various diverse services and satisfying their stringent performance requirements in terms of connectivity, mobility, reliability, latency, peak data rate, and coverage will impose unprecedented challenges to 5G network design and performance optimization. This will be achieved with the 5G terminology of networks slicing. To this end, the link adaptation considering the spatial-temporal time varying propagation channel in the various cells that provide different services will remain one of the most important problems for the optimum design of the future satellite systems, including also their synergetic architectures. Regarding the current status of the propagation research, there are numerous measurement campaigns in various environments and different frequencies and also many theoretical approaches for statistical channel models [1; 2; 3; 4; 5; 6]. Nevertheless in experimental campaigns have not studied the temporal variation of the large scale fading that is due to the movement of the local environment scatterers, especially for millimeter wave frequencies. Wireless channel models consist of an indispensable tool for the efficient design and testing of modern wireless communication systems. The emerging need for higher data payloads demands more sophisticated exploitation of the channel's capabilities, which in turn imposes further requirements for the development and application of more advanced channel models. In this paper we focus on large scale fading or shadowing. This kind of fading, that is mainly caused by obstructions, has been commonly accepted to be modeled as a lognormal random variable for outdoor [7] and indoor environments [8]. Whereas shadowing is a purely spatial phenomenon for a specific configuration of the propagation environment, temporal variability is induced mainly by the user's mobility but also by moving obstructions. The impact of shadowing caused by moving obstructions, even for fixed locations, may have an important role in the system's performance, especially in densely populated environments. In this context, shadowing can be considered as a spatio-temporal process, i.e., a random field evolving in time. Moreover, the impact of shadowing correlation is considered nowadays as a key parameter to account for in order to obtain more realistic channel model frameworks. Taking into account the correlation structure of the shadowing field impels shadowing modeling one step further towards reality, as shadowing correlation significantly affects handover behavior, interference power and the performance of diversity schemes [9].