## 1 Introduction  
The use of mobile networks has been steadily increasing in recent decades. A service that began only for the benefit of conversations and audio content has been extended to include a variety of text message, web browsing, photos, and video files. Such applications require larger bandwidths serving more users, and higher channel capacities. The demand for more spectrum continues to rise also due to the requirements of available and reliable links and for serving developing applications such as internet of things, smart homes, and even smart cities [1].  
Due to the vast amount of bandwidth available in the extremely high frequencies [1], millimeter waves are being considered for the fifth generation of cellular communications [2; 3]. Bands within the mmW regime are allocated for this purpose.  
Recently, national and international committees have begun to write regulations regarding the utilization of new bands in the electromagnetic spectrum. The Federal Communications Commission (FCC) in the United States have made spectrum available for licensed use in the 28 GHz and 37-39 GHz bands. They have also recently designated the 64-71 GHz band for unlicensed use, which increases the total amount of unlicensed spectrum to 14 GHz. Table 1 summarizes the features of the different mmW bands allocated for the 5 th generation of cellular communications [4].  
In fact, there are already works studying the possibility to utilize spectrum even in the THz frequencies [5]. Designation of wireless links in millimeter waves requires consideration of the weather conditions, including fog and rain, which have an impact on its propagation in the atmosphere [6]. The effects expected to play a role on the mmW propagation are different than that influencing optical transmissions in infrared [7; 8].  
Due to increased propagation losses of millimeter waves over longer distances and in order to maintain cost-effective deployment of a 5G network, the mmW links will serve \"small cells\" [8; 9], covering limited distances. Besides the obvious general importance that this new implementation scheme has with regard to future practical deployment of a 5G network, this development is of special importance to our research, as it restricts and defines the expected distances over which our study is focused on.  
As a comparison, current systems use a \"macro-cell\" implementation in rural environments, with a base station radius of 1-20 km [10]. Urban environments favor a \"micro-cell\" implementation, with a base station covering between 100 m and a few kilometers [11].  
Our research focuses on absorptive as well as dispersive effects caused by propagation in foggy conditions. The experiments were carried out in a fog chamber, specially constructed to study electromagnetic transmission in controlled foggy environment, enabling generation of extremely dense fog with low visibility (less than 1 m). It is aimed at studying mmW propagation in the Ka-Band frequencies allocated for 5G spectrum. Table 2 summarizes some of the previous studies carried out in different bands in the millimeter wavelength regime.  
Preliminary experimental study was conducted in sub-millimeter waves with an artificial fog seeded by high volume'smoke machines'. It was found that the fog generates attenuation, and group delay may affect radar accuracy [16; 17]. These findings led to further experimental study of the radiation dispersive effects emerging in the presence of fog, on wireless communication links operating in mmW frequencies designated for the 5G cellular communication, which is described in this paper.