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Abstract-Existing cellular technologies are rapidly coming to their performance limits. This is due not only to the growth in data traffic and in the number of connected terminals, but also because we are on the verge of new era, where everyone and everything will be connected, with more demanding and varied requirements that cannot be satisfied by current networks. On account of this, efforts are being made all over the world to design new wireless technologies that will support the expected demands for the next decade. These technologies, embraced under the commercial name of 5 th generation, are currently being studied, and in this tutorial paper we will give an overview of the main trends that are likely to make their way in the next-generation standards.

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In this paper we present the results of an extensive measurement campaign performed at two large iron ore mining centers in Brazil at the 2.6 GHz band. Although several studies focusing on radio propagation in underground mines have been published, measurement data and careful analyses for open-pit mines are still scarce. Our results aim at filling this gap in the literature. The research is motivated by the ongoing mine automation initiatives, where connectivity becomes critical. This paper presents the first set of results comprising measurements under a gamut of propagation conditions. A second paper detailing sub-GHz propagation is also in preparation. The results indicate that conventional wisdom is wrong, in other words, radio-frequency (RF) propagation in surface mines can be far more elaborate than plain free-space line-of-sight conditions. Additionally, the old mining adage "no two mines alike" seems to remain true in the RF domain.

This paper presents a measurement-based comparison of cm-wave propagation in urban and suburban scenarios at 24 GHz with transmitter antennas located above rooftop level. Different sets of directional measurements, exploring the full azimuth and the range from -30 to +30 degrees in elevation, were performed with horn antennas located close to street level, in order to explore the spatial characteristics of the channel in both LOS and NLOS conditions. The statistical analysis of different directional indicators shows how, at 24 GHz, outdoor propagation is quite different in the suburban scenario as compared to the urban case. Increased spatial multipath, in average 1.23 times higher, is observed in the suburban scenario, mainly due to the strong presence of vegetation. This results in reduced suburban NLOS path loss exponents (3.4) in comparison to the urban scenario (3.7), as detailed in the outdoor path loss analysis. The paper also highlights the potential of using beam combining techniques in order to improve cell-edge coverage by 17% and 37% in the urban and suburban scenarios, respectively. Outdoor-to-indoor propagation was also investigated, finding an average penetration loss of 6.5 dB for buildings composed of light construction materials. The different results and observations provided in the paper are useful for modeling and simulation of future wireless networks operating at 24 GHz in urban and suburban scenarios.

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