In this paper, we compare the radio propagation channels characteristics between 28 and 140 GHz bands based on the wideband (several GHz) and directional channel sounding in a shopping mall environment. The measurements and data processing are conducted in such a way to meet requirements for a fair comparison of large-and small-scale channel parameters between the two bands. Our results reveal that there is high spatial-temporal correlation between 28 and 140 GHz channels, similar numbers of strong multipath components, and only small variations in the large-scale parameters between the two bands. Furthermore, when including the weak paths there are higher total numbers of clusters and paths in 28 GHz as compared to those in 140 GHz bands. With these similarities, it would be very interesting to investigate the potentials of using 140 GHz band in the future mobile radio communications.

Millimeter-wave radios operating at unlicensed 60 GHz and licensed 70 GHz bands are attractive solutions to realize short-range backhaul links for flexible wireless network deployment. We present a measurement-based spatio-temporal statistical channel model for short-range millimeter-wave links in large office rooms, shopping mall, and station scenarios. Channel sounding in these scenarios at 60 and 70 GHz revealed that spatio-temporal channel characteristics of the two frequencies are similar, making it possible to use an identical channel model framework to cover the radio frequencies and scenarios. The sounding also revealed dominance of a line-of-sight and specular propagation paths over diffuse scattering because of weak reverberation of propagating energy in the scenarios. The main difference between 60 and 70 GHz channels lies in power levels of the specular propagation paths and diffuse scattering which affect their visibility over the noise level in the measurements, and the speed of power decay as the propagation delay increases. Having defined the channel model framework, a set of model parameters has been derived for each scenario at the two radio frequencies. After specifying the implementation recipe of the proposed channel model, channel model outputs are compared with the measurements to show validity of the channel model framework and implementation. Validity was demonstrated through objective parameters, i.e., pathloss and root-mean-square delay spread, which were not used as defining parameters of the channel model.Index Terms-Channel model, millimeter-wave, short-range communications.

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The main objective of this paper is to present major challenges regarding the fifth generation (5G) mobile communications propagation modelling work in the European 7th framework project METIS (Mobile and wireless communications Enablers for the Twenty-twenty Information Society). The goal of the propagation work in METIS is to provide adequate propagation models for 5G. For this purpose corresponding deficiencies of present commonly used models are identified. Further, the lack of available channel models for several propagation scenarios has been assessed. Based on this assessment the framework of 5G channel modelling is sketched. As propagation measurement campaigns are a crucial part of this work they are illustrated with a few examples