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In the fifth-generation (5G) system, millimeter-wave (mmWave) communication has been recognized as a candidate technique. To overcome the high transmission loss of mmWave, distributed antenna systems that consist of a base station (BS) connecting with multiple remote radio units (RRUs) were studied to improve the energy efficiency. In this letter, by utilizing the propagation characteristics of mmWave, we propose a cooperative multiuser beamforming method for energy-efficient transmissions in mmWave distributed antenna systems. The RRUs first decide the local serving group separately and the BS makes an optimization globally with limited data exchange. From simulation results, compared to the state-of-the-art method, it is shown that higher energy efficiency can be realized by the proposed method for the multiuser mmWave distributed system. [ABSTRACT FROM AUTHOR]

A simplified analytical model is presented to predict the specific attenuation for propagation through a tree canopy in a residential environment for frequencies of up to 2 GHz. In this approach, the canopy of a tree is modeled as an ensemble of leaves and branches all having prescribed location and orientation statistics. The Foldy-Lax discrete scattering theory is used to find the specific attenuation of a tree associated with the mean field. Explicit formulas are presented to calculate the specific attenuation of a tree canopy. It is shown that the specific attenuation of a tree canopy depends on the frequency, polarization, electrical and geometrical characteristics of branches and leaves, biophysical parameters of a tree, and statistical distribution of branches and leaves in reference to the angle of incidence of the plane wave. It is also shown that for deciduous trees, as opposed to coniferous trees, the inclination angle distribution of the branches is more vertical, producing a higher specific attenuation for the vertical-polarization incident wave than for the horizontal-polarization incident wave. [ABSTRACT FROM AUTHOR]

This paper concerns the measurement-based comparison of urban microcellular mobile radio channel characteristics at 1.9 GHz and a higher frequency, i.e., 5.8 GHz, where future wireless systems could operate. Characteristics that are reported include transmission loss, root-mean-square delay spread, frequency correlation, and envelope fading statistics. Conclusions are drawn concerning whether significant differences in the performance of mobile radio links operating under the same signal-to-noise ratio conditions in the two bands would be expected in the area where the measurements were made. [ABSTRACT FROM AUTHOR]