Comparison of reflection mechanisms from smooth and rough surfaces at 62 GHz
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Mobile broadband services (MBS) have been assigned frequency bands around 40 and 60 GHz and will allow wireless access at 155 Mb/s. Such services are expected to be delivered by systems operating in urban microcells employing low powered base stations with antennas which are elevated by a few meters above the ground. One technique that may be used to model the channel characteristics is ray-tracing. In a microcellular mobile radio channel the phases and amplitudes of the rays undergo some modifications when they are reflected from or transmitted through a particular material. Reflection and transmission mechanisms are dependent on the nature of the surface (smooth or rough), its dielectric parameters (permittivity and conductivity) and polarisation. The objective of the study reported is to measure and characterise the reflection mechanisms from smooth and rough building surfaces at 62.4 GHz. Results from experiments, made inside an anechoic chamber, on various smooth and rough building materials to measure the reflection and transmission coefficients as functions of the incident angle are given. A model based on multiple successive internal reflections inside the slab has been successfully used to describe these mechanisms for smooth surfaces with a thickness not too large compared to a wavelength. However results from rough surfaces, constructed by impregnating concrete slabs with angular stones, are compared with predictions obtained from the Kirchhoff approximation assuming random rough surfaces.