Page 49 - ITU Journal: Volume 2, No. 1 - Special issue - Propagation modelling for advanced future radio systems - Challenges for a congested radio spectrum

ITU Journal: ICT Discoveries, Vol. 2(1), December 2019

[ ] = 92.4 + 20 ( [ ] ) + 20 ( [ ] ) + Table 5 – Total specific attenuation in dB/km at 300 GHz
( + + + ) [ ] (8)

0

Description in [14, 15, 16]. Atten.
where, : represents specific attenuation due to dB/km
0
dry air, : specific attenuation due to water vapour, Bangkok, temp. 35°C, relative humidity 90%, no rain 32.1

: specific attenuation due to rain, and : specific Bangkok, temp. 35°C, relative humidity 90%, , rain 51.1

attenuation due to fog and clouds. (50 mm/h)
Basra, temp. 43°C, relative humidity 30%, dust (10 m
Methods for the calculation of specific attenuations visibility) 27.8
can be found in three ITU-R Recommendations: Berkeley, temp. 20°C, relative humidity 60%, fog
ITU-R P.676-11 on attenuation by atmospheric (100m visibility) 9.5
gases and related effects, ITU-R P.838-3 on specific Bellingham, temp. 22°C, relative humidity 50%, rain 10.5
attenuation model for rain for use in prediction (4 /ℎ)
methods and ITU-R P.840-6 on measurements of Boulder, temp. 20°C, relative humidity 44% 5.8
ionospheric and related characteristics. Exemplary Buffalo, temp. -10°C, relative humidity 30% 0.4
results of the total specific attenuation at 300 GHz Boulder, with clouds (100m of large cumulus 44.7
for different regions in the world with various clouds), temp. 20°C, relative humidity 44%
weather conditions [15-16] are presented in 6.2 Models for close-proximity
Table 5 using (8) and the ITU-R Recommendations. communications.
Ray-optical modeling in indoor environments
The transmission with ultra-high data rates of very
For propagation modeling in indoor environments short distances, the so-called close-proximity
at THz frequencies ray-optical approaches show communication, has recently drawn some
reasonably good agreement with channel attraction involving propagation phenomena,
measurements [17]. While such ray-optical which are specific to such environments: (1) in the
approaches are known from lower frequencies, the so-called kiosk downloading applications multiple
electromagnetic modeling of the scattering and bouncing signals between the metallic parts of the
reflection processes is different at THz frequencies set-up are casing a high degree of inter-symbol
due to the small wavelength, which becomes less interference which needs to be taken into account
than 1 mm at carrier frequencies beyond 300 GHz. in link-level simulations for the design and
Therefore, structures on the order of a wavelength standardization of new systems. For these
have to be taken into account. These include: (1) simulations, typically stochastic channel models are
diffuse scattering off the specular direction from applied [21]; (2) in intra-device applications
walls and objects with a surface roughness of less wireless transmission is realized for example
than 1 mm (i.e. standard deviation of the height between mother boards of computers or between a
variation). This was shown by THz time-domain sensor and a memory card inside a camera. In these
spectroscopy and simulations using modified cases the modeling of reflection and scattering
reflections coefficients [18]. Although the diffuse processes in metallic enclosures [22] and at printed
scattering field may be weak in comparison to the circuit boards (PCB) are of interest [23]
specular direction, it is still high enough to enable
NLOS links over short distances; (2) layered media 7. CONCLUSION
with layer thickness on the order of a wavelength
may cause multiple reflections causing destructive In this paper, propagation models and
interference if the reflected waves are at discrete measurements for typical environments for 5G and
scattering angles [19]. Recent channel sounder beyond have been presented. Below 6 GHz
measurements in a real data center at 300 GHz [20] frequency bands have been investigated for
with a great deal of highly reflective materials have massive MIMO and vehicular propagation,
shown, that despite the high path loss significant extending the COST 2100 model to cover these new
multipath propagation can be observed. applications. Vehicular communication in a corner
scenario and a crossroad below 6 GHz and in the
millimeter wave bands have been modeled from
measurements and simulations. Path-loss models
for body area networks for short-range in-body and
in-body-to-off-body scenarios, as well as in office
and ferry environments are discussed. The impact

© International Telecommunication Union, 2019 33