Page 29 - 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

4.4 Concurrent standard deviation at the two
bands
As described above the two converging links have
an angular difference of about 17º and the distance
between the points where the links cross a plane at
1000 m altitude is several hundreds of meters.
Nevertheless, a very high correlation between the
scintillation variance at the two frequencies has
been always observed. This means that the spatial
stationarity of the turbulence is of the same order of
the distance between the points where the links
cross the turbulence.
Fig. 8 depicts the high correlation mentioned above,
with the peculiarity that the Ka-band receiver has Fig. 9 – Year scatter plot of the hourly averaged scintillation
been upgraded during this month; for the last variance at the two frequencies
10 days of the month a higher was already A frequency scaling factor for the variance was
0
available. It is notorious that the presence of two estimated, for example for the April data depicted in
data sets being the lower set collected already with Fig. 10, by performing a linear fitting to the
the better estimated to be about 6.5 dB wrt to variances scatter plot. A value of 0.288 was
0
the actual performance of the receiver (the receiver obtained for the slope that is very close to the
NF had a fast CNR degradation during the last two variance scaling factor obtained by using the
months of operation). frequencies, elevation angles and antenna
reduction factors that can be found in several
models.

Fig. 8 – May 2018 scatter plot of the hourly averaged
scintillation variance at the two frequencies; CNR Fig. 10 – A month scatter plot of the variance at the two bands
improvement is observed and a linear fitting to the data
The annual scatter plot results presented in Fig. 9
show the high correlation between the two 5. SCINTILLATION MODELS
variances that were, nevertheless, expected from A few essays of some available scintillation models
the diurnal variation discussion in section 11. The have been performed, such as, the scintillation fades
obtained annual correlation was 0.772 and is quite and enhancements using the Otung [7], ITU [10]
similar throughout all the months. (only for fades), van de Kamp [11] and the

Karasawa [5] models. Fig. 11 and Fig. 12 were
obtained for the Ka-band using the yearly average
measured =51.5, the antenna variance
averaging factors of about 0.86 and 0.95
(respectively for the Ka and Q-band) computed for
a turbulent layer height of 1 km (ITU and Otung
models) and 2 km (for the Karasawa model) and,

© International Telecommunication Union, 2019 13