Page 19 - 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

GNSS L1-band, down from 1559 MHz, a powerful clock and common-antenna set-up, and despite
signal more than 35 dB above the GNSS spread- being from the same manufacturer even if of
spectrum power level is clearly visible. A space to different types, both units are not reacting to the
ground telecommunication signal would add just a jamming signal in the same way. We also noticed
few dB on the noise level. We also checked with some large time offsets of a few ns between OPM9
other laboratories in the Paris suburbs that the and OPMT. But there was some coupling with
signal was not visible there. Hence the transmitter temperature effects typically affecting OPM9, which
could only be ground based in the vicinity of OP. We are not the subject of this paper. Hence OPM9 is
observed that the jamming signal was not disregarded here. Significantly, no abnormal offset
continuously transmitting. between OPMT and OPM2 was detected over that
period of time.

Fig. 3 – Offset between OP71 and OPMT based on CV of GPS P3
CGGTTS data, recorded from 24 to 28 November 2018 (MJD
58446 to 58450)

Fig. 4 – Frequency spectrum observed on 16 January 2019.
The center frequency is 1575.2 MHz. The span is 200 MHz. The
Y-axis scale is 6 dBm/div. The GNSS allocated L1-band from
1559 MHz to 1610 MHz is highlighted in green.
Fig. 5 shows the simultaneous effects of the
jamming signal on different GNSS stations in OP
over the period from 10 to 14 January 2019. Even if
the amplitude is not at the same level, the offsets of
OPM6 and OP71 against OPMT are significant when Fig. 5 – Based on CV of GPS P3 CGGTTS data, offsets between OP71 and
the jamming signal is on. We obtained similar plots OPMT (top), OPM6 and OPMT (middle), and OPM6 and OP71 (bottom),
against OPM2 (not shown in the figure). In addition, recorded from 10 to 14 January 2019. When the jamming signal is on
the offset between OPM6 and OP71 is also plotted after the middle of the period, amplitudes of a few ns are largely above
in Fig. 5. Despite being implemented in a common- the usual uncertainties for such local time offsets, even if the different
operational stations are not affected in the same way.

© International Telecommunication Union, 2019 3