# On Vulnerability of Selected IoT Systems to Radio Jamming--A Proposal of Deployment Practices
## 6 The Measurement of the Weightless and Sigfox Susceptibility to Interference
### Discussion of Results  
Measurement results of two PER profiles obtained for Weightless, representing its slowest and fastest operational modes, and a single profile for SigFox, are shown in Figure 5. As one can immediately notice, OQPSK modulation in Weightless provides a 15-decibel more robust operation than GMSK in terms of immunity to low CNIR. It allows the reception of data with PER \(<\) 50% at the level of c.a. CNIR \(=\) \(-\)15 dB but at data rates of c.a. 1 kb/s (a value still sufficient for a number of IoT applications). The configuration that proved to be the least robust to interference was the one offering \(R_{b}\) = 100 kb/s and needed 15 dB greater CNIR to sustain PER \(<\) 50%. As for SigFox, in turn, since no spectrum spread techniques are involved, positive CNIR was required, from 4 dB up to 14 dB that turned out to be optimal for the system uninterrupted operation. The 50% PER threshold was attained at CNIR = 11 dB, the positive sign being due to the lack of signal spreading in SigFox. The resulting values of CNIR for which 50% of packets were successfully received (i.e., PER = 50%), collected for all eight Weightless modes and the one for SigFox, are shown in Figure 6. It can be seen there that all the other Weightless modes (not shown in Figure 5) perform with 50% success at CNIR between \(-\)15 dB and 0 dB, i.e., between the two extreme analyzed modes (0.625 kb/s and 100 kb/s).  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & _A Set-up Element_ & _Parameter_ & _Value/Type_ \\ \hline \multirow{3}{*}{\(\bullet\)} & \multirow{3}{*}{The wideband interference source} & An arbitrary signal generator & Tektronix AWG 70002 \\  & & Output power, \(P_{gen}\) & 14, 13, 12... \(-\)16 dBm \\  & & Interfering signal BW & \(\bullet\) 350 kHz \\ \hline \multicolumn{2}{c}{The measurement infrastructure} & Localization & An anechoic chamber \\ \hline \multirow{3}{*}{\(\bullet\)} & \multirow{3}{*}{Weightless} & EIRP & 14 dBm \\  & & Channel bandwidth, \(BW\) & 12.5 kHz, 100 kHz \\  & & Center frequency & \(\bullet\) 863.1 MHz \\ \cline{3-4}  & & Data rate, \(R_{b}\) & 0.625 kb/s, 100 kb/s \\  & & Spreading factor, \(SF\) & 8 and 1 \\  & & Modulation, \(MOD\) & OQPSK, GMSK \\  & & Coding rate, \(R\) & \(\bullet\) 0.5 and 1 \\ \hline \multirow{3}{*}{\(\bullet\)} & \multirow{3}{*}{SigFox} & EIRP & 14 dBm \\  & & Channel bandwidth, \(BW\) & 100 Hz \\ \cline{3-4}  & & Frequency band & 868.034–868.226 MHz \\ \cline{3-4}  & & Data rate, \(R_{b}\) & 100 b/s \\ \cline{3-4}  & & Modulation, \(MOD\) & DBPSK \\ \cline{3-4}  & & Coding rate, \(R\) & \(\bullet\) 1 \\ \hline \hline \end{tabular}
\end{table}
Table 2: A table of the set-up of the measurement.  
Figure 5: The Weightless packet error rate (PER) response to interference (jamming) expressed by carrier to interference and noise (CNIR) for two extreme operational modes.  
It is assumed that since the jammer intends to interfere with the BS entire traffic, it has to radiate its power distributed over the whole reception frequency range (represented by the term _\"band\"_ in Equation (3)), stretched over 600 kHz (the \"M\" band width) in Weightless and 192 kHz in SigFox. This means that only a fraction of the jammer total radiated power will actually affect the receiving BS, namely 0.1/192 for a SigFox BS and 12.5/600 or 100/600 for a Weightless BS. This fractional jammer occupancy is reflected in the third term of Equation (3).