# 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  
### The Measurement Set-Up  
Electromagnetically-isolated chambers, in particular anechoic chambers (AC) and reverberation chambers (RC), create convenient environments for measuring wireless systems, by providing controlled electromagnetic background. This feature is particularly crucial when investigating systems at very high pathloss conditions, causing them to work with received signal power close to their sensitivity, at which point any unwanted signal from outside could easily disturb measurements. The usability of such artificial environments for precise investigation of wireless systems in general has been demonstrated, for example, in [29] and [30]. Demonstration of their applicability to specific wireless systems can be found in [3], [19] or [31]. Due to their superb shielding properties, chambers attenuate all external signals by c.a. 85 dB (as in our experiment) which ensures that receivers placed inside a chamber will be unaffected by any signals other than those arriving either from a transmitter or an intentional interferer (also located inside of it). To make measurements even more credible, chambers allow only antennas to be placed inside while leaving any signal-generating devices (e.g., terminals, base stations, signal generators etc.) outside, to prevent any unwanted radiation from on-board electronics from affecting results. The radiated power, in turn, is controlled with the use of variable attenuators connected to signal-generating devices. Accordingly, in the current experiment a set-up was organized in a way presented in Figure 4 with the receive (Rx) and transmit (Tx) antennas spaced 6 m apart and the cabling connecting the actual transmitter (i.e., an end-device) and receiver (i.e., a base station), laid down under a layer of absorbers covering the AC floor. During measurements, the receiving antenna was subjected to varying level of interference generated with the use of an arbitrary signal generator AWG 70002 (by Tektronix, Beaverton, OR, USA) and radiated from a directional antenna oriented directly towards an investigated system's Rx antenna. The radio frequency (RF) interfering signal was generated in the form of a continuous 350 kHz wide additive white Gaussian noise (AWGN) signal, with the output power \(P_{gen}\) set to 14 dBm. At this power level the observed PER in both, Weightless and Sigfox, equaled 100%, which corresponded to totally corrupted transmission conditions. \(P_{gen}\) was then successively decreased at 1 dB steps down to \(-\)16 dBm, in which process connectivity was being restored due to the continually growing Carrier-Noise and Interference Ratio (CNIR) resulting in PER decreasing to 0 % (i.e., a successful reception of all packets). The purpose of this campaign was to obtain curves translating PER to CNIR. These will be used in Section 4 as inputs to the jamming immunity theoretical model derived there, which takes these values as crucial parameters for estimating resilience of an IoT system to intentional jamming intended to corrupt the base station. The over-the-air measurements were set up in an anechoic chamber, as shown schematically in Figure 4. The assumed  
Figure 3: A captured output from a SigFox end-device (with EIRP = 14 dBm). acceptable PER threshold was set to 50%, i.e., regarding a transmission as successful even if every second packed was dropped due to interference. The term \"packet\", throughout the experiment, was meant as a single message containing e.g., sensor readings. Thus, in calculating PER, only those packets were considered that were eventually successfully detected and delivered to an end-user, after having been processed by error-correcting techniques available in those systems. The Weightless devices used in experiments were Ubiik platform modules. The evaluation kit consisted of: a base station that served as a receiver interfered by the interfering signal (_I_) in the form of AWGN noise and an end-device serving as a transmitter.