## 4 Numerical Results
Figure 3: Comparisons of OP at coupled IoT relay \(R_{r}\) and IoT devices with (**a**) fixed pre-defined bit-rate threshold \(\mathcal{R}=0.1\,\mathrm{b/s/Hz}\) versus PS factors \(\lambda_{R_{r}}=\{0,\ldots,1\}\) while (**b**) fixed PS factor \(\lambda_{R_{r}}=0.4\) versus pre-defined bit-rate threshold \(\mathcal{R}=\{0,\ldots,0.5\}\,\mathrm{b/s/Hz}\). The system throughput results in Figure 5a,b tended to pre-defined bit-rate threshold \(\mathcal{R}\) when SNR \(\rho\to\infty\). It is important to notice that IoT devices' throughput performance reached in Figure 5b is higher IoT devices' throughput performance reached in Figure 5a since IoT devices' bit-rate threshold \(\mathcal{R}=0.499\) b/s/Hz is greater than fixed IoT devices' bit-rate threshold \(\mathcal{R}=0.1\) b/s/Hz. To verify the potential threat affecting the information propagated on the proposed IoT network, the study investigated the probability that an eavesdropper successfully decoded information from the wiretapping signal as shown in Figure 6. Unfortunately, the results obtained plotted that eavesdropper \(E\) has a better probability result than legitimate IoT devices decoding their own proprietary information. In other words, the results shown in Figure 6 are better than those shown in Figure 4a. It is worth explaining cause eavesdropper \(E\) has better probability results in decoding information than legitimate IoT devices. Please note that the expression (52) becomes (45), where \(\delta=0\). In addition, the distance from the eavesdropper \(E\) to the IoT relays (\(d_{R_{r},E}=4\) m) is less than the distance from the IoT devices to the IoT relays (\(d_{R_{r},D_{1}}=5\) m, \(d_{R_{r},D_{2}}=7\) m, \(d_{R_{r},D_{3}}=12\) m). As a consequence, eavesdropper \(E\) has channel gain (\(\sigma_{R_{r},E}=0.0625\)) that is greater than the channel gains possessed by IoT devices (\(\sigma_{R_{r},D_{1}}=0.04\), \(\sigma_{R_{r},D_{2}}=0.0204\), \(\sigma_{R_{r},D_{3}}=0.0069\)). Thus, we obtained probability results that eavesdropper \(E\) can successfully decode the information better than IoT devices can. In other words \(IP_{E\to D_{n}}<OP_{D_{n}}\), where \(\delta=0\) and \(d_{R_{r},E}<d_{R_{r},D_{n}}\). In contrast, the major aim of this study is to improve the security of an individual IoT wireless network as shown in Figure 1. There are two cases. In the first case, transmission script is unknown at eavesdropper \(E\). Eavesdropper \(E\) randomly selected a received signal (30) or (31) for SIC. In the second case, the transmission script is well-known at eavesdropper \(E\), eavesdropper \(E\) selected signal as (30) for SIC in odd transmission block and then signal as (31) for SIC in even transmission block. Figure 7a shows the potential threat when eavesdropper \(E\) is able to decode messages of legitimate devices from the wiretapping signal. For example, the eavesdropper \(E\) had \(IP_{E\to D_{n}}(t)\approx 0.2\) probability to decode message \(x_{3}\) successfully at SNR \(\rho=30\) dB. However, IP performance reached \(IP_{E\to D_{n}}(t)\approx 1\) approximately at SNR \(\rho=30\) dB. In particular, the eavesdropper \(E\) had just \(IP_{E\to D_{n}}(t)\approx 0.9986\) even \(\rho\to\infty\) since the impact of the friendly jamming signal as shown in Figure 7b. Figure 5: Comparisons of system throughput at IoT devices with (**a**) fixed PS factor \(\lambda_{R_{r}}=0.4\) and fixed bit-rate threshold \(\mathcal{R}=0.1\), (**b**) optimized bit-rate threshold and PS factors.