# SDR Proof-of-Concept of Full-Duplex Jamming for Enhanced Physical Layer Security
## 5 Evaluation
### Favorable and Unfavorable Setups Results  
With the LMS algorithm established, the effect of the SDRs' positions are now evaluated by also considering the remaining Setups II and III.  
We start by considering the additional metrics of PLR and BER for Setup I, as depicted in Figure 9. There is a clear gap between [PERSON] and [PERSON] with respect to PLR and BER values, meaning that a relevant security level is attained through SI cancellation mechanisms at Bob. Particularly, at 26 dBm [PERSON] has a very low PLR being capable to obtain almost all packets (PLR = 6.67 \(\times\) 10\({}^{-5}\)), while [PERSON] only recovers nearly 1/3 of the packets (PLR = 3.39 \(\times\) 10\({}^{-1}\)). From those packets recovered by [PERSON], only about 28% of the bits are received without error, thus severely compromising [PERSON]'s ability to retrieve the original data. Increasing the jamming power, worsens the PLR and BER for [PERSON] up to a certain point, albeit with a corresponding penalty for [PERSON] as well. Note that the BER and PLR values for [PERSON] are omitted when we had a lack of precision in the real-world prototype results.  
When comparing Setup I (fairest) with Setup II (unfavorable to [PERSON]), since the distance from [PERSON] to [PERSON] was not changed the SI cancellation capability of [PERSON] remains roughly the same, as depicted in Figure 10. With [PERSON] at a larger distance from [PERSON], we note a left shift on [PERSON]'s PLR and BER curves, i.e., [PERSON] experiences higher PLR and BER for lower levels of jamming power. This leads to a larger gap between [PERSON] and [PERSON] which is favorable from a security perspective, but expected due to the unfavorable setup for [PERSON] at a larger distance from [PERSON].  
With [PERSON] located further away from [PERSON] than [PERSON] (Setup III) the gap between [PERSON] and [PERSON] is reduced due to an increase in PLR for [PERSON]. In this case, increasing the jamming power is not an effective mechanism, since it will also increase [PERSON]'s PLR, as depicted in  
Figure 8: Error vector magnitude (EVM) as function of jamming power for [PERSON] and [PERSON] at Setup 1.  
Figure 9: Packet loss rate (PLR) and bit error rate (BER) plots of Setup I (fairest) when using least mean square (LMS).  
the left-hand side of Figure 11. However, when packets go through to [PERSON], somewhat surprisingly [PERSON]'s BER remains low and there is still a large gap between [PERSON] and [PERSON], as depicted on the right-hand side of Figure 11. This means that it is still possible to increase the jamming power up to some point (altough not as high as in the previous setups) and achieve an acceptable BER level, as long as we are willing to accept a trade-off with the increasing PLR for [PERSON]. For example, for a jamming power of 26 dBm [PERSON] has a PLR of \(2.4\times 10^{-3}\), but an acceptable BER of \(8.5\times 10^{-6}\), with [PERSON] still being affected in her reception capability through a high PLR of \(9.9\times 10^{-1}\) and a high BER of \(3.2\times 10^{-1}\).  
In summary, this assessment allowed us to perform a realistic prototype evaluation of the effectiveness of SI cancellation mechanisms for security purposes. However, with different trade-offs, these mechanisms have shown to be effective in facilitating a security gap between [PERSON] and [PERSON] by taking advantage of the knowledge of the interference signal on [PERSON]'s side. In particular, be it a favorable or unfavorable scenario, self-interference generation with SI cancellation is adequate to provide a relevant security gap between [PERSON] and [PERSON]. Naturally, this gap narrows when [PERSON] is in an advantageous situation, but even for that case we have shown that it is possible to achieve a prescribed security level, as long as one is willing to accept a penalty in the packet-loss rate.