# SDR Proof-of-Concept of Full-Duplex Jamming for Enhanced Physical Layer Security
## 4 Setup and Metrics  
Three different configurations were created to evaluate the SI cancellation capability of the adaptive algorithm to be chosen and the secrecy of information achieved.  
The first setup (Setup I) recreates the fairest possible scenario, where all SDRs are evenly separated as illustrated in Figure 5. In this scenario, the signal power from [PERSON] to [PERSON] equals the signal power to [PERSON], thus, [PERSON] needs to generate a noise signal which can superimpose the information signal on [PERSON], and at the same time cancel the SI.  
Figure 4: [PERSON]’s flow graph of the real-world prototype generating noise and perform self-interference (SI) cancellation.  
Figure 3: [PERSON]’s flow graph of the real-world prototype.  
Figure 6 depicts Setup II, where [PERSON] has an advantage because the distance between [PERSON] and [PERSON] is half of the [PERSON] distance. This allows for [PERSON] to receive a better signal from [PERSON] than [PERSON]; hence, [PERSON] has a SNR significantly lower than [PERSON], which will allow degradation of the information signal with the same jamming power without affecting the SI capability of [PERSON].  
Finally, Setup III explores a disadvantageous scenario for [PERSON], where his distance to [PERSON] is twice that of [PERSON]'s distance, as shown on Figure 7. Therefore, [PERSON] is receiving lower signal power from [PERSON] than [PERSON], which will pressure [PERSON] to decrease his jamming signal, otherwise he will not be able to recover the signal, and consequently, [PERSON] will receive [PERSON]'s signal with higher power.  
To assess reception quality we will measure the error vector magnitude (EVM), i.e., the distance between the received constellation symbols and the ideal ones. A smaller EVM value, means better approximation to the constellation points, thus, better possibilities to correctly retrieve the information. In packet-based transmissions it is also possible to use as a metric the packet loss rate (PLR) and the bit error rate (BER). A packet loss occurs when some packet fails to successfully reach its destination in a network communication, either caused by errors in the transmission channel or by network congestion. The PLR is a practical metric that measures the percentage of lost packets relative to the total packets sent. Finally, the BER takes into account only the bits of successfully received packets at the output of the decoder and compares them with the original ones of the transmitted message. All of these metrics can be used in practical scenarios to evaluate  
Figure 5: Setup I—Fairest setup possible.  
Figure 6: Setup II—Setup advantageous to [PERSON].  
Figure 7: Setup III—Setup advantageous to [PERSON].  
security by stipulating reliability (for [PERSON]) and secrecy (for [PERSON]) levels based on each of these metrics, and computing the difference (i.e., gap) between the SNRs for which [PERSON] and [PERSON] achieve them.  
Furthermore for statistically relevant results, in each evaluation and for each considered jamming power value, we perform 30 transmissions of \(3.2\times 10^{6}\) bits each, for which the used metrics' mean and 95% confidence interval were calculated.