Secure Throughput Optimization of Selective Decode-and-Forward with Finite Blocklength

Physical-Layer Security in the Finite Blocklength Regime Over Fading Channels

“…Theorem 6: n * = N is optimal for maximizing T A in (26). Proof 11: The proof is similar to that of Theorem 1.…”

“…• Numerous useful insights into the design of secure transmissions are provided with finite blocklength. For example, 1) increasing the blocklength can improve both reliability and secrecy, with properly exploiting the instantaneous CSI of the main channel and the statistical CSI of the wiretap channel, which has not been revealed by existing literature, e.g., [16]- [20]; 2) using the maximal blocklength is profitable for boosting the secrecy throughput, which is distinguished from the observation in [26]; 3) due to the finite blocklength penalty, there is a critical secrecy rate that can maximize the secrecy throughput even for the adaptive scheme, rather than always employing the maximal available secrecy rate, which is fundamentally different from the phenomenon with infinite blocklength, e.g., [21], [22].…”

“…Proof 2: Please refer to Appendix B. Theorem 1 reveals that exploiting a larger blocklength is beneficial for improving the secrecy throughput under given channel gains. This result is nontrivial in light of [26] where there exists a critical value of the blocklength, instead of the maximal one, that can achieve the maximal secrecy throughput. The main reason behind the two different results lies in that, Bob's instantaneous CSI is available here and is adequately exploited, and the codeword rate will not exceed Bob's channel capacity under the on-off policy such that using a larger blocklength can always lower the decoding error probability for Bob.…”

“…Indeed, the blocklength itself is an optimization variable, and it couples with other variables in a sophisticated manner which makes the optimization problem intractable. For instance, the authors in a recent work [26] investigated the secrecy throughput of a relay-aided secure transmission with finite blocklength, where neither the instantaneous channel state information (CSI) with respect to (w.r.t.) the legitimate receiver nor the eavesdropper is available at the transmitter side.…”

“…Yet, the potential of exploiting the instantaneous CSI to alleviate the negative impact of finite blocklength on the performance of secure communications has not been exploited. Furthermore, only the single-antenna transmitter scenario has been considered, e.g., [16]- [20], [26], and the design of the optimal signaling and code rates for multi-antenna systems with finite blocklength is still an open issue. This research work aims to provide an analytical framework and design schemes to address the abovementioned problems.…”