Full-duplex vs. half-duplex secret-key generation

Secret-key agreement from reciprocal wireless channels has been considered a valuable supplement for security at the physical-layer. On the one hand, full-duplex (FD) communication is regarded as one of the key technologies in future 5G systems. On the other hand, the success of 5G depends, among other things, on the ability to allow for secure communication. However, most key agreement models are based on half-duplex (HD) setups. Therefore, in this work, we propose representations of key generation models in both HD and FD modes. We analyze the performance of FD vs. HD modes by utilizing the key-communication function of secret-key agreement. It turns out that, for the application of key agreement, the FD approach enables advantages over the conventional HD setups. In particular, we derive a condition that guarantees improved performance of FD over HD mode in the high SNR regime.