A Half-Duplex Self-Protection Jamming Approach for Improving Secrecy of Block Transmissions in Underwater Acoustic Channels

Block transmissions are commonly used in underwater acoustic communications due to the large delay spread of the underlying channels. In this paper, we propose a novel jamming protocol based on the half-duplex nature of the underwater transceivers and the block-based transmission structure, taking advantage of the large propagation delays of underwater acoustic channels to create interference at the eavesdropper without affecting the reception of the intended user. This half-duplex jamming protocol acts like a self-protection scheme, which does not need any helpers but instead relies on the legitimate receiver itself to transmit jamming signals for the improvement of secrecy rate. The simulation results evaluate the secrecy rate improvement as a function of the eavesdropper locations.