Polar Coding for Physical-Layer Security

Inhalt:
In physical-layer security schemes, coding and modulation are used to prevent successful eavesdropping without the need for secret keys. In this paper, we analyze practical polar coding schemes w.r.t. the BER-based security gap metric in a Gaussian wiretap channel scenario. Thereby, individual secrecy metrics are derived for the information symbols conveyed within a codeword. The unequal protection of communicated information symbols is revealed and a trade-off between secure transmission rate and secrecy is presented. Further, a suitable combination of polar codes with (information-symbol) scrambling schemes is derived by taking the inherent scrambling of common polar encoding strategies into account. The theoretical findings are supported by numerical simulations.