A practical regular LDPC coded scheme for physical-layer information security

In this paper, we aim to design a practical low complexity low-density parity-check (LDPC) coded scheme to build a secure open channel and protect information from eavesdropping. To this end, we first propose a punctured LDPC coded scheme, where the information bits in a codeword are punctured and only the parity check bits are transmitted to the receiver. We further propose a notion of check node type distribution and derive multi-edge type extrinsic information transfer functions to estimate the security performance, instead of the well-known weak metric bit error rate. We optimize the check node type distribution in terms of the signal-to-noise ratio (SNR) gap and modify the progressive edge growth algorithm to design finite-length codes. Numerical results show that our proposed scheme can achieve a lower computational complexity and a smaller security gap, compared to the existing scrambling and puncturing schemes.