$1 \times K$ Differential Space-Time Line Code with Phase-Shift Keying Modulation and Code Hopping for Secure Communications

This study proposed a code-hopping strategy to strengthen the limited secrecy capability of a conventional differential space-time line code (Diff-STLC) scheme. By randomly switching two Diff-STLC structures, i.e., the Diff-STLC hopping, a legitimate receiver who knows the hopping pattern can successfully decode the Diff-STLC signals. In contrast, an illegal eavesdropper without the secured hopping pattern cannot decode the hopping Diff-STLC signals. Consequently, the proposed Diff-STLC hopping scheme can significantly improve secure communication performance, as validated by numerical results.