Multipath-Enhanced Directional Modulation for Secure mmWave On-Body Communication

This paper proposes Directional Modulation (DM) for secure millimeter-wave (mmWave) on-body communication, where security is enhanced by leveraging multipath propagation. The double two-ray ground reflection model is employed to analyze a two-antenna Multi-Input Single-Output (MISO) system placed on human skin. The system operates at 24 GHz with polarization tangential to the skin. Key parameters such as antenna-separation, antenna-to-skin spacing and phase difference between transmitter antennas are varied to analyze the resulting path gain. The results obtained from analytical model are experimentally validated using Yagi antennas placed over a forearm phantom. Based on the findings, the DM technique is implemented. The results demonstrate successful demodulation at the intended receiver location with Bit error rate (BER) <10^-4, while at the eavesdropper’s location the BER >0.2 for all investigated transmitter–receiver antenna separations. The experimental results confirm the effectiveness and validity of the proposed concept.