Metasurface based positional modulation design

Directional modulation (DM) can transmit information to the desired direction or directions with known constellation mappings, but with scrambled ones in other directions. However, one problem of the design is that when desired receivers and eavesdroppers are in the same transmission direction, their beam responses cannot be distinguished, as steering vectors for these locations are the same. To solve the problem, positional modulation (PM) is introduced where a given modulation pattern can only be received at certain desired positions. In this work, the multi-path effect is exploited for positional modulation with the aid of metasurface acting as a low-cost flexible reflecting surface. Design examples are provided to show the effectiveness of the proposed design.