Physical Layer Security Enhancement Using an Expanded Signal Constellation

We present an effective scheme for preventing eavesdropping in wireless communication systems. In the proposed scheme, the modulation scheme is designed to change based on an expanded signal constellation, in such a way that the eavesdropper cannot be aware of the change. As compared to previously proposed schemes that rely on specific relay nodes, the proposed scheme is advantageous in that it can keep the transmit messages secure without requiring any assistance of relays.