Static and Dynamic Finite Constellation Decomposition for Wireless Physical Layer Security

Security is a critical element in the design of communication systems. However, despite its essential role in enabling low-cost implementations and robust theoretical foundations, physical layer security is often overlooked in developing countermeasures against eavesdropping. In this work, we propose practical physical-layer countermeasures that enhance secrecy with low computational overhead. Our approach decomposes the constellation diagram using basis vectors, constructing the original message symbol in the main lobe aimed at the intended receiver, while projecting randomized constellation points in other directions to mislead potential eavesdroppers. When the eavesdropper's location is known, we use static basis vectors, achieving a higher level of secrecy in that direction. When the location is unknown, we dynamically change the basis vectors to provide information-theoretic security in all directions through basis vector randomization. This design enables the intended receiver to operate without knowledge of the basis vectors, reducing receiver overhead. We evaluate the scheme's secrecy performance through bit error rate and secrecy rate analyses, demonstrating its potential to improve physical layer security.