SER -Constrained Symbol-Level Precoding for Physical-Layer Security

Symbol-level precoding (SLP)has been extensively used to transform multi-user interference (MUI)into a useful power gain at the receiver. This paper exploits this concept for physical-layer security purposes, where in addition to the power gains at the intended users, we achieve more security by increasing the symbol-error rate (SER)at the eavesdropper (Eve). We consider a multi-user multiple-input single output (MU-MISO)downlink system in the presence of an Eve. Two use cases are investigated. In the first one, the system protects the data of one user, and in the second one, it protects the data of all users. To this aim, we formulate a power minimization problem, for each use case, that is optimally solved and derive a closed-form expression of a lower bound on the SER at the Eve. Numerical results show that our proposed scheme outperforms the benchmark scheme in terms of the effective SER at the Eve, which is achieved at the expense of a small additional power consumption.