Jamming-Based Covert Communication for Rate-Splitting Multiple Access

We investigate secure communications for a rate-splitting multiple access (RSMA) system. In particular, a jamming-based covert communication (CC) technique is used to effectively prevent a warden from detecting the data communications. As the jamming signals also degrades the data rate of the users, we formulate an optimization problem that maximizes the minimum data rate over all the users subject to the constraints on the security requirement and power budgets of the transmitter and optimize the data rate, transmit power, and jamming power. The max-min problem is non-convex, and we propose a fast exponential algorithm which can produce a global optimal solution to the problem. The simulation results show that our proposed algorithm outperforms the sequential quadratic programming algorithm, a powerful algorithmic tool for solving nonlinear optimization problems, in terms of min-rate and execution time (for a small number of users), given the same security requirement. Additionally, it is observed through simulation that RSMA can achieve up to three times better than non-orthogonal multiple access (NOMA) in terms of min-rate.