Rate-Splitting Multiple Access for Covert Communications

This paper explores downlink multi-antenna covert communications using rate-splitting multiple access (RSMA). Specifically, RSMA is utilized to enhance covertness and address the challenge of integrating covert services while maintaining concealment from regular subscribers. The paper formulates an optimization problem aimed at maximizing the minimal communication rate among all covert users. An iterative algorithm is proposed, employing matrix lifting and fractional programming. Our scheme is also applicable to space division multiple access (SDMA) and non-orthogonal multiple access (NOMA). Numerical results confirm RSMA's superiority over SDMA and NOMA counterparts in achieving higher covert rates in both underloaded and overloaded user deployments.