Ergodic secrecy sum rate maximization in downlink sparse code multiple access network

Sparse code multiple access (SCMA) has been recognized as a promising candidate technique for fifth generation (5G) cellular network to improve spectral efficiency (SE). In this paper, physical layer security (PLS) in a downlink single-input single-output (SISO) SCMA system is investigated, which includes one base station (BS), multiple legitimate users and one eavesdropper. The aim of this paper is to maximize the ergodic secrecy sum rate (ESSR) of the SCMA system under the constraint of the transmit power of BS. A novel many-to-many two-side matching algorithm is then proposed. After a limited number of iterations, the algorithm converges to a pair-stable matching. Finally, simulation results indicate that the proposed algorithm outperforms the random scheme and the orthogonal multiple access (OMA) scheme.