Semi-NOMA enabled Coexisting Semantic and Bit Communications

The coexistence of the emerging semantic trans-mission and the conventional bit-based transmission in future networks. The semantic rate is considered for measuring the performance of the semantic transmission. To obtain a closed-form expression of the key parameter, namely the semantic similarity, we propose a data regression method, where the semantic similarity is approximated by a generalized logistic function. Using the obtained tractable function, we propose a novel semi non-orthogonal multiple access (semi-NOMA) scheme for enabling an access point simultaneously to send the semantic and bit streams to one semantics-interested user (S-user) and one bit-interested user (B-user). More specifically, the bit stream in semi-NOMA is split into two streams, one is transmitted with the semantic stream over the shared frequency sub-band and the other is transmitted over the separate orthogonal frequency sub-band. An optimal resource allocation procedure is derived for characterizing the boundary of the semantic-versus-bit (SvB) rate region achieved by the proposed semi-NOMA. Finally, our numerical results demonstrate that semi-NOMA is superior to both conventional NOMA and orthogonal multiple access schemes in the considered coexisting semantic and bit transmission.