Power-Efficient Optimization for Coexisting Semantic and Bit-Based Users in NOMA Networks

Semantic communication focuses on transmitting the meaning of data, aiming for efficient, relevant communication, while non-orthogonal multiple access (NOMA) enhances spectral efficiency by allowing multiple users to share the same spectrum. Integrating semantic users into a NOMA network with bit-based users improves both transmission and spectrum efficiency. However, the performance metric for semantic communication differs significantly from that of traditional communication, posing challenges in simultaneously meeting individual user demands and minimizing transmission power, especially in scenarios with coexisting semantic and bit-based users. Furthermore, the different hardware architectures of semantic and bit-based users complicate the implementation of successive interference cancellation (SIC). To address these challenges, in this paper, we propose a clustered framework to mitigate the complexity of SIC and two multiple access (MA) schemes, e.g., pure cluster-based NOMA (P-CNOMA) and hybrid cluster-based NOMA (H-CNOMA), to minimize the total transmission power. The P-CNOMA scheme can achieve the minimum transmission power, but may not satisfy the high quality of service (QoS) requirement. In contrast, H-CNOMA addresses these issues with a slight increase in power and a reduced semantic rate. These two schemes complement each other, enabling an adaptive MA selection mechanism that adapts to specific network conditions and user requirements.