Toward Opportunistic Semantic and Bit Communications: A NOMA Enabled Approach

In this paper, we address the challenge of enhancing communication efficiency in non-orthogonal multiple access (NOMA) networks by exploring a novel paradigm known as opportunistic semantic and bit communication (OSBC). Our goal is to maximize the ergodic semantic rate while ensuring robust communication under variable channel conditions. Firstly, we propose an adaptive communication strategy that integrates semantic and bit level communications for two NOMA users, tailored to the fading characteristics of each channel state. Next, we introduce a resource allocation scheme that optimizes resource usage by adjusting communication paradigm and transmission power according to the channel conditions, thereby ensuring a minimum guaranteed rate for the near user (N-user) while maximizing the rate for the far user (F-user). Finally, we validate the effectiveness of our proposed scheme through extensive simulations. The results indicate that our approach significantly outperforms existing methods, such as orthogonal multiple access (OMA) strategies, in terms of reducing the overall communication resources and improving the ergodic semantic rate under diverse communication scenarios.