A novel semantics-empowered two-user uplink non-orthogonal multiple access (NOMA) framework is proposed for resource efficiency enhancement. More particularly, a secondary far user (F-user) employs the semantic communication (SemCom) while a primary near user (N-user) employs the conventional bit-based communication (BitCom). The fundamental performance limit, namely semantic-versus-bit (SvB) rate region, of the proposed semantics-empowered NOMA framework is characterized. The equivalent SvB rate region achieved by the conventional BitCom-based NOMA is provided as the baseline scheme. It unveils that, compared to BitCom, SemCom can significantly improve the F-user's performance when its permitted transmit power is strictly capped, but may perform worse when its permitted transmit power is high. Guided by this result, the proposed semantics-empowered NOMA framework is investigated over fading channels. An opportunistic SemCom and BitCom scheme is proposed, which enables the secondary F-user to participate in NOMA via the most suitable communication method at each fading state, thus striking a good tradeoff between its own achieved performance and the interference imposed to the primary N-user. Two scenarios are considered for employing the opportunistic scheme, namely on-off resource management and continuous resource management. For each scenario, the optimal communication policy over fading channels is derived for maximizing the ergodic semantic rate achieved at the secondary F-user, subject to the minimum ergodic bit rate constraint of the primary N-user. Numerical results show that the proposed opportunistic scheme in both scenarios can achieve higher communication performance for NOMA than the baseline schemes merely employing SemCom or BitCom.

翻译：为了提高资源使用效率,提议了一个新型的语义和二手双用户双向上链接非正统多重访问(NOMA)框架。更具体地说,一个二级远端用户(Fuser)使用语义通信(SemCom),而一个初级近端用户(Nuser)使用常规的位基通信(BitCom)。基本性能限制,即语义-反比(SvB)比率(SvB)区域,是拟议的语义-超标(NOMA)框架的特征。一种机会式的SemCom和BitCom计划,使得基于常规的BitCom Com IMA达到的SvB比率(NOMA)作为基线方案的基准。它披露,与BitCom相比,SemCom(Fuser)在允许的传输能力被严格限制的情况下,可以显著改善F用户的性能,但在允许的传输能力被允许时,其表现可能更差。 由此,拟议的语义-反比FSlormantal 管理模式的自我实现最佳性表现。