Non-orthogonal multiple access (NOMA) as a promising technology, can achieve enhanced connectivity and spectral efficiency. However, the asymmetric channels in uplink NOMA systems can bring distinct uncertainty of the bit error rate (BER) and throughput performances to the users. To address this problem, an asymmetric adaptive modulation (AAM) framework for uplink NOMA systems is introduced in this paper. We first derive the closed-form BER expressions for uplink NOMA systems, then we propose a principle for reducing the performance uncertainty. Finally, we develop an AAM algorithm for uplink NOMA systems by studying the closed-form BER expressions. Numerical results demonstrate the correctness of the BER expressions we derived, and show that our AAM algorithm outperforms the benchmark in terms of the system sum throughput.

中文翻译：

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上行链路 NOMA 系统的非对称自适应调制


非正交多址（NOMA）作为一种有前途的技术，可以实现增强的连接性和频谱效率。然而，上行NOMA系统中的非对称信道会给用户带来明显的误码率（BER）和吞吐量性能的不确定性。为了解决这个问题，本文引入了一种用于上行链路 NOMA 系统的非对称自适应调制（AAM）框架。我们首先推导出上行链路 NOMA 系统的封闭式 BER 表达式，然后提出减少性能不确定性的原则。最后，我们通过研究闭式 BER 表达式，开发了一种用于上行链路 NOMA 系统的 AAM 算法。数值结果证明了我们推导的 BER 表达式的正确性，并表明我们的 AAM 算法在系统总吞吐量方面优于基准。