Non-orthogonal multiple access (NOMA) has a great potential to offer a higher spectral efficiency of multi-user wireless networks than orthogonal multiples access (OMA). Previous work has established the condition, referred to quasi-degradation (QD) probability, under which NOMA has no performance loss compared to the capacity-achieving dirty paper coding for the two-user case. Existing results assume Rayleigh fading channels without line-of-sight (LOS). In many practical scenarios, the channel LOS component is critical to the link quality where the channel gain follows a Rician distribution instead of a Rayleigh distribution. In this work, we analyze the QD probability over multi-input and single-output (MISO) channels subject to Rician fading. The QD probability heavily depends on the angle between two user channels, which involves a matrix quadratic form in random vectors and a stochastic matrix. With the deterministic LOS component, the distribution of the matrix quadratic form is non-central that dramatically complicates the derivation of the QD probability. To remedy this difficulty, a series of approximations is proposed that yields a closed-form expression for the QD probability over MISO Rician channels. Numerical results are presented to assess the analysis accuracy and get insights into the optimality of NOMA over Rician fading channels.
翻译:非垂直多重存取( NOMA) 具有巨大的潜力, 能够提供多用户无线网络的光谱效率高于正方数存取( OMA ) 。 先前的工作已经设定了条件, 提到了准降解( QD) 概率, 在这种概率下, NOMA 与双用户案例中达到的脏纸编码能力相比没有性能损失。 现有结果假设雷利脱色通道没有直观( LOS) 。 在许多实际情景中, 频道的LLOS 元件对于连接质量至关重要, 频道在通过里氏分布而不是雷利分布获得联系质量。 在这项工作中, 我们分析了多输入和单输出( IMO) 通道的QD概率。 QD 概率在很大程度上取决于两个用户频道之间的角度, 后者包括随机矢量矩阵和随机矩阵。 在确定性LOS 组件中, 矩阵二次形式分布并不集中, 使QD 映射到QD 直径通道的推断结果变得非常复杂 。 IMA 分析 的模型是用于 QD 最佳解析测 的概率 。 。