Owing to the eminent performance gain, non-orthogonal multiple access (NOMA) has been regarded as a promising approach to achieve high throughput and low latency for the next-generation networks. Nevertheless, potential adversaries can still pose a threat to secure transmission in NOMA systems. Hence, in this article, secure transmission schemes based on beamforming optimization are designed to combat both internal and external eavesdropping for downlink multi-input single-output NOMA networks. Using the transmit beamforming design, we first propose two schemes to protect the privacy of a specific NOMA user in the presence of untrusted users. Then, the sum secrecy rate optimization problem is studied to combat the external eavesdropper through optimizing the precoding vectors, when the channel state information (CSI) is available. In addition, two secure beamforming strategies with the help of artificial noise and inter-user interference are proposed without eavesdropping CSI, respectively. Simulation results are presented to demonstrate the effectiveness of the proposed schemes, and some open issues are discussed as well.

中文翻译：

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通过波束成形优化实现NOMA网络的安全传输

由于性能的显着提高，非正交多路访问（NOMA）被视为实现下一代网络高吞吐量和低延迟的一种有前途的方法。尽管如此，潜在的对手仍可能对NOMA系统中的安全传输构成威胁。因此，在本文中，设计了基于波束成形优化的安全传输方案，以应对下行链路多输入单输出NOMA网络的内部和外部窃听。使用发射波束成形设计，我们首先提出两种方案，以在存在不信任用户的情况下保护特定NOMA用户的隐私。然后，研究了总保密率优化问题，以在信道状态信息（CSI）可用时通过优化预编码向量与外部窃听者作斗争。此外，分别提出了两种在不窃听CSI的情况下借助人工噪声和用户间干扰的安全波束成形策略。仿真结果表明了所提方案的有效性，并讨论了一些未解决的问题。