Non-orthogonal multiple access (NOMA) and massive multiple-input multiple-output (MIMO) systems are highly efficient. Massive MIMO systems are inherently resistant to passive attackers (eavesdroppers), thanks to transmissions directed to the desired users. However, active attackers can transmit a combination of legitimate user pilot signals during the channel estimation phase. This way they can mislead the base station (BS) to rotate the transmission in their direction, and allow them to eavesdrop during the downlink data transmission phase. In this paper, we analyse this vulnerability in an improved system model and stronger adversary assumptions, and investigate how physical layer security can mitigate such attacks and ensure secure (confidential) communication. We derive the secrecy outage probability (SOP) and a lower bound on the ergodic secrecy capacity, using stochastic geometry tools when the number of antennas in the BSs tends to infinity. We adapt the result to evaluate the secrecy performance in massive orthogonal multiple access (OMA). We find that appropriate power allocation allows NOMA to outperform OMA in terms of ergodic secrecy rate and SOP.
翻译:非垂直多重存取(NOMA)和大规模多投入多输出(MIMO)系统效率很高。 大型MIMO系统对被动攻击者(窃听者)具有内在的抵抗力,这要归功于向理想用户发送的信号。 但是,主动攻击者可以在频道估计阶段传输合法用户试验信号的组合。 这样他们就可以误导基地台(BS),将传输方向旋转,并允许它们在数据传输的下行阶段进行窃听。 在本文中,我们用改进的系统模型和更强的对立假设分析这种脆弱性,并调查物理层安全如何减轻这种攻击并确保安全(机密)通信。 我们从保密概率(SOP)和对机密性(SOP)能力进行推断,在BS天线的数量趋向无限的时候,使用随机性测量工具来测量。 我们通过调整结果来评估大规模或多位访问(OMA)中的保密性表现。 我们发现,适当的电力分配使得NOMA能够以超过OMA, ERGDI的保密率和SOP。