This paper proposes a new scheme to enhance the secrecy performance of a NOMA-based coordinated direct relay transmission system (NOMA-CDRT) with an untrusted relay. The physical-layer network coding and the non-orthogonal multiple access scheme are combined to improve the spectrum efficiency. Furthermore, inter-user interference and friendly jamming signals are utilized to suppress the eavesdropping ability of the untrusted relay without affecting the acceptance quality of legitimate users. Specifically, the far user in the first slot and the near user in the second slot act as jammers to generate jamming signals to ensure secure transmissions of the confidential signals. We investigate the secrecy performance of the proposed scheme in NOMA-CDRT systems and derive the closed-form expression for the ergodic secrecy sum rate. The asymptotic analysis at high signal-to-noise ratio is performed to obtain more insights. Finally, simulation results are presented to demonstrate the effectiveness of the proposed scheme and the correctness of the theoretical analysis.
翻译:本文提出一个新的计划,用一个不信任的中继器,提高基于NOMA的协调型直接中继传输系统(NOMA-CDRT)的保密性能;将物理层网络编码和非横向多功能访问机制结合起来,以提高频谱效率;此外,用户之间的干扰和友好干扰信号被用来压制未受信任的中继器的窃听能力,同时不影响合法用户的接受质量;具体地说,第一个空格中最远的用户和第二个空格中最接近的用户充当干扰器,产生干扰信号,以确保保密信号的安全传输;我们调查NOMA-CDRT系统中拟议中的系统保密性能,并得出ERGodic保密总和率的封闭式表达方式;对高信号对音比进行静音分析,以获得更多的洞察力;最后,提出模拟结果,以证明拟议方案的有效性和理论分析的正确性。