In this paper, we design a secure transmission scheme in hybrid automatic repeat request (HARQ) assisted cognitive non-orthogonal multiple access (NOMA) networks, where a security-required user (SRU) is paired with a quality of service (QoS)-sensitive user (QSU) to perform NOMA. To elaborate, the QoS requirement of the QSU is guaranteed by a cognitive power allocation scheme, while the HARQ technique is employed to mitigate the successive interference cancellation (SIC) errors and improve the secrecy performance of the SRU. For reducing information leakage, a randomized retransmission NOMA (RR-NOMA) scheme is designed, where the retransmitted signals are generated from independent randomized codebooks. In this scheme, the closed-form expressions for the connection outage probability (COP), the average number of transmission (ANT), the secrecy outage probability (SOP), and effective secrecy throughput (EST) of the SRU are derived. In addition, as benchmarks, the performance analyses for the fixed retransmission (FR-NOMA) scheme and the randomized retransmission orthogonal multiple access (RR-OMA) scheme are also provided. Results show a trade-off between SOP and COP or EST, which is denoted by security-reliability trade-off (SRT) or security-efficiency trade-off (SET). Furthermore, simulation results show that the HARQ technique improves SRT and the RR-NOMA scheme achieves better SET than the FR-NOMA scheme in the low SOP region. We further conduct asymptotic analysis in the RR-NOMA, FR-NOMA and RR-OMA schemes. Asymptotic results demonstrate that the three schemes achieve the same ANT and the RR-NOMA scheme obtains better secrecy performance than the RR-OMA scheme and equal secrecy performance to the FR-NOMA scheme in terms of both EST and SOP.

中文翻译：

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HARQ辅助认知NOMA网络中的安全传输设计


在本文中，我们设计了混合自动重传请求（HARQ）辅助认知非正交多址（NOMA）网络中的安全传输方案，其中安全要求用户（SRU）与服务质量（QoS）配对 -敏感用户 (QSU) 执行 NOMA。具体来说，QSU的QoS要求通过认知功率分配方案来保证，同时采用HARQ技术来减轻连续干扰消除(SIC)错误并提高SRU的保密性能。为了减少信息泄漏，设计了随机重传NOMA（RR-NOMA）方案，其中重传信号是从独立的随机码本生成的。在该方案中，推导了SRU的连接中断概率(COP)、平均传输次数(ANT)、保密中断概率(SOP)和有效保密吞吐量(EST)的封闭式表达式。此外，作为基准，还提供了固定重传（FR-NOMA）方案和随机重传正交多址（RR-OMA）方案的性能分析。结果显示 SOP 和 COP 或 EST 之间存在权衡，用安全可靠性权衡（SRT）或安全效率权衡（SET）表示。此外，仿真结果表明，HARQ技术提高了SRT，并且RR-NOMA方案在低SOP区域中比FR-NOMA方案实现了更好的SET。我们进一步对RR-NOMA、FR-NOMA和RR-OMA方案进行渐近分析。渐近结果表明，三种方案均达到了相同的ANT，并且RR-NOMA方案在EST和SOP方面比RR-OMA方案获得了更好的保密性能，并且与FR-NOMA方案具有相同的保密性能。