有限字母物理层安全的伪噪声叠加
Pseudo-Noise Superposition for Finite-Alphabet Physical Layer Security
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中文总结 AI 辅助
该研究针对6G无线系统，分析$M$-QAM调制下PN辅助系统的保密性能，发现高SNR时信息速率对PN功率分配不敏感，可实现近乎完美保密，凸显有限字母安全机制的实用性。
中文摘要 AI 辅助
基于伪噪声（PN）叠加的物理层安全是缓解未来无线系统中窃听问题的有前景方法。然而，在采用高斯信号的香农容量框架下实现保密通常需要为PN分配大量发射功率，导致可实现信息速率显著降低，限制了实际应用。当采用有限字母调制方案（如M元正交幅度调制，即$M$-QAM，这是实际6G收发机的预期配置）时，该限制得到缓解。本研究使用互信息分析了PN辅助系统在$M$-QAM信号下的信息速率性能，并推导了对应的可实现保密速率。在不同调制阶数和信道条件下，研究了PN功率分配对合法用户和窃听者的影响。进行了蒙特卡洛仿真，以评估不同用户和窃听者信道条件下的系统行为，并考察PN功率分配如何影响保密性能。结果表明，在足够高的信噪比（SNR）下，信息速率对PN功率分配的敏感度大幅降低，使得采用$M$-QAM调制时可实现近乎完美的保密——这凸显了与基于香农容量的保密分析的关键差异，并强调了有限字母安全机制对6G无线系统的实用性。
英文摘要
Physical-layer security based on pseudo-noise (PN) superposition is a promising approach for mitigating eavesdropping in future wireless systems. However, under Shannon's capacity formulation with Gaussian signaling, achieving secrecy typically requires allocating substantial transmit power to PN, resulting in a significant reduction in achievable information rate and limiting practical applicability. This limitation is alleviated when finite-alphabet modulation schemes, such as M-ary Quadrature Amplitude Modulation ($M$-QAM), are employed, as expected in practical 6G transceivers. In this work, we analyze the information rate performance of PN-assisted systems under $M$-QAM signaling using mutual information and derive the corresponding achievable secrecy rate. The impact of PN power allocation on both the legitimate user and the eavesdropper is investigated across different modulation orders and channel conditions. Monte Carlo simulations are conducted to evaluate system behavior under varying user and eavesdropper channel conditions and to examine how PN power allocation influences secrecy performance. The results show that, at sufficiently high signal-to-noise ratio (SNR), the information rate becomes largely insensitive to PN power allocation, enabling near-perfect secrecy with $M$-QAM modulation-highlighting a key departure from Shannon-capacity-based secrecy analyses and underscoring the practicality of finite-alphabet security mechanisms for 6G wireless systems.
