无蜂窝大规模MIMO下行链路的导频欺骗攻击：来自攻击者视角的研究
Pilot Spoofing Attack on the Downlink of Cell-Free Massive MIMO: From the Perspective of Adversaries
AI总结：
该研究从攻击者视角分析无蜂窝大规模MIMO系统的下行导频欺骗攻击，推导攻击下的速率闭式解，优化攻击功率分配，并对比导频欺骗与随机干扰两类攻击的破坏效果。
摘要：
与蜂窝式大规模多输入多输出（mMIMO）系统相比，无蜂窝mMIMO系统的信道硬化效应不够显著，因此需要估计下行链路有效信道增益以保障良好性能。但下行链路训练无意中为对抗节点发动导频欺骗攻击（PSA）创造了机会。首先，我们证明对抗性分布式接入点（AP）会严重降低可实现的下行链路速率：它们在上行链路训练阶段估计自身到用户的信道，再在下行链路训练阶段对合法AP使用的相同导频序列进行预编码并发送。随后，通过严格推导单用户可实现下行链路速率的闭式表达式，研究了下行PSA的影响。对抗性AP采用最小-最大准则优化功率分配系数，可将下行传输的最大单用户可实现速率降至最低。作为下行PSA的替代方案，对抗性AP也可选择在下行数据传输阶段预编码随机干扰，以破坏合法通信；针对该场景，我们推导了可实现下行链路速率，并开发了相应的功率优化算法。我们通过数值结果展示了下行PSA的破坏性影响，并对比了两类攻击的效果。
英文摘要：
The channel hardening effect is less pronounced in the cell-free massive multiple-input multiple-output (mMIMO) system compared to its cellular counterpart, making it necessary to estimate the downlink effective channel gains to ensure decent performance. However, the downlink training inadvertently creates an opportunity for adversarial nodes to launch pilot spoofing attacks (PSAs). First, we demonstrate that adversarial distributed access points (APs) can severely degrade the achievable downlink rate. They achieve this by estimating their channels to users in the uplink training phase and then precoding and sending the same pilot sequences as those used by legitimate APs during the downlink training phase. Then, the impact of the downlink PSA is investigated by rigorously deriving a closed-form expression of the per-user achievable downlink rate. By employing the min-max criterion to optimize the power allocation coefficients, the maximum per-user achievable rate of downlink transmission is minimized from the perspective of adversarial APs. As an alternative to the downlink PSA, adversarial APs may opt to precode random interference during the downlink data transmission phase in order to disrupt legitimate communications. In this scenario, the achievable downlink rate is derived, and then power optimization algorithms are also developed. We present numerical results to showcase the detrimental impact of the downlink PSA and compare the effects of these two types of attacks.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
