In this paper, we investigate joint power control and access point (AP) selection scheme in a cell-free massive multiple-input multiple-output (CF-mMIMO) system under an active eavesdropping attack, where an eavesdropper tries to overhear the signal sent to one of the legitimate users by contaminating the uplink channel estimation. We formulate a joint optimization problem to minimize the eavesdropping spectral efficiency (SE) while guaranteeing a given SE requirement at legitimate users. The challenging formulated problem is converted into a more tractable form and an efficient low-complexity accelerated projected gradient (APG)-based approach is proposed to solve it. Our findings reveal that the proposed joint optimization approach significantly outperforms the heuristic approaches in terms of secrecy SE (SSE). For instance, the $50\%$ likely SSE performance of the proposed approach is $265\%$ higher than that of equal power allocation and random AP selection scheme.

翻译：本文研究了主动窃听攻击下无小区大规模多输入多输出（CF-mMIMO）系统中的联合功率控制与接入点（AP）选择方案，其中窃听者通过污染上行信道估计试图窃听发送给合法用户之一的信号。我们构建了一个联合优化问题，旨在最小化窃听频谱效率（SE），同时保证合法用户满足给定的SE需求。将所提出的挑战性问题转化为更易处理的形式，并提出了一种高效低复杂度的加速投影梯度（APG）方法进行求解。研究结果表明，所提出的联合优化方法在保密频谱效率（SSE）上显著优于启发式方法。例如，所提方法的$50\%$可能SSE性能比等功率分配与随机AP选择方案高出$265\%$。