This letter studies the legitimate surveillance with one half-duplex legitimate monitor (E) over the suspicious multichannel relaying system, where the suspicious transmitter (ST) and relay (SR) implement the optimal power allocation over all orthogonal channels under a joint sum-power constraint to maximize the communication rate of the suspicious system. Under this setup and considering that SR operates in amplify-and-forward (AF) or decode-and-forward (DF) mode, E aims to i) determine the optimal set of sub-channels for jamming and ii) optimize its jamming power over these sub-channels in order to deliberately force ST and SR reallocating power to the unjammed sub-channels to the most, so as to increase the perceived power of E over the unjammed sub-channels and then maximize the eavesdropping rate. In particular, for the AF case, the formulated problem is non-convex, for which the slack variables are introduced and successive convex approximation is exploited. For the DF case, some insights are provided for the optimization process. Results present the considerable gain of the proposed strategy compared to intuitive schemes.

中文翻译：

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多通道中继系统中的干扰合法监控


这封信研究了使用一个半双工合法监视器（E）对可疑多通道中继系统进行的合法监视，其中可疑发射机（ST）和中继站（SR）在联合总功率下在所有正交通道上实现最佳功率分配最大程度地提高可疑系统的通信速率的约束。在此设置下，考虑到 SR 在放大转发 (AF) 或解码转发 (DF) 模式下运行，E 的目标是 i) 确定用于干扰的最佳子信道集，以及 ii) 优化其干扰功率目的是故意强制ST和SR将功率最大程度地重新分配给未受干扰的子信道，从而增加E在未受干扰的子信道上的感知功率，从而最大化窃听率。特别是，对于 AF 情况，公式化的问题是非凸的，为此引入了松弛变量并利用了逐次凸逼近。对于 DF 案例，为优化过程提供了一些见解。结果表明，与直观方案相比，所提出的策略具有相当大的增益。