Secrecy transmission is investigated for a cooperative jamming scheme, where a multi-antenna jammer generates artificial noise (AN) to confuse eavesdroppers. Two kinds of eavesdroppers are considered: passive eavesdroppers who only overhear the legitimate information, and active eavesdroppers who not only overhear the legitimate information but also jam the legitimate signal. Existing works only treat the passive and active eavesdroppers separately. Different from the existing works, we investigate the achievable secrecy rate in presence of both active and passive eavesdroppers. For the considered system model, we assume that the instantaneous channel state information (CSI) of the active eavesdroppers is available at the jammer, while only partial CSI of the passive eavesdroppers is available at the jammer. A new zero-forcing beamforming scheme is proposed in the presence of both active and passive eavesdroppers. For both the perfect and imperfect CSI cases, the total transmission power allocation between the information and AN signals is optimized to maximize the achievable secrecy rate. Numerical results show that imperfect CSI between the jammer and the legitimate receiver will do more harm to the achievable secrecy rate than imperfect CSI between the jammer and the active eavesdropper.

中文翻译：

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使用主动和被动窃听者进行安全传输的协作干扰

针对协作干扰方案研究了保密传输，其中多天线干扰器产生人工噪声 (AN) 以迷惑窃听者。考虑两种窃听者：只偷听合法信息的被动窃听者，和既偷听合法信息又干扰合法信号的主动窃听者。现有作品仅将被动窃听者和主动窃听者分开处理。与现有工作不同，我们研究了在主动和被动窃听者存在的情况下可实现的保密率。对于所考虑的系统模型，我们假设主动窃听者的瞬时信道状态信息 (CSI) 在干扰器处可用，而在干扰器处仅被动窃听器的部分 CSI 可用。在存在主动和被动窃听者的情况下，提出了一种新的迫零波束成形方案。对于完美和不完美的 CSI 情况，信息和 AN 信号之间的总传输功率分配被优化以最大化可实现的保密率。数值结果表明，干扰者和合法接收者之间的不完善 CSI 比干扰者和主动窃听者之间的不完善 CSI 对可达到的保密率造成更大的危害。