保密通信中同相和正交通道失衡对干扰抑制性能的影响

针对同时存在恶意干扰与非法窃听的通信环境，提出一种协作干扰(cooperative jamming, CJ)掩护的保密通信架构，收发信机之间采用跳频技术躲避恶意干扰，并采用协作干扰技术阻塞非法窃听。但该架构的通信带宽较大，会在收发频率振荡器中引起显著的同相和正交(in-phase and quadrature, IQ)通道失衡。鉴于此，对收发IQ通道失衡引起的信号失真进行数学建模，给出接收机处信干噪比的数学表达式，并给出干扰抑制比的闭合表达式。仿真结果表明，收发IQ通道失衡引起的信号失真的功率远大于热噪声功率。随着收发IQ通道失衡加剧，所提架构的信干噪比和干扰抑制比性能均会急剧下降，当幅度和相位失衡分别达到0.95和π/50时，信干噪比和干扰抑制比均损失了47 dB。

Impact of transceiver IQ imbalances on cooperative jamming suppression in confidential communications

For the transmission design problem in an IRS(intelligent reflecting surface)-enabled network, by jointly designing the transmit beamforming and IRS reflecting coefficient, the goal of this paper was to maximize the weighted sum rate for multiply ground users, subject to the transmit power and the unit modulus constraint. To solve the non-convex objective, we developed an alternating optimization method, where the phase shifter optimization was solved by the RMG(Riemannian manifold gradient) method, and the beamforming was obtained by the bisection search method. Furthermore, an element-wise block coordinate descent-based method was proposed to reduce the complexity of the RMG method. Simulation results verify the effectiveness of the proposed algorithm, and demonstrate that IRS can significantly improve the spectrum efficiency, when the reflecting coefficients are properly optimized.