Secure and Energy-Efficient Communication Scheme for MISO Systems Assisted by Intelligent Reflecting Surfaces

‍ ‍As an innovative 6G technology， an intelligent reflecting surface （IRS） can enhance the energy efficiency and security of future B5G/6G networks. Focusing on the high security risks and high energy consumption of IRS-assisted downlink multiple input single output systems， this study analyzed the impact of transmit beamforming and an IRS phase shift matrix on system security and energy-saving communication. Then， we considered a transmission power minimization problem under secrecy rate constraints. A second-order cone programming algorithm based on successive convex approximation was proposed to iteratively solve this non-convex multivariable coupling problem. In contrast to traditional iterative optimization algorithms， this algorithm simultaneously updated all the optimization variables in each iteration and finally obtained a suboptimal solution to the original problem. The findings from the simulations indicated that compared with the three benchmark schemes （the no-IRS scheme， random phase shift scheme， and SDR iterative optimization scheme）， the algorithm proposed here achieved a lower transmission power while ensuring the confidentiality of legitimate users， which proved the effectiveness of the algorithm and great potential of IRSs in future secure and energy-saving communication systems.