Active IRS -Assisted Resource Allocation for MISO System

As an emerging technology, intelligent reflecting surface (IRS) has attached attention of academia because it can customize a favorable wireless propagation environment. However, for the traditional passive structure, IRS can merely alter the phase of the incident signal, which limits the maximum attainable beamforming gain. In order to give full play to the potential of IRS, in this paper, we employ an active IRS, which is able to alter the phase and amplify the amplitude of the incident signals simultaneously because there exists an additional power supply. So as to improve the performance of active IRS-assisted communication system, the reflection matrix of the IRS and the beamforming vector of the base station (BS) are jointly considered and optimized to minimize the transmit power of the BS. Design the algorithm of power resource allocation usually be converted into an optimization problem, and must meet the maximum power margin of active IRS and satisfy the quality of service (QoS) requirements of users. Aiming at solving the nonconvex problem, we designed a high calculation efficiency algorithm on the strength of the internal approximation (IA) method and bilinear transformation. The algorithm guarantees convergence to the local optimal solution of the problem under consideration. Simulation indicates that this scheme is effective compared with the two blank control schemes. In addition, the results indicate that compared with passive IRS, deploying active IRS has great advantages for boosting the performance of communication systems, especially in the presence of strong direct links.