PowerMin Problem Optimisation: Enhance Energy Efficiency in Multi-User IRS-Assisted MISO Downlink

In the proposed work, enhanced efficiency in multi user intelligent reflection surface (IRS) - assisted MISO down-link is presented. IRS have made a significant technological breakthrough with the potential to revolutionize future wireless systems. By harnessing this capability and have the remarkable ability to significantly enhance spectral efficiency and reduce power usage in wireless communication systems. The versatility of IRSs allows them to extend the range, reliability, and overall efficiency of wireless connections. One of the most critical aspects in wireless communication system design is the reduction of total power consumption, making the Transmit Power Minimization (PowerMin) problem of utmost importance. When comparing two methods for initializing phase-shift at the Reconfigurable Intelligent Surface (RIS), it is observed that the random initialization of phase angles uniformly distributed in the range from 0 to 2 outperforms unit initialization. Notably, the random initialization approach demonstrates superior results, especially in scenarios featuring a substantial number of users. Conversely, the second approach, which entails unit initialization, is advantageous in terms of power requirements. When examining the impact of IRS reflecting elements on transmitted power, it is observed that the transmitted power diminishes by a factor of 1/N
²
with the increase in the number of reflection elements, denoted as N, at the IRS. This reduction in transmitted power is a noteworthy phenomenon to consider in the context of IRS-based communication systems.