Energy Efficiency Analysis of Active RIS Enhanced Wireless Networks under Independent Power Constraints

In this paper, the main factors affecting global energy efficiency (GEE) in active reconfigurable intelligent surface (RIS) assisted wireless communication network in Rayleigh fading channels is studied. Using the law of large numbers, asymptotic expressions for GEE with respect to the number N of RIS elements, the transmission power at base station (BS), the reflection power at RIS, the noise at RIS and the noise at user are derived. Theoretical analysis shows that when N tends towards a large-scale, the asymptotic performance of GEE is better. In addition, as transmission power at BS and the reflection power at RIS approach infinity, GEE gradually approaches 0. When the noise at RIS and the noise at user approach infinitesimal, GEE converges to a fixed value. The simulation results validate the correctness of the theoretical analysis. The GEE performance of active RIS assisted system has decreased due to the influence of noise. As N increases, the GEE performance of passive RIS assisted system gradually surpasses that of active RIS system.