Energy-Spectral Efficiency Trade-Off in IRS-Assisted NOMA Systems: A Weighted Product Method

The deployment of intelligent reflecting surfaces (IRS) in non-orthogonal multiple access (NOMA), known as IRS-assisted NOMA-based systems, has recently been considered a potential solution to address the complicated demands of beyond-fifth-generation communication networks. This paper investigates a multi-objective allocation resource allocation technique for an IR-assisted hybrid time division multiple access (TDMA)-NOMA network. To reflect the requirements of such a system, two conflicting performance metrics, namely energy efficiency (EE) and spectral efficiency (SE), are simultaneously optimized under a set of quality-of-service constraints. The proposed SE-EE trade-off design is formulated as a multi-objective optimization (MOO) framework. However, such an MOO problem cannot be solved by conventional approaches. Therefore, the weighted product method (WPM) is proposed to transform the MOO problem into a conventional single-objective optimization (SOO) problem. Meanwhile, the SOO problem through the WPM approach is non-convex in nature, where the optimization parameters, namely the power allocation and the reflecting coefficients of the IRS elements, are jointly designed. As a result, an iterative technique is designed to address this problem and assess the optimization variables. The simulation results demonstrate that the proposed WPM for the SE-EE trade-off resource allocation technique can balance competing optimization variables alongside meeting the system’s demands.