Comparative analysis of intelligent reflecting surfaces and AF/DF relaying for energy efficient wireless communication

(2025) 2025:26 Yadav et al. J Wireless Com Network https://doi.org/10.1186/s13638-025-02453-0 EURASIP Journal on Wireless Communications and Networking Open Access RESEARCH Comparative analysis of intelligent reflecting surfaces and AF/DF relaying for energy efficient wireless communication Kuldeep Yadav1* , Himanshu Parashar2 and Soumen Mondal3 *Correspondence: 1 Vellore Institute of Technology, Chennai, India 2 Galgotias University, Greater Noida, India 3 National Institute of Technology, Durgapur, India Abstract This paper presents a comparative analysis of intelligent reflecting surface (IRS) technology versus conventional amplify-and-forward (AF) and decode-and-forward (DF) relay schemes in wireless communication. By focusing on transmit power, energy efficiency, and the minimum IRS elements required to outperform traditional relaying, we explore IRS’s potential as an energy efficient alternative. Our analysis shows that IRS configurations, especially with optimal phase shifts, achieve substantial power savings and superior energy efficiency over to AF and DF relays. Moreover, IRS requires fewer elements to meet or exceed relaying performance under higher data rate demands, making it an ideal choice for energy conscious, high performance network designs. These results highlight IRS technology as a promising solution for sustainable, nextgeneration communication networks. Keywords: Intelligent reflecting surface, AF relay, DF relay, Energy efficiency 1 Introduction The increasing demand for higher data speeds in emerging and future wireless networks, such as fifth generation (5 G) and beyond, has raised significant concerns about energy consumption [1]. To address these challenges, strategies for energy efficient 5 G networks have emphasized renewable energy integration, green resource allocation, and advanced signal processing algorithms [2]. Among the hardware solutions, intelligent reflecting surfaces (IRS) have emerged as a transformative technology for reducing energy consumption [3–5]. IRS technology employs reflective metasurfaces integrated with electronics to control electromagnetic wave propagation, enabling efficient signal redirection without requiring active power amplification [6, 7]. Its passive operation eliminates the need for power amplifiers, making it inherently energy efficient and particularly appealing for energy constrained applications, such as IoT networks. Furthermore, its lightweight and compact design facilitates seamless integration into diverse environments, including building facades, ceilings, and wearable devices [8, 9]. While traditional MIMO systems offer excellent spatial multiplexing and high data rates, their reliance on active components significantly increases power consumption © The Author(s) 2025. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http:// creativecommons.org/licenses/by/4.0/. Yadav et al. J Wireless Com Network (2025) 2025:26 Page 2 of 15 and implementation complexity [10, 11]. In contrast, IRS provides a scalable and cost effective alternative with simplified hardware requirements. However, its performance depends heavily on precise phase alignment and accurate channel state information (CSI), which are challenging to achieve in dynamic environments. Despite the energy efficiency benefits of IRS, its achievable gain may not always exceed that of traditional relay systems with an equivalent number of antennas as IRS elements. Thus, whether IRS-based systems consistently outperform conventional relay systems in terms of energy efficiency remains unclear [12–15]. Previous studies have predominantly focused on comparing IRS with decode-and-forward (DF) relays, evaluating energy efficiency and data rates [16]. However, comprehensive analyses comparing IRS to both amplifyand-forward (AF) and DF relays remain limited, despite the distinct advantages offered by each relay type under varying channel conditions. Such a study is essential to determine the viability of IRS as a replacement for traditional relaying systems. In this paper, we present a comparative analysis of IRS, AF, and DF relaying schemes, with a focus on key performance metrics such as transmit power, energy efficiency, and the minimum number of IRS elements required to surpass traditional relay performance. Our study is conducted in Rayleigh fading channels, and we explore configurations that include optimal and random phase shifts for IRS. The proposed IRS-assisted system model has practical applications across various wireless communication scenarios. IRS can enhance coverage in dense urban environments suffering from severe path loss, enable energy efficient IoT connectivity, and improve signal reliability in UAV assisted communications for disaster recovery and remote sensing. These use cases highlight the relevance of IRS as an energy efficient solution for next-generation networks. The remainder of the paper is organized as follows: Sect. 2 details the system model. Section 3 presents the comparative analysis of IRS, AF, and DF relaying schemes. Section 4 discusses results and their implications for system efficiency. Finally, Sect. 5 concludes the paper. The list of notations is shown in Table 1 for the purpose of clarity. 2 Methods and system model This study develops a system model to analyze the performance of IRS in wireless communication. Analytical formulations are derived for key performance metrics, including achievable data rate, transmit power, and energy efficiency, under Rayleigh fading channels. Monte Carlo simulations validate the analytical results and provide statistical Table 1 List of notations Notation Description ∼ Distributed as CN (., .) Complex Gaussian distribution Italic letters Scalars Boldface italic letters Vectors (.)∗ Conjugate operator ∈ Belongs to C Complex-valued matrix |.| Modulus Yadav et al. J Wireless Com Network (2025) 2025:26 Page 3 of 15 accuracy across a range of scenarios. The simulations incorporate realistic propagation parameters, such as path loss, noise, and channel fading, ensuring the results are applicable to real world wireless communication environments. 2.1 System model The system model, illustrated in Fig. (...truncated)