Performance of Cooperative Communication System With Multiple Reconfigurable Intelligent Surfaces Over Nakagami-m Fading Channels

Abstract

In this paper, the advantages of multiple reconfigurable intelligent surfaces (RISs) assisted wireless systems and direct link between two terminals are exploited by considering a cooperative communication system where reflecting links created by multiple RISs and the direct link are combined at the receiver. We mathematically analyze the performance of the cooperative multiple RISs -direct link (RIS-D) system over Nakagami-m fading channels by obtaining the symbol error probability (SEP) expression. In addition, the SEP of the single-input single-output (SISO) system without RISs (i.e., there is only direct link between two terminals) is also obtained for convenience in comparison the performance of the cooperative RIS-D and SISO systems. We demonstrate the correctness of the derived expressions via Monte-Carlo simulations. Numerical results show that the SEP of the cooperative RIS-D system significantly lower than that of the SISO system for a certain transmission power of the transmitter. Also, for a certain SEP target, the cooperative RIS-D system can greatly save energy consumption in comparison with the SISO system. Specifically, increasing the number of RISs or the number of reflecting elements (REs) in the RISs can remarkably reduce the SEP of the cooperative RIS-D system. On the other hand, the impacts of the system parameters such as the number of RISs, the number of REs, and the Nakagami-m fading channels are fully investigated to clearly indicate their influences on the SEP of the cooperative RIS-D system.

Joint Beamforming Optimization Design and Performance Evaluation of RIS-Aided Wireless Networks: A Comprehensive State-of-the-Art Review

“…Therefore, future research should focus on developing more accurate analytical models to evaluate the performance of the considered system, particularly in scenarios with a small number of RUs. The authors of [187] have explored a system model similar to that of [186], in which a single-antenna source communicates with a single-antenna destination with the aid of multiple RISs over a Nakagami-m fading channel, and in the presence of a direct link. The RISs are placed between the source and destination in different locations across different scenarios, and each RIS is equipped with several RUs.…”

“…Most studies conducted so far have primarily focused on analyzing the performance of a single RIS. Nevertheless, there exist a limited number of works in the literature that have considered the case of multiple RISs [69], [186], [187], [188], [192], [193], [194], [195]. While these studies have provided valuable insights into system design and parameters, they have often relied on simplified system models that incorporate SISO scenarios, which may not fully capture real-world complexities.…”

“…The majority of studies on RIS-based systems have primarily relied on CLT-based approximation [65], [66], [67], [172], [175], [178], [186], while others have explored the use of the Gamma approximation [68], [69], [166], [187]. It is important to note that while the CLT approximation guarantees accurate results when there is a large number of RUs, its reliability diminishes when the number of RUs is small [170].…”

PhysFad: Physics-Based End-to-End Channel Modeling of RIS-Parametrized Environments with Adjustable Fading

“…where H RX−RIS and H T X−RIS are random matrices emulating fading (e.g., Rayleigh) between the multi-antenna transceivers and the RIS, and Φ RIS contains the reflection coefficients of the RIS elements [50]- [58]. Such formulations represent an one-way cascade of multiple scattering events, followed by one interaction with the RIS and further multiple scattering events.…”

Multiple RISs-Aided Networks: Performance Analysis and Optimization

“…fading channels scenario. Most recently, a study that investigates the error probability performance of a multi-RIS-aided network has been proposed in [25]. Closed-form expression was derived for the system SEP assuming i.i.d.…”