On Performance of Two-Way Full-Duplex Communication System With Reconfigurable Intelligent Surface

Ba Cao Nguyen,Le The Dung,Tran Manh Hoang,Taejoon Kim

doi:10.1109/access.2021.3086067

Abstract

In this paper, we apply a reconfigurable intelligent surface (RIS) to a two-way (TW) full-duplex (FD) wireless communication system, where a RIS has N reflecting elements and operates as a relay station forwarding signals between two FD terminals. To demonstrate the advantages of RIS compared with traditional relay, we also present the system and signal models of the TW-FD amplify-and-forward relay (AFR) system. We mathematically analyze the performance of the TW-FD-RIS system by deriving the exact closed-form expressions of the average outage probability (AOP) and the average symbol error rate (ASER) in the case N=1, and approximate expressions of the AOP and the ASER in the case N ≥ 2. Besides, we provide the exact closed-form expression of the AOP and approximate expression of the ASER of the TW-FD-AFR system. Monte-Carlo simulations validate all derived mathematical expressions. Numerical results demonstrate that using the RIS greatly improves the TW-FD communication system's performance compared with using amplify-and-forward (AF) relay. Specifically, even the RIS with one element ( N=1), the AOP and ASER of the TW-FD-RIS system are still lower than those of the TW-FD-AFR system in the low signal-to-noise ratio (SNR) regime. However, in the high SNR regime, the AOP and ASER of the TW-FD-RIS system are higher. In the case N ≥ 2, the AOP and ASER of the TW-FD-RIS system are significantly reduced. On the other hand, the impact of residual self-interference (SI) due to FD transmission mode on the performance of TW-FD-RIS and TW-FD-AFR systems is remarkable, making the AOP and ASER of these two systems reach the error floor in the high SNR regime. Fortunately, the usage of RIS with N ≥ 2 can greatly reduce this impact and avoid the error floor for the TW-FD-RIS system.

Highlights

Smart radio environments are expected to enhance the coverage, quality, and reliability of wireless communication systems
Motivated by the advantages of reconfigurable intelligent surface (RIS) and its application in future wireless networks, in this paper, we conducted a mathematical analysis of a TW-FD communication system assisted with a RIS and an AF relay
We successfully derived the approximate expressions of the Average Outage Probability (AOP) and the Average Symbol Error Rate (ASER) of the TW-FD-RIS system in the case N ≥ 2 and the exact closedform expressions in the case N = 1

Summary

Introduction

Smart radio environments are expected to enhance the coverage, quality, and reliability of wireless communication systems. Reflective surfaces such as reconfigurable intelligent surface (RIS), large intelligent surface (LIS), and intelligent reflective surface (IRS) have been introduced to assist wireless communication systems [1], [2]. By controlling the characteristics of reflection, refraction, and scattering of radio waves, RIS can provide better performance than the traditional relay techniques in terms of the outage probability (OP) and energy efficiency [1]– [4]. RIS-assisted wireless communication systems become a promising solution that can be exploited in the sixth generation (6G) and beyond wireless networks [3], [5], [6]. FD can enhance the spectral efficiency (SE) two times in comparison with conventional half-duplex (HD) transmission because FD transmission enables wireless devices to transmit and receive signals at the same time and on

Methods

Results

Conclusion