Ergodic capacity analysis of multiple IRS‐aided dual‐hop DF relaying system

Abstract

Intelligent reflecting surface (IRS) is regarded as a promising emerging technology, which has shown enormous potentials for performance enhancement. This paper investigates the multiple IRS-aided dual-hop DF relaying system for both single-user and multi-user scenarios over Nakagami-m fading. Based on a scenario with non-orthogonal multiple access users, tight upper bounds for the ergodic capacity in perfect channel state information(pCSI) scenario are first derived, and then approximate expressions are obtained in imperfect CSI (ipCSI) mode. Moreover, the performance of multiple IRS-aided DF relaying system are compared with multi-IRSs-only system and DF relaying-only system. Finally, all the analytical results are verified using Monte Carlo simulations. INTRODUCTIONRecently, with the rapid growth of data traffic over wireless networks, more and more attention are attracted to spectrum, energy and cost efficient design for the future sixth-generation (6G). Intelligent reflecting surface (IRS) technology has been newly proposed as a promising emerging solution to enhance the performance of wireless communication networks from various aspects such as coverage extension, capacity enlargement, and secrecy improvement by artificially reconfiguring the propagation environment of electromagnetic waves [1-3]. Compared to the conventional active relays supporting massive multiple input multiple-output (MIMO) systems [4], a typical IRS does not need decode or amplify, which contains a large number of passive reflecting elements. By contrast, it simply reflects the incident signals toward one or multiple desired directions by designing its amplitudes and phase-shifts [5]. Thus, IRS can improve spectrum efficiency, decrease energy consumption and enhance wireless physical layer security [6-8].Considerable efforts have been made to study the IRSassisted wireless communication in recent years. For example, symbol error probability (SEP) for both intelligent and random phase adjustments at the IRS reflectors is analytically investigated in ref. [9], besides, it confirms that an increase of reflective elements on the IRS has a significantly positive impact onThis is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Performance analysis of partial NOMA-based layered D2D communications

“…The cooperative transmission method has subsequently been employed in conventional NOMA systems [5][6][7][8][9] to exploit spatial diversity, with varying assumptions on channel state information (CSI) and channel models [10][11][12]. These approaches enable reduced system redundancy and improved fairness to be achieved.…”