Reconfigurable Intelligent Surface Enabled Over-the-Air Uplink NOMA

Abstract

Innovative reconfigurable intelligent surface (RIS) technologies are rising and recognized as promising candidates to enhance 6G and beyond wireless communication systems. RISs acquire the ability to manipulate electromagnetic signals, thus, offering a degree of control over the wireless channel and the potential for many more benefits. Furthermore, active RIS designs have recently been introduced to combat the critical double fading problem and other impairments passive RIS designs may possess. In this paper, the potential and flexibility of active RIS technology are exploited for uplink systems to achieve virtual non-orthogonal multiple access (NOMA) through power disparity over-the-air rather than controlling transmit powers at the user side. Specifically, users with identical transmit power, path loss, and distance can communicate with a base station sharing time and frequency resources in a NOMA fashion with the aid of the proposed hybrid RIS system. Here, the RIS is partitioned into active and passive parts and the distinctive partitions serve different users aligning their phases accordingly while introducing a power difference to the users' signals to enable NOMA. First, the end-to-end system model is presented considering two users. Furthermore, outage probability calculations and theoretical error probability analysis are discussed and reinforced with computer simulation results.

Performance Analysis of RIS-assisted 6G Vehicular Networks with NOMA under Diverse Channel Conditions

“…For further improvement in the coverage, capacity, and connectivity of 6G vehicular networks, RIS can be integrated with NOMA [29], [30]. To exploit the benefits of RIS and NOMA, many researchers have integrated NOMA and RIS to improve the performance of wireless networks [31][32][33][34][35][36]. There are a couple of existing works reported in the literature that use NOMA in RIS-assisted vehicular networks.…”

Artificial Noise and RIS-Aided Physical Layer Security: Optimal RIS Partitioning and Power Control

“…where γb = 2 QoS b − 1; γe = 2 QoS e − 1; QoS e = ζQoS b , with ζ is the variable that determines the threshold of QoS e with 0 < ζ ≤ 1; the constraints C 1 1 and C 2 1 are QoS constraints; C 3 1 requires the power allocated for s and n not to exceed maximum transmit power P t ; and C 4 1 specifies the domain of optimization variables while C 5 1 indicates the feasibility values for ρ. In (9), P s and P n can be solved using geometric programming (CVX) for fixed values of ρ.…”

“…R ECONFIGURABLE intelligent surface (RIS) has been proposed as an emerging technology for next-generation wireless networks to enhance spectral efficiency [1]. The passive beamforming nature of RIS has been integrated into various wireless technologies, such as mmWave [2], fullduplex [3], non-orthogonal multiple access (NOMA) [4], wireless power transfer, wireless security [5], to improve endto-end performance at low power and hardware cost.…”

Competitive IRS Assignment for IRS-Based NOMA System

“…Inspired by the potential capabilities of IRS, several emerging multiple access (MA) approaches have been recently integrated with IRS [3], such as orthogonal MA (OMA), multiple antennas [4] [5], non-orthogonal MA (NOMA) [6] [7], and hybrid OMA-NOMA. To be specific, the IRS-aided hybrid OMA-NOMA systems are expected to have a crucial role in B5G due to its several benefits.…”