This paper investigates a relay assisted simultaneous wireless information and power transfer (SWIPT) for downlink in cellular systems. Cooperative non-orthogonal multiple access (C-NOMA) is employed along with power splitting protocol to enable both energy harvesting (EH) and information processing (IP). A downlink model consists of a base station (BS) and two users is considered, in which the near user (NU) is selected as a relay to forward the received signal from the BS to the far user (FU). Maximum ratio combining is then employed at the FU to combine both the signals received from the BS and NU. Closed form expressions of outage propability, throughput, ergodic rate and energy efficiency (EE) are firstly derived for the SWIPT based C-NOMA considering both scenarios of with and without direct link between the BS and FU. The impacts of EH time, EH efficiency, power-splitting ratio, source data rate and distance between different nodes on the performance are then investigated. The simulation results show that the C-NOMA with direct link achieves an outperformed performance over C-NOMA without direct link. Moreover, the performance of C-NOMA with direct link is also higher than that for OMA. Specifically, (1) the outage probability for C-NOMA in both direct and relaying link cases is always lower than that for OMA. (2) the outage probability, throughput and ergodic rate vary according to $$\beta$$β , (3) the EE of both users can obtain in SNR range of from $$-10$$- 10 to 5 dB and it decreases linearly as SNR increases. Numerical results are provided to verify the findings.

In recent years, the rapid advancements in wireless communication technologies have necessitated more efficient and integrated systems. An emerging paradigm addressing this need is the integration of Intelligent Reflecting Surfaces (IRS) with Non-Orthogonal Multiple Access (NOMA) for Integrated Sensing and Communication (ISAC). This paper offers a comprehensive survey of the state-of-the-art IRS-NOMA technologies, emphasizing their potential to enhance ISAC systems. We examine the fundamental principles of IRS and NOMA, investigating how their combined integration can markedly improve spectral and energy efficiencies, system capacity, and overall performance. The survey methodically categorizes and reviews recent research contributions, highlighting key innovations, design methodologies, advancement in the sophisticated algorithms and performance metrics. Furthermore, we address the practical challenges and implementation issues associated with IRS-NOMA in ISAC, such as hardware limitations, signal processing complexities, and security concerns. Additionally, we outline open research directions and future prospects, aiming to stimulate further advancements in this promising field. Also we highlight the interplay between the IRS assisted ISAC NOMA with the other emerging technologies towards the realization of 6G. Last we present and summarize the lessons learned from this study. This survey serves as an invaluable resource for researchers and practitioners interested in understanding and advancing IRS-NOMA for next-generation integrated sensing and communication systems.

Spectrum and energy efficiency with simultaneous wireless information and power transfer (SWIPT) to prolong the lifetime of power-constrained wireless devices in cooperative relaying nonorthogonal multiple access (CR-NOMA) has received great attention in the last decade. This paper investigates a two-way relay channel in a CR-NOMA system where two users exchange data with the assistance of a relay. Power-splitting relaying (PSR) and time-switching relaying (TSR) protocols are employed at the relay to harvest RF energy and process information from two users. We firstly derive the exact expressions of outage probability (OP) and system throughput (ST). The impacts of signal quality, energy coefficients, the distance of the nodes, and the data rate of two users on these performance metrics are then evaluated through several system settings to reflect practical network scenarios. It is shown that the OP and ST of the TSR are superior to that of the PSR protocol. Specifically, numerical results indicate that a higher throughput of up to 8% can be achieved with the TSR when compared to the PSR. It is further revealed that the OP and ST of the PSR are strongly affected by energy harvesting (EH) coefficients, while the performance obtained with the TSR is nearly independent of the EH capability at the relay.