RIS-Assisted Fixed NOMA: Outage Probability Analysis and Transmit Power Optimization

Abstract

Reconfigurable intelligent surface (RIS)-assisted non-orthogonal multiple access (NOMA) has the ability to overcome the challenges of the wireless environment like random fluctuations, shadowing, and mobility in an energy efficient way when compared to multiple input-multiple output (MIMO)-NOMA systems. The NOMA system can deliver controlled channel gains, improved coverage, increased energy efficiency, and enhanced fairness in resource allocation with the help of RIS. RIS-assisted NOMA will be one of the primary potential components of sixth-generation (6G) networks, due to its appealing advantages. The analytical outage probability expressions for smart RIS-assisted fixed NOMA (FNOMA) are derived in this paper, taking into account the instances of RIS as a smart reflector (SR) and an access point (AP). The analytical and simulation findings are found to be extremely comparable. In order to effectively maximize the sum capacity, the formulas for optimal powers to be assigned for a two-user case are also established. According to simulations, RIS-assisted FNOMA surpasses FNOMA in terms of outage and sum capacity. With the aid of RIS and the optimal power assignment, RIS-AP-FNOMA offers ≈62% improvement in sum capacity over the FNOMA system for a signal-to-noise ratio (SNR) of 10 dB and 32 elements in RIS. A significant improvement is also brought about by the increase in reflective elements.

Precoding for RIS-Assisted Multi-User MIMO-DQSM Transmission Systems

“…For example, considering orthogonal frequency division multiplexing (OFDM) systems, the proposed technique could be improved in its spectral efficiency and system capacity. On the other hand, incorporating techniques such as non-orthogonal multiple access (NOMA) could result in a system with the ability to overcome the challenges of the wireless environment like random fluctuations, shadowing, and mobility in an energy-efficient way [35].…”

Differential Evolution Optimized Non-Orthogonal Multiple Access for Sum Rate Maximization

“…where 𝑥 and 𝑃 are the data and power allocated to user-i, 𝑖 = 1,2. The PA for us given by The expression for the transmitted signal from the BS is [17,18]…”

“…Figure 1. Downlink transmission model for two-user NOMA system.The expression for the transmitted signal from the BS is[17,18] 𝑺 = 𝒙 𝟏 𝑷 𝟏 + 𝒙 𝟐 𝑷 𝟐 , 𝑷 𝟐 > 𝑷 𝟏…”

Machine Learning Strategies for Reconfigurable Intelligent Surface-Assisted Communication Systems—A Review

“…The most important property of an RIS is its capability to modify dynamically the wireless communication environment [9]. Due to the aforementioned properties, RISs are raising interest for a variety of applications such as power transfer, physical layer security [10,11], unnamed aerial vehicles communication [12,13], IoT and sensor networks [14], non-orthogonal multiple access (NOMA) [15,16], spatial modulation (SM) [16,17], among others. In 6G communications, the RIS has become a leading technology for mmWave communications [18,19].…”