Large Intelligent Surface-Assisted Nonorthogonal Multiple Access for 6G Networks: Performance Analysis

Abstract

Large intelligent surface (LIS) has recently emerged as a potential enabling technology for 6G networks, offering extended coverage and enhanced energy and spectral efficiency. In this work, motivated by its promising potentials, we investigate the error rate performance of LIS-assisted non-orthogonal multiple access (NOMA) networks. Specifically, we consider a downlink NOMA system, in which data transmission between a base station (BS) and L NOMA users is assisted by an LIS comprising M reflective elements. First, we derive the probability density function of the end-to-end wireless fading channels between the BS and NOMA users. Then, by leveraging the obtained results, we derive an approximate expression for the pairwise error probability (PEP) of NOMA users under the assumption of imperfect successive interference cancellation. Furthermore, accurate expressions for the PEP for M = 1 and large M values (M > 10) are presented in closed-form. To gain further insights into the system performance, an asymptotic expression for the PEP in high signal-to-noise ratio regime, the asymptotic diversity order, and a tight union bound on the bit error rate are provided. Finally, numerical and simulation results are presented to validate the derived mathematical results. Index terms-Asymptotic diversity order, bit error rate, large intelligent surfaces, NOMA, pairwise error probability, union bound, 6G.

Battery Recharging Time Models for Reconfigurable Intelligent Surfaces-Assisted Wireless Power Transfer Systems

“…Therefore, its PDF can be formulated in a closed-form in an approximated expression by using the moment-based density approximants method presented in [63]. The evaluation of the first four moments, ensuring an accurate approximation for the PDF of B, are obtained in [64] and are presented here for clarity and completeness of the work. Specifically, the first, second, third, and fourth moments are expressed as ( 13), ( 14), (15), and (16), respectively.…”

Performance of Reconfigurable Intelligent Surfaces in the Presence of Generalized Gaussian Noise

“…We assume that the direct link between S and D is subject to strong attenuation, as a result of deep fading, or shadowing effects, caused by surrounding physical obstacles, or both, and therefore, this link does not exist. It is worth mentioning that such an assumption is followed in the literature of RISassisted communications [2], [3], where RIS is considered to be deployed in environments that experience high blockage.…”

“…Moreover, in (1), θ i specifies the adjustable phase induced by the i-th RE of the RIS [3]. We further consider that optimal phase shifting, i.e., θ i = −(φ hi +φ gi ), is provided by the RIS, since it is assumed that the RIS has perfect knowledge of the channel phases of h i and g i , denoted respectively as φ hi and φ gi [2], [3], [7]. In this letter, we assume that the amplitude of the reflection coefficient of each RE is equal to 1 for all i ∈ N [3].…”

“…To reap the full potentials brought by RIS and cater for their unique challenges, exploring the performance limits of RIS-assisted wireless communications analytically has become an active research topic [2]- [5]. Specifically, in [2], the error probability performance is investigated for RIS-assisted nonorthogonal multiple access (NOMA) and backscatter communication systems, respectively. Furthermore, [3] investigated the performance of RIS-assisted wireless systems, based on outage probability, symbol error rate, and ergodic capacity.…”

“…Although the results from [2]- [7] are insightful, the performance of the considered systems is studied under the additive white Gaussian noise (AWGN) assumption. While this assumption accurately models the distribution of thermal noise, which is due to the random motion of free electrons at the receiver, it ignores the impulsive nature of electromagnetic interference, atmospheric noise and/or man-made noise, which might be dominant in numerous applications and lead to severe performance degradation.…”