Imperfect Successive Interference Cancellation Research Articles

Achievable Rate Analysis of the STAR-RIS-Aided NOMA Uplink in the Face of Imperfect CSI and Hardware Impairments

Reconfigurable intelligent surfaces (RIS) are capable of beneficially ameliorating the propagation environment by appropriately controlling the passive reflecting elements. To extend the coverage area, the concept of simultaneous transmitting and reflecting reconfigurable intelligent surfaces (STAR-RIS) has been proposed, yielding supporting 360° coverage user equipment (UE) located on both sides of the RIS. In this paper, we theoretically formulate the ergodic sum-rate of the STAR-RIS assisted non-orthogonal multiple access (NOMA) uplink in the face of channel estimation errors and hardware impairments (HWI). Specifically, the STAR-RIS phase shift is configured based on the statistical channel state information (CSI), followed by linear minimum mean square error (LMMSE) channel estimation of the equivalent channel spanning from the UEs to the access point (AP). Afterwards, successive interference cancellation (SIC) is employed at the AP using the estimated instantaneous CSI, and we derive the theoretical ergodic sum-rate upper bound for both perfect and imperfect SIC decoding algorithm. The theoretical analysis and the simulation results show that both the channel estimation and the ergodic sum-rate have performance floor at high transmit power region caused by transceiver hardware impairments.

On the Performance of End-to-End Cooperative NOMA-Based IoT Networks With Wireless Energy Harvesting

This paper studies the end-to-end uplink (UL) and downlink (DL)-outage probability (OP) of an Internet of Things (IoT) network with radio frequency (RF) energy harvesting (EH) over Nakagami-m fading channels. Power-domain nonorthogonal multiple access (NOMA) is adopted to support both the UL and DL transmissions to increase the network spectral efficiency. The system end-to-end UL and DL outage probabilities are analyzed where exact closed-form expressions are derived. The system performance is explored for various system parameters such as time allocation for EH, transmission power, fading conditions, number of IoT devices (IoDs), and data rate. The obtained analytical results are corroborated using Monte Carlo simulation for various operating scenarios. The obtained results show that the optimum harvesting time may broadly vary based on the adopted system parameters. Moreover, the results show that the system OP is highly sensitive to the harvesting time where OP may vary drastically if the harvesting time deviates from the optimum. The impact of the perfect successive interference cancellation (SIC) (PSIC) is also evaluated and compared with imperfect SIC (ISIC), and the obtained results show that the OP of the system can be significantly underestimated with the PSIC assumption. Therefore, the commonly used PSIC assumption may cause substantial deviation from the practical case where the detection process experiences ISIC.

RSMA for Hybrid RIS-UAV-Aided Full-Duplex Communications With Finite Blocklength Codes Under Imperfect SIC

In this work, we consider a hybrid aerial full-duplex (FD) relaying consisting of a reconfigurable intelligent surface (RIS) mounted over an FD unmanned aerial vehicle (UAV) relay operating in decode and forward mode to assist the information transfer between the base station and multiple users. For better spectral efficiency, we investigate the use of rate splitting multiple access (RSMA) in such networks and focus on joint optimization of RSMA parameters, 3D-coordinates of the UAV/RIS, and phase shift matrix at the RIS along with analyzing the outage probability, block error rate (BLER) and achievable weighted sum rate for finite blocklength (FBL) and infinite blocklength (IBL) codes under imperfect successive interference cancellation (SIC) at each user and residual-self interference (RSI) at the UAV. We first formulate the weighted sum rate maximization problem and adopt the block coordinate descent (BCD) method to deal with the non-convex nature of the problem. Thereafter, we propose a BCD-based algorithm that jointly optimizes these parameters using a heuristic approach for optimum power allocation, a Riemannian conjugate gradient-based algorithm to get the optimal phase shift at the RIS, and an iterative algorithm to obtain the optimal UAV/RIS position. It also distributes the common rate among the users optimally. Next, with obtained optimal parameters, we further analyze the performance of the network and derive the closed-form expressions of BLER, outage probability, and average weighted sum rate. We present Monte Carlo simulation-based results to validate the accuracy of the proposed algorithms and derived expressions, and demonstrate the superiority of RSMA over non-orthogonal multiple access (NOMA) and conventional orthogonal multiple access (OMA) schemes.

Performance Analysis of Selective DF Cooperative NOMA in Presence of Practical Impairments

In this article, we investigate a selective decode-and-forward (DF)-aided cooperative nonorthogonal multiple access (NOMA) system performance in the presence of practical impairments using imperfect successive interference cancellation (SIC) and channel estimation error (CEE). The base station communicates directly and via a relay with the two NOMA users in two-time phases. In particular, the selective DF with synchronized direct and relay transmission relaying protocol is proposed for the considered downlink NOMA system to offer enhanced quality of service and improved data reliability compared with the conventional NOMA and DF NOMA systems. The closed-form of exact and asymptotic expressions of the average bit error rate (ABER) at both NOMA users are derived considering the impact of imperfect SIC and CEE. Furthermore, the outage probability is also obtained. Finally, the improvement in the system performance acquired by the proposed scheme over the existing methods is corroborated by Monte Carlo simulations.

Secrecy Outage Probability Analysis for Downlink RIS-NOMA Networks With On-Off Control

Reconfigurable intelligent surface (RIS) has been regarded as a promising technology since it has ability to create the favorable channel conditions. This paper investigates the secure communications of RIS assisted non-orthogonal multiple access (NOMA) networks, where both external and internal eavesdropping scenarios are taken into consideration. More specifically, novel approximate and asymptotic expressions of secrecy outage probability (SOP) for the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> -th legitimate user (LU) are derived by invoking imperfect successive interference cancellation (ipSIC) and perfect successive interference cancellation (pSIC). To characterize the secrecy performance of RIS-NOMA networks, the diversity order of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> -th LU with ipSIC/pSIC is obtained in the high signal-to-noise ratio region. The secrecy system throughput of RIS-NOMA networks is discussed in delay-limited transmission mode. Numerical results are presented to verify theoretical analysis that: i) The SOP of RIS-NOMA networks is superior to that of RIS assisted orthogonal multiple access (OMA) and conventional cooperative communication schemes; ii) As the number of reflecting elements increases, the RIS-NOMA networks are capable of achieving the enhanced secrecy performance; and iii) The RIS-NOMA networks have better secrecy system throughput than that of RIS-OMA networks and conventional cooperative communication schemes.

NOMA cooperative VLC systems: design and performance analysis with OOK and L-PPM modulation.

Visible light communication (VLC) allows white LEDs to communicate while lighting, which improves resource consumption. Multiple relay approaches can be employed in conjunction with cooperative communications to achieve large gains in spatial diversity, expand the coverage, and possibly boost system capacity. In this paper, the nonorthogonal multiple access (NOMA) cooperative techniques for VLC systems using on-off keying (OOK) and L-pulse-position modulation (L-PPM) are proposed. The maximum ratio combining (MRC) schemes is adopted at the receiving node to combine the signals received from cooperative transmissions. Further, the decode-and-forward relaying protocol is considered for cooperation. The proposed system is analyzed for a multiuser scenario that is followed by a two- and three-user scenario for detailed analysis. This study calculates the bit error probability (BEP) of an OOK/L-PPM modulated NOMA cooperative VLC system under perfect and imperfect successive interference cancellation. Simulation results are presented to validate the produced analytical BEP results.

Outage Performance Analysis of Improper Gaussian Signaling for Two-User Downlink NOMA Systems with Imperfect Successive Interference Cancellation.

The improper Gaussian signaling (IGS) technique can improve the achievable rate of an interference-limited network by fully exploiting the second-order statistics of complex signaling. This paper addresses the outage performance analysis of a two-user downlink non-orthogonal multiple access (NOMA) system using the IGS technique in the presence of imperfect successive interference cancellation (SIC). The strong channel user (SU) adopts the IGS, while the weak channel user (WU) adopts the traditional proper Gaussian signaling (PGS). Considering a practical scenario where the transmitter has obtained the statistics of the channel coefficients instead of the instantaneous channel state information (CSI), the expressions of the achievable rates of both users under residual interference due to imperfect SIC are derived, together with their outage probabilities, subject to predetermined target rates and channel statistics. Given a fixed transmit power of the WU, both the transmit power and the degree of impropriety of the SU are optimized to minimize the outage probability subject to the outage constraint of the WU. Numerical results are provided to assess the benefits of the proposed IGS-based downlink NOMA system, which are consistent with the analysis.

Two-way UAV-aided systems with short packet communications

In this paper, we investigate a two-way unmanned aerial vehicle (UAV)-aided system, where two sources communicate with each other with the aid of an UAV relay. Two downlink transmission schemes consisting of non-orthogonal multiple access (NOMA) and network coding (NC) have been studied under finite blocklength regime. Considering imperfect successive interference cancellation (SIC), we have derived the exact and approximate expressions of the systems’ average block-error rates (BLERs). In particular, we propose a solution to maximize system throughput by optimizing packet length. In addition, we have also quantified the effects of the system parameters on the BLER performance, including the transmit power, the power allocation coefficients, and the UAV’s altitude. Numerical results demonstrate that the performance gap between the NOMA-based and NC-based systems is negligible.

NOMA Assisted Semi-Grant-Free Transmission Scheme in Satellite Systems

This paper investigates the uplink semi-grant-free (SGF) transmission in satellite communication systems. Specifically, based on the available statistical channel state information, we first propose a non-orthogonal multiple access assisted SGF scheme, which enables many multi-antenna mobile terminals and one earth station to access the satellite network within the same resource block. Then, by assuming that the satellite channels undergo shadow-Rician distribution, we derive the closed-form throughput expression of the considered system, where the effect of imperfect successive interference cancelation is taken into account. Finally, simulation results validate the effectiveness of the theoretical analysis and the superiority of our proposed scheme. Besides, the influence of typical parameters on the system performance is also revealed.

Adaptive Decoding Mechanisms for UAV-Enabled Double-Uplink Coordinated NOMA

In this paper, we propose a novel adaptive decoding mechanism (ADM) for the unmanned aerial vehicle (UAV)-enabled uplink (UL) non-orthogonal multiple access (NOMA) communications. Specifically, considering a harsh UAV environment, where ground-to-ground links are regularly unavailable, the proposed ADM overcomes the challenging problem of conventional UL-NOMA systems whose performance is sensitive to the transmitter's statistical channel state information and the receiver's decoding order. To evaluate the performance of the ADM, we derive closed-form expressions for the system outage probability (OP) and system throughput. In the performance analysis section, we provide novel expressions for practical air-to-ground and ground-to-air channels, while taking into account the practical implementation of imperfect successive interference cancellation (SIC) in UL-NOMA. Moreover, the obtained expression can be adopted to characterize the OP of various systems under a Mixture of Gamma (MG) distribution-based fading channels. Next, we propose a sub-optimal Gradient Descent-based algorithm to obtain the power allocation coefficients that result in maximum throughput with respect to each location on UAV's trajectory. To determine the significance of the proposed ADM in nonstationary environments, we consider the ground users and the UAV to move according to the Random Waypoint Mobility (RWM) and Reference Point Group Mobility (RPGM) models, respectively. Accurate formulas for the distance distributions are also provided. Numerical solutions demonstrate that the ADM-enhanced NOMA not only outperforms Orthogonal Multiple Access (OMA), but also improves the performance of UAV-enabled UL-NOMA even in mobile environments.

Secrecy performance analysis of UAV-based full-duplex two-way relay NOMA system

In this paper, we investigate the secrecy performance of an unmanned aerial vehicle (UAV)-based full-duplex (FD) two-way relay non-orthogonal multiple access (TWR-NOMA) system with two terrestrial users and an eavesdropper. To ensure secure communications, a UAV acts as an aerial relay station, which not only forwards confidential information to legitimate users but also keeps emitting the jamming signal to degrade the performance of any potential eavesdropper. The ergodic secrecy rate (ESR) and secrecy outage probability (SOP) of users and the system are successfully investigated under the assumption of imperfect successive interference and self-interference cancellation. In addition, to provide a better understanding of the secrecy performance, mathematical expressions of asymptotic ESR, secrecy slope, asymptotic SOP, and secrecy diversity order are also studied. Simulation results demonstrate that the FD TWR-NOMA system attains better secrecy performance than that of the FD TWR-NOMA system with a terrestrial relay, the FD TWR-NOMA system without jamming signal, as well as the half-duplex TWR-NOMA system. The secrecy performance of the system is significantly enhanced when UAVs approach the remote user. Furthermore, there is a reasonable power allocation value for jamming and legitimate signals on the UAV to improve secrecy performance.

RIS Partition-Assisted Non-Orthogonal Multiple Access (NOMA) and Quadrature-NOMA With Imperfect SIC

Reconfigurable intelligent surface (RIS)-assisted power-domain non-orthogonal multiple access (PD-NOMA) system has emerged as a revolutionary technology to enhance the spectrum efficiency for future wireless networks. This work introduces two novel RIS systems, namely, RIS partition-assisted (RISP) PD-NOMA (RISP-PD-NOMA) and RISP-Quadrature-NOMA (RISP-Q-NOMA), to maximize the diversity order and to improve the signal quality of all users by dedicating fixed RIS units to each user. The closed-form expressions of average sum-rate, outage probability, and diversity order are evaluated for both systems under the Rician fading channel for perfect and imperfect successive interference cancellation (SIC) operations. Further, the performance of both RISP-PD-NOMA and RISP-Q-NOMA systems is compared with RIS partitioned PD-NOMA, RIS-assisted PD-NOMA, and PD-NOMA systems. It is noticed from the analysis that under perfect SIC, RISP-PD-NOMA outperforms all other systems. However, under imperfect SIC, RISP-Q-NOMA demonstrates superior performance to other systems due to the lesser number of SIC operations that reduce detection delay and decoding complexity. Furthermore, the analytical expression for bit error rate (BER) of RISP-PD-NOMA and RISP-Q-NOMA is derived, and then the closed-form expression of average-BER is evaluated. Numerical results demonstrate that RISP-Q-NOMA is superior to RISP-PD-NOMA.

Outage analysis of cognitive inspired NOMA networks in the presence of imperfect SIC, CCI, and non-ID fading channels

This paper analyzes the outage performance of cognitive-inspired non-orthogonal multiple access (NOMA) network under imperfect successive interference cancellation (SIC), co-channel interference (CCI), and non-identical distributed fading channels. Firstly, we aim to derive the cumulative distribution function (CDF) for the optimum channel with beamforming design, the selected channel maximization, and the selected channel minimization and the probability density function (PDF) for channel interference in order to facilitate the outage performance analysis. Secondly, we obtain the closed-form expressions of outage probability for the primary and secondary destinations according to two strategies: (1) the primary destination is near secondary transmitter and (2) the primary destination is far from secondary transmitter. Thirdly, to provide some useful insights into system designs, we carry out the asymptotic analysis for the three power setting scenarios. Finally, we validate the derived theoretical analyses using Monte-Carlo method.

Performance Analysis of NOMA-Based Hybrid Satellite-Terrestrial Relay Networks With CCI

Hybrid satellite-terrestrial relay networks (HSTRNs) which exploit relay cooperative technology in the integrated system of satellites and terrestrial base stations (BSs) are expected to offer enhanced transmission performance benefited from the spatial gain of independent fading paths. To enable multi-user accessing and resource sharing among users, non-orthogonal multiple access (NOMA) technique can be applied in HSTRNs. In this paper, we consider a NOMA-based HSTRN where a satellite transmits signals to a relay base station (RBS) and a destination ground station (DGS), and RBS also serves a cellular user (CU) and DGS simultaneously by leveraging NOMA scheme. We assume that the satellite shares spectrum with a number of cellular small BSs (SBSs), hence SBSs will cause co-channel interference (CCI) to DGS, RBS and CU. We examine the transmission characteristics of the satellite and terrestrial links, and derive the closed-form expressions of the outage probability (OP) and average symbol error rate (ASER) of DGS and CU, respectively. Specially, we consider the effect of perfect and imperfect successive interference cancellation (SIC) on the ASER performance of CU. Then, considering the stochastic characteristics of satellite links and CCI, we analyze the mean energy efficiency (MEE) of the satellite and propose an optimal power allocation scheme which maximizes the MEE of the satellite and achieves system performance optimization. Simulation results demonstrate the effectiveness of the theoretical analysis and the proposed power allocation scheme.

Perfect and imperfect successive interference cancellation for channel decoding in downlink visible light non-orthogonal multiple access network

This paper exploits perfect and imperfect-successive interference cancellation (SIC) technique for channel decoding in downlink visible light-non-orthogonal multiple access (VL-NOMA) communication networks. A light-emitting-diode (LED) is used as a carrier transmitting signal to the two users (near- and far-user) as they are placed at different locations in the indoor environment. The power allocation technique uses power levels to effectively distribute information to the two users while the superposition coding (SC) encodes the two signals into one simultaneously. The SIC decodes the interference notice in the sub-channels until each user receives a better signal strength with the same resources (at the same time and frequency). The imperfect SIC which is a practical scenario, is experienced during the decoding process when a fraction residue at the channel-information properties is left due to an SIC error. This is because the VL channel properties uncertainty creates an interference when the NOMA is deployed with imperfect SIC to decode the signal, while the NOMA with perfect SIC is taken based on known channel pieces of information. The NOMA communication systems with imperfect SIC performs better than that of the perfect SIC in terms of bit-error-rate (BER). We have observe changes in the near-user and far-user at the channel, then SC is performed. MATLAB software tool is used for the simulation results.

Deep learning based BER improvement for NOMA-VLC systems with perfect and imperfect successive interference cancellation

This paper focuses in the improvement of the BER performance of multiple-input multiple-output (MIMO) systems is investigated utilizing non-orthogonal multiple access-visible light communication (NOMA-VLC). Applying multi-user downlink MIMO-NOMA-VLC system within equal gain combiner at the receiver is used with two types of modulation; On–Off Keying (OOK) and L-Pulse Position Modulation, with L = 4 and 8. The perfect and imperfect successive interference cancellation scenario is used in this system, and the scenario is considered for two and three users. Our proposed framework is divided into two stages. First, data is collected using the MATLAB software. Second, two deep learning models (DLMs); ResNet50V2 and InceptionResNetV2 which are trained and tested. Python software is then used to develop and train the DLMs. The obtained results assures the superiority of ResNet50V2 over InceptionResNetV2, in different cases and for all users. The BER performance is also studied versus α for two and three users OOK modulation single-input single-output (SISO), (2 × 2) and (3 × 2) MIMO-NOMA-VLC systems based on the two DL techniques; ResNet50V2 and InceptionResNetV2. Again, ResNet50V2 achieves better results than InceptionResNetV2. The obtained results are compared with the previously published ones, showing that the proposed system and techniques achieve better results.

Robust Beamforming Design for RIS-Aided NOMA Secure Networks With Transceiver Hardware Impairments

Integrating reconfigurable intelligent surface (RIS) and non-orthogonal multiple access (NOMA) provides a promising solution to support large-scale secure communications. However, reducing the impact of transceiver hardware impairments (HWI) on the performance of RIS-aided NOMA secure networks remains a challenge. In this paper, we propose a robust transmission scheme for RIS-aided NOMA secure networks with transceiver HWI under two proposed eavesdropping scenarios and two artificial noise methods. A closed-form expression for the distortion noise power caused by transceiver HWI in NOMA networks is derived to quantify transceiver HWI. The sum secrecy rate of NOMA users with imperfect successive interference cancellation (SIC) is maximized under distortion noise for more robust security. Further, to tackle the resulting non-convex problem, we decompose it into two sub-problems. Both of them are converted into convex problems using the multi-dimensional quadratic transform (MDQT) method, semi-definite relaxation (SDR) technique, and the successive convex approximation (SCA) algorithm, and then employing the alternate optimization (AO) algorithm solve them. Numerical results demonstrate that the proposed scheme has superior security performance over orthogonal multiple access (OMA) networks, time division multiple access (TDMA) networks, and traditional NOMA networks, achieving more robust performance than the conventional scheme that ignores HWI and imperfect SIC.

Performance Analysis of NOMA-Based Spectrum Sharing System With Imperfect SIC

This paper presents a non-orthogonal multiple access (NOMA)-based spectrum sharing scheme with imperfect successive interference cancellation (i-SIC), where the secondary user assists the primary to achieve cooperative multiplexing. The proposed scheme allows primary and secondary transmitters to transmit in alternate time slots and, hence, no primary transmitter's (PT) interference at the secondary receiver (SR). However, since the relay node and secondary transmitter (ST) are transmitting simultaneously on the same frequency spectrum, ST causes interference to the primary user. Therefore, the proposed scheme imposes the variable interference threshold constraint (v-ITC) to ST transmit power to improve the performance of both primary and secondary networks. We derive the closed-form expressions for the outage probability and ergodic rate of the proposed system. Furthermore, numerical results are presented to manifest the advantages of the v-ITC scheme on outage performance and the ergodic rate of the secondary network (SN).

Sensing-Communication Coexistence vs. Integration

The design options of sensing-communication coexistence (SCC) vs. integrated sensing and communications (ISAC) relying on non-orthogonal downlink transmission (NO-DLT) and transmit antenna selection are investigated. To be practical, both realistic residual hardware impairments (RHI) and imperfect successive interference cancellation are considered. The performance of the SCC and ISAC NO-DLT frameworks is characterized by deriving both the exact and the asymptotic outage probabilities (OPs) as well as the probability of successful target detection (PoD). Our numerical results demonstrate the accuracy of the theoretical analysis and confirm that: 1) The ISAC NO-DLT framework is superior to the SCC NO-DLT framework both in terms of its OP and PoD; 2) The realistic RHI degrades the S&C performance of both the SCC and ISAC NO-DLT frameworks.

Performance Analysis and Deep Learning Assessment of Full-Duplex Overlay Cognitive Radio NOMA Networks Under Non-Ideal System Imperfections

In this paper, we investigate the effectiveness of an overlay cognitive radio (OCR) coupled with non-orthogonal multiple access (NOMA) system using a full-duplex (FD) cooperative spectrum access with a maximal ratio combining (MRC) scheme under the various non-ideal system imperfections. In view of practical realization, we ponder the impact of loop self-interference, transceiver hardware impairments, imperfect successive interference cancellation, and channel estimation errors on the system performance. We investigate the performance of the proposed system by obtaining closed-form expressions for outage probability and ergodic rate for primary as well as secondary users using Nakagami-m fading channels. As a result, we reveal some notable ceiling effects and present efficacious power allocation strategy for cooperative spectrum access. We further evaluate the system throughput and ergodic sum-rate (ESR) to assess the system’s overall performance. Our findings manifest that the FD-based OCR-NOMA can comply with the non-ideal system imperfections and outperform the competing half-duplex (HD) and orthogonal multiple access (OMA) counterparts. Due to the massive complexity of the suggested system model, direct derivation of the closed-form formula for the ESR becomes cumbersome. To address this problem, we develop a deep neural network (DNN) framework for ESR prediction in real-time situations.