Non-orthogonal Multiple Access Research Articles

STAR-RIS-aided NOMA communication for mobile edge computing using hybrid deep reinforcement learning

Reconfigurable intelligent surface (RIS) is expected to be able to significantly reduce task processing delay and energy consumptions of mobile users (MUs) in mobile edge computing (MEC) by intelligently adjusting its reflecting elements’ phase-shifts and amplitudes. Nevertheless, both the passive and active RISs have the disadvantage of only reflecting the received signals, which means that the transmitters and receivers must be located on the same side of the RIS. This may be unrealistic due to the movement of MUs. Simultaneously transmitting and reflecting (STAR) RIS, which can simultaneously transmit and reflect incident signals to achieve full-area coverage, has been recognized as a revolutionary technique to solve the above-mentioned problem. For the STAR-RIS-aided non-orthogonal multiple access (NOMA) communication MEC, we first formulate an optimization problem to minimize the sum of weighted delay and energy consumptions of all MUs which can move randomly at low speeds. Then, under the practical coupled phase-shift model of STAR-RIS, we propose a hybrid deep reinforcement learning (DRL) scheme, in which we determine the amplitudes and phase-shifts of STAR-RIS, task offloading decisions of MUs, and computation resource allocations of MEC servers by using the deep deterministic policy gradient (DDPG) and Dueling deep Q learning (DQN). Finally, we validate and evaluate the performances of our proposed scheme through extensive simulations, which show that our proposed scheme outperforms the existing baseline schemes and its performance can indeed be improved due to the use of STAR-RIS.

Research on Resource Allocation Algorithm for Non-Orthogonal Multiple Access Backscatter-Based Cognitive Radio Networks

Research on Resource Allocation Algorithm for Non-Orthogonal Multiple Access Backscatter-Based Cognitive Radio Networks

Statistical-based detection of pilot contamination attack for NOMA in 5G networks

Fifth-generation (5G) communication technologies, such as millimeter wave communication, massive multiple-input-multiple-output and non-orthogonal-multiple-access (NOMA) are playing a pivotal role in promoting the modern applications of the Internet-of-Things. Using non-orthogonal resource allocation, NOMA can increase spectrum efficiency and achieve wide connectivity with low transmission delay and signaling cost. Despite the high potential of NOMA in 5G communications, NOMA is susceptible to a pilot contamination attack (PCA), in which an attacker resents the same pilot signals as authorized users. Currently, using the available detection methods in NOMA gives high false positive probability since the time-division-duplex or orthogonal resource block can be allocated by many authorized user. Since the pilot contamination attack changes the signal reception at the legitimate receiver, this work introduces a novel detection scheme for identifying Pilot Contamination attack (PCA) that statistically investigates the asymmetry in received signal power levels. The main idea of the proposed detection scheme is to use various statistical measurements for normal traffic attributes (CSI) as a reference profile. Then, compute the Mahalanobis distance between the reference profile and CSI for the incoming connection and use the probability of the uniform distribution to make the final detection decision. The performance of the proposed detection technique in terms of its detection rate and false positive probabilities has been evaluated through extensive simulation. The simulation results show that the proposed scheme succeeded in detecting the pilot contamination attack with a detection rate of up to 98% and a precision reached 97.88%.

Novel techniques for efficient PAPR reduction in NOMA systems for future wireless networks

ABSTRACT Fifth-generation (5G) networks are designed to overcome critical challenges, including achieving high data rates, supporting massive device connectivity, and ensuring low latency. Non-Orthogonal Multiple Access (NOMA) significantly enhances spectral efficiency and network capacity within this framework. NOMA has a problem with a high Peak-to-Average Power Ratio (PAPR). This creates nonlinear distortion, reduces power amplifier efficiency, and increases out-of-band radiation, making it less useful in 5G and B5G networks. To address this, two PAPR reduction methods are proposed: Improved Salp Swarm Algorithm-based Partial Transmit Sequence (PTS-ISSA) and Iterative Sub-block Phase Rotation (ISPR). PTS-ISSA minimizes PAPR by phase rotation of sub-blocks, offering the best reduction but at higher computational complexity, making it ideal for systems with abundant resources. ISPR, on the other hand, employs iterative phase rotation without side information, balancing performance with lower complexity, making it suitable for resource-constrained applications. Evaluated under Rician fading and AWGN channels, both methods outperform traditional techniques in PAPR reduction and Bit Error Rate (BER) performance. While PTS-ISSA is optimal for high-performance systems, ISPR serves lightweight, real-time applications. These methodologies show potential for the next-generation wireless networks, supporting scenarios from IoT to ultra-reliable low-latency communications by optimizing the trade-off between performance and complexity.

A User Pairing Algorithm for the Uplink NOMA With Imperfect CSI

ABSTRACTIn this paper, the problem of user pairing across subcarriers is investigated for the uplink non‐orthogonal multiple‐access (NOMA) systems, in which every subcarrier is assigned to exactly two users. Considering fixed transmit power for all users, we pair users such that sum‐rate is maximized over all subcarriers. While different (near) optimum allocation schemes exist in the literature, they pertain to perfect channel state information (CSI), which is impractical. To overcome this limitation, we assume statistical CSI is available in the form of the first two moments of channel gains. Then, we maximize a lower bound on the sum rate over user pairings utilizing a block coordinate ascent (BCA) approach with guaranteed convergence to a suboptimal solution. Numerical results corroborate a satisfactory performance for our proposed algorithm versus the perfect CSI benchmark and a simple random assignment approach. For high signal to noise ratios (SNRs) and the more challenging frequency selective fading setup, the solution of our proposed algorithm comes close to those of the optimal pairing with perfect CSI. Furthermore, simulations revealed that if the proposed BCA is utilized assuming perfect CSI, it performs similar to the well‐known global optimum in the frequency flat fading setup and outperforms the best existing near‐optimal solution in the frequency selective fading scenario. These observations offer a testament to the strength of the proposed BCA algorithm in both perfect and imperfect CSI conditions.

Twin-shift co-existence non-orthogonal multiple access

Twin-shift co-existence non-orthogonal multiple access

Adaptive Handover Management in High-Mobility Networks for Smart Cities

The seamless handover of mobile devices is critical for maximizing the potential of smart city applications, which demand uninterrupted connectivity, ultra-low latency, and performance in diverse environments. Fifth-generation (5G) and beyond-5G networks offer advancements in massive connectivity and ultra-low latency by leveraging advanced technologies like millimeter wave, massive machine-type communication, non-orthogonal multiple access, and beam forming. However, challenges persist in ensuring smooth handovers in dense deployments, especially in higher frequency bands and with increased user mobility. This paper presents an adaptive handover management scheme that utilizes reinforcement learning to optimize handover decisions in dynamic environments. The system selects the best target cell from the available neighbor cell list by predicting key performance indicators, such as reference signal received power and the signal–interference–noise ratio, while considering the fixed time-to-trigger and hysteresis margin values. It dynamically adjusts handover thresholds by incorporating an offset based on real-time network conditions and user mobility patterns. This adaptive approach minimizes handover failures and the ping-pong effect. Compared to the baseline LIM2 model, the proposed system demonstrates a 15% improvement in handover success rate, a 3% improvement in user throughput, and an approximately 6 sec reduction in the latency at 200 km/h speed in high-mobility scenarios.

Enhancing covert communication in NOMA systems with joint security and covert design.

The explosion of Internet-of-Thing enables several interconnected devices but also gives rise chance for unauthorized parties to compromise sensitive information through wireless communication systems. Covert communication therefore has emerged as a potential candidate for ensuring data privacy in conjunction with physical layer transmission to render two lines of defense. In this paper, we aim to enhance the individual transmission of nearby users in non-orthogonal multiple access (NOMA) systems under scenarios of an eavesdropper who monitors covert transmission before decoding covert information. For this problem, we first provide a comprehensive analysis of the NOMA system in terms of outage probability (OP), secrecy outage probability (SOP), and detection error probability (DEP), where all of them are quantified in exact and asymptotic closed-form expressions. Besides, we have also derived closed-form formulas for users' covert and public rates. Under the system requirements of the maximal OP and SOP and the minimal DEP, we formulate the optimization of resource power allocation to: 1) minimize the OP of covert communication and 2) maximize the covert rate. Thanks to the developed analytical expressions, we obtain closed-form expressions for the sub-optimal power allocation coefficient for each problem. Simulation results validate the efficacy of the analytical mathematical frameworks and reveal that the proposed approaches of power allocation can provide attractive performance improvement compared to fixed power allocations only.

Sparse Code Multiple Access With Time Spreading and Repetitive Transmissions

ABSTRACTFor the next‐generation communication systems, to improve spectral efficiency and increase the data rate, new multiple access techniques have been investigated. Orthogonal multiple access techniques are widely used in traditional communication systems while nonorthogonal multiple access (NOMA), proposed in 5G, has been a promising technology for satisfying the demand for future wireless communication networks. Sparse code multiple access (SCMA) is a code‐domain NOMA method that provides diversity gain with signal constellation coding. However, to increase the performance of SCMA, there are only limited works provided in the literature in terms of codebook design and receiver design. In this paper, a new multiple‐access model is proposed by applying various diversity techniques for downlink SCMA. The performance of the proposed model is evaluated with both computer simulations and theoretical analysis. Results show that the proposed model provides a 1.6 dB gain in terms of the bit error rate (BER) under the Rayleigh fading channel.

Transmit Antenna Selection for Full‐Duplex Relay Millimeter‐Wave Communications Employing Rate‐Splitting Multiple Access

ABSTRACTThis article suggests using rate‐splitting multiple access (RSMA) and transmit antenna selection (TAS) within a full‐duplex relay (FDR) system that operates at high millimeter‐wave (MW) frequencies. We perform a mathematical analysis to derive closed‐form formulas for the outage probabilities (OPs) and throughputs for two users in the proposed RSMA‐MW system with TAS, taking into account the effects of residual self‐interference (RSI) at the FDR. Additionally, we consider practical system and channel parameters in our analysis. The numerical results indicate that the OPs in the RSMA‐MW system are significantly lower than those in a conventional nonorthogonal multiple access (NOMA)‐MW system. Importantly, high MW frequencies have a considerable impact on the OPs and throughputs of the RSMA‐MW system. In this context, using multiple antennas at the base station with TAS can greatly enhance the performance of the RSMA‐MW system. Furthermore, we thoroughly assess the effects of RSI caused by FDR, the distances between transmitters and receivers, transmit power, common and private rates, power allocation coefficients, and frequencies. Based on the observed behaviors of the RSMA‐MW system, several strategies are proposed to reduce OPs and increase throughputs. Finally, Monte Carlo simulations are performed to validate the derived formulas.

Design of effective non-orthogonal multiple access system by maximising spectral and energy efficiency using hybrid heuristic optimisation approach

Design of effective non-orthogonal multiple access system by maximising spectral and energy efficiency using hybrid heuristic optimisation approach

Cooperative Non-Orthogonal Multiple Access With Index Modulation for Air-Ground Multi-UAV Networks

Cooperative Non-Orthogonal Multiple Access With Index Modulation for Air-Ground Multi-UAV Networks

Game-based resource allocation in heterogeneous downlink CR-NOMA network without subchannel sharing

This paper explores how to manage resources in a two-tier, diverse cognitive radio network using a sophisticated technique called non-orthogonal multiple access. In this setup, secondary base stations (BSs), equipped with cognitive capabilities, act as bridges between the main BS and the secondary users (SUs). The main goal is to maximize the throughput of the secondary network by efficiently relaying information to capable SUs without the knowledge of their channel characteristics. To achieve this, we set out to solve a complex problem involving maximizing throughput while staying within transmission power limits, meeting minimum data rate requirements, and controlling interference power. Our approach introduces a new SU clustering method based on fuzzy logic, paired with a hierarchical learning method inspired by the well-known UCB1 algorithm to allocate power effectively to these clusters. We frame this joint optimization of SU cluster formation and power allocation as a cooperative multi-armed bandit game. Through extensive simulations, we demonstrate the effectiveness of our proposed methods. We also explore how different parameters affect the performance of the system, shedding light on the intricate workings of this network architecture.

Delay Minimization for BAC-NOMA Offloading in UAV Networks.

The rapid deployment and enhanced communication capabilities of unmanned aerial vehicles (UAVs) have enabled numerous real-time sensing applications. These scenarios often necessitate task offloading and execution under stringent transmission delay constraints, particularly for time-critical applications such as disaster rescue and environmental monitoring. This paper investigates the improvement of MEC-based task offloading services in energy-constrained UAV networks using backscatter communication (BackCom) with non-orthogonal multiple access (BAC-NOMA). The proposed BAC-NOMA protocol allows uplink UAVs to utilize downlink signals for backscattering tasks instead of transmitting through uplink NOMA. A resource allocation problem is formulated, aimed at minimizing offloading delays for uplink users. By converting the initially non-convex problem into a convex one, an iterative algorithm is developed to solve it. Simulation results demonstrate that the proposed protocol significantly reduces offloading delays relative to existing benchmarks.

An RF-powered multi-device diamond relay IoT network using A-NOMA for WBAN

ABSTRACT This article presents an energy-efficient multi-device (MD) diamond relay network (DRN) using radio frequency (RF) energy harvesting (EH) using an improved adaptive non-orthogonal multiple access (A-NOMA) protocol for wireless body area network (WBAN) scenario. To understand the practical application of A-NOMA in WBAN, a realistic virtual environment has been modelled in Netsim v13.1, and subsequently the simulated values are processed in Matlab to compare the achievable sum rate (ASR) with OMA and NOMA. Next, theoretical derivations of ASR and energy efficiency (EE) are carried out and validated through extensive simulations. Moreover, the bit error rate (BER) analysis has been performed and compared with the baseline models. Additionally, an in-depth evaluation of EE with respect to ASR has been performed. Results show that our proposed approach is more effective than the existing benchmarks and reveal an intriguing trade-off between ASR and EE.

Optimizing Spectrum Efficiency With MIMO NOMA PD Approach in a 5G Cooperative Spectrum Sharing Environment

ABSTRACTThe fifth generation (5G) of cellular communication networks has introduced various advanced technologies to address the increasing demand for higher data rates and improved spectrum utilization. One of these technologies, non‐orthogonal multiple access (NOMA), has gained significant attention due to its ability to enhance spectral efficiency by allowing multiple users to share the same time‐frequency resource block. NOMA affords a number of advantageous features including increased spectrum efficiency (SE). It comes in various forms, such as power‐domain (PD) NOMA and code‐domain (CD) NOMA. This paper attentions mainly on enhancing the SE of downlink (DL) PD‐NOMA in a 5G cooperative spectrum sharing environment using single input single output (SISO), massive MIMO (M‐MIMO), and multiple input multiple output (MIMO). Two methods are approached here. In the first one, the NOMA handlers access the free/unconstrained channels using competing channel (C‐Ch) approach, whereas the next one uses dedicated channel (D‐Ch) approach. Five users are considered at distances of 1000, 800, 600, 400, and 200 m from the base station (BS) with different power allocation coefficients at transmitting power of 40 dBm and bandwidth of 70 MHz. Quadrature phase shift keying (QPSK) is used with successive interference cancellation (SIC) at the receiver side and superposition coding (SC) at the transmitter side under frequency selective Rayleigh fading environment. The PD DL NOMA system's results demonstrated that combining 32 × 32 MIMO, 64 × 64 MIMO, and 128 × 128 M‐MIMO in a single cell and the same network with cooperative cognitive radio network (CoCRN) significantly improved the SE reliability. The user Ur5 produces an optimal SE performance of 3.753 bps/Hz/cell for PD DL NOMA with SISO, 5.77 bps/Hz/cell for CoCRN PD DL NOMA with SISO using C‐Ch, and 7.45 bps/Hz/cell for CoCRN DL PDNOMA with SISO using D‐Ch with a 40 dBm transmitting power. Furthermore, the SE for Ur5 (nearest user) was increased to 64%, 67%, and 69%, respectively, using PD‐NOMA with 32 × 32 MIMO, PD‐NOMA with 32 × 32 MIMO using C‐Ch, and DL NOMA PD with 32 × 32 MIMO using D‐Ch. DL PD‐NOMA with MIMO(64 × 64) using D‐Ch improved the SE rate by 77% having transmission power of 40 dBm in comparison with the SE outcome for DL PDNOMA with SISO; however, DL PD‐NOMA with MIMO (64 × 64) most dramatically upgraded the SE rate for Ur5 by 73%. Using C‐Ch and CoCRN DL PD‐NOMA with MIMO (64 × 64), the SE performance was boosted by 76%. The best user, Ur5, had an 82% improvement in SE performance when DL PD‐NOMA with M‐MIMO (128 × 128) was compared to DL NOMA with SISO. With a 40 dBm transmission power, CoCRN DL NOMA with 128 × 128 M‐MIMO using C‐Ch showed an 88% improvement, whereas CoCRN DL PD‐NOMA with M‐MIMO (128 × 128) using D‐Ch experienced an 89% improvement.

Non-orthogonal multiple access scheme based on color-coded four-dimensional constellation pairing mapping.

This paper proposes a short-range optical access method based on four-dimensional non-orthogonal multiple access (4D-NOMA), utilizing 4D constellation pairing mapping and two-dimensional inverse discrete Fresnel transform (2D-IDFnT) technology, achieving high compatibility with OFDM systems. An innovative color-coded 4D constellation pair mapping scheme was designed, introducing two types of four-dimensional spatial structures with 32 constellation points. By extending the three-dimensional constellation to four dimensions through color coding, the constellation figure of merit (CFM) increased by 22.2%. A 43.29 Gb/s 4D-NOMA transmission over a seven-core optical fiber was successfully demonstrated, verifying the feasibility and superiority of the proposed solution. Compared to conventional low-dimensional constellations, 4D-NOMA exhibits significant improvements in bit error rate and signal transmission sensitivity. Under the HD-FEC threshold, it provides approximately 0.9 dB and 1.3 dB sensitivity gains over traditional three-dimensional and two-dimensional constellations, respectively. This study indicates that the four-dimensional constellation structure and the 4D-NOMA scheme hold great potential for future short-range optical access systems.

Non orthogonal multiple access (NOMA) with energy harvesting from vibrations

Non orthogonal multiple access (NOMA) with energy harvesting from vibrations

Hybrid Multiple Access Techniques Performance Analysis Of Dynamic Resource Allocation

The Non-Orthogonal Multiple Access (NOMA) and the Orthogonal Frequency Division Multiple Access (OFDMA) are promising techniques for next-generation wireless systems. Although much attention in the literature considered these techniques, an effective combination between such systems as hybrid multiple access (HMA) needs more attention. For this reason, this paper devotes to proposing two different scenarios of HMA using multi-user OFDM (MU-OFDM) and power domain (PD) NOMA for downlink transmission to overcome the limitations of both Orthogonal Multiple Access (OMA) and NOMA. Due to the randomness of a wireless channel, different user grouping strategies and dynamic power allocation (DPA) strategies are employed to satisfy users’ requirements. The proposed systems give high flexibility utilizing bitrate allocation and user fairness. System results show superior performance to traditional OMA and NOMA systems. The achieved variety of fairness is helpful for the diversity of applications which is a principal requirement for beyond-fifth-generation (B5G) networks. The next step in this analysis is to enhance the proposed systems’ spectral efficiency (SE) by introducing beamforming for massive Multiple-Input Multiple-Output (MIMO) systems. The bit error rate (BER) result of the proposed system achieves almost the same error floor with a benefit of approximately 10 dB signalto-noise ratio (SNR) when 90 resource blocks (RBs) are used.

Interleaving based SCMA Codebook Design Using Arnold’s Cat Chaotic Map

Non-orthogonal multiple access (NOMA) technology is a significant topic of the present 5G investigation. A possible NOMA approach is Sparse Code Multiple Access (SCMA), increasing next-generation communication's ability to handle multiple users. In SCMA, codebook designing and optimization are crucial components that define the performance of multiple access systems. In this work, the complete design procedure of the SCMA codebook based on interleaving is explained and simulated. Furthermore, a chaotic interleaving based onArnold’sCat map is proposed to reduce the computational complexity. The performance of the SCMA codebook based on interleaving is evaluated through comparison with selected codebooks for SCMA multiplexing. The measures used for performance evaluation include Bit Error rate (BER), Peak to Average Power Ratio(PAPR), and minimum EuclidianDistance(MED). The results show that the proposed codebook with chaotic interleaving achieves comparable performance to the traditional codebook based on interleaving and less MED and higher BER compared to computer-generated and 16-star QAM codebook design methods but with reduced complexity.