NOMA Techniques Research Articles

Analysis of interference effect in VL‐NOMA network considering signal power parameters performance

AbstractThis study analyses the interference effect in a visible light‐non‐orthogonal multiple access (VL‐NOMA) network that considers the signal power parameters performance for near and far users. The light‐emitting diode (LED) as a carrier transmits signals, and we investigate the interference effect. The interference effect challenge is a result of unaligned signal power parameters, thereby producing noise or echo during the signal transmission. The signal power parameters are successfully aligned, and NOMA techniques are deployed, which improves the signal performance in terms of bit‐error rate (BER), achieved data rate, and signal‐to‐interference plus noise ratio (SINR). Furthermore, the deployed NOMA techniques, such as power allocations (PA) to assign the signals appropriately, then superposition coding (SC) encodes the entire signal, and successive interference cancellation (SIC) cancels the interference within the signals. The signal behavior of the aligned and the unaligned signal power parameters performance are used to investigate the interference effect. We observed that unaligned signal power parameters reduce the signal performance of achieved data rate, BER, and SINR. Further, the aligned signal power parameter with NOMA techniques improves the signal performance. Moreover, in the aligned signal power scenario of NOMA, the near user performed better than the far user.

Transit Archimedes optimization algorithm enabled deep learning for power and resource allocation NOMA technique for 5G cellular systems

Summary5G communication technology is projected to provide extreme data rates that surpass user exposure, low power consumption, and greater short latency. A diverged multi‐layer approach is implemented by cellular networks with macro‐cells and various schemes of small cells to aid users with diverged quality of service (QoS) that affects more research by employing intervention management in 5G networks. Along with the escalating requirement for cellular services and adequate resources to furnish it and capable of handling the network traffic has become a resource distribution concern. The major concern is to facilitate the network jam having QoS. To overcome this concern, a potent investigation is developed for power and resource allocation, which is named as transit Archimedes optimization algorithm (TAOA). First, the non‐orthogonal multiple access (NOMA) system module is created with the aid of power consumption and energy modules. Then, user clustering (UC) is performed to gather the NOMA users into single or multiple clusters utilizing deep embedded clustering (DEC) in accordance with user grouping parameters, like signal‐to‐interference and noise ratio (SINR), position, initial power, and channel gain. After that, sub‐channel assignment and power allocation are done by the back propagation neural network (BPNN). Lastly, the presented module TAOA is performed to update the network parameters of BPNN, where TAOA is developed by the fusion of transit search (TS) optimization and Archimedes optimization algorithm (AOA). The analytic metrics utilized for finding the performance of the proposed TAOA‐BPNN are achievable rate, energy efficiency, sum rate, and throughput. The experimental results demonstrate that the proposed method offers good performance with the achievable rate of 3.273 Mbits, energy efficiency of 0.00000000473 J, sum rate of 0.00000248 s, and throughput of 0.00000346 Mbps.

Improving Performance of the Typical User in the Indoor Cooperative NOMA Millimeter Wave Networks with Presence of Walls

INTRODUCTION: The beyond 5G millimeter wave cellular network system is expecting to provide the high quality of service in indoor areas. OBJECTIVES: Due to the high density of obstacles, the cooperative communication technique is employed to improve the user's desired signal power by finding more than one appropriate station to serve that user. METHODS: While the conventional system utilizes additional equipment such as Reconfigurable Intelligent Surfaces (RIS) and relays to enable the cooperative features, the paper introduces a new network paradigm that utilizes the second nearest Base Station (BS) of the typical user as the Decode and Forward (DF) relay. Thus, depends on the success of decoding the message from the user' serving BS of the second nearest BS, the typical user can work with and without assistance from the relay whose operation follows the discipline of the power-domain NOMA technique. In the case of with relay assistance, the Maximum Ratio Combining technique is utilized by the typical user to combine the desired signals. RESULTS: To examine the performance of the proposed system, the Nakagami-m and the newly developed path loss model, which considers the density of walls and their properties, are adopted to derive the coverage probability of the user with and without relay assistance. The closed-form expressions of this performance metric are derived by Gauss quadrature and Welch-Satterthwaite approximation.

Beam-space MIMO-NOMA Technique for mm-Wave Communication Systems

The multi-input-multi-output-antenna Scheme is regarded as the most promising method for next-generation wireless communication networks that employ millimeter-wave (mm-wave) frequencies and enable them to have a large information throughput. As a result of the large number of radio frequency chains, MIMO mm-wave technology has difficulty with energy consumption. The beam space MIMO (or BS-MIMO for short) reduces the total number of radio frequency components or chains (RF-Chains) without degrading performance significantly. Yeti, VS-MIMO restricts the number of clients that can be supported at the same time-frequency domain (cannot exceed the overall RF-chains number ). In order to cope with such problems, it has been intended to include the NOMA technique (which stands for Non-Orthogonal-Multiple-Access) with the concept of beam space to create the extra model of Non-Orthogonal beam space-MIMO (NOMA-BS-MIMO). With such a scheme the base station can support the service for more than one client (supposed to have correlated channels) through the same beam employing the same radio frequency chain, causing the total clients number greater than the number of employed radio chains in the system. In this research, the Spectral Efficiency of a proposed Non-Orthogonal beam space-MIMO has been considered. More specifically, the research proposes and develops a simple iterative algorithm with near-perfect performance in terms of system Spectral Efficiency. To achieve rate balancing across users, the proposed method, SLNR-IV, employs the signal-to-leakage-plus-noise ratio (SLNR) and the intermediate value method. Considering algorithm validity and a particular parameter setting scenario, the proposed strategy improves bandwidth efficiency by around 15% in comparison to the conventional approach based on OFDM and Zero-forcing digital precoder.

Joint MU-mMIMO-OFDM with Hybrid Beamforming System Spectral Efficiency Improvement based NOMA Technique

Joint MU-mMIMO-OFDM with Hybrid Beamforming System Spectral Efficiency Improvement based NOMA Technique

Performance study of HF communication using NOMA over narrowband HF channel

AbstractHigh frequency systems (HF) are still used in many communication applications. Data can be sent for hundreds of kilometers at a low power cost with only one drawback, low bitrate. To increase the bitrate, several methods were reported using the single‐Tone modulation with 24 kHz bandwidth, but still not practical in real‐time applications because, the 24 kHz is unavailable due to the instability of the ionosphere layer. In this work, we propose a structured method built on the Non‐Orthogonal Multiple Access technique (NOMA) to increase the bit rate per HF narrowband channel. To increase the data rate, two parts of the data are divided and sent to one user over two different power levels. We use the NOMA technique on the receiver's side to recognize the two parts of data. The results show a significant improvement (up to 45%) using NOMA in narrowband 3 kHz channels. The bit rate at the receiver has increased up to 200 Kb/s concerning, while the maximum bit rate recorded by conventional methods used in previous studies is 138 Kb/s. The system is built on the SDR platform and tested in multiple channels, weather, and power conditions in real‐time experiments to validate its reliability.

Key management scheme of distributed IoT devices based on blockchains

AbstractWith the rapid development of Internet of Things devices and communication technology, the number of devices connected to the Internet of Things is growing exponentially. However, in the context of the rapid increase in the number of devices, data security issues such as data leakage and data tampering also follow. Therefore, communication security between devices is particularly important. However, in the traditional network environment, the identity authentication and information encryption methods to ensure communication security mostly adopt centralized network structure, relying on the central equipment to manage the access edge equipment. However, due to the heterogeneity of IoT devices and limited resources, the traditional centralized management scheme does not fully comply with the IoT system. In order to solve the above problems, this paper proposes a blockchain distributed IoT device key management scheme under the blockchain technology framework, which proposes a blockchain based distributed IoT architecture, and designs a hash chain based identity authentication scheme and a key distribution scheme based on network security coding on the basis of this architecture. Because blockchain technology has the characteristics of openness, immutability, traceability and fault tolerance, it can ensure the privacy of data transmission in the IoT scene, thus providing a secure communication environment. In this paper, the performance indexes related to the scheme are evaluated, and the experimental analysis confirms the efficiency and scalability of the proposed scheme.

Energy-Efficient Mobile Edge Computing in RIS-Aided OFDM-NOMA Relay Networks

In this paper, the design of task offloading and computing strategy in a mobile edge computing (MEC) system deployed over a reconfigurable intelligent surface (RIS)-aided orthogonal frequency division multiplexing based non-orthogonal multiple access (OFDM-NOMA) relay network is studied, where both a relay node and an MEC server located at an access point help a user terminal accomplish task computing. Our objective is to minimize energy consumption for communication and computation at the user terminal and the relay subject to a given task executing delay constraint. To this end, a novel protocol is first proposed to enable the user terminal and the relay to fully utilize the high passive beamforming gain provided by RIS and the high spectral efficiency offered by OFDM and NOMA techniques for task offloading. Then, under the newly proposed protocol, a resource allocation optimization problem is formulated, where RIS reflection coefficients, task offloading and computing time allocation, subcarrier and power allocation, task partition, and CPU frequency of the MEC server are jointly optimized. Because the numerous optimization variables are coupled with each other and integer programming is involved for subcarrier allocation optimization, the formulated problem is a mixed integer programming and highly non-convex problem that is hard to tackle. To address this problem, an efficient algorithm is devised to achieve its solution by employing alternating optimization, layer optimization, big-M formulation and successive convex approximation techniques. Simulation results validate that substantial energy savings can be achieved by employing RIS and OFDM-NOMA techniques in wireless relaying-based MEC systems.

Non-orthogonal multiple access system based on time diversity for 5G applications

Novel coding and modulation methods are required for fulfilling the demands of 5G and beyond cellular communication systems. In this paper, an innovative time diversity non-orthogonal multiple access (TD-NOMA) approach is proposed for 5G applications. The suggested system uses time diversity (TD) in conjunction with NOMA to improve the system bit error rate (BER) performance. The NOMA technique basically employes data transmission based on non-orthogonal basis functions. The data pass through the channel, and the desired signal can be obtained by a successive interference cancelation (SIC) receiver. Using different subcarriers and channel models, different modulation schemes such as QPSK and BPSK are investigated. When compared to conventional methodologies, the simulation results reveal that the proposed system outperforms them; it reduces the effect of fading for the multipath channel and enhances the BER.

A Cooperative D2D Content Sharing Scheme Using NOMA Under Social Ties

With the merit of bypassing the base station (BS) to directly communicate between user equipment (UE), D2D content sharing between socially connected users has revealed promising potential in future networks. However, D2D receivers (DRs) in different D2D pairs (DPs) may also have demand for additional content sharing services from the D2D transmitters (DTs), who also have considerable social ties with them, in other surrounding DPs to enhance or supplement their received sharing services. In this letter, we propose a cooperative D2D content sharing scheme using NOMA technique under social ties, where the DRs in different DPs, who have social similarities in interested files, separately spare a portion of the transmit power of their corresponding DT to each other to improve the received sharing services in DRs. Based on this, the performance of the proposed scheme underlaying cellular network with partial channel state information (CSI) is analyzed, which is suitable for distributed deployment. Finally, the simulations validate the effectiveness of our proposed scheme.

Improving Secrecy Rate and Social Welfare by NOMA Technique in D2D Communications Network

Improving Secrecy Rate and Social Welfare by NOMA Technique in D2D Communications Network

Reconfigurable intelligent surface assisted downlink INOMA system

AbstractNonorthogonal multiple access (NOMA) and reconfigurable intelligent surface (RIS) methods are explored to enhance spectral and energy efficiency of a wireless network. In this article, we have proposed a downlink RIS‐assisted index modulation NOMA for next‐generation wireless systems, and it is referred to as R‐INOMA. In the proposed R‐INOMA system, a base station transmits information through RIS to three users, the first user is assigned in the spatial domain and the remaining two users are multiplexed using power domain NOMA. We provide an analytical analysis of bit error probability (BEP) for the proposed R‐INOMA system. Impact of number of surfaces, transmit antennas, modulation order, diversity order, and imperfect channel estimation is analyzed for the R‐INOMA. Simulation results show that the proposed R‐INOMA achieved better BEP and sum‐rate over existing NOMA techniques. In the R‐INOMA, doubling of the reflecting surfaces provides a 4 dB gain for a fixed error probability, and the sum‐rate improves as the number of transmitting antennas and reflecting surfaces increases.

Integrating Wireless Sensor Network with Li-Fi Wireless Communication Technology based on NOMA Technique: A Survey

Integrating Wireless Sensor Network with Li-Fi Wireless Communication Technology based on NOMA Technique: A Survey

Link Connectivity-Based Access Selection Method for Multi-UAV Heterogeneous Networks

While UAV ad hoc networks have made significant progress, implementing it in most of real-application scenarios is challenging due to data explosion. Instead of only ad hoc mode, this work simultaneously considers non-orthogonal multiple access technique (NOMA) and ad hoc mode to handle the problem. We further propose an effective framework to seamlessly integrate these two techniques, namely Multi-UAV heterogeneous networks. Specifically, we formulate the framework as a mixed integer nonlinear programming, in which original problem can be decomposed into two sub-problems, e.g., access mode selection for UAV to UAV mode (U2U) and UAV to Ground Base mode (U2G), and transmission rate optimization. For the access mode selection, to reduce the computational complexity at each UAV, a candidate set is constructed based on the connection time and link quality. After that, the component in candidate set that maximizes the objective function is selected as the access point. Due to the different communication techniques in U2U mode and U2G mode, we can obtain the optimal rate for each UAV by using the NOMA technique in U2G mode and channel prediction method with local information in U2U mode, respectively. For the transmission rate optimization, an effective algorithm is proposed for U2G mode and U2U mode, which considers the effects of the network connectivity and link quality on the optimization performance. Simulation results show that our method can reduce the outage rate and improve the network throughput effectively.

Intelligent Reflecting Surface-Assisted Uplink SCMA System

Intelligent reflecting surface (IRS) is a promising technique to enhance performance of wireless systems due to its ability to smartly reconfigure the signal propagation environment. Sparse code multiple access (SCMA) is code-domain non-orthogonal multiple access technique suitable for the next-generation wireless networks. In this letter, we consider IRS-assisted uplink SCMA (I-SCMA) for energy and spectrally-efficient wireless systems. Message passing algorithm (MPA)-based signal detection is proposed to detect multiple users’ symbols in uplink I-SCMA. The diversity orders of I-SCMA for random and coherent phase shifting are derived. The symbol error rate and the sum-rate performance of the uplink I-SCMA system are analyzed. Further, the impact of overloading factor, the number of reflecting surfaces, the number of phase shifts of reflected signals are studied. Simulation results demonstrate the benefits of I-SCMA in terms of the spectral and energy efficiency over conventional SCMA and other NOMA techniques.

Partial-Beam Non-Orthogonal Multiple Access (PB-NOMA) With Fuzzy Clustering

This letter proposes a partial-beam non-orthogonal multiple access (PB-NOMA) system for millimeter wave (mmWave) channels. In the proposed system, the user terminals (UT)s partially belong to different user groups and power-domain partial NOMA (P-NOMA) technique is exploited in their allocated spectrum. While an individual beam serves the UTs in one group, the UTs in the same group, including the overlapped beam UTs, employ the P-NOMA scheme. Overlapped beam UTs are present when two near UTs are closely correlated and when they are equally belonging to two user groups. Fuzzy C-means (FCM) clustering method, which considers the channel correlation coefficient as a similarity measure, is proposed to group the users. Then, user pairing is performed based on the channel gain differences and fuzzy membership values. Simulation results reveal that the sum-rate performance of the proposed PB-NOMA scheme with fuzzy clustering is shown to be better than that of the conventional P-NOMA systems by adjusting overlapped beam ratio (OBR) and lower near UT overlap ratio (NOR) in a preferable group.

Sum-rate optimization for NOMA based two-tier hetnets with massive MIMO enabled wireless backhauling

In this paper, massive MIMO and NOMA techniques are jointly considered in a two tier heterogeneous network for accommodating huge traffic. In addition, full duplex communication is used at SBS to enhance system performance. First, SINR and rate equations are modeled while considering imperfect channel state information and zero-forcing beamforming. In the proposed framework, both macro base station and small cell base station can serve multiple users by using NOMA. Since, existing literature mainly focuses on orthogonal multiple access (OMA) based UA schemes, it is necessary to re-design user association (UA) schemes for NOMA. Hence, based on the proposed framework, a joint UA and power allocation (PA) optimization problem is designed with the perspective of optimizing the sum-rate of the system while accounting for quality of service and backhaul constraints. Since, the initially formulated problem is non-convex, a distributive algorithm is propounded where a joint problem is separated into two convex subproblems (viz., UA and PA). Furthermore, the complexity of the proposed algorithm is examined and Jain’s fairness index is measured. Simulation results demonstrate the effectiveness of the proposed algorithm by comparing with optimal solution and other base-line algorithms.

An Extended NOMA Technique to Confront Interferences for Future Cellular Networks

In this paper, a new scheme called an extended non-orthogonal multiple access (E-NOMA) is proposed, in which the effect of the inter-network interference is investigated. Even though the bandwidth efficiency challenge, as an uprising topic in 5G networks, is ameliorated by proposing NOMA schemes, their performances extensively suffer from interference. Such interferences make errors in users’ estimated signals and also spread error propagation through successive interference cancellation (SIC) process. E-NOMA network exploits the spectrum sensing (SS) scheme to mitigate inter-network interferences. The analytical and simulation results demonstrate that compared with conventional NOMA and TDMA as an orthogonal multiple access (OMA), not only the detection performance in E-NOMA improves but also the throughput of the whole network increases.

Low-Complexity SCMA Detection for Unsupervised User Access

Non-orthogonal multiple access schemes (NOMA), such as sparse code multiple access (SCMA), are among the most promising technologies to support massive numbers of connected devices. Still, to minimize the transmission delay and to maximize the utilization of the transmission channel, “grant-free” NOMA techniques are required that eliminate any prior information exchange between the users and the base-stations. However, if a large number of users transmit simultaneously in an “unsupervised” manner, (i.e., without any prior signaling for controlling the number of users and the corresponding transmission patterns), it is likely that a large number of users may share the same frequency-resource element, rendering the corresponding user detection impractical. In this context, we present a new multi-user detection approach, which aims to maximize the detection performance, with respect to given processing and latency limitations. We show that our approach enables practical detection for grant-free SCMA schemes that support hundreds of interfering users, with a complexity that is up to two orders of magnitude less than that of conventional detection approaches.

Handover scheme for 5G small cell networks with non-orthogonal multiple access

The enormous developments in new generation networks reveal the high bandwidth requirements of mobile users. Therefore, wireless communications technologies move higher frequencies with a small coverage area. The small cell concept exposes these advancements for 5G network framework. The small cell issue is a part of 5G networks with non-orthogonal multiple access, millimeter-wave communications, massive MIMO technology, IoT, spectrum sharing, ultra-dense networks, D2D communications, etc. The small cell with small coverage area and seamless communications needs of the mobile users reveal the dense networks with explosive data traffic. The handover process undertakes an important task for 5G networks according to the dense network, small coverage area, and user mobility specifications. In this study, we aim to investigate classic RSSI based handover scheme and fuzzy logic based handover scheme with NOMA for 5G networks. We take into consideration RSSI, BER, and Outage Probability parameters for fast and seamless handover decisions and utilize NOMA technique for users’ multiple access. This is the first study for 5G small cell networks fuzzy logic-based handover scheme with NOMA in the literature.