Downlink multi-user algorithms for millimeter-wave wideband linear arrays on PD-NOMA-based squint steering beams

NOMA (Non- orthogonal Multiple Access) is an early candidate for 5G that concentrates on networks capacity expansion. It can be broadly classified into two major categories; Power-Domain NOMA (PD-NOMA) and Code-Domain NOMA (CD-NOMA). This research focuses on PD-NOMA. The significance of PD- NOMA is that concurrent transmission and reception can be accomplished on the same frequency and with this spectral efficiency can be enhanced. The objective of this research is to investigate the impact of error propagation caused due to AWGN (Additive White Gaussian Noise) channel in PD-NOMA 5G system. A 2 × 2 PD-NOMA system is simulated in Matlab version 2019a. In the Uplink, the raw data is BPSK modulated and transmitted to the Base Station (BS). In the downlink, from the BS, User 1 data is transmitted with a power level of 0.25 watts and User 2 with 0.75 watts based on their placement. In the Reception section, Successive Interference Cancellation (SIC) is executed to segregate the data which is further recovered through decoding process. To analyze the performance, AWGN channel is introduced in the proposed simulated system model. The Signal to Noise Ratio is varied from 5 to 25 dB. From the results obtained, it is inferred that, Bit Error Rate experienced by the users varies from 0.1 to 1.

This study introduces a low-complexity, short-code-based strategy that combines energy harvesting for power domain non-orthogonal multiple access (PD-NOMA) techniques. Due to its non-orthogonal nature, PD-NOMA is relatively more exposed to security vulnerabilities, rapid battery depletion in users due to multi-level SIC, and significant outage probability in congested environments. The presented work uses coded cooperation and short block-length codes to make it harder for unlicensed users to manipulate or steal the data of licensed users. This makes it less likely that unlicensed users will be able to find and decode data belonging to licensed users in the NOMA system. To optimize performance and reduce the frequent outage probability in the NOMA system, we developed a novel user clustering technique. Due to multi-level successive interference cancellation (SIC) at the cell center, users’ batteries quickly drain out in congested NOMA networks, leading to their declaration as energy-constrained. To overcome this issue, we use simultaneous wireless information and power transfer (SWIPT) at user-located cell centers based on the received radio frequency signals. Furthermore, it allows cell-center users to assist cell-edge users through the coded multi-user cooperation (coded Cop-PD-NOMA) technique, thereby enhancing the base station’s (gNodeB) network coverage. During the validation process, the proposed design offers secure NOMA communication, a novel user-clustering technique, and the application of SWIPT to cooperation in the PD-NOMA infrastructure. Bit-error rate (BER) and outage probability (OP) tests show that novel user-clustering and multiuser-coded Cop-PD-NOMA outperform single-user cooperation. Simulation results show that the proposed approach significantly reduces the outage probability (OP) and improves bit-error-rate (BER) performance by approximately 6.5 dB, which is only 2.5 dB in single-user cooperation.

The fifth generation (5G) of wireless communication accompanied by the advancement of mobile internet and the Internet of Things (IoT) will create stormy data traffic. The 5G challenges like higher spectral efficiency, massive connectivity, and low latency are addressed by the Non-Orthogonal Multiple Access (NOMA) in recent years. NOMA is proven to be a promising technique from its capability to accommodate a larger number of users in contrast to the conventional orthogonal multiple access (OMA) schemes. NOMA comprises two distinct techniques such as Power-Domain NOMA and Code-Domain NOMA. The non-orthogonal resource allocation in Power-Domain NOMA is practically realized by the Superposition Coding (SC) at the Base Station (BS) and an advanced Successive Interference Cancellation at the User Equipment (UE). In this manuscript, the basic concepts of NOMA, on comparing its channel gain with OMA are discussed first. Specifically, a comprehensive survey of various SIC techniques applied under perfect and imperfect Channel State Information (CSI) uncertainties are summarized in terms of outage probability, ergodic capacity, and system performance. In addition, the sophisticated SIC techniques, when NOMA is integrated with modern wireless communication technologies such as multiple-input multiple-output (MIMO-NOMA) and Cooperative (C-NOMA) communications are investigated. Furthermore, the challenges to be solved with their corresponding opportunities and future research directions of NOMA are explored.

Non-orthogonal multiple access (NOMA) on shared resources has been identified as a promising technology in 5G to improve resource efficiency and support massive access in all kinds of transmission modes. Power domain and code domain NOMA have been extensively studied and evaluated in both literatures and 3GPP standardization, especially for the uplink where large number of users would like to send their messages to the base station. Though different in the transmitter side design, power domain NOMA and code domain NOMA share the same need of the advanced multi-user detection (MUD) design at the receiver side. Various multi-user detection algorithms have been proposed, balancing performance and complexity in different ways, which is important for the implementation of NOMA in practical networks. In this paper, we introduce a unified variational inference (VI) perspective on various universal NOMA MUD algorithms such as belief propagation (BP), expectation propagation (EP), vector EP (VEP), approximate message passing (AMP) and vector AMP (VAMP), demonstrating how they could be derived from and adapted to each other within the VI framework. Moreover, we unveil and prove that conventional elementary signal estimator (ESE) and linear minimum mean square error (LMMSE) receivers are special cases of EP and VEP, respectively, thus bridging the gap between classic linear receivers and message passing based nonlinear receivers. Such a unified perspective would not only help the design and adaptation of NOMA receivers, but also open a door for the systematic design of joint active user detection and multi-user decoding for sporadic grant-free transmission.

In this work, resource allocation of Cooperative Power Domain Non-Orthogonal Multiple Access (PD-NOMA) with energy harvesting technique using Multiple Input Single Output (MISO) is examined. This paper focuses on improvement of bit error rate (BER), spectral efficiency and capacity compared to conventional Non-Orthogonal Multiple Access (NOMA). Two users scenario is considered, where an user is near to the base station (BS) while the other one is far away from the base station. As both users with different power levels exist in the same spectrum, co-channel interference is inevitable. To alleviate this, an interference cancellation technique known as Successive Interference Cancellation (SIC) is used. The simulation results of cooperative NOMA with energy harvesting are compared with conventional NOMA and it can be inferred that cooperative NOMA performance is better than NOMA.

The power domain non-orthogonal multiple access (NOMA) technique introduces one of the fundamental characteristics and it exhibits the possibility of users to decode the messages of the other paired users on the same resources. In cognitive radio inspired NOMA (CR-NOMA), the base station (BS) has to serve untrusted users or users with different security clearance. This phenomenon raises a security threat particularly in such CR-NOMA. This paper develops a tractable analysis framework to evaluate the security performance of cooperative non-orthogonal multiple access (NOMA) in cognitive networks, where relay is able to serve two far NOMA users in the presence of external eavesdropper. In particular, we study the secrecy outage probability in a two-user NOMA system. This situation happens in practical the BS is pairing a legitimate user with another untrusted user. Main reason is that the non-uniform distribution in terms of trusted and untrusted users in the cell. By performing numerical results demonstrate the performance improvements of the proposed NOMA scheme in comparison to that of several situations in terms of different parameters. Furthermore, the security performance of NOMA is shown to verify the derived expressions.

This research aims to optimize the performance of Successive Interference Cancellation (SIC) in Power Domain Non-Orthogonal Multiple Access (PD-NOMA) technology by applying spatial concepts through the use of beamforming techniques. User clustering is a key element in achieving this goal, and this research applies various supervised machine learning classification algorithms including Decision Tree, K-Nearest Neighbors (K-NN), Support Vector Machine (SVM), Random Forest, Logistic Regression, and Naive Bayes. The experimental results show that Random Forest achieves the highest accuracy in classifying users, followed by Decision Tree. In addition, in measuring performance using ROC (Receiver Operating Characteristic) and AUC (Area Under the Curve) curves, Decision Tree and Random Forest achieved the best results as well. While in terms of experimentation process time, decision tree has a faster time than random forest. Overall, Random Forest and Decision Tree algorithms are suitable for the task of user clustering in the context of PD-NOMA which utilizes the spatial concept of user to Base Station (BS).

To meet the 5G requirements on spectral efficiency and connection density, non-orthogonal multiple access (NMA) is becoming an important candidate technology. This paper focuses on power-domain NMA (PNMA) due to the relatively low design complexity and standardization impact. In PNMA, the data of more than one user equipment (UE) are superposed with different transmission power setting at the transmitter, and are separated by utilizing interference cancellation at the receiver. The theoretical performance of PNMA has been shown in some previous research. In this paper, we gives our proposals on PNMA practical system design aspects including base station (BS) scheduling, UE receiver implementation and network signaling, aiming to seek for good trade-off between overall performance and complexity. System-level simulations validate that compared to orthogonal multiple access (OMA), PNMA with our proposed scheduling algorithm can bring 14.16% and 23.88% gain in cell average spectral efficiency (SE) and cell edge SE respectively, as well as improve the number of connected UEs by 55%.

A novel power-domain non-orthogonal multiple access (NOMA) scheme with high-dimensional modulation is proposed. Signals for two users, each of which selected from a high-dimensional modulation constellation matrix, are superimposed on the same time-frequency resource for transmissions. While inter-user interference is treated as noise at the receiver of the far user, successive interference cancellation is used at the receiver of the near user. By analyzing the upper bounds of the detection errors, the power allocation factor is derived, which depends only on the relative power gain of the two users, i.e., the ratio between the squared of the two channel gains, but not on the operating signal-to-noise ratio. This nice feature allows us to perform user pairing easily for a system with more than two users. The optimal user pairing strategy that minimizes the total power consumption is analytically derived. Simulation results show that our proposed design outperforms some benchmark scheme.

This letter investigates uplink random access (RA) systems based on power-domain non-orthogonal multiple access (NOMA) with multichannel. In NOMA RA systems, users transmit their packet with transmit power by inverting their channel gain, i.e., channel inversion, such that the received power of their packet at the base station (BS) can be one of the predefined values. While this facilitates the decoding process based on successive interference cancellation (SIC), it can incur excessive transmit power consumption upon low channel gains. To reduce transmit power (improve energy efficiency), this letter considers multichannel selection diversity, where users choose one channel whose channel gain is the maximum of all. We characterize the stability of multichannel NOMA RA systems with the cusp catastrophe and analyze diversity gain in terms of energy efficiency.

This study examined how to improve system performance by equipping multiple antennae at a base station (BS) and all terminal users/mobile devices instead of a single antenna as in previous studies. Experimental investigations based on three NOMA down-link models involved (1) a single-input-single-output (SISO) scenario in which a single antenna was equipped at a BS and for all users, (2) a multi-input-single-output (MISO) scenario in which multiple transmitter antennae were equipped at a BS and a single receiver antenna for all users and (3) a multi-input-multi-output (MIMO) scenario in which multiple transmitter antennae were equipped at a BS and multiple receiver antenna for all users. This study investigated and compared the outage probability (OP) and system throughput assuming all users were over Rayleigh fading channels. The individual scenarios also each had an eavesdropper. Secure system performance of the individual scenarios was therefore also investigated. In order to detect data from superimposed signals, successive interference cancellation (SIC) was deployed for users, taking into account perfect, imperfect and fully imperfect SICs. The results of analysis of users in these three scenarios were obtained in an approximate closed form by using the Gaussian-Chebyshev quadrature method. However, the clearly and accurately presented results obtained using Monte Carlo simulations prove and verify that the MIMO-NOMA scenario equipped with multiple antennae significantly improved system performance.

In this paper, a unified framework of non-orthogonal multiple access (NOMA) networks is proposed, which can be applied to code-domain NOMA (CD-NOMA) and power-domain NOMA (PD-NOMA). Since the detection of NOMA users mainly depend on efficient successive interference cancellation (SIC) schemes, both imperfect SIC (ipSIC) and perfect SIC (pSIC) are taken into considered. To characterize the performance of this unified framework, the exact and asymptotic expressions of outage probabilities as well as delay-limited throughput for CD/PD-NOMA with ipSIC/pSIC are derived. Based on the asymptotic analysis, the diversity orders of CD/PD-NOMA are provided. It is confirmed that due to the impact of residual interference (RI), the outage probability of the n-th user with ipSIC for CD/PD-NOMA converges to an error floor in the high signal-to-noise ratio (SNR) region. Numerical simulations demonstrate that the outage behavior of CD-NOMA is superior to that of PD-NOMA.

Non-orthogonal multiple access (NOMA) is a rapidly emerging paradigm with the capability to improve the spectral efficiency of data-driven, intelligence inspired, and highly digitized sixth-generation (6G) wireless networks. In the backdrop of ever-evolving NOMA techniques, this article presents a novel resource optimization framework for maximizing the spectral efficiency (SE) of the Internet-of-things (IoT) networks using power domain NOMA. The proposed framework considers a limited number of frequency blocks in the IoT network and provides an optimal power and frequency block allocation method. Different practical constraints like successive interference cancellation (SIC) complexity, ensuring the minimum gap of received power among different IoT equipment over the same frequency block for successful SIC operation, quality of services requirements, and IoT equipment's transmit powers have also been taken into account. Accordingly, a non-convex optimization problem has been formulated for resource management where the objective of spectral efficiency is coupled by both frequency block and power allocation. To effectively solve this problem, the resource optimization problem is decoupled into two subproblems for frequency block assignment and power allocation. A suboptimal algorithm has been designed for frequency block assignment and a new optimal sequential quadratic programming (SQP) approach is employed to solve the non-convex power control subproblem. For the sake of fair comparison, a low complexity suboptimal NOMA power allocation scheme, based on Karush-Kuhn-Tucker (KKT) conditions, and conventional orthogonal multiple access (OMA) scheme are also provided. The results demonstrate that the proposed optimal resource management scheme significantly improves the system performance compared to other schemes.

The power-domain nonorthogonal multiple access (NOMA) based on successive interference cancellation (SIC) provides opportunities for fast media access in industrial wireless networks. In this article, given the traffic loads of wireless sensors, we study the shortest uplink scheduling (SUS) problem by joint power allocation and wireless sensor (WS) scheduling. A key term named maximum decoded level (MDL), which models the transmitting characteristics of WSs under SIC, and thus, lays the foundations for revealing a sufficient and necessary condition for successive transmissions under SIC, is presented in the first step. Then, guided by the theoretical condition that decouples WS scheduling from power allocation, we present a two-step greedy algorithm for the SUS problem in the case of continuous transmit powers. We also prove that the proposed algorithm is optimal for two regular cases. One is for any traffic loads under 2-SIC, the other is for unit traffic load under k-SIC. Furthermore, in the case of discrete transmit powers, we further propose an optimal algorithm under 2-SIC and an approximation algorithm under k-SIC by adapting the above-mentioned greedy algorithm for the case of discrete transmit powers. Experimental evaluations reveal the effectiveness of the three algorithms.

The fourth Industrial Revolution is expected to lead to an era of technological innovation and digitization that would require connectivity by the users, anywhere and anytime. The fifth generation of wireless communication systems and the technologies therein are being explored to cater to high connectivity needs that encompass high data rates, very low latencies, energy‐efficient systems, etc. A multiuser environment is anticipated that would require multiple access techniques, such as Nonorthogonal Multiple Access (NOMA). The user data in the power domain NOMA is superimposed, at the transmitter base station, which is in turn subjected to Successive Interference Cancellation at the user end. In the multiuser downlink, the desired user’s signal is subjected to imperfect SIC due to incomplete cancellation of the undesired user’s signal. Pulse‐shaping of NOMA symbols using wavelet transform is proposed to mitigate the multiuser interference due to imperfect SIC. Closed‐form symbol error rate (SER) expression is derived for the wavelet NOMA system for a three‐user scenario. Analytical results show that wavelet transform pulse‐shaped NOMA performs better compared to Fourier transform pulse‐shaped NOMA symbols in mitigating SIC and thereby minimize the residual error due to imperfect SIC.