Analysis of Non-Orthogonal Multiple Access Technique Performance Using Nakagami-m Fading Distribution

Due to the successive interference cancellation (SIC) technique, Non orthogonal multiple Access (NOMA) users have the capability of decoding the other paired users sharing the same resource bloc. As a result, NOMA technique is not only exposed to external eavesdropping, but also to internal eavesdropping which raises security risks regarding NOMA users' privacy. Therefore, this research aims to analyse a Multi-antenna cooperative NOMA system where both Decode and Forward (DF) and Amplify and Forward (AF) strategies are studied. In this context, we investigate the secrecy performance of our system with both internal and external eavesdropping scenarios. Closed-form expressions of the secrecy outage probability (SOP) and the strictly positive secrecy capacity (SPSC) metrics are derived. Numerical results are given to illustrate the validity of the obtained theoretical results.

In recent years, fifth-generation (5G) is receiving attention in wide research and progress efforts from the wireless communication society. 5G provides a new frequency bands alongside amid the wider spectral bandwidth per frequency channel. To solve the new challenges in 5G, different kind of new modulation techniques and multiple access (MA) schemes have to be adopted. To increase spectral efficiency new techniques called orthogonal multiple access (OMA) and nonorthogonal multiple access (NOMA) techniques are used in 5G wireless system. Here, we propose a class of polyphase sequences called Zadoff Chu sequences which have uniform amplitude, and these sequences bear good correlation properties. Since these sequences are also identified as constant amplitude zero autocorrelation (CAZAC) sequences, Zadoff Chu sequences are used to spread data in OMA and NOMA schemes for 5G networks. The simulation result shows that Zadoff Chu sequence has good correlation properties, and ZCT precoded-based OFDM system is capable of reducing the PAPR significantly.

Internet-of-Things (IoT) technology is envisioned to enable a variety of real-time applications by interconnecting billions of sensors/devices. These IoT devices rely on low-power wide-area wireless connectivity for transmitting, mostly fixed- but small-size, status updates of the random processes observed by them. Owing to their ubiquity, cellular networks are seen as a natural candidate for providing reliable wireless connectivity to IoT devices. Given the massive number of IoT devices, enabling non-orthogonal multiple access (NOMA) for the mobile users and IoT devices is appealing in terms of the efficient utilization of spectrum compared to the orthogonal multiple access (OMA). For instance, the uplink NOMA can also be configured such that the mobile users adapt their transmission rates depending upon the channel conditions while the IoT devices transmit at a fixed rate. For this setting, we analyze the ergodic capacity of the mobile users and the mean local delay of IoT devices using stochastic geometry. Our analysis demonstrates that the aforementioned NOMA configuration provides better ergodic capacity for mobile users compared to OMA when delay constraint of IoT devices is strict. We also show that NOMA supports a larger packet size at IoT devices than OMA under the same delay constraint.

The fifth-generation (5G) and beyond 5G (B5G) wireless networks introduced massive machine-type communications (mMTC) to cope with the growing demand of massive Internet of Things (IoT) applications. However, the heterogeneous characteristics of massive IoT and diverse quality of service (QoS) requirements may lead to severe interference that could degrade the expected QoS of the cellular ecosystem. Therefore, this article studies the impact of interference caused by mMTC connections. We theoretically model the intercell interference (ICI) minimization problem for the existing orthogonal multiple access (OMA) technique and propose its corresponding solution. Furthermore, we jointly solve the ICI and the cochannel interference minimization problem for the IoT users when the nonorthogonal multiple access (NOMA) technique is used. For the proposed OMA and NOMA schemes, we design a cooperative scheduler to reduce the impact of such interference. The results show that our proposed schemes provide up to 58%, 75%, and 100% more improvements in terms of user’s data rates, energy consumption, and connection density, respectively.

Non-Orthogonal Multiple Access (NOMA) is known as one of the promising techniques in the fifth generation of wireless communication. The classification of users in (NOMA) is based on power, while it is based on time, frequency and code in Orthogonal Multiple Access (OMA). In this study the downlink NOMA includes two users, one strong and one weak. The comparison of NOMA and OMA properties shows a range of Power Allocation Factors (PAF) for the two users within which NOMA properties have proved to be better than OMA. It was also shown that the achieved PAF is a function of channel gains of two users. Then, the coverage region is defined for multiple access channel; and by considering the Base Station (BS) as a fixed one in the center of the cell, the coverage region for both NOMA and OMA is calculated. The theoretical and analytical results show that the achieved coverage region of NOMA for both weak and strong users has been increased compared to OMA.

Among the key technologies that have been identified as capacity boosters for fifth generation - 5G - mobile networks, are millimeter wave (mmWave) transmissions and non-orthogonal multiple access (NOMA). The large amount of spectrum available at mmWave frequencies combined with a more effective use of available resources, helps improving the overall capacity. NOMA, unlike orthogonal multiple access (OMA) methods, allows sharing the same frequency resources at the same time, by implementing adaptive power allocation. In this paper we present a performance analysis of NOMA in mmWave cells, using OMA as a benchmark. The results show that up to 70% channel capacity gain can be achieved when using NOMA instead of OMA. Most of the NOMA studies to the date focus mainly on the capacity gain; therefore we also present an analysis of the required signal-to-interference-plus-noise ratio (SINR) in NOMA, needed to achieve a target block error rate (BLER). The results show that an average SINR penalty of 12 dB is present when choosing NOMA over OMA.

Cell-Free massive MIMO (cf-mMIMO) is an incarnation of distributed massive MIMO, which provides high spectral efficieny (SE). However, when the number of users increases, the SE of cf-mMIMO will decrease. In order to increase the SE when the number of users is large, many researchers investigated cf-mMIMO with non-orthogonal multiple access (NOMA). In the existing research, cf-mMIMO with NOMA requires the number of users in each cluster to be equal, which is inflexible. This paper investigates the multiple access technology for cf-mMIMO. A more flexible scheme which uses the orthogonal multiple access (OMA) and NOMA at the same time is proposed in this paper. This scheme does not require the number of users in each cluster to be equal and it combines the advantages of both NOMA and OMA. An achievable SE of this scheme is derived. It is proved that under certain number of users and the length of the channel’s coherence time conditions, using OMA and NOMA at the same time in the cf-mMIMO is able to obtain higher SE than using OMA or NOMA alone.KeywordsCell free massive MIMONOMAOMASuccessive interference cancellation

Non-orthogonal multiple access (NOMA) is a potential enabler for the development of 5G and beyond wireless networks. By allowing multiple users to share the same time and frequency, NOMA can scale up the number of served users, increase spectral efficiency, and improve user-fairness compared to existing orthogonal multiple access (OMA) techniques. While single-cell NOMA has drawn significant attention recently, much less attention has been given to multi-cell NOMA. This article discusses the opportunities and challenges of NOMA in a multi-cell environment. As the density of base stations and devices increases, inter-cell interference becomes a major obstacle in multi-cell networks. As such, identifying techniques that combine interference management approaches with NOMA is of great significance. After discussing the theory behind NOMA, this article provides an overview of the current literature and discusses key implementation and research challenges, with an emphasis on multi-cell NOMA.

Non-orthogonal multiple access (NOMA) is a potential enabler for the development of 5G and beyond wireless networks. By allowing multiple users to share the same resource (time/frequency/code/space), NOMA can scale up the number of served users, increase the spectral efficiency, and improve user-fairness compared to existing orthogonal multiple access (OMA) techniques. The basic premise behind NOMA in a single-cell network is to reap the benefits promised by information theory for the downlink and uplink transmission of wireless systems, modeled respectively by the broadcast channel (BC) and multiple access channel (MAC). The capacity regions of the BC and MAC have been established several decades ago, and concurrent non-orthogonal transmission is the optimal transmission strategy in both cases. Unlike the single-cell setting, the capacity region of multi-cell wireless networks, commonly modeled by the interference channel (IC), is in general unknown. However, it is known that OMA is suboptimal. This chapter reviews what information theory promises and proposes for NOMA in single- and multi-cell networks with both single- and multi-antenna nodes. Furthermore, relevant physical layer security channel models are proposed and discussed.

This work develops a distributed approach to user allocation in hybrid Internet of Things (IoT) networks, where nonorthogonal multiple access (NOMA) and orthogonal multiple access (OMA) techniques coexist for wireless user access. This hybrid approach facilitates massive connections of IoT devices with limited resources, exploiting the best of both multiplexing strategies. The directional beamforming environment is considered for mitigating user interference and providing spatial gains. Under this configuration, it aims at determining transmission techniques for individual users with the dual consideration of resource availability and geometric adjacency. To this challenge, an efficient distributed algorithm is developed via a novel realization techniques with a message-passing framework. The developed algorithm is rigorously investigated by in-depth theoretical analysis that ensures the optimality and the convergence of the global solution. Furthermore, numerical results also approve to outperform existing schemes consistently over a variety of network configurations that happen in wireless IoT networks.

Recently, non-orthogonal multiple access (NOMA) has been proposed to improve spectral efficiency greatly over conventional orthogonal multiple access (OMA). However, it is still challenging to implement NOMA into transmission of video. In this research, we investigate video broadcasting design over NOMA systems. When video transmission is considered, quality of experience (QoE) is a better metric for NOMA design than throughput. Therefore, we design a QoE-driven scalable video broadcasting (SVB) scheme over NOMA systems. To achieve scalable transmission performance, power allocation is optimized among multiple video layers, which are requested by users with different channel conditions. Specifically, we formulate the power allocation problem to maxmize the system overall QoE while guaranteeing the basic service of users. Although this problem is non-convex and discontinuous, an optimal algorithm is proposed based on the hidden monotonicity of the problem. Simulation results show that the proposed SVB scheme over NOMA systems outperforms existing OMA and NOMA based schemes in various broadcast scenarios in terms of QoE.

SummaryThe next generation wireless access technology highly relies on nonorthogonal multiple access (NOMA) technique. This paper proposes a novel power domain cyclic spread multiple access (PDCSMA) scheme for the design of NOMA system with power domain superposition coding (SC) and cyclic spreading at the transmitter concurrent with symbol level successive interference cancellation (SL‐SIC) at the receiver. Based on acceptable difference in channel gain, the users are grouped together to form PDCSMA clusters, and the unique power is allotted to each user in a cluster. The user with good channel condition is allotted less power, and the user with poor channel condition is allotted more power. Each PDCSMA cluster has its own spreading code, and the data of every user in a cluster are cyclic spread with the same code. Each cluster supports the number of multipath components equivalent to the length of the spreading code. The use of cyclic spreading makes the signal suffered by multipath fading less prone to intra cluster interference. The user signal is decoded by minimum mean square error‐frequency domain equalization (MMSE‐FDE) or maximal ratio combining (MRC)–based receiver in which weak user is detected with hard decision, and strong user is detected with SIC. Compared with conventional power domain NOMA (PDNOMA) and interleaved NOMA, the proposed PDCSMA achieves better bit error rate (BER) performance and assures guaranteed detection.

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.

Internet of Things (IoT) technology has become ubiquitous in a multitude of applications and its use is growing. However, the expansion of IoT faces a major difficulty: scalability, that is, very dense deployment of communicating devices is currently limited. In long-range networks, such as LoRa, the downlink is critical because it limits the number of acknowledgements that can be sent, and consequently reliability. It also limits the possibility to update the devices, which could be critical when they are deployed for decades. To overcome those problems, we propose a solution, inspired by Non Orthogonal Multiple Access (NOMA) techniques, to increase by at least one order of magnitude the number of devices that can be addressed. While the approach differentiates the devices by the power allocated to them, it differs from the vast majority of previous works on power domain NOMA because it does not require interference cancellation. Instead, it benefits from the spectrum spreading of the modulation scheme (chirp spread spectrum), where, at the end of the decoding phase, the information carried by a symbol is found in the position of a peak in the Fourier domain. In the vast majority of cases, the information from different users results in different peak positions, not creating any interference. In that sense, we get closer to avoidance schemes such as time or frequency hopping, but without using a code. In this article, we propose a new solution for NOMA in the power domain that does not suffer from the limitations induced by interference cancellation residues. The proposed system, including preamble detection and channel estimation, is presented and evaluated by simulations. We demonstrate that our proposed scheme increases the number of devices by one order of magnitude compared to the current system which allows addressing only one user at a time and maintains full compatibility with the LoRa physical layer standard.

In this paper, we investigate the performance of non-orthogonal multiple access (NOMA)-based overlay cognitive integrated satellite-terrestrial relay network with secondary network selection, where the selected secondary network accesses the licensed spectrum by assisting the communication of primary network with amplify-and-forward protocol. Besides, NOMA techniques are used to improve the spectrum efficiency. Specifically, the closed-form expressions of outage probability (OP) for both primary network and secondary network are obtained. To get inherent insights, the asymptotic analysis of OP is further derived at high signal-to-noise ratios. Moreover, the diversity orders of the both networks are further provided. Finally, Monte Carlo simulations are given to valuate our analysis, and the effects of key parameters on system performance are revealed. Through the comparison between orthogonal multiple access (OMA) scheme and NOMA scheme, the superiority of our proposed scheme is proved.