A Tutorial on Nonorthogonal Multiple Access for 5G and Beyond

Today's wireless networks allocate radio resources to users based on the orthogonal multiple access (OMA) principle. However, as the number of users increases, OMA based approaches may not meet the stringent emerging requirements including very high spectral efficiency, very low latency, and massive device connectivity. Nonorthogonal multiple access (NOMA) principle emerges as a solution to improve the spectral efficiency while allowing some degree of multiple access interference at receivers. In this tutorial style paper, we target providing a unified model for NOMA, including uplink and downlink transmissions, along with the extensions tomultiple inputmultiple output and cooperative communication scenarios. Through numerical examples, we compare the performances of OMA and NOMA networks. Implementation aspects and open issues are also detailed.Comment: 25 pages, 10 figure

Effective relaying mechanisms in future device to device communication : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in School of Food and Advanced Technology at Massey University, Palmerston North, New Zealand

Listed in 2020 Dean's List of Exceptional ThesesFuture wireless networks embrace a large number of assorted network-enabled devices such as mobile phones, sensor nodes, drones, smart gears, etc., with different applications and purpose, but they all share one common characteristic which is the dependence on strong network connectivity. Growing demand of internet-connected devices and data applications is burdensome for the currently deployed cellular wireless networks. For this reason, future networks are likely to embrace cutting-edge technological advancements in network infrastructure such as, small cells, device-to-device communication, non-orthogonal multiple access scheme (NOMA), multiple-input-multiple out, etc., to increase spectral efficiency, improve network coverage, and reduce network latency. Individual devices acquire network connectivity by accessing radio resources in orthogonal manner which limits spectrum utilisation resulting in data congestion and latency in dense cellular networks. NOMA is a prominent scheme in which multiple users are paired together and access radio resources by slicing the power domain. While several research works study power control mechanisms by base station to communicate with NOMA users, it is equally important to maintain distinction between the users in uplink communication. Furthermore, these users in a NOMA pair are able to perform cooperative relaying where one device assists another device in a NOMA pair to increase signal diversity. However, the benefits of using a NOMA pair in improving network coverage is still overlooked. With a varierty of cellular connected devices, use of NOMA is studied on devices with similar channel characteristics and the need of adopting NOMA for aerial devices has not been investigated. Therefore, this research establishes a novel mechanism to offer distinction in uplink communication for NOMA pair, a relaying scheme to extend the coverage of a base station by utilising NOMA pair and a ranking scheme for ground and aerial devices to access radio resources by NOMA

Efficient Transmission in Multi-user Relay Networks with Node Clustering and Network Coding

This is the author accepted manuscript. The final version is available from IEEE via the DOI in this recordThis paper investigates the communication problem in a class of multi-user dual-hop networks in which multiple source terminals desire to distribute their independent messages to multiple destinations through the assistance of multiple relay terminals. We consider an efficient transmission strategy that combines network coding and non-orthogonal transmission techniques to balance the achievability of spatial diversity and channel utilization. Specifically, in addition to applying a class of finite-field network codes in the relays, we divide the sources and the relays into clusters such that terminals within each cluster can access the same channel resource. The achievable error performance under Nakagami-m fading environment is derived and is shown to significantly outperform the conventional transmission methods.National Natural Science Foundation of ChinaEuropean Union Horizon 202

Non-Orthogonal Multiple Access schemes for Next Generation Cellular Networks: System Model and Performance Consideration

The dissertation deals with next generation cellular networks, especially in regard to the integration of wireless networks which apply non-orthogonal multiple access (NOMA) and other advanced techniques such as multi-antennae, radio frequency energy harvesting (EH), physical layer security (PLS) and satellite communication. Firstly, the dissertation investigates a multi-antenna transmission model to enhance the performance of communications. A novel model of power distribution to NOMA users, who joined both direct link and relay link, is designed to improve transmission quality. Further, we deploy the power beacon, which is able to feed energy to power-constraint relay node to further support transmission to destinations. Secondly, the dissertation studies the secrecy performance of a PLS in cognitive radio (CR)-NOMA networks. The multi-input single-output (MISO) architecture combining transmit antenna selection (TAS) strategy is considered to achieve secure performance analysis such as the secrecy outage probability (SOP). Further, optimal power allocation (PA) factor can be obtained to optimize SOP performance. Since the presence of an illegitimate user, we improve the SOP by adopting relay selection (RS) combining decode-and-forward (DF) with full-duplex (FD)relaying. Finally, as the strongest contribution of the dissertation, an application of the NOMA technique, which improves the spectral efficiency, in satellite networks is introduced. Satellite communication systems integrate with emerging small-cell networks to provide seamless connectivity and high-speed broadband access for mobile users in future wireless networks. In the dissertation, we study a hybrid satellite-terrestrial relay system (HSTRS). To characterizing the HSTRS-assisted small-cell network, Shadowed-Rician fading for satellite links and Nakagami-m fading for terrestrial links are adopted.Disertační práce se zabývá buňkovými sítěmi příští generace, zejména s ohledem na integraci bezdrátových sítí, které používají neortogonální vícenásobný přístup (NOMA) a další pokročilé techniky, jako jsou víceanténové systémy, získávání energie z elektromagnetického záření (EH), zabezpečení fyzické vrstvy (PLS) a satelitní komunikace. Disertační práce nejprve zkoumá model komunikace s více anténami s cílem dosáhnout vyšší efektivity přenosu. Nový model distribuce energie uživatelům NOMA, kteří se připojili přímým spojem anebo zprostředkovaně (přes realy uzel), je navržen tak, aby zlepšil kvalitu přenosu. Dále je v modelu navržen výkonový maják, který je schopen dodávat energii do relay uzlu, aby podpořil přenos k příjemcům. Za druhé, disertační práce studuje výkonnost PLS v sítích kognitivního rádia (CR)-NOMA. V návrhu je uvažována architektura více vstupů s jedním výstupem (MISO) kombinující strategii výběru vysílací antény (TAS), přičemž úroveň zabezpečení je zkoumána metrikou pravděpodobnosti výpadku utajení (SOP). Dále lze pro optimalizaci výkonu SOP získat faktor optimálního přidělování energie (PA). Vzhledem k předpokládané přítomnosti nelegitimního uživatele vylepšujeme SOP pomocí výběru relay uzlu (RS) kombinující režimy dekóduj a přepošli (DF) s plně duplexním (FD) přenosem. A konečně, jako nejsilnější přínos disertační práce, je představena aplikace techniky vícenásobného přístupu NOMA v satelitních sítích, která vylepšuje spektrální účinnost. Satelitní komunikační systémy se integrují s nově vznikajícími buňkovými sítěmi malého dosahu. Zajišťují bezproblémové připojení a vysokorychlostní širokopásmový přístup pro mobilní uživatele v budoucích bezdrátových sítích. V disertační práci studujeme hybridní satelitně-terestrický relay systém (HSTRS). K popisu sítě malých buněk s asistencí HSTRS je v případě satelitní komunikace použit útlumový model "Shadowed-Rician" a v případě terestrické pak "Nakagami-m."440 - Katedra telekomunikační technikyvyhově

On the Non-Orthogonal Layered Broadcast Codes in Cooperative Wireless Networks

A multi-fold increase in spectral efficiency and throughput are envisioned in the fifth generation of cellular networks to meet the requirements of International Telecommunication Union (ITU) IMT-2020 on massive connectivity and tremendous data traffic. This is achieved by evolution in three aspects of current networks. The first aspect is shrinking the cell sizes and deploying dense picocells and femtocells to boost the spectral reuse. The second is to allocate more spectrum resources including millimeter-wave bands. The third is deploying highly efficient communications and multiple access techniques. Non-orthogonal multiple access (NOMA) is a promising communication technique that complements the current commercial spectrum access approach to boost the spectral efficiency, where different data streams/users’ data share the same time, frequency and code resource blocks (sub-bands) via superimposition with each other. The receivers decode their own messages by deploying the successive interference cancellation (SIC) decoding rule. It is known that the NOMA coding is superior to conventional orthogonal multiple access (OMA) coding, where the resources are split among the users in either time or frequency domain. The NOMA based coding has been incorporated into other coding techniques including multi-input multi-output (MIMO), orthogonal frequency division multiplexing (OFDM), cognitive radio and cooperative techniques. In cooperative NOMA codes, either dedicated relay stations or stronger users with better channel conditions, act as relay to leverage the spatial diversity and to boost the performance of the other users. The advantage of spatial diversity gain in relay-based NOMA codes, is deployed to extend the coverage area of the network, to mitigate the fading effect of multipath channel and to increase the system throughput, hence improving the system efficiency. In this dissertation we consider the multimedia content delivery and machine type communications over 5G networks, where scalable content and low complexity encoders is of interest. We propose cross-layer design for transmission of successive refinement (SR) source code interplayed with non-orthogonal layered broadcast code for deployment in several cooperative network architectures. Firstly, we consider a multi-relay coding scheme where a source node is assisted by a half-duplex multi-relay non-orthogonal amplify-forward (NAF) network to communicate with a destination node. Assuming the channel state information (CSI) is not available at the source node, the achievable layered diversity multiplexing tradeoff (DMT) curve is derived. Then, by taking distortion exponent (DE) as the figure of merit, several achievable lower bounds are proved, and the optimal expected distortion performance under high signal to noise ratio (SNR) approximation is explicitly obtained. It is shown that the proposed coding can achieve the multi-input single-output (MISO) upper bound under certain regions of bandwidth ratios, by which the optimal performance in these regions can be explicitly characterized. Further the non-orthogonal layered coding scheme is extended to a multi-hop MIMO decode-forward (DF) relay network where a set of DE lower bounds is derived. Secondly, we propose a layered cooperative multi-user scheme based on non-orthogonal amplify-forward (NAF) relaying and non-orthogonal multiple access (NOMA) codes, aiming to achieve multi-user uplink transmissions with low complexity and low signaling overhead, particularly applicable to the machine type communications (MTC) and internet of things (IoT) systems. By assuming no CSI available at the transmitting nodes, the proposed layered codes make the transmission rate of each user adaptive to the channel realization. We derive the close-form analytical results on outage probability and the DMT curve of the proposed layered NAF codes in the asymptotic regime of high SNR, and optimize the end-to-end performance in terms of the exponential decay rate of expected distortion. Thirdly, we consider a single relay network and study the non-orthogonal layered scheme in the general SNR regime. A layered relaying scheme based on compress-forward (CF) is introduced, where optimization of end to end performance in terms of expected distortion is conducted to jointly determine network parameters. We further derive the explicit analytical optimal solution with two layers in the absence of channel knowledge. Finally, we consider the problem of multicast of multi-resolution layered messages over downlink of a cellular system with the assumption of CSI is not available at the base station (BS). Without loss generality, spatially random users are divided into two groups, where the near group users with better channel conditions decode for both layers, while the users in the second group decode for base layer only. Once the BS launches a multicast message, the first group users who successfully decoded the message, deploy a distributed cooperating scheme to assist the transmission to the other users. The cooperative scheme is naive but we will prove it can effectively enhance the network capacity. Closed form outage probability is explicitly derived for the two groups of users. Further it is shown that diversity order equal to the number of users in the near group is achievable, hence the coding gain of the proposed distributed scheme fully compensate the lack of CSI at the BS in terms of diversity order