Unified Performance Analysis of Near and Far User in Downlink NOMA System over η - μ Fading Channel

The non-orthogonal multiple access (NOMA) scheme is considered as a frontier technology to cater the requirements of 5G and beyond 5G (B5G) communication systems. To fully exploit the essence of NOMA, it is very important to explore the behavior of NOMA users over the most realistic nonhomogenous fading conditions. In this paper, we derive unified closed-form expressions of the basic performance metrics of the NOMA users. Their performance is evaluated in terms of average bit error rate (ABER), average channel capacity (ACC) and outage probability (OP) over η−μ fading channel. These expressions are in terms of popular functions, such as Meijer G-function and Gauss hypergeometric function, leading to their versatile use in analytical research. Unlike the existing outage probability expressions in terms of Yacoub integral, the derived expressions are easier to implement in software packages like MATLAB. Moreover, we compare the obtained results with a reference system, consisting of genie-aided NOMA system. We interpret that genie-aided performance results provide benchmark bounds for the metrics. Extensive simulations are carried out to validate the derived analytical expressions

Reliability of Spectrum-Efficient Mixed Satellite-Underwater Systems

The combination of radio-frequency (RF) communication and underwater optical wireless communication (UOWC) plays a vital role in the underwater Internet of Things (UIoT). This correspondence proposes a dual-hop hybrid satellite underwater system that exploits non-orthogonal multiple access (NOMA) as a spectrum-efficient access technique. The RF link from the satellite to the relay on an oil platform is presumptively subject to a Shadowed-Rician (SR) fading, while the UOWC channels from the relay to the underwater destinations are suggested to follow Exponential-Generalized Gamma (EGG) distributions. The reliability of the system is characterized in terms of both underwater destinations and system outage probabilities (OPs). We derive new closed-form expressions for the OPs under imperfect successive interference cancellation (SIC) conditions. Furthermore, the asymptotic OP and the diversity order (DO) are obtained to learn more about the system’s performance. The results are verified through an extensive representative Monte-Carlo simulation. Also, we investigate the performance against the turbulence of the salty water, air bubbles level (BL), temperature gradients (TG), shadowing parameters, and satellite pointing errors due to satellite motion, even if the beam is pointed at the center of the directive antenna relay, the beam will randomly oscillate. Finally, we contrast our approach with the conventional orthogonal multiple access (OMA) scheme to demonstrate its superiority

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

Security and Reliability Analysis of Satellite-Terrestrial Multi-Relay Networks with Imperfect CSI

This work investigates the security and reliabil- ity analysis for a novel satellite-terrestrial (SatTer) network. Specifically, a satellite attempts to transmit confidential infor- mation to a ground user (GU) via the support of multiple relay nodes in the presence of an eavesdropper that tries to overhear the information. A friendly jammer is deployed to improve the secure transmission between the satellite and the relays. Furthermore, satellite-to-relay generalized Rician fading channels and imperfect channel state information (CSI) are deployed to examine a general system model. In this context, the closed-formed expressions for the outage probability (OP) and intercept probability (IP) are derived corresponding to an amplify-and-forward (AF)-based relaying scheme, which is challenging and has not been studied before. Finally, the exactness of the mathematical analyses is validated through Monte Carlo simulations. Furthermore, the effects of various key parameters (e.g., channel estimation errors, satellite’s transmit power, relay’s transmit power, number of relays, and fading severity parameter) are examine

Komunikace na milimetrových vlnách v 5G a dalších sítích: Nové systémové modely a analýza výkonnosti

The dissertation investigates different network models, focusing on three important features for next generation cellular networks with respect to millimeter waves (mmWave) communications: the impact of fading and co-channel interference (CCI), energy efficiency, and spectrum efficiency. To address the first aim, the dissertation contains a study of a non-orthogonal multiple access (NOMA) technique in a multi-hop relay network which uses relays that harvest energy from power beacons (PB). This part derives the exact throughput expressions for NOMA and provides a performance analysis of three different NOMA schemes to determine the optimal parameters for the proposed system’s throughput. A self-learning clustering protocol (SLCP) in which a node learns its neighbor’s information is also proposed for determining the node density and the residual energy used to cluster head (CH) selection and improve energy efficiency, thereby prolonging sensor network lifetime and gaining higher throughput. Second, NOMA provides many opportunities for massive connectivity at lower latencies, but it may also cause co-channel interference by reusing frequencies. CCI and fading play a major role in deciding the quality of the received signal. The dissertation takes into account the presence of η and µ fading channels in a network using NOMA. The closed-form expressions of outage probability (OP) and throughput were derived with perfect successive interference cancellation (SIC) and imperfect SIC. The dissertation also addresses the integration of NOMA into a satellite communications network and evaluates its system performance under the effects of imperfect channel state information (CSI) and CCI. Finally, the dissertation presents a new model for a NOMA-based hybrid satellite-terrestrial relay network (HSTRN) using mmWave communications. The satellite deploys the NOMA scheme, whereas the ground relays are equipped with multiple antennas and employ the amplify and forward (AF) protocol. The rain attenuation coefficient is considered as the fading factor of the mmWave band to choose the best relay, and the widely applied hybrid shadowed-Rician and Nakagami-m channels characterize the transmission environment of HSTRN. The closed-form formulas for OP and ergodic capacity (EC) were derived to evaluate the system performance of the proposed model and then verified with Monte Carlo simulations.Dizertační práce zkoumala různé modely sítí a zaměřila se na tři důležité vlastnosti pro buňkové sítě příští generace s ohledem na mmW komunikace, kterými jsou: vliv útlumu a mezikanálového rušení (CCI), energetická účinnost a účinnost spektra. Co se týče prvního cíle, dizertace obsahuje studii techniky neortogonálního vícenásobného přístupu (NOMA) v bezdrátové multiskokové relay síti využívající získávání energie, kde relay uzly sbírají energii z energetických majáků (PB). Tato část přináší přesné výrazy propustnosti pro NOMA a analýzu výkonnosti se třemi různými schématy NOMA s cílem určit optimální parametry pro propustnost navrženého systému. Dále byl navržen samoučící se shlukovací protokol (SLCP), ve kterém se uzel učí informace o sousedech, aby určil hustotu uzlů a zbytkovou energii použitou k výběru hlavy shluku CH pro zlepšení energetické účinnosti, čímž může prodloužit životnost sensorové sítě a zvýšit propustnost. Za druhé, přístup NOMA poskytl mnoho příležitostí pro masivní připojení s nižší latencí, NOMA však může způsobovat mezikanálové rušení v důsledku opětovného využívání kmitočtů. CCI a útlum hrají klíčovou roli při rozhodování o kvalitě přijímaného signálu. V této dizertace je brána v úvahu přítomnost η a µ útlumových kanálů v síti užívající NOMA. Odvozeny jsou výrazy v uzavřené formě pro pravděpodobnost výpadku (OP) a propustnost s dokonalým postupným rušením rušení (SIC) a nedokonalým SIC. Dále se dizertace zabývá integrací přístupu NOMA do satelitní komunikační sítě a vyhodnocuje výkonnost systému při dopadech nedokonalé informace o stavu kanálu (CSI) a CCI. Závěrem disertační práce představuje nový model pro hybridní družicově-terestriální přenosovou síť (HSTRN) založenou na NOMA vícenásobném přístupu využívající mmWave komunikaci. Satelit využívá NOMA schéma, zatímco pozemní relay uzly jsou vybaveny více anténami a aplikují protokol zesilování a předávání (AF). Je zaveden srážkový koeficient, který je uvažován jako útlumový faktor mmWave pásma při výběru nejlepšího relay uzlu. Samotné přenosové prostředí HSTRN je charakterizováno pomocí hybridních Rician a Nakagami-m kanálů. Vztahy pro vyhodnocení výkonnosti systému navrženého modelu vyjadřující ergodickou kapacitu (EC) a pravděpodobnost ztrát (OP) byly odvozeny v uzavřené formě a následně ověřeny pomocí simulační numerické metody Monte Carlo.440 - Katedra telekomunikační technikyvyhově

New Approaches Using Cognitive Radio in Green Networking

The green networks are energy-efficient network architectures and we consider them as the basis of the wireless communication optimizing energy usage. Indeed, future communication technologies are moving in this direction, meaning that they will be less energy-intensive and, in some cases, even energy self-sufficient. Specifically, cognitive radio (CR) networks, cooperative relay networks, and non-orthogonal multiple access (NOMA) techniques have been considered as effective means to facilitate energy harvesting (EH) and a power spectrum allocation for the minimization of total transmit power, hence, making the wireless communication greener. The dissertation consists of three research sections corresponding to the aims. The first aim deals with an radio frequency (RF) wireless energy transfer model for D2D systems. In order to harvest more energy, a multiple-antenna base station and a power beacon are adopted for the D2D transmission network. We derive expressions outage probability in closed-forms. Further, independent simulations are used to validate the exactness of the theoretical expressions. In the second aim, new cooperative system models are proposed and studied. To reach the second aim, the secondary source acts as a relay and employs Amplify and Forward (AF) mode to serve distant NOMA users under a given interference constraint. To provide a detailed examination of the system performance metrics, we derived closed-form formulas for the outage probability and average throughput of the multi-users in the presence of interference constraints. In the last aim of the dissertation, we designed a new system model for a hybrid satellite-terrestrial cognitive network (HSTCN) relying on NOMA interconnecting a satellite and multiple terrestrial nodes. Reliability and security of transmission were studied to minimize the total transmit power. To reach the third aim, we examined the following performance factors: outage probability, hardware impairment, intercept probability, and average throughput. The novel closed-forms expressions of these performance factors are derived. The last but not at least, we simulated the new HSTCN system model. The achieved results figured that the new proposed approaches make it possible to take into account service quality requirements and are applicable in future green networking.Zelené sítě jsou energeticky efektivní síťové architektury a považujeme je za základ bezdrátové komunikace optimalizující spotřebu energie. Tímto směrem se ubírají budoucí komunikační technologie, což znamená, že budou méně energeticky náročné a v některých případech dokonce energeticky soběstačné. Kognitivní rádiové (CR) sítě, kooperativní relay sítě a neortogonální vícenásobné přístupové (NOMA) techniky jsou považovány za účinný prostředek k usnadnění získávání energie (EH) a přidělování výkonového spektra pro minimalizaci celkového vysílacího výkonu, díky čemuž je bezdrátová komunikace zelenější. Disertační práce se skládá ze tří výzkumných částí odpovídajících cílům. První cíl se zabývá modelem bezdrátového přenosu radiofrekvenční (RF) energie pro systémy D2D. Aby bylo možné získat více energie, jsou pro přenosovou D2D síť použity základnové stanice s více anténami a napájecím radiomajákem. Pro navržený model jsou odvozeny pravděpodobnosti výpadků, kdy tyto výrazy jsou v uzavřené formě. Dále jsou k ověření platnosti získaných teoretických výrazů použity nezávislé simulace. Ve druhém cíli jsou navrženy a zkoumány nové modely kooperativního systému. Aby bylo dosaženo druhého cíle, sekundární zdroj funguje jako relay uzel a využívá režim AF (Amplify and Forward), který slouží vzdáleným NOMA uživatelům za specifických interferenčních podmínek. Abychom poskytli podrobné zhodnocení výkonnostních metrik systému, odvodili jsme vztahy v uzavřené formě pro pravděpodobnost výpadků a průměrnou propustnost více uživatelů za přítomnosti interferenčních omezení. V posledním cíli disertační práce jsme navrhli nový systémový model pro hybridní satelitně-terestrickou kognitivní síť (HSTCN) založenou na neortogonálním vícenásobném přístupu (NOMA) propojující satelit a více terestrických uzlů. Zkoumána byla spolehlivost a zabezpečení přenosu s důrazem na minimalizaci celkového vysílacího výkonu. Pro dosažení třetího cíle jsme zkoumali následující výkonnostní faktory: pravděpodobnost výpadku, poškození hardwaru, pravděpodobnost zachycení a průměrnou propustnost. Pro tyto výkonnostní faktory jsou odvozeny v uzavřených formách nové výrazy. V neposlední řadě jsme rovněž simulovali nový systémový HSTCN model. Dosažené výsledky potvrdily, že nově navržené přístupy umožňují zohledňovat požadavky na kvalitu služeb a jsou použitelné v budoucích zelených sítích.440 - Katedra telekomunikační technikyvyhově

Stochastic Geometry-Based Analysis of Cache-Enabled Hybrid Satellite-Aerial-Terrestrial Networks With Non-Orthogonal Multiple Access

Due to the emergence of non-terrestrial platformswith extensive coverage, flexible deployment, and reconfigurablecharacteristics, the hybrid satellite-aerial-terrestrial networks(HSATNs) can accommodate a great variety of wireless accessservices in different applications. To effectively reduce the trans-mission latency and facilitate the frequent update of files withimproved spectrum efficiency, we investigate the performanceof cache-enabled HSATN, where the user retrieves the requiredcontent files from the cache-enabled aerial relay or the satellitewith the non-orthogonal multiple access (NOMA) scheme. If therequired content files of the user are cached in the aerial relay,the cache-enabled relay would serve directly. Otherwise, the userwould retrieve the content file from the satellite system, where thesatellite system seeks opportunities for proactive content pushingto the relay during the user content delivery phase. Specifically,taking into account the uncertainty of the number and locationof aerial relays, along with the channel fading of terrestrialusers, the outage probability and hit probability of the considerednetwork are, respectively, derived based on stochastic geometry.Numerical results unveil the effectiveness of the cache-enabledHSATN with the NOMA scheme and proclaim the influence ofkey factors on the system performance. The realistic, tractable,and expandable framework, as well as associated methodology,provide both useful guidance and a solid foundation for evolvednetworks with advanced configurations in the performance ofcache-enabled HSATN

5G embraces satellites for 6G ubiquitous IoT : basic models for integrated satellite terrestrial networks

Terrestrial communication networks mainly focus on users in urban areas but have poor coverage performance in harsh environments, such as mountains, deserts, and oceans. Satellites can be exploited to extend the coverage of terrestrial fifth-generation (5G) networks. However, satellites are restricted by their high latency and relatively low data rate. Consequently, the integration of terrestrial and satellite components has been widely studied, to take advantage of both sides and enable the seamless broadband coverage. Due to the significant differences between satellite communications (SatComs) and terrestrial communications (TerComs) in terms of channel fading, transmission delay, mobility, and coverage performance, the establishment of an efficient hybrid satellite-terrestrial network (HSTN) still faces many challenges. In general, it is difficult to decompose a HSTN into a sum of separate satellite and terrestrial links due to the complicated coupling relationships therein. To uncover the complete picture of HSTNs, we regard the HSTN as a combination of basic cooperative models that contain the main traits of satellite-terrestrial integration but are much simpler and thus more tractable than the large-scale heterogeneous HSTNs. In particular, we present three basic cooperative models, i.e., model X, model L, and model V, and provide a survey of the state-of-the-art technologies for each of them. We discuss future research directions towards establishing a cell-free, hierarchical, decoupled HSTN. We also outline open issues to envision an agile, smart, and secure HSTN for the sixth-generation (6G) ubiquitous Internet of Things (IoT)

Wireless networks physical layer security : modeling and performance characterization

Intrigued by the rapid growth and expand of wireless devices, data security is increasingly playing a significant role in our daily transactions and interactions with different entities. Possible examples, including e-healthcare information and online shopping, are becoming vulnerable due to the intrinsic nature of wireless transmission medium and the widespread open access of wireless links. Traditionally, the communication security is mainly regarded as the tasks at the upper layers of layered protocol stack, security techniques, including personal access control, password protection, and end-to-end encryption, have been widely studied in the open literature. More recently, plenty of research interests have been drawn to the physical layer forms of secrecy. As a new but appealing paradigm at physical layer, physical layer security is based on two pioneering works: (i) Shannon’s information-theoretic formulation and (ii) Wyner’s wiretap formulation. On account of the fundamental of physical layer security and the different nature of various wireless network, this dissertation is supposed to further fill the lacking of the existing research outcomes. To be specific, the contributions of this dissertation can be summarized as three-fold:(i) exploration of secrecy metrics to more general fading channels; (ii) characterization a new fading channel model and its reliability and security analysis in digital communication systems; and (iii) investigation of physical layer security over the random multiple-input multiple-output (MIMO) α −μ fading channels. Taking into account the classic Alice-Bob-Eve wiretap model, the first contribution can be divided into four aspects: (i) we have investigated the secrecy performance over single-input single-output (SISO) α −μ fading channels. The probability of non-zero (PNZ) secrecy capacity and the lower bound of secrecy outage probability (SOP) are derived for the special case when the main channel and wiretap channel undergo the same non-linearity fading parameter, i.e., α. Later on, for the purpose of filling the gap of lacking closed-form expression of SOP in the open literature and extending the obtained results in chapter 2 to the single-input multiple-output (SIMO) α − μ wiretap fading channels, utilizing the fact that the received signal-tonoise ratios (SNRs) at the legitimate receiver and eavesdropper can be approximated as new α −μ distributed random variables (RVs), the SOP metric is therefore derived, and given in terms of the bivariate Fox’s H-function; (ii) the secrecy performance over the Fisher-Snedecor F wiretap fading channels is initially considered. The SOP, PNZ, and ASC are finalized in terms of Meijer’s G-function; (iii) in order to generalize the obtained results over α −μ and Fisher-Snedecor F wiretap fading channels, a more flexible and general fading channel, i.e., Fox’s H-function fading model, are taken into consideration. Both the exact and asymptotic analysis of SOP, PNZ, and average secrecy capacity (ASC), are developed with closed-form expressions; and (iv) finally, motivated by the fact that the mixture gamma (MG) distribution is an appealing tool, which can be used to model the received instantaneous SNRs over wireless fading channels, the secrecy metrics over wiretap fading channels are derived based on the MG approach. Due to the limited transmission power and communication range, cooperative relays or multi-hop wireless networks are usually regarded as two promising means to address these concerns. Inspired by the obtained results in Chapters 2 and 3, the second main contribution is to propose a novel but simple fading channel model, namely, the cascaded α −μ. This new distribution is advantageous since it encompasses the existing cascaded Rayleigh, cascaded Nakagami-m, and cascaded Weibull with ease. Based on this, both the reliability and secrecy performance of a digital system over cascaded α −μ fading channels are further evaluated. Closed-form expressions of reliability metrics (including amount of fading (AF), outage probability, average channel capacity, and average symbol error probability (ABEP).) and secrecy metrics (including SOP, PNZ, and ASC) are respectively provided. Besides, their asymptotic behaviors are also performed and compared with the exact results. Considering the impacts of users’ densities, spatial distribution, and the path-loss exponent on secrecy issue, the third aspect of this thesis is detailed in Chapter 8 as the secrecy investigation of stochastic MIMO system over α −μ wiretap fading channels. Both the stochastic geometry and conventional space-time transmission (STT) scheme are used in the system configuration. The secrecy issue is mathematically evaluated by three metrics, i.e., connection outage, the probability of non-zero secrecy capacity and the ergodic secrecy capacity. Those three metrics are later on derived regarding two ordering scheme, and further compared with Monte-Carlo simulations