Review on Radio Resource Allocation Optimization in LTE/LTE-Advanced using Game Theory

Recently, there has been a growing trend toward ap-plying game theory (GT) to various engineering fields in order to solve optimization problems with different competing entities/con-tributors/players. Researches in the fourth generation (4G) wireless network field also exploited this advanced theory to overcome long term evolution (LTE) challenges such as resource allocation, which is one of the most important research topics. In fact, an efficient de-sign of resource allocation schemes is the key to higher performance. However, the standard does not specify the optimization approach to execute the radio resource management and therefore it was left open for studies. This paper presents a survey of the existing game theory based solution for 4G-LTE radio resource allocation problem and its optimization

Resource allocation in networks via coalitional games

The main goal of this dissertation is to manage resource allocation in network engineering problems and to introduce efficient cooperative algorithms to obtain high performance, ensuring fairness and stability. Specifically, this dissertation introduces new approaches for resource allocation in Orthogonal Frequency Division Multiple Access (OFDMA) wireless networks and in smart power grids by casting the problems to the coalitional game framework and by providing a constructive iterative algorithm based on dynamic learning theory.  Software Engineering (Software)Algorithms and the Foundations of Software technolog

In-band relays for next generation communication systems

Next generation mobile communication systems will operate at high system bandwidths of up to 100MHz and at carrier frequencies beyond 2GHz to provide peak data rates of up to 1Gbit/s with similar average revenues per user as todays cellular networks. High bit rates should be available to all users in a cell which is challenging due to the unfavorable propagation conditions in these bands. In-band relays are a seen as a promising technology for cellular networks to extend the high bit rate coverage and to enable cost efficient network deployments. The research in this thesis has contributed to the development of the relaying concept within the European research project WINNER. WINNER has designed a next generation radio system concept based on Orthogonal Frequency Division Multiple Access (OFDMA) with the inclusion of relays as one of the major innovations. In our work we have identified the radio resource management as the most important function to exploit the potential benefits of relay based deployments. We develop a flexible radio resource management framework that adapts to a wide range of deployments, whereas our main focus is on metropolitan area deployments. Here we propose to utilize a dynamic resource assignment based on soft frequency reuse. Further, we propose a practical way to integrate cooperative relaying in a relay network. This concept allows the cooperation of multiple radio access points within a relay enhanced cell with low overhead and small delays. In system simulations we compare the performance of relay deployments to base station only deployments in a metropolitan area network. Our results show that relay deployments are cost efficient and they increase both the network throughput as well as the high bit rate coverage of the network. Further, they show that our proposed soft frequency reuse scheme outperforms competing interference coordination schemes in the studied metropolitan area scenario. Even though the results have been obtained for WINNER system parameters, the conclusions can also be applied to OFDMA based systems such as 3GPP Long Term Evolution and WiMAX

Design of static intercell interference coordination schemes for realistic lte-based cellular networks

Today, 3.5 and 4G systems including Long Term Evolution (LTE) and LTE-Advanced (LTE-A) support packet-based services and provide mobile broadband access for bandwidth-hungry applications. In this context of fast evolution, new and challenging technical issues must be e ectively addressed. The nal target is to achieve a signi cant step forward toward the improvement of the Quality of Experience (QoE). To that end, interference management has been recognized by the industry as a key enabler for cellular technologies based on OFDMA. Indeed, with a low frequency reuse factor, intercell interference (ICI) becomes a major concern since the Quality of Service (QoS) is not uniformly delivered across the network, it remarkably depends on user position. Hence, cell edge performance is an important issue in LTE and LTE-A. Intercell Interference Coordination (ICIC) encompasses strategies whose goal is to keep ICI at cell edges as low as possible. This alleviates the aforementioned situation. For this reason, the novelties presented in this Ph.D. thesis include not only developments of static ICIC mechanisms for data and control channels, but also e orts towards further improvements of the energy e ciency perspective. Based on a comprehensive review of the state of the art, a set of research opportunities were identi ed. To be precise, the need for exible performance evaluation methods and optimization frameworks for static ICIC strategies. These mechanisms are grouped in two families: the schemes that de ne constraints on the frequency domain and the ones that propose adjustments on the power levels. Thus, Soft- and Fractional Frequency Reuse (SFR and FFR, respectively) are identi ed as the base of the vast majority of static ICIC proposals. Consequently, during the rst part of this Ph.D. thesis, interesting insights into the operation of SFR and FFR were identi ed beyond well-known facts. These studies allow for the development of a novel statistical framework to evaluate the performance of these schemes in realistic deployments. As a result of the analysis, the poor performance of classic con gurations of SFR and FFR in real-world contexts is shown, and hence, the need for optimization is established. In addition, the importance of the interworking between static ICIC schemes and other network functionalities such as CSI feedback has also been identi ed. Therefore, novel CSI feedback schemes, suitable to operate in conjunction with SFR and FFR, have been developed. These mechanisms exploit the resource allocation pattern of these static ICIC techniques in order to improve the accuracy of the CSI feedback process. The second part is focused on the optimization of SFR and FFR. The use of multiobjective techniques is investigated as a tool to achieve e ective network-speci c optimization. The approach o ers interesting advantages. On the one hand, it allows for simultaneous optimization of several con icting criteria. On the other hand, the multiobjective nature results in outputs composed of several high quality (Pareto e cient) network con gurations, all of them featuring a near-optimal tradeo between the performance criteria. Multiobjective evolutionary algorithms allow employing complex mathematical structures without the need for relaxation, thus capturing accurately the system behavior in terms of ICI. The multiobjective optimization formulation of the problem aims at achieving e ective adjustment of the operational parameters of SFR and FFR both at cell level and network-wide. Moreover, the research was successfully extended to the control channels, both the PDCCH and ePDCCH. Finally, in an e ort to further improve the network energy e ciency (an aspect always considered throughout the thesis), the framework of Cell Switch O (CSO), having close connections with ICIC, is also introduced. By means of the proposed method, signi cant improvements with respect to traditional approaches, baseline con gurations, and previous proposals can be achieved. The gains are obtained in terms of energy consumption, network capacity, and cell edge performance.Actualmente los sistemas 3.5 y 4G tales como Long Term Evolution (LTE) y LTE-Advanced (LTE-A) soportan servicios basados en paquetes y proporcionan acceso de banda ancha m ovil para aplicaciones que requieren elevadas tasas de transmisi on. En este contexto de r apida evoluci on, aparecen nuevos retos t ecnicos que deben ser resueltos e cientemente. El objetivo ultimo es conseguir un salto cualitativo importante en la experiencia de usuario (QoE). Con tal n, un factor clave que ha sido reconocido en las redes celulares basadas en Orthogonal Frequency- Division Multiple Access (OFDMA) es la gesti on de interferencias. De hecho, la utilizaci on de un factor de reuso bajo permite una elevada e ciencia espectral pero a costa de una distribuci on de la calidad de servicio (QoS) que no es uniforme en la red, depende de la posici on del usuario. Por lo tanto, el rendimiento en los l mites de la celda se ve muy penalizado y es un problema importante a resolver en LTE y LTE-A. La coordinaci on de interferencias entre celdas (ICIC, del ingl es Intercell Interfe- rence Coordination) engloba las estrategias cuyo objetivo es mantener la interferencia intercelular (ICI) lo m as baja posible en los bordes de celda. Esto permite aliviar la situaci on antes mencionada. La contribuci on presentada en esta tesis doctoral incluye el dise~no de nuevos mecanismos de ICIC est atica para los canales de datos y control, as como tambi en mejoras desde el punto de vista de e ciencia energ etica. A partir de una revisi on completa del estado del arte, se identi caron una serie de retos abiertos que requer an esfuerzos de investigaci on. En concreto, la necesidad de m etodos de evaluaci on exibles y marcos de optimizaci on de las estrategias de ICIC est aticas. Estos mecanismos se agrupan en dos familias: los esquemas que de nen restricciones sobre el dominio de la frecuencia y los que proponen ajustes en los niveles de potencia. Es decir, la base de la gran mayor a de propuestas ICIC est aticas son la reutilizaci on de frecuencias de tipo soft y fraccional (SFR y FFR, respectivamente). De este modo, durante la primera parte de esta tesis doctoral, se han estudiado los aspectos m as importantes del funcionamiento de SFR y FFR, haciendo especial enfasis en las conclusiones que van m as all a de las bien conocidas. Ello ha permitido introducir un nuevo marco estad stico para evaluar el funcionamiento de estos sistemas en condiciones de despliegue reales. Como resultado de estos an alisis, se muestra el pobre desempe~no de SFR y FFR en despliegues reales cuando funcionan con sus con guraciones cl asicas y se establece la necesidad de optimizaci on. Tambi en se pone de mani esto la importancia del funcionamiento conjunto entre esquemas ICIC est aticos y otras funcionalidades de la red radio, tales como la informaci on que env an los usuarios sobre el estado de su canal downlink (feedback del CSI, del ingl es Channel State Information). De este modo, se han propuesto diferentes esquemas de feedback apropiados para trabajar conjuntamente con SFR y FFR. Estos mecanismos explotan el patr on de asignaci on de recursos que se utiliza en ICIC est atico para mejorar la precisi on del proceso. La segunda parte se centra en la optimizaci on de SFR y FFR. Se ha investigado el uso de t ecnicas multiobjetivo como herramienta para lograr una optimizaci on e caz, que es espec ca para cada red. El enfoque ofrece ventajas interesantes, por un lado, se permite la optimizaci on simult anea de varios criterios contradictorios. Por otro lado, la naturaleza multiobjetivo implica obtener como resultado con guraciones de red de elevada calidad (Pareto e cientes), todas ellas con un equilibrio casi- optimo entre las diferentes m etricas de rendimiento. Los algoritmos evolucionarios multiobjetivo permiten la utilizaci on de estructuras matem aticas complejas sin necesidad de relajar el problema, de este modo capturan adecuadamente su comportamiento en t erminos de ICI. La formulaci on multiobjetivo consigue un ajuste efectivo de los par ametros operacionales de SFR y FFR, tanto a nivel de celda como a nivel de red. Adem as, la investigaci on se extiende con resultados satisfactorios a los canales de control, PDCCH y ePDCCH. Finalmente, en un esfuerzo por mejorar la e ciencia energ etica de la red (un aspecto siempre considerado a lo largo de la tesis), se introduce en el an alisis global el apagado inteligente de celdas, estrategia con estrechos v nculos con ICIC. A trav es del m etodo propuesto, se obtienen mejoras signi cativas con respecto a los enfoques tradicionales y propuestas previas. Las ganancias se obtienen en t erminos de consumo energ etico, capacidad de la red, y rendimiento en el l mite de las celdas.Actualment els sistemes 3.5 i 4G tals com Long Term Evolution (LTE) i LTE- Advanced (LTE-A) suporten serveis basats en paquets i proporcionen acc es de banda ampla m obil per a aplicacions que requereixen elevades taxes de transmissi o. En aquest context de r apida evoluci o, apareixen nous reptes t ecnics que han de ser resolts e cientment. L'objectiu ultim es aconseguir un salt qualitatiu important en l'experi encia d'usuari (QoE). Amb tal , un factor clau que ha estat reconegut a les xarxes cel lulars basades en Orthogonal Frequency-Division Multiple Access (OFDMA) es la gesti o d'interfer encies. De fet, la utilizaci o d'un factor de re us baix permet una elevada e ci encia espectral per o a costa d'una distribuci o de la qualitat de servei (QoS) que no es uniforme a la xarxa, dep en de la posici o de l'usuari. Per tant, el rendiment en els l mits de la cel la es veu molt penalitzat i es un problema important a resoldre en LTE i LTE-A. La coordinaci o d'interfer encies entre cel les (ICIC, de l'angl es Intercell Interfe- rence Coordination) engloba les estrat egies que tenen com a objectiu mantenir la interfer encia intercel lular (ICI) el m es baixa possible en les vores de la cel la. Aix o permet alleujar la situaci o abans esmentada. La contribuci o presentada en aquesta tesi doctoral inclou el disseny de nous mecanismes de ICIC est atica per als canals de dades i control, aix com tamb e millores des del punt de vista d'e ci encia energ etica. A partir d'una revisi o completa de l'estat de l'art, es van identi car una s erie de reptes oberts que requerien esfor cos de recerca. En concret, la necessitat de m etodes d'avaluaci o exibles i marcs d'optimitzaci o de les estrat egies de ICIC est atiques. Aquests mecanismes s'agrupen en dues fam lies: els esquemes que de neixen restriccions sobre el domini de la freq u encia i els que proposen ajustos en els nivells de pot encia. Es a dir, la base de la gran majoria de propostes ICIC est atiques s on la reutilitzaci o de freq u encies de tipus soft i fraccional (SFR i FFR, respectivament). D'aquesta manera, durant la primera part d'aquesta tesi doctoral, s'han estudiat els aspectes m es importants del funcionament de SFR i FFR, fent especial emfasi en les conclusions que van m es enll a de les ben conegudes. Aix o ha perm es introduir un nou marc estad stic per avaluar el funcionament d'aquests sistemes en condicions de desplegament reals. Com a resultat d'aquestes an alisis, es mostra el pobre acompliment de SFR i FFR en desplegaments reals quan funcionen amb les seves con guracions cl assiques i s'estableix la necessitat d'optimitzaci o. Tamb e es posa de manifest la import ancia del funcionament conjunt entre esquemes ICIC est atics i altres funcionalitats de la xarxa radio, tals com la informaci o que envien els usuaris sobre l'estat del seu canal downlink (feedback del CSI, de l'angl es Channel State Information). D'aquesta manera, s'han proposat diferents esquemes de feedback apropiats per treballar conjuntament amb SFR i FFR. Aquests mecanismes exploten el patr o d'assignaci o de recursos que s'utilitza en ICIC est atic per millorar la precisi o del proc es. La segona part se centra en l'optimitzaci o de SFR i FFR. S'ha investigat l' us de t ecniques multiobjectiu com a eina per aconseguir una optimitzaci o e ca c, que es espec ca per a cada xarxa. L'enfocament ofereix avantatges interessants, d'una banda, es permet l'optimitzaci o simult ania de diversos criteris contradictoris. D'altra banda, la naturalesa multiobjectiu implica obtenir com resultat con guracions de xarxa d'elevada qualitat (Pareto e cients), totes elles amb un equilibri gaireb e optim entre les diferents m etriques de rendiment. Els algorismes evolucionaris multiobjectiu permeten la utilitzaci o d'estructures matem atiques complexes sense necessitat de relaxar el problema, d'aquesta manera capturen adequadament el seu comportament en termes de ICI. La formulaci o multiobjectiu aconsegueix un ajust efectiu dels par ametres operacionals de SFR i FFR, tant a nivell de cel la com a nivell de xarxa. A m es, la recerca s'est en amb resultats satisfactoris als canals de control, PDCCH i ePDCCH. Finalment, en un esfor c per millorar l'e ci encia energ etica de la xarxa (un aspecte sempre considerat al llarg de la tesi), s'introdueix en l'an alisi global l'apagat intel ligent de cel les, estrat egia amb estrets vincles amb ICIC. Mitjan cant el m etode proposat, s'obtenen millores signi catives pel que fa als enfocaments tradicionals i propostes pr evies. Els guanys s'obtenen en termes de consum energ etic, capacitat de la xarxa, i rendiment en el l mit de les cel les

Efficient resource allocation algorithm for dense femtocell networks

La couverture d'intérieur pauvre et la basse capacité d'utilisateur représentent deux défis importants pour les opérateurs cellulaires. Plusieurs solutions (telles que les antennes distribuées) ont été proposées pour résoudre ces problèmes. Cependant, aucune de ces solutions ne fournit le niveau désiré de l'évolutivité et elles manquent l'aspect pratique. Pour ces raisons, une solution attrayante caractérisée par sa faible puissance et son prix faible connue sous le nom de femto-cellule a été introduite pour offrir une meilleure capacité et couverture d'utilisateur. Malgré tous les avantages provoqués par l'intégration de cette nouvelle technologie femto-cellule, plusieurs nouveaux défis ont émergé. Ces défis sont principalement présentés dans deux genres d'interférences ; connu comme interférence cross-tier et interférence co-tier. Tandis que l'impact d'interférence cross-tier (provoqué en partageant le spectre de fréquence) peut être réduit en mettant en application des algorithmes efficaces de réutilisation de fréquence, l'interférence co-tier continue à présenter un défi difficile pour les opérateurs et les chercheurs dans le domaine de réseaux cellulaires. Le déploiement non planifié et mal organisé des stations de base femto-cellule a comme conséquence une réduction radicale de la capacité d'utilisateur qui peut mener à une déconnexion des utilisateurs. L'impact de l'interférence co-tier devient plus provocant dans un déploiement dense des femto-cellule où les utilisateurs demandent des services en temps réel (par exemple, taux de données constant). Afin de réduire l'interférence co-tier, plusieurs solutions ont été proposées dans la littérature comprenant des algorithmes de contrôle de puissance, des techniques de détection avancées et des schémas d'allocation de ressources intelligentes. Dans ce projet, nous proposons une stratégie intelligente d'attribution des fréquences avec une stratégie avancée d'association de station de base femto-cellule pour les réseaux femto-cellule basés sur LTE. L'objectif des deux stratégies proposées est d'atténuer l'interférence co-tier et de réduire la probabilité de panne des utilisateurs en augmentant le nombre d'utilisateurs actifs par station de base femto-cellule. Nous montrons par simulations l'efficacité de notre solution proposée.\ud ______________________________________________________________________________ \ud MOTS-CLÉS DE L’AUTEUR : femtocell base station, interference management, resource block assignment, base station assignment, outage probability

Avaliação da probabilidade de erro de bit e da eficiência espectral de sistemas celulares MC-CDMA que utilizam detecção multiusuário

Orientador: Celso de AlmeidaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: Uma técnica que combina múltiplo acesso por divisão de código (CDMA) e multiplexação por divisão de frequências ortogonais (OFDM) foi proposta como uma opção para futuros padrões de comunicações móveis. Esta técnica é conhecida como múltiplo acesso por divisão de código com multiportadoras (MC-CDMA), a qual além de herdar as vantagens das técnicas CDMA e OFDM, também possui uma inerente diversidade em frequência. Apesar de ser uma técnica de múltiplo acesso, MC-CDMA foi tipicamente estudada usando detectores de um único usuário no receptor. Além disso, alguns trabalhos que têm estudado seu desempenho com detectores multi-usuário usam apenas simulações. Ademais, cenários de uma célula são tipicamente considerados, embora sistemas móveis operem em ambientes celulares. Esta dissertação visa complementar parcialmente as pesquisas prévias sobre MC-CDMA. Em geral, este trabalho aborda o desempenho do enlace reverso de sistemas MC-CDMA em termos da taxa de erro de bit (BER) e da eficiência espectral celular. Para isto, um sistema celular que usa os esquemas de reuso de frequências fracionário (FFR) e suave (SFR) é suposto. Entrelaçamento no domínio da frequência é usado no transmissor dos equipamentos dos usuários e, detecção multiusuário e um arranjo de antenas são considerados nos receptores das estações radio base. O transmissor dos equipamentos dos usuários também realiza controle de potência perfeito. Além disso, ruído aditivo Gaussiano branco, perda de percurso e desvanecimento lento e seletivo que segue a distribuição de Rayleigh são considerados no modelo do canal. As contribuições desta dissertação são resumidas a seguir. Expressões fechadas são obtidas para avaliar a BER média de um sistema celular que usa os detectores multiusuário: zero-forcing (ZF), minimum mean square error (MMSE) e maximum likelihood detector (MU-MLD). Adicionalmente, a técnica signal space diversity (SSD) é usada no sistema celular MC-CDMA. Para isto, o MU-MLD precisa ser empregado no receptor da estação radio base. Uma expressão precisa para avaliar a BER média neste cenário é também derivada. Ademais, uma análise assintótica das expressões da BER é feita para se obter mais informações sobre a ordem da diversidade e o comportamento do sistema no regime de alta relação sinal-ruído mais interferência. A complexidade computacional dos detectores multi-usuário também é obtida em termos do número de operações complexas realizadas durante o processo de detecção. Em particular, o MU-MLD é implementado através de um algoritmo de decodificação esférica (SD), a fim de reduzir sua complexidade. Algumas técnicas são fornecidas para reduzir ainda mais a complexidade da SD. Finalmente, uma expressão para avaliar a eficiência espectral celular média do sistema MC-CDMA nos cenários FFR e SFR é obtida. Esta análise é baseada em um algoritmo que calcula os raios de cobertura da célula para cada modulação usada no sistema, assumindo que modulação adaptativa é empregada. Para todos os cenários, modulações BPSK e M-QAM são consideradas. Simulações de Monte Carlo corroboram a precisão da análise matemática apresentadaAbstract: A hybrid technique combining code division multiple access (CDMA) and orthogonal frequency division multiplexing (OFDM) has been proposed as an option for future mobile communication standards. This technique is known as multicarrier code division multiple access (MC-CDMA), which, besides inheriting the advantages of CDMA and OFDM techniques, also possesses an inherent frequency diversity. Despite being a multiple access technique, MC-CDMA has been typically studied employing single-user detectors in the receiver. Moreover, some works that have studied their performance with multiuser detectors have done so far using only simulations. Furthermore, single cell scenarios are typically considered although mobile systems operate in cellular environments. This dissertation aims to partially complement previous research on MC-CDMA. In general, this work addresses the uplink performance of MC-CDMA systems in terms of the bit error rate (BER) and the cellular spectral efficiency. For this, a cellular system employing fractional frequency reuse (FFR) and soft frequency reuse (SFR) schemes is assumed. Frequency domain interleaving is performed in the transmitter into the user equipments and, multiuser detection and an antenna array are considered in the receivers at the base stations. The transmitter into the user equipments also performs perfect power control. Furthermore, additive white Gaussian noise, path-loss and slow frequency-selective Rayleigh fading are considered in the channel model. The contributions of this dissertation are summarized in the following. Closed-form expressions are derived to evaluate the mean BER of MC-CDMA cellular systems using the multiuser detectors: zero-forcing (ZF), minimum mean square error (MMSE) and maximum likelihood detector (MU-MLD). In addition, signal space diversity (SSD) is used in the MC-CDMA cellular system. For this, MU-MLD must be employed in the receiver at the base station. An accurate expression to evaluate the mean BER in this scenario is also derived. Moreover, an asymptotic analysis of the BER expressions is performed to obtain further insights of the diversity order and system behavior at the high signal-to-noise-plus-interference ratio regime. The computational complexity of the multiuser detectors is also obtained in terms of the number of complex operations performed during the detection process. In particular, MU-MLD is implemented via a sphere decoder (SD) algorithm in order to reduce its complexity. Some techniques are provided in order to further reduce the SD complexity. Finally, an expression to evaluate the mean cellular spectral efficiency of the MC-CDMA system in FFR and SFR scenarios is obtained. This analysis is based on an algorithm that calculates the cell coverage radius for each modulation used in the system, assuming that adaptive modulation is employed. For all analyzed scenarios, BPSK and M-QAM modulations are considered. Monte Carlo simulations corroborate the accuracy of the presented mathematical analysisDoutoradoTelecomunicações e TelemáticaDoutor em Engenharia ElétricaCAPE

Hybrid Radio Resource Management with Limited Channel Feedback Information in Relay enhanced OFDMA Networks

In orthogonal frequency division multiple access based mobile networks buffer aided nontransparent in-band half duplex decode-and-forward relay nodes aim to improve coverage and capacity under fairness considerations. The existing centralized radio resource management and inter-cell interference coordination schemes can achieve this goals, although at the cost of a heavy signalling overhead. This cost is a critical issue, particularly for the frequency division duplex downlink transmission. On the other hand, the fully decentralized schemes often focus on different types of frequency reuse schemes with smaller amount of necessary feedback. Here, it is often overseen that in a practical deployment, the backhaul link quality is the bottleneck of the two-hop transmission, and the backhaul link is often modelled way too optimistically. Moreover, it is necessary to allocate radio resources to single hop mobile stations as well, which further limits the possible data rates of the relay-attached users. The research presented in this Thesis aims to improve the backhaul link quality in relay-assisted cellular networks under full consideration of practical constraints. In order to minimize the required channel feedback overhead this work proposes a hybrid radio resource management scheme consisting of three adapted procedures. The hybrid radio resource management scheme includes an adapted decentralized cell selection metric which improves the possibility to gain from the relays in the system for each user. A macro cell-centralized synchronous procedure is proposed, which is responsible to allocate the radio resources in each transmission time interval. Furthermore, an asynchronous network-centralized subband power allocation scheme with very limited feedback is proposed to maximize the wireless backhaul link quality with no losses for single-hop Mobile Station (MS)s. Comprehensive system level simulation results show stable fairness and improved throughput of the proposed hybrid radio resource management scheme. In addition possible energy savings for the shared channel are presented

AN EFFICIENT INTERFERENCE AVOIDANCE SCHEME FOR DEVICE-TODEVICE ENABLED FIFTH GENERATION NARROWBAND INTERNET OF THINGS NETWOKS’

Narrowband Internet of Things (NB-IoT) is a low-power wide-area (LPWA) technology built on long-term evolution (LTE) functionalities and standardized by the 3rd-Generation Partnership Project (3GPP). Due to its support for massive machine-type communication (mMTC) and different IoT use cases with rigorous standards in terms of connection, energy efficiency, reachability, reliability, and latency, NB-IoT has attracted the research community. However, as the capacity needs for various IoT use cases expand, the LTE evolved packet core (EPC) system's numerous functionalities may become overburdened and suboptimal. Several research efforts are currently in progress to address these challenges. As a result, an overview of these efforts with a specific focus on the optimized architecture of the LTE EPC functionalities, the 5G architectural design for NB-IoT integration, the enabling technologies necessary for 5G NB-IoT, 5G new radio (NR) coexistence with NB-IoT, and feasible architectural deployment schemes of NB-IoT with cellular networks is discussed. This thesis also presents cloud-assisted relay with backscatter communication as part of a detailed study of the technical performance attributes and channel communication characteristics from the physical (PHY) and medium access control (MAC) layers of the NB-IoT, with a focus on 5G. The numerous drawbacks that come with simulating these systems are explored. The enabling market for NB-IoT, the benefits for a few use cases, and the potential critical challenges associated with their deployment are all highlighted. Fortunately, the cyclic prefix orthogonal frequency division multiplexing (CPOFDM) based waveform by 3GPP NR for improved mobile broadband (eMBB) services does not prohibit the use of other waveforms in other services, such as the NB-IoT service for mMTC. As a result, the coexistence of 5G NR and NB-IoT must be manageably orthogonal (or quasi-orthogonal) to minimize mutual interference that limits the form of freedom in the waveform's overall design. As a result, 5G coexistence with NB-IoT will introduce a new interference challenge, distinct from that of the legacy network, even though the NR's coexistence with NB-IoT is believed to improve network capacity and expand the coverage of the user data rate, as well as improves robust communication through frequency reuse. Interference challenges may make channel estimation difficult for NB-IoT devices, limiting the user performance and spectral efficiency. Various existing interference mitigation solutions either add to the network's overhead, computational complexity and delay or are hampered by low data rate and coverage. These algorithms are unsuitable for an NB-IoT network owing to the low-complexity nature. As a result, a D2D communication based interference-control technique becomes an effective strategy for addressing this problem. This thesis used D2D communication to decrease the network bottleneck in dense 5G NBIoT networks prone to interference. For D2D-enabled 5G NB-IoT systems, the thesis presents an interference-avoidance resource allocation that considers the less favourable cell edge NUEs. To simplify the algorithm's computing complexity and reduce interference power, the system divides the optimization problem into three sub-problems. First, in an orthogonal deployment technique using channel state information (CSI), the channel gain factor is leveraged by selecting a probable reuse channel with higher QoS control. Second, a bisection search approach is used to find the best power control that maximizes the network sum rate, and third, the Hungarian algorithm is used to build a maximum bipartite matching strategy to choose the optimal pairing pattern between the sets of NUEs and the D2D pairs. The proposed approach improves the D2D sum rate and overall network SINR of the 5G NB-IoT system, according to the numerical data. The maximum power constraint of the D2D pair, D2D's location, Pico-base station (PBS) cell radius, number of potential reuse channels, and cluster distance impact the D2D pair's performance. The simulation results achieve 28.35%, 31.33%, and 39% SINR performance higher than the ARSAD, DCORA, and RRA algorithms when the number of NUEs is twice the number of D2D pairs, and 2.52%, 14.80%, and 39.89% SINR performance higher than the ARSAD, RRA, and DCORA when the number of NUEs and D2D pairs are equal. As a result, a D2D sum rate increase of 9.23%, 11.26%, and 13.92% higher than the ARSAD, DCORA, and RRA when the NUE’s number is twice the number of D2D pairs, and a D2D’s sum rate increase of 1.18%, 4.64% and 15.93% higher than the ARSAD, RRA and DCORA respectively, with an equal number of NUEs and D2D pairs is achieved. The results demonstrate the efficacy of the proposed scheme. The thesis also addressed the problem where the cell-edge NUE's QoS is critical to challenges such as long-distance transmission, delays, low bandwidth utilization, and high system overhead that affect 5G NB-IoT network performance. In this case, most cell-edge NUEs boost their transmit power to maximize network throughput. Integrating cooperating D2D relaying technique into 5G NB-IoT heterogeneous network (HetNet) uplink spectrum sharing increases the system's spectral efficiency and interference power, further degrading the network. Using a max-max SINR (Max-SINR) approach, this thesis proposed an interference-aware D2D relaying strategy for 5G NB-IoT QoS improvement for a cell-edge NUE to achieve optimum system performance. The Lagrangian-dual technique is used to optimize the transmit power of the cell-edge NUE to the relay based on the average interference power constraint, while the relay to the NB-IoT base station (NBS) employs a fixed transmit power. To choose an optimal D2D relay node, the channel-to-interference plus noise ratio (CINR) of all available D2D relays is used to maximize the minimum cell-edge NUE's data rate while ensuring the cellular NUEs' QoS requirements are satisfied. Best harmonic mean, best-worst, half-duplex relay selection, and a D2D communication scheme were among the other relaying selection strategies studied. The simulation results reveal that the Max-SINR selection scheme outperforms all other selection schemes due to the high channel gain between the two communication devices except for the D2D communication scheme. The proposed algorithm achieves 21.27% SINR performance, which is nearly identical to the half-duplex scheme, but outperforms the best-worst and harmonic selection techniques by 81.27% and 40.29%, respectively. As a result, as the number of D2D relays increases, the capacity increases by 14.10% and 47.19%, respectively, over harmonic and half-duplex techniques. Finally, the thesis presents future research works on interference control in addition with the open research directions on PHY and MAC properties and a SWOT (Strengths, Weaknesses, Opportunities, and Threats) analysis presented in Chapter 2 to encourage further study on 5G NB-IoT

Energy-efficient cooperative resource allocation for OFDMA

Energy is increasingly becoming an exclusive commodity in next generation wireless communication systems, where even in legacy systems, the mobile operators operational expenditure is largely attributed to the energy bill. However, as the amount of mobile traffic is expected to double over the next decade as we enter the Next Generation communications era, the need to address energy efficient protocols will be a priority. Therefore, we will need to revisit the design of the mobile network in order to adopt a proactive stance towards reducing the energy consumption of the network. Future emerging communication paradigms will evolve towards Next Generation mobile networks, that will not only consider a new air interface for high broadband connectivity, but will also integrate legacy communications (LTE/LTE-A, IEEE 802.11x, among others) networks to provide a ubiquitous communication platform, and one that can host a multitude of rich services and applications. In this context, one can say that the radio access network will predominantly be OFDMA based, providing the impetus for further research studies on how this technology can be further optimized towards energy efficiency. In fact, advanced approaches towards both energy and spectral efficient design will still dominate the research agenda. Taking a step towards this direction, LTE/LTE-A (Long Term Evolution-Advanced) have already investigated cooperative paradigms such as SON (self-Organizing Networks), Network Sharing, and CoMP (Coordinated Multipoint) transmission. Although these technologies have provided promising results, some are still in their infancy and lack an interdisciplinary design approach limiting their potential gain. In this thesis, we aim to advance these future emerging paradigms from a resource allocation perspective on two accounts. In the first scenario, we address the challenge of load balancing (LB) in OFDMA networks, that is employed to redistribute the traffic load in the network to effectively use spectral resources throughout the day. We aim to reengineer the load-balancing (LB) approach through interdisciplinary design to develop an integrated energy efficient solution based on SON and network sharing, what we refer to as SO-LB (Self-Organizing Load balancing). Obtained simulation results show that by employing SO-LB algorithm in a shared network, it is possible to achieve up to 15-20% savings in energy consumption when compared to LTE-A non-shared networks. The second approach considers CoMP transmission, that is currently used to enhance cell coverage and capacity at cell edge. Legacy approaches mainly consider fundamental scheduling policies towards assigning users for CoMP transmission. We build on these scheduling approaches towards a cross-layer design that provide enhanced resource utilization, fairness, and energy saving whilst maintaining low complexity, in particular for broadband applications