469 research outputs found

    Separation Framework: An Enabler for Cooperative and D2D Communication for Future 5G Networks

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    Soaring capacity and coverage demands dictate that future cellular networks need to soon migrate towards ultra-dense networks. However, network densification comes with a host of challenges that include compromised energy efficiency, complex interference management, cumbersome mobility management, burdensome signaling overheads and higher backhaul costs. Interestingly, most of the problems, that beleaguer network densification, stem from legacy networks' one common feature i.e., tight coupling between the control and data planes regardless of their degree of heterogeneity and cell density. Consequently, in wake of 5G, control and data planes separation architecture (SARC) has recently been conceived as a promising paradigm that has potential to address most of aforementioned challenges. In this article, we review various proposals that have been presented in literature so far to enable SARC. More specifically, we analyze how and to what degree various SARC proposals address the four main challenges in network densification namely: energy efficiency, system level capacity maximization, interference management and mobility management. We then focus on two salient features of future cellular networks that have not yet been adapted in legacy networks at wide scale and thus remain a hallmark of 5G, i.e., coordinated multipoint (CoMP), and device-to-device (D2D) communications. After providing necessary background on CoMP and D2D, we analyze how SARC can particularly act as a major enabler for CoMP and D2D in context of 5G. This article thus serves as both a tutorial as well as an up to date survey on SARC, CoMP and D2D. Most importantly, the article provides an extensive outlook of challenges and opportunities that lie at the crossroads of these three mutually entangled emerging technologies.Comment: 28 pages, 11 figures, IEEE Communications Surveys & Tutorials 201

    A Comprehensive Survey of Potential Game Approaches to Wireless Networks

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    Potential games form a class of non-cooperative games where unilateral improvement dynamics are guaranteed to converge in many practical cases. The potential game approach has been applied to a wide range of wireless network problems, particularly to a variety of channel assignment problems. In this paper, the properties of potential games are introduced, and games in wireless networks that have been proven to be potential games are comprehensively discussed.Comment: 44 pages, 6 figures, to appear in IEICE Transactions on Communications, vol. E98-B, no. 9, Sept. 201

    A Practical Cooperative Multicell MIMO-OFDMA Network Based on Rank Coordination

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    An important challenge of wireless networks is to boost the cell edge performance and enable multi-stream transmissions to cell edge users. Interference mitigation techniques relying on multiple antennas and coordination among cells are nowadays heavily studied in the literature. Typical strategies in OFDMA networks include coordinated scheduling, beamforming and power control. In this paper, we propose a novel and practical type of coordination for OFDMA downlink networks relying on multiple antennas at the transmitter and the receiver. The transmission ranks, i.e.\ the number of transmitted streams, and the user scheduling in all cells are jointly optimized in order to maximize a network utility function accounting for fairness among users. A distributed coordinated scheduler motivated by an interference pricing mechanism and relying on a master-slave architecture is introduced. The proposed scheme is operated based on the user report of a recommended rank for the interfering cells accounting for the receiver interference suppression capability. It incurs a very low feedback and backhaul overhead and enables efficient link adaptation. It is moreover robust to channel measurement errors and applicable to both open-loop and closed-loop MIMO operations. A 20% cell edge performance gain over uncoordinated LTE-A system is shown through system level simulations.Comment: IEEE Transactions or Wireless Communications, Accepted for Publicatio

    Joint Interference Management in Ultra-Dense Small Cell Networks:A Multi-Domain Coordination Perspective

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    Extensive deployment of heterogeneous small cells in cellular networks results in ultra-dense small cell networks (USNs). USNs have been established as one of the vital networking architectures in the 5G to expand system capacity and augment network coverage. However, intensive deployment of cells results in a complex interference problem. In this paper, we propose a distributed multi-domain interference management scheme among cooperative small cells. The proposed scheme mitigates the interference while optimizing the overall network utility. Additionally, we jointly investigate OFDMA scheduling, TDMA scheduling, interference alignment (IA), and power control. We model small cells’ coordination behavior as an overlapping coalition formation game (OCFG). In this game, each base station can make an autonomous decision and participate in more than one coalition to perform IA and suppress intra-coalition interference. To achieve this goal, we propose a distributed joint interference management (JIM) algorithm. The proposed algorithm allows each small cell base station to self-organize and interact into a stable overlapping coalition structure and reduce interference gradually from multi-domain, thus achieving an optimal tradeoff between costs and benefits. Compared with existing approaches, the proposed JIM algorithm provides appreciable performance improvement in terms of total throughput, which is demonstrated by simulation results

    EficiĂȘncia energĂ©tica avançada para sistema OFDMA CoMP coordenação multiponto

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    Doutoramento em Engenharia EletrotĂ©cnicaThe ever-growing energy consumption in mobile networks stimulated by the expected growth in data tra ffic has provided the impetus for mobile operators to refocus network design, planning and deployment towards reducing the cost per bit, whilst at the same time providing a signifi cant step towards reducing their operational expenditure. As a step towards incorporating cost-eff ective mobile system, 3GPP LTE-Advanced has adopted the coordinated multi-point (CoMP) transmission technique due to its ability to mitigate and manage inter-cell interference (ICI). Using CoMP the cell average and cell edge throughput are boosted. However, there is room for reducing energy consumption further by exploiting the inherent exibility of dynamic resource allocation protocols. To this end packet scheduler plays the central role in determining the overall performance of the 3GPP longterm evolution (LTE) based on packet-switching operation and provide a potential research playground for optimizing energy consumption in future networks. In this thesis we investigate the baseline performance for down link CoMP using traditional scheduling approaches, and subsequently go beyond and propose novel energy e fficient scheduling (EES) strategies that can achieve power-e fficient transmission to the UEs whilst enabling both system energy effi ciency gain and fairness improvement. However, ICI can still be prominent when multiple nodes use common resources with di fferent power levels inside the cell, as in the so called heterogeneous networks (Het- Net) environment. HetNets are comprised of two or more tiers of cells. The rst, or higher tier, is a traditional deployment of cell sites, often referred to in this context as macrocells. The lower tiers are termed small cells, and can appear as microcell, picocells or femtocells. The HetNet has attracted signiffi cant interest by key manufacturers as one of the enablers for high speed data at low cost. Research until now has revealed several key hurdles that must be overcome before HetNets can achieve their full potential: bottlenecks in the backhaul must be alleviated, as well as their seamless interworking with CoMP. In this thesis we explore exactly the latter hurdle, and present innovative ideas on advancing CoMP to work in synergy with HetNet deployment, complemented by a novel resource allocation policy for HetNet tighter interference management. As system level simulator has been used to analyze the proposed algorithm/protocols, and results have concluded that up to 20% energy gain can be observed.O aumento do consumo de energia nas TICs e em particular nas redes de comunicação mĂłveis, estimulado por um crescimento esperado do trĂĄfego de dados, tem servido de impulso aos operadores m oveis para reorientarem os seus projectos de rede, planeamento e implementa ção no sentido de reduzir o custo por bit, o que ao mesmo tempo possibilita um passo signicativo no sentido de reduzir as despesas operacionais. Como um passo no sentido de uma incorporação eficaz em termos destes custos, o sistema mĂłvel 3GPP LTE-Advanced adoptou a tĂ©cnica de transmissĂŁo Coordenação Multi-Ponto (identificada na literatura com a sigla CoMP) devido Ă  sua capacidade de mitigar e gerir InterferĂȘncia entre CĂ©lulas (sigla ICI na literatura). No entanto a ICI pode ainda ser mais proeminente quando v arios n os no interior da cĂ©lula utilizam recursos comuns com diferentes nĂ­veis de energia, como acontece nos chamados ambientes de redes heterogĂ©neas (sigla Het- Net na literatura). As HetNets sĂŁo constituĂ­das por duas ou mais camadas de cĂ©lulas. A primeira, ou camada superiora, constitui uma implantação tradicional de sĂ­tios de cĂ©lula, muitas vezes referidas neste contexto como macrocells. Os nĂ­veis mais baixos sĂŁo designados por cĂ©lulas pequenas, e podem aparecer como microcells, picocells ou femtocells. A HetNet tem atra do grande interesse por parte dos principais fabricantes como sendo facilitador para transmissĂ”es de dados de alta velocidade a baixo custo. A investigação tem revelado at e a data, vĂĄrios dos principais obstĂĄculos que devem ser superados para que as HetNets possam atingir todo o seu potencial: (i) os estrangulamentos no backhaul devem ser aliviados; (ii) bem como sua perfeita interoperabilidade com CoMP. Nesta tese exploramos este ultimo constrangimento e apresentamos ideias inovadoras em como a t ecnica CoMP poder a ser aperfeiçoada por forma a trabalhar em sinergia com a implementação da HetNet, complementado ainda com uma nova perspectiva na alocação de recursos rĂĄdio para um controlo e gestĂŁo mais apertado de interferĂȘncia nas HetNets. Com recurso a simulação a nĂ­Ă­vel de sistema para analisar o desempenho dos algoritmos e protocolos propostos, os resultados obtidos concluĂ­ram que ganhos at e a ordem dos 20% poderĂŁo ser atingidos em termos de eficiĂȘncia energĂ©tica

    Improving Macrocell - Small Cell Coexistence through Adaptive Interference Draining

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    The deployment of underlay small base stations (SBSs) is expected to significantly boost the spectrum efficiency and the coverage of next-generation cellular networks. However, the coexistence of SBSs underlaid to an existing macro-cellular network faces important challenges, notably in terms of spectrum sharing and interference management. In this paper, we propose a novel game-theoretic model that enables the SBSs to optimize their transmission rates by making decisions on the resource occupation jointly in the frequency and spatial domains. This procedure, known as interference draining, is performed among cooperative SBSs and allows to drastically reduce the interference experienced by both macro- and small cell users. At the macrocell side, we consider a modified water-filling policy for the power allocation that allows each macrocell user (MUE) to focus the transmissions on the degrees of freedom over which the MUE experiences the best channel and interference conditions. This approach not only represents an effective way to decrease the received interference at the MUEs but also grants the SBSs tier additional transmission opportunities and allows for a more agile interference management. Simulation results show that the proposed approach yields significant gains at both macrocell and small cell tiers, in terms of average achievable rate per user, reaching up to 37%, relative to the non-cooperative case, for a network with 150 MUEs and 200 SBSs

    Optimisation de la gestion des interférences inter-cellulaires et de l'attachement des mobiles dans les réseaux cellulaires LTE

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    Driven by an exponential growth in mobile broadband-enabled devices and a continue dincrease in individual data consumption, mobile data traffic has grown 4000-fold over the past 10 years and almost 400-million-fold over the past 15 years. Homogeneouscellular networks have been facing limitations to handle soaring mobile data traffic and to meet the growing end-user demand for more bandwidth and betterquality of experience. These limitations are mainly related to the available spectrumand the capacity of the network. Telecommunication industry has to address these challenges and meet exploding demand. At the same time, it has to guarantee a healthy economic model to reduce the carbon footprint which is caused by mobile communications.Heterogeneous Networks (HetNets), composed of macro base stations and low powerbase stations of different types, are seen as the key solution to improve spectral efficiency per unit area and to eliminate coverage holes. In such networks, intelligent user association and interference management schemes are needed to achieve gains in performance. Due to the large imbalance in transmission power between macroand small cells, user association based on strongest signal received is not adapted inHetNets as only few users would attach to low power nodes. A technique based onCell Individual Offset (CIO) is therefore required to perform load balancing and to favor some Small Cell (SC) attraction against Macro Cell (MC). This offset is addedto users’ Reference Signal Received Power (RSRP) measurements and hence inducing handover towards different eNodeBs. As Long Term Evolution (LTE) cellular networks use the same frequency sub-bands, mobile users may experience strong inter-cellxv interference, especially at cell edge. Therefore, there is a need to coordinate resource allocation among the cells and minimize inter-cell interference. To mitigate stronginter-cell interference, the resource, in time, frequency and power domain, should be allocated efficiently. A pattern for each dimension is computed to permit especially for cell edge users to benefit of higher throughput and quality of experience. The optimization of all these parameters can also offer gain in energy use. In this thesis,we propose a concrete versatile dynamic solution performing an optimization of user association and resource allocation in LTE cellular networks maximizing a certainnet work utility function that can be adequately chosen. Our solution, based on gametheory, permits to compute Cell Individual Offset and a pattern of power transmission over frequency and time domain for each cell. We present numerical simulations toillustrate the important performance gain brought by this optimization. We obtain significant benefits in the average throughput and also cell edge user through put of40% and 55% gains respectively. Furthermore, we also obtain a meaningful improvement in energy efficiency. This work addresses industrial research challenges and assuch, a prototype acting on emulated HetNets traffic has been implemented.Conduit par une croissance exponentielle dans les appareils mobiles et une augmentation continue de la consommation individuelle des donnĂ©es, le trafic de donnĂ©es mobiles a augmentĂ© de 4000 fois au cours des 10 derniĂšres annĂ©es et prĂšs de 400millions fois au cours des 15 derniĂšres annĂ©es. Les rĂ©seaux cellulaires homogĂšnes rencontrent de plus en plus de difficultĂ©s Ă  gĂ©rer l’énorme trafic de donnĂ©es mobiles et Ă  assurer un dĂ©bit plus Ă©levĂ© et une meilleure qualitĂ© d’expĂ©rience pour les utilisateurs.Ces difficultĂ©s sont essentiellement liĂ©es au spectre disponible et Ă  la capacitĂ© du rĂ©seau.L’industrie de tĂ©lĂ©communication doit relever ces dĂ©fis et en mĂȘme temps doit garantir un modĂšle Ă©conomique pour les opĂ©rateurs qui leur permettra de continuer Ă  investir pour rĂ©pondre Ă  la demande croissante et rĂ©duire l’empreinte carbone due aux communications mobiles. Les rĂ©seaux cellulaires hĂ©tĂ©rogĂšnes (HetNets), composĂ©s de stations de base macro et de diffĂ©rentes stations de base de faible puissance,sont considĂ©rĂ©s comme la solution clĂ© pour amĂ©liorer l’efficacitĂ© spectrale par unitĂ© de surface et pour Ă©liminer les trous de couverture. Dans de tels rĂ©seaux, il est primordial d’attacher intelligemment les utilisateurs aux stations de base et de bien gĂ©rer les interfĂ©rences afin de gagner en performance. Comme la diffĂ©rence de puissance d’émission est importante entre les grandes et petites cellules, l’association habituelle des mobiles aux stations de bases en se basant sur le signal le plus fort, n’est plus adaptĂ©e dans les HetNets. Une technique basĂ©e sur des offsets individuelles par cellule Offset(CIO) est donc nĂ©cessaire afin d’équilibrer la charge entre les cellules et d’augmenter l’attraction des petites cellules (SC) par rapport aux cellules macro (MC). Cette offset est ajoutĂ©e Ă  la valeur moyenne de la puissance reçue du signal de rĂ©fĂ©rence(RSRP) mesurĂ©e par le mobile et peut donc induire Ă  un changement d’attachement vers diffĂ©rents eNodeB. Comme les stations de bases dans les rĂ©seaux cellulaires LTE utilisent les mĂȘmes sous-bandes de frĂ©quences, les mobiles peuvent connaĂźtre une forte interfĂ©rence intercellulaire, en particulier en bordure de cellules. Par consĂ©quent, il est primordial de coordonner l’allocation des ressources entre les cellules et de minimiser l’interfĂ©rence entre les cellules. Pour attĂ©nuer la forte interfĂ©rence intercellulaire, les ressources, en termes de temps, frĂ©quence et puissance d’émission, devraient ĂȘtre allouĂ©s efficacement. Un modĂšle pour chaque dimension est calculĂ© pour permettre en particulier aux utilisateurs en bordure de cellule de bĂ©nĂ©ficier d’un dĂ©bit plus Ă©levĂ© et d’une meilleure qualitĂ© de l’expĂ©rience. L’optimisation de tous ces paramĂštres peut Ă©galement offrir un gain en consommation d’énergie. Dans cette thĂšse, nous proposons une solution dynamique polyvalente effectuant une optimisation de l’attachement des mobiles aux stations de base et de l’allocation des ressources dans les rĂ©seaux cellulaires LTE maximisant une fonction d’utilitĂ© du rĂ©seau qui peut ĂȘtre choisie de maniĂšre adĂ©quate.Notre solution, basĂ©e sur la thĂ©orie des jeux, permet de calculer les meilleures valeurs pour l’offset individuelle par cellule (CIO) et pour les niveaux de puissance Ă  appliquer au niveau temporel et frĂ©quentiel pour chaque cellule. Nous prĂ©sentons des rĂ©sultats des simulations effectuĂ©es pour illustrer le gain de performance important apportĂ© par cette optimisation. Nous obtenons une significative hausse dans le dĂ©bit moyen et le dĂ©bit des utilisateurs en bordure de cellule avec 40 % et 55 % de gains respectivement. En outre, on obtient un gain important en Ă©nergie. Ce travail aborde des dĂ©fis pour l’industrie des tĂ©lĂ©coms et en tant que tel, un prototype de l’optimiseur a Ă©tĂ© implĂ©mentĂ© en se basant sur un trafic HetNets Ă©mulĂ©

    Interference mitigation in cognitive femtocell networks

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    “A thesis submitted to the University of Bedfordshire, in partial fulfilment of the requirements for the degree of Doctor of Philosophy”.Femtocells have been introduced as a solution to poor indoor coverage in cellular communication which has hugely attracted network operators and stakeholders. However, femtocells are designed to co-exist alongside macrocells providing improved spatial frequency reuse and higher spectrum efficiency to name a few. Therefore, when deployed in the two-tier architecture with macrocells, it is necessary to mitigate the inherent co-tier and cross-tier interference. The integration of cognitive radio (CR) in femtocells introduces the ability of femtocells to dynamically adapt to varying network conditions through learning and reasoning. This research work focuses on the exploitation of cognitive radio in femtocells to mitigate the mutual interference caused in the two-tier architecture. The research work presents original contributions in mitigating interference in femtocells by introducing practical approaches which comprises a power control scheme where femtocells adaptively controls its transmit power levels to reduce the interference it causes in a network. This is especially useful since femtocells are user deployed as this seeks to mitigate interference based on their blind placement in an indoor environment. Hybrid interference mitigation schemes which combine power control and resource/scheduling are also implemented. In a joint threshold power based admittance and contention free resource allocation scheme, the mutual interference between a Femtocell Access Point (FAP) and close-by User Equipments (UE) is mitigated based on admittance. Also, a hybrid scheme where FAPs opportunistically use Resource Blocks (RB) of Macrocell User Equipments (MUE) based on its traffic load use is also employed. Simulation analysis present improvements when these schemes are applied with emphasis in Long Term Evolution (LTE) networks especially in terms of Signal to Interference plus Noise Ratio (SINR)

    Técnicas de cooperação entre estaçÔes base para sistemas celulares

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    Mestrado em Engenharia ElectrĂłnica e TelecomunicaçÔesA cooperação entre cĂ©lulas Ă© uma das ĂĄreas de pesquisa em maior crescimento, sendo uma solução promissora para sistemas celulares sem fio, por forma a amenizar a interferĂȘncia entre as cĂ©lulas, melhorar a equidade do sistema e aumentar a capacidade nos anos vindouros. Esta tecnologia jĂĄ estĂĄ em estudo no LTE-Advanced sob o conceito de coordenação multiponto (CoOMP). Esta dissertação insere-se na ĂĄrea de comunicaçÔes sem fios e tem como principal objectivo, estudar, implementar e avaliar o desempenho de esquemas de cooperação entre estaçÔes base, projectados para os futuros sistemas de comunicaçÔes mĂłveis de portadora mĂșltipla (OFDM/A). Especificamente, o sistema cooperativo estudado Ă© constituĂ­do por duas estaçÔes base equipadas com um agregado de antenas, ligadas a uma unidade de processamento central, e dois terminais mĂłveis equipados cada um com apenas uma antena. O sistema referido foi implementado de acordo com as especificaçÔes do LTE e avaliado em diversos cenĂĄrios de propagação. As tĂ©cnicas desenvolvidas permitem contornar os problemas relacionados com a mĂĄ qualidade de canal entre emissor e receptor, melhorando o seu desempenho, especificamente ao nĂ­vel da taxa de erros de transmissĂŁo.Multicell cooperation is one of the fastest growing areas of research, and it is a promising solution for cellular wireless systems to mitigate intercell interference, improve system fairness and increase capacity in the years to come. This technology is already under study in LTE-Advanced under the coordinated multipoint (CoOMP) concept. This dissertation is inserted in the wireless communications area, with its main objective being the study, implementation and evaluation of the performance of cooperative schemes between base stations designed for the future mobile communication multiple carrier systems (OFDM/A). Specifically, the cooperative system studied consists of two base stations, each with multiple antenna, connected to a central processing unit, and two mobile terminals, each equipped with only one antenna. The system referred to was implemented in accordance with the specifications of LTE and was tested in various different propagation situations. The developed techniques ensure the mitigation of problems related to interference between the portable terminals namely at the cell edges, improving specifically the bit error rate performance
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