263 research outputs found

    Power adjustment and scheduling in OFDMA femtocell networks

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    Densely-deployed femtocell networks are used to enhance wireless coverage in public spaces like office buildings, subways, and academic buildings. These networks can increase throughput for users, but edge users can suffer from co-channel interference, leading to service outages. This paper introduces a distributed algorithm for network configuration, called Radius Reduction and Scheduling (RRS), to improve the performance and fairness of the network. RRS determines cell sizes using a Voronoi-Laguerre framework, then schedules users using a scheduling algorithm that includes vacancy requests to increase fairness in dense femtocell networks. We prove that our algorithm always terminate in a finite time, producing a configuration that guarantees user or area coverage. Simulation results show a decrease in outage probability of up to 50%, as well as an increase in Jain's fairness index of almost 200%

    Recent advances in radio resource management for heterogeneous LTE/LTE-A networks

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    As heterogeneous networks (HetNets) emerge as one of the most promising developments toward realizing the target specifications of Long Term Evolution (LTE) and LTE-Advanced (LTE-A) networks, radio resource management (RRM) research for such networks has, in recent times, been intensively pursued. Clearly, recent research mainly concentrates on the aspect of interference mitigation. Other RRM aspects, such as radio resource utilization, fairness, complexity, and QoS, have not been given much attention. In this paper, we aim to provide an overview of the key challenges arising from HetNets and highlight their importance. Subsequently, we present a comprehensive survey of the RRM schemes that have been studied in recent years for LTE/LTE-A HetNets, with a particular focus on those for femtocells and relay nodes. Furthermore, we classify these RRM schemes according to their underlying approaches. In addition, these RRM schemes are qualitatively analyzed and compared to each other. We also identify a number of potential research directions for future RRM development. Finally, we discuss the lack of current RRM research and the importance of multi-objective RRM studies

    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

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

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    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

    Cooperation strategies for inter-cell interference mitigation in OFDMA systems

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    Recently the use of modern cellular networks has drastically changed with the emerging Long Term Evolution Advanced (LTE-A) technology. Homogeneous networks which were initially designed for voice-centric and low data rates face unprecedented challenges for meeting the increasing traffic demands of high data-driven applications and their important quality of service requirements. Therefore, these networks are moving towards the so called Heterogeneous Networks (HetNets). HetNets represent a new paradigm for cellular networks as their nodes have different characteristics such as transmission power and radio frequency coverage area. Consequently, a HetNet shows completely different interference characteristics compared to homogeneous deployment and attention must be paid to these disparities when different tiers are collocated together. This is mostly due to the potential spectrum frequency reuse by the involved tiers in the HetNets. Hence, efficient inter-cell interference mitigation solutions in co-channel deployments of HetNets remain a challenge for both industry and academic researchers. This thesis focuses on LTE-A HetNet systems which are based on Orthogonal Frequency Division Multiplexing Access (OFDMA) modulation. Our aim is to investigate the aggressive interference issue that appears when different types of base stations are jointly deployed together and especially in two cases, namely Macro-Femtocells and Macro-Picocells co-existence. We propose new practical power adjustment solutions for managing inter-cell interference dynamically for both cases. In the first part dedicated to Femtocells and Macrocell coexistence, we design a MBS-assisted femtocell power adjustment strategy which takes into account femtocells users performance while mitigating the inter-cell interference on victim macrocell users. Further, we propose a new cooperative and context-aware interference mitigation method which is derived for realistic scenarios involving mobility of users and their varying locations. We proved numerically that the Femtocells are able to maintain their interference under a desirable threshold by adjusting their transmission power. Our strategies provide an efficient means for achieving the desired level of macrocell/femtocell throughput trade-off. In the second part of the studies where Picocells are deployed under the umbrella of the Macrocell, we paid a special attention and efforts to the interference management in the situation where Picocells are configured to set up a cell range expansion. We suggest a MBS-assisted collaborative scheme powered by an analytical model to predict the mobility of Macrocell users passing through the cell range expansion area of the picocell. Our goal is to adapt the muting ratio ruling the frequency resource partitioning between both tiers according to the mobility behavior of the range-expanded users, thereby providing an efficient trade-off between Macrocell and Picocell achievable throughputs.RĂ©cemment, l'utilisation des rĂ©seaux cellulaires a radicalement changĂ© avec l’émergence de la quatriĂšme gĂ©nĂ©ration (4G) de systĂšmes de tĂ©lĂ©communications mobiles LTE/LTE-A (Long Term Evolution-Advanced). Les rĂ©seaux de gĂ©nĂ©rations prĂ©cĂ©dentes (3G), initialement conçus pour le transport de la voix et les donnĂ©es Ă  faible et moyen dĂ©bits, ont du mal Ă  faire face Ă  l’augmentation accrue du trafic de donnĂ©es multimĂ©dia tout en rĂ©pondant Ă  leurs fortes exigences et contraintes en termes de qualitĂ© de service (QdS). Pour mieux rĂ©pondre Ă  ces besoins, les rĂ©seaux 4G ont introduit le paradigme des RĂ©seaux HĂ©tĂ©rogĂšnes (HetNet).Les rĂ©seaux HetNet introduisent une nouvelle notion d’hĂ©tĂ©rogĂ©nĂ©itĂ© pour les rĂ©seaux cellulaires en introduisant le concept des smalls cells (petites cellules) qui met en place des antennes Ă  faible puissance d’émission. Ainsi, le rĂ©seau est composĂ© de plusieurs couches (tiers) qui se chevauchent incluant la couverture traditionnelle macro-cellulaire, les pico-cellules, les femto-cellules, et les relais. Outre les amĂ©liorations des couvertures radio en environnements intĂ©rieurs, les smalls cells permettent d’augmenter la capacitĂ© du systĂšme par une meilleure utilisation du spectre et en rapprochant l’utilisateur de son point d’accĂšs au rĂ©seau. Une des consĂ©quences directes de cette densification cellulaire est l’interfĂ©rence gĂ©nĂ©rĂ©e entre les diffĂ©rentes cellules des diverses couches quand ces derniĂšres rĂ©utilisent les mĂȘmes frĂ©quences. Aussi, la dĂ©finition de solutions efficaces de gestion des interfĂ©rences dans ce type de systĂšmes constitue un de leurs dĂ©fis majeurs. Cette thĂšse s’intĂ©resse au problĂšme de gestion des interfĂ©rences dans les systĂšmes hĂ©tĂ©rogĂšnes LTE-A. Notre objectif est d’apporter des solutions efficaces et originales au problĂšme d’interfĂ©rence dans ce contexte via des mĂ©canismes d’ajustement de puissance des petites cellules. Nous avons pour cela distinguĂ©s deux cas d’étude Ă  savoir un dĂ©ploiement Ă  deux couches macro-femtocellules et macro-picocellules. Dans la premiĂšre partie dĂ©diĂ©e Ă  un dĂ©ploiement femtocellule et macrocellule, nous concevons une stratĂ©gie d'ajustement de puissance des femtocellules assistĂ© par la macrocellule et qui prend en compte les performances des utilisateurs des femtocells tout en attĂ©nuant l'interfĂ©rence causĂ©e aux utilisateurs des macrocellules sur leurs liens montants. Cette solution offre l’avantage de la prise en compte de paramĂštres contextuels locaux aux femtocellules (tels que le nombre d’utilisateurs en situation de outage) tout en considĂ©rant des scĂ©narios de mobilitĂ© rĂ©alistes. Nous avons montrĂ© par simulation que les interfĂ©rences sur les utilisateurs des macrocellules sont sensiblement rĂ©duites et que les femtocellules sont en mesure de dynamiquement ajuster leur puissance d'Ă©mission pour atteindre les objectifs fixĂ©s en termes d’équilibre entre performance des utilisateurs des macrocellules et celle de leurs propres utilisateurs. Dans la seconde partie de la thĂšse, nous considĂ©rons le dĂ©ploiement de picocellules sous l'Ă©gide de la macrocellule. Nous nous sommes intĂ©ressĂ©s ici aux solutions d’extension de l’aire picocellulaire qui permettent une meilleure association utilisateur/cellule permettant de rĂ©duire l’interfĂ©rence mais aussi offrir une meilleure efficacitĂ© spectrale. Nous proposons donc une approche basĂ©e sur un modĂšle de prĂ©diction de la mobilitĂ© des utilisateurs qui permet de mieux ajuster la proportion de bande passante Ă  partager entre la macrocellule et la picocellule en fonction de la durĂ©e de sĂ©jour estimĂ©e de ces utilisateurs ainsi que de leur demandes en bande passante. Notre solution a permis d’offrir un bon compromis entre les dĂ©bits rĂ©alisables de la Macro et des picocellules
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