268 research outputs found

    Dynamic Time-domain Duplexing for Self-backhauled Millimeter Wave Cellular Networks

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    Millimeter wave (mmW) bands between 30 and 300 GHz have attracted considerable attention for next-generation cellular networks due to vast quantities of available spectrum and the possibility of very high-dimensional antenna ar-rays. However, a key issue in these systems is range: mmW signals are extremely vulnerable to shadowing and poor high-frequency propagation. Multi-hop relaying is therefore a natural technology for such systems to improve cell range and cell edge rates without the addition of wired access points. This paper studies the problem of scheduling for a simple infrastructure cellular relay system where communication between wired base stations and User Equipment follow a hierarchical tree structure through fixed relay nodes. Such a systems builds naturally on existing cellular mmW backhaul by adding mmW in the access links. A key feature of the proposed system is that TDD duplexing selections can be made on a link-by-link basis due to directional isolation from other links. We devise an efficient, greedy algorithm for centralized scheduling that maximizes network utility by jointly optimizing the duplexing schedule and resources allocation for dense, relay-enhanced OFDMA/TDD mmW networks. The proposed algorithm can dynamically adapt to loading, channel conditions and traffic demands. Significant throughput gains and improved resource utilization offered by our algorithm over the static, globally-synchronized TDD patterns are demonstrated through simulations based on empirically-derived channel models at 28 GHz.Comment: IEEE Workshop on Next Generation Backhaul/Fronthaul Networks - BackNets 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

    Next Generation Dynamic Inter-Cellular Scheduler

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    Orthogonal frequency division multiple access (OFDMA) in Long Term Evolution (LTE) can effectively eliminate intra-cell interferences between the subcarriers in a single serving cell. But, there is more critical issue that, OFDMA cannot accomplish to decrease the inter-cell interference. In our proposed method, we aimed to increase signal to interference plus noise ratio (SINR) by dividing the cells as cell center and cell edge. While decreasing the interference between cells, we also aimed to increase overall system throughput. For this reason, we proposed a dynamic resource allocation technique that is called Experience-Based Dynamic Soft Frequency Reuse (EBDSFR). We compared our proposed scheme with different resource allocation schemes that are Dynamic Inter-cellular Bandwidth Fair Sharing FFR (FFRDIBFS) and Dynamic Inter-cellular Bandwidth Fair Sharing Reuse-3 (Reuse3DIBFS). Simulation results indicate that, proposed EBDSFR benefits from overall cell throughput and obtains higher user fairness than the reference schemes

    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©

    Analytical Model of Proportional Fair Scheduling in Interference-limited OFDMA/LTE Networks

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    Various system tasks like interference coordination, handover decisions, admission control etc. in upcoming cellular networks require precise mid-term (spanning over a few seconds) performance models. Due to channel-dependent scheduling at the base station, these performance models are not simple to obtain. Furthermore, upcoming cellular systems will be interference-limited, hence, the way interference is modeled is crucial for the accuracy. In this paper we present an analytical model for the SINR distribution of the \textit{scheduled} subcarriers of an OFDMA system with proportional fair scheduling. The model takes the precise SINR distribution into account. We furthermore refine our model with respect to uniform modulation and coding, as applied in LTE networks. The derived models are validated by means of simulations. In additon, we show that our models are approximate estimators for the performance of rate-based proportional fair scheduling, while they outperform some simpler prediction models from related work significantly.Comment: 7 pages, 6 figures. This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl
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