Tesis sobre el tema "Inter-cell interference coordination (ICIC)"

Grâce aux avancées technologiques dans le domaine des réseaux cellulaires et des équipements mobiles, le nombre d'applications multimédia à haut débit dans les réseaux mobiles ne cesse d'augmenter. On prévoit que le trafic de données dans les réseaux mobiles en 2017 sera 13 fois plus important que celui en 2012. Pour satisfaire aux besoins des équipements mobiles, de nouvelles approches pour la gestion des ressources radio et des puissances de transmission sont requises.Dans le cadre de cette thèse, on s'intéresse à proposer des solutions pour remédier aux problèmes des interférences intercellulaires dans les réseaux mobiles de dernière génération. Nous enquêtons d'une manière exhaustive les différentes techniques de coordination des interférences intercellulaires existantes. Ces techniques sont qualitativement comparées, puis classées selon le taux de coopération requis entre les différentes stations de base, mais aussi selon leurs principes de fonctionnement. Nous abordons également le problème multicellulaire d'allocation des ressources et des puissances de transmission d'une manière centralisée. Nous formulons ce problème d'optimisation centralisé, puis nous le décomposons en deux sous-problèmes indépendants : l'allocation de ressources et l'allocation des puissances de transmission. De plus, une approche distribuée basée sur la théorie des jeux est proposée pour l'allocation des puissances de transmission. Les techniques centralisées de minimisation des interférences intercellulaires offrent la solution optimale au prix d'une grande charge de signalisation. Par contre, les solutions décentralisées réduisent le trafic de signalisation sans garantir l'optimalité de la solution obtenue. Nous proposons ensuite une heuristique de contrôle de puissance qui modifie localement l'allocation des puissances de transmission de manière à éviter le gaspillage d'énergie et pour réduire les interférences ressenties par les utilisateurs des stations de base voisines. Nous proposons également une technique autonome qui gère la distribution des ressources radio entre les différentes zones de chaque cellule. Cette technique répond aux besoins des utilisateurs dans chaque zone en adaptant la distribution des ressources d'une manière dynamique. Nous abordons aussi le compromis entre les techniques de gestion d'interférences intercellulaires centralisées et décentralisées. Nous proposons une approche hybride où l'allocation des ressources radio et des puissances de transmission est faite d'une manière coopérative entre les différentes cellules. Dans un premier lieu, les cellules voisines collaborent afin d'ajuster les puissances de transmission allouées aux ressources radio. Ensuite, la distribution des ressources entre les différentes zones de chaque cellule est modifiée localement, selon les besoins des utilisateurs dans chaque zone
The exponentially increasing demand for mobile broadband communications have led to the dense deployment of cellular networks with aggressive frequency reuse patterns. The future Fifth Generation (5G) networks are expected to overcome capacity and throughput challenges by adopting a multi-tier architecture where several low-power Base Stations (BSs) are deployed within the coverage area of the macro cell. However, Inter-Cell Interference (ICI) caused by the simultaneous usage of the same spectrum in different cells, creates severe problems. ICI reduces system throughput and network capacity, and has a negative impact on cell-edge User Equipment (UE) performance. Therefore, Inter-Cell Interference Coordination (ICIC) techniques are required to mitigate the impact of ICI on system performance. In this thesis, we address the resource and power allocation problem in multiuser Orthogonal Frequency Division Multiple Access (OFDMA) networks such as LTE/LTE-A networks and dense small cell networks. We start by overviewing the state-of-the-art schemes, and provide an exhaustive classification of the existing ICIC approaches. This qualitative classification is followed by a quantitative investigation of several interference mitigation techniques. Then, we formulate a centralized multi-cell joint resource and power allocation problem, and prove that this problem is separable into two independent convex optimization problems. The objective function of the formulated problem consists in maximizing system throughput while guaranteeing throughput fairness between UEs. ICI is taken into account, and resource and power allocation is managed accordingly in a centralized manner. Furthermore, we introduce a decentralized game-theoretical method to solve the power allocation problem without the need to exchange signaling messages between the different cells. We also propose a decentralized heuristic power control algorithm based on the received Channel Quality Indication (CQI) feedbacks. The intuition behind this algorithm is to avoid power wastage for UEs that are close to the serving cell, and reducing ICI for UEs in the neighboring cells. An autonomous ICIC scheme that aims at satisfying throughput demands in each cell zone is also introduced. The obtained results show that this technique improves UE throughput fairness, and it reduces the percentage of unsatisfied UEs without generating additional signaling messages. Lastly, we provide a hybrid ICIC scheme as a compromise between the centralized and the decentralized approaches. For a cluster of adjacent cells, resource and power allocation decisions are made in a collaborative manner. First, the transmission power is adjusted after receiving the necessary information from the neighboring cells. Second, resource allocation between cell zones is locally modified, according to throughput demands in each zone

Inter-cell interference coordination in 3GPP Long Term Evolution system received much attention in recent years. However, most of the studies are based on ideal system with regular hexagon-shaped cell. The indoor environment has special characteristics that the building shape and BS locations are irregular; the traffic load has great variation compared to urban and rural area. So, conventional ICIC scheme may not be used in indoor situation directly. In this thesis, ICIC scheme is employed for indoor environment. Based on different quality of backhaul, static and dynamic schemes will be proposed. The performances of proposed schemes and the performance of system without ICIC will be simulated and compared. At last, how much the improvement of the system can acquire after applying ICIC schemes will be analyzed, and the question about whether it is good to apply ICIC scheme in indoor environment will be answered.

OFDMA is accepted as the most appropriate air-interface for 4G OFDMA based systems by both researchers in industry and academia. A major problem that arises in OFDMA based systems is inter-cell interference that stems from aggressive frequency reuse and is particularly worse in cell-edge areas. Therefore, Inter-Cell Interference Coordination (ICIC) has been proposed as a promising method to mitigate inter-cell interference (ICI) mainly in the overlapping (cell-edge) areas of a multi-cell cellular network. The main objectives of this thesis are to investigate inter-cell interference in a heterogeneous system comprising of both macro and femto cells, propose and evaluate less complex novel inter-cell interference coordination/avoidance techniques that increase both cell-edge throughput and overall cell throughput. Initially, our scenario focuses on the investigation of co-channel interference in macrocell deployments. In this direction, we propose a static ICIC technique for OFDMA macrocell networks based on cyclic difference sets a branch of combinatorial mathematics to minimize the inter-cell interference. Then, we formulate the dynamic ICIC problem in a linear way in order to minimize the complexity issues with the scalability of the problem. We show that with minimal loss of optimality, this linear problem can be simplified into two smaller problems i.e. the multi-user scheduling (base station) problem and the multi-cell scheduling (network) problem. Simulation results confirm the increased effectiveness of proposed ICIC schemes in both metrics (i.e. cell-edge and total cell throughput) over a number of state-of-the-art (static and dynamic) interference avoidance schemes. After, the ICIC technique is optimized to minimize the total transmit power by employing inter-cell and intra-cell power control without compromising the cell-edge throughput. Here, we formulate the multi-objective problem as a multi-dimensional knapsack problem. Our simulation results of the proposed scheme show its increased energy efficiency and user fairness compared with the state-of-the-art energy efficient schemes. Finally, the complexity of the ICIC problem and the need of a centralised controller are further reduced in order to benefit small-cell deployments. Here, it is shown that the complexity of the ICIC version can be further reduced by employing a dual decomposition method from optimization theory. Extensive simulation results show a significant improvement of the proposed scheme compared with some distributed reference schemes in terms of cell-edge and total cell throughput and thus it is a promising candidate for next generation mobile systems.

L'elaborato affronta il tema dell'Inter-Cell Interference Coordination (ICIC) applicato ad un sistema 5G. Il sistema viene modellato mediante il software di simulazione ns-3. L'approccio utilizzato è quello di unire gli algoritmi di Frequency Reuse, che rappresentano un approccio statico di coordinamento dell'interferenza inter-cella, e il beamforming, caratteristica fondamentale introdotta dallo standard 5G, allo scopo di ottimizzare l'allocazione di risorse verso tutti gli utenti che il sistema cellulare copre. Lo studio effettuato affronta in maniera sistematica le specifiche dello standard 5G, con una particolare attenzione al modo in cui questo viene implementato all'interno del software di simulazione, con lo scopo di attuare modifiche in maniera consapevole delle caratteristiche che lo standard presenta. Infatti, proprio perché lo scenario di partenza non comprende l'applicazione di algoritmi di ICIC, è stato necessario modificare l'architettura iniziale della network già impostata all'interno di ns-3 e realizzare un interfacciamento con gli algoritmi di Frequency Reuse, andando a modificare il modo in cui la Base Station alloca le risorse. Inoltre, è stato necessario introdurre tutta la componente di segnali che utenti e Base Station si scambiano per fornirsi informazioni utili al coordinamento dell'interferenza inter-cella. In particolare, mediante il software viene modellato uno scenario di partenza, rappresentato da un generico stadio, e vengono valutate le performance del sistema in termini di pacchetti ricevuti sui totali pacchetti trasmessi. Con l'applicazione di un coordinamento dell'interferenza tra le celle si raggiungono risultati significativi, che portano ad un incremento delle performance del sistema. Il risultato finale mostra come l'utilizzo di algoritmi di ICIC migliori le performance del sistema grazie alla riduzione dell'interferenza, che permette un'allocazione di maggiori risorse con una perdita di pacchetti significativamente ridotta.

The exponentially increasing demand for mobile broadband communications has led to the dense deployment of cellular networks with aggressive frequency reuse patterns. The future Fifth Generation (5G) networks are expected to overcome capacity and throughput challenges by adopting a multi-tier architecture where several low-power Base Stations (BSs) are deployed within the coverage area of the macro cell. Hence, Inter-Cell Interference (ICI) caused by the simultaneous usage of the same spectrum in different cells creates severe problems. ICI reduces system throughput and network capacity, and has a negative impact on cell-edge users and overall system performance. Therefore, effective interference coordination techniques are required, especially, for user-to-cell association and resource allocation to mitigate severe impact of ICI on system performance in 5G heterogeneous networks (HetNets). This is to improve Quality of Service (QoS) and maximize system throughput arising from the deployment of small cell overlay on macro BSs in heterogeneous cellular networks, which creates traffic load imbalance due to varying transmit power of different BSs in the downlink. In this research, a cell association scheme based on Cell Range Expansion (CRE), integrated with power control techniques is proposed. Simulation results are presented to show the ability of this technique to protect offloaded users from severe ICI and maximize throughput while achieving desirable QoS and load balancing for users of different tiers. With the advancement of information and computer technology, the envisioned 5G wireless communication is expected to encompass an unprecedented heterogeneous and ultra-dense communication environment. Vehicular communications play a vital role in 5G wireless network and have been widely studied recently due to its great potential to ensure reliability and support intelligent transportation and various safety applications. This research therefore exploits the tractability of stochastic geometry to analyze the coverage of urban vehicular networks, by deriving a closed-form expression to maximize the ergodic capacity of cellular users (CUEs) and mitigate interference, taking into consideration the QoS requirements of both vehicle-to-vehicle (V2V) and vehicleto-infrastructure (V2I) links. Consequently, the latency and reliability requirements of V2V/V2I links are formulated as optimization constraints, involving joint power allocation and spectrum sharing (PASS), taking into account the slow varying and large scale channel state information (CSI) measurements. Due to non-convex nature of the problem, the optimization is transformed into sub-optimal convex equivalence, while a low complexity Algorithm that yields optimal resource allocation is then designed to solve it. Simulation results are used to show enhanced performance in our approach compared to related works. Finally, the upsurge in the number of connected devices, such as smart cars, to the envisioned 5G technology is expected to pose high capacity and data rate demands on the network. The conventional access techniques (i.e., CDMA, TDMA and OFDMA) may not meet stringent requirements, such as ultra-low latency, high reliability, improved spectral efficiency and massive device connectivity. This work further investigates non-orthogonal multiple access (NOMA) technique as promising solution to improve spectral efficiency and reduce interference in 5G Ultra Dense Network (UDN). The NOMA scheme is combined with two promising capacity and bandwidth enhancement techniques - massive multiple input and multiple output (MIMO) and carrier aggregation (CA), for overall network performance. In particular, for the proposed novel NOMA-CA approach, we justify the importance of maintaining green communication as a key requirement for 5G with Energy Efficiency (EE) analysis. Firstly, a proportional fairness scheduler is used to perform resource allocation and maintain fairness among users based on their channel condition. Secondly, an optimization problem to maximize the EE weighted-sum under joint power and bandwidth allocation on each aggregated component carrier (CC) is formulated. Conventionally, the formulated optimization is transformed from non-convex to convex problem. An iteratively adaptive Algorithm is then developed to find optimal solution for the problem. Simulation results show better improvement in EE and sum rate compared to the traditional OMA scheme.

Avec la progression de l'utilisation des smartphones, les modèles de systèmes ont rapidement évolué pour répondre aux besoins croissants en terme de capacité dans les réseaux sans fil. En effet, les progrès technologiques ont été considérables, depuis les communications point à point mono-utilisateur et mono-antenne jusqu'aux réseaux cellulaires multi-cellules et multi-antennes. Depuis la 3G, la technologie MIMO (multiple-input multiple-output) pour les communications sans fil est désormais intégrée aux normes de la large bande sans fil. L'ajout de plusieurs antennes, tant du côté de l'émetteur que du côté du récepteur, permet le multiplexage spatial (c'est-à-dire l'envoi simultané de plusieurs flux de données), qui permet d'augmenter les débits de données, et l'exploitation de la diversité spatiale, améliorant considérablement la qualité des liaisons. MIMO Multi-Utilisateurs (MU) a été un sujet bien étudié dans le domaine des communications sans fil en raison du grand potentiel qu'il offre pour améliorer le débit du système. Par conséquent, différents critères de conception pour les communications MIMO MU ont été étudiés dans la littérature. La plupart des conceptions de liaisons descendantes prennent en compte les problèmes d'optimisation de la capacité totale de tous les utilisateurs. D'autre part, la principale limitation des communications sans fil modernes est l'interférence (intracellulaire et intercellulaire) due à la réutilisation des fréquences. Ainsi, dans un scénario MIMO MU, lors de l'optimisation de l'efficacité globale, l'allocation de puissance se concentre sur les bons canaux, c'est-à-dire que les utilisateurs soumis à une forte interférence (e.g., les utilisateurs en bordure de cellule) sont délaissés. Il en résulte une répartition inéquitable de puissance entre les utilisateurs. Pour pallier ce problème, différentes notions d'équité sont introduites, comme l'équité max-min, l'équité pondérée ou l'équité proportionnelle. Dans cette thèse, nous nous concentrons sur l'équité max-min pondérée. En particulier, nous étudions le problème de l'équilibrage du débit pondéré par utilisateur dans un système MIMO multi-cellules MU. Nous abordons ce dernier dans le cadre d'une formulation conjointe du problème de beamforming et d'allocation de puissance, visant à satisfaire l'exigence d'équité. Dans la première partie, nous considérons la connaissance parfaite du canal pour résoudre le problème. Dans ce cas, nous maximisons le débit minimum pondéré via i) la dualité liaison montante/descendante et ii) la dualité Lagrangienne. Dans la deuxième partie, nous considérons la connaissance partielle du canal. Nous optimisons le problème d'équilibrage de débit ergodique via i) l'erreur quadratique moyenne pondérée (EQM) en exploitant la relation débit - EQM, et ii) deux approximations du débit estimé comme le débit de signal et de puissance d'interférence estimés (ESIP) au niveau du flux et du signal reçu. Par ailleurs, nous proposons une stratégie d'efficacité énergétique au moyen des approches d'équilibrage des débits proposées
With the rise in smartphone usage, the system models have rapidly evolved to meet ever-growing needs for capacity in wireless networks. Indeed, there have been large advances in technology, from single-user single-antenna point-to-point communications to multi-cell multi-antenna cellular networks. In fact, multiple-input multiple-output (MIMO) technology for wireless communications is now incorporated into wireless broadband standards since 3G. Adding multiple antennas at both the transmitter and the receiver sides enables spatial multiplexing (i.e. sending multiple data streams simultaneously), which allows to increase data rates, and spatial diversity exploitation, which allows to greatly improve link quality. The multi-user MIMO downlink (so-called Broadcast Channel (BC)) has been a well investigated subject in wireless communications because of the high potential it offers in improving the system throughput. Therefore, different design criteria for multi-user MIMO communication have been investigated in the literature. Most of the downlink designs consider optimization problems w.r.t. the sum-capacity of all users. On the other hand, the major bottleneck of modern wireless communication is the interference (intracell and intercell) due to frequency reuse. Thus, in a multi-user MIMO scenario, when optimizing the overall efficiency, the power allocation is focused on the good channels, i.e., users that are subject to strong interference (e.g. cell-edge users) are neglected. The result is an unfair distribution of rate among users. In order to avoid this effect, different fairness notions have been introduced, like max-min fairness, weighted fairness, or proportional fairness. In this thesis, we focus on the weighted max-min fairness. In particular, we study the (weighted) user rate balancing problem in a multi-cell multi-user MIMO system. We address this problem by joint beamforming and power allocation optimization, aiming to satisfy the fairness requirements. In the first part, we consider perfect knowledge of the channel to solve the problem. Therein, we maximize the minimum (weighted) rate via i) weighted user Mean Square Error (MSE) uplink/downlink duality and ii) Lagrangian duality. In the second part, we consider partial knowledge of the channel. We optimize the ergodic rate balancing problem via i) weighted expected MSE by exploiting the rate – MSE relation, and ii) two approximations of the expected rate as the Expected Signal and Interference Power (ESIP) rate at the stream level and the received signal level. Furthermore, we study the transmit power minimization problem with fixed user-rate targets and provide a strategy exploiting the proposed rate balancing approaches

Conduit par une croissance exponentielle dans les appareils mobiles et une augmentation continue de la consommation individuelle des données, le trafic de données mobiles a augmenté de 4000 fois au cours des 10 dernières années et près de 400millions fois au cours des 15 dernières années. Les réseaux cellulaires homogènes rencontrent de plus en plus de difficultés à gérer l’énorme trafic de données mobiles et à assurer un débit plus élevé et une meilleure qualité d’expérience pour les utilisateurs.Ces difficultés sont essentiellement liées au spectre disponible et à la capacité du réseau.L’industrie de télécommunication doit relever ces défis et en même temps doit garantir un modèle économique pour les opérateurs qui leur permettra de continuer à investir pour répondre à la demande croissante et réduire l’empreinte carbone due aux communications mobiles. Les réseaux cellulaires hétérogènes (HetNets), composés de stations de base macro et de différentes stations de base de faible puissance,sont considérés comme la solution clé pour améliorer l’efficacité spectrale par unité de surface et pour éliminer les trous de couverture. Dans de tels réseaux, il est primordial d’attacher intelligemment les utilisateurs aux stations de base et de bien gérer les interférences afin de gagner en performance. Comme la différence 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 adaptée dans les HetNets. Une technique basée sur des offsets individuelles par cellule Offset(CIO) est donc nécessaire 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 ajoutée à la valeur moyenne de la puissance reçue du signal de référence(RSRP) mesurée par le mobile et peut donc induire à un changement d’attachement vers différents eNodeB. Comme les stations de bases dans les réseaux cellulaires LTE utilisent les mêmes sous-bandes de fréquences, les mobiles peuvent connaître une forte interférence intercellulaire, en particulier en bordure de cellules. Par conséquent, il est primordial de coordonner l’allocation des ressources entre les cellules et de minimiser l’interférence entre les cellules. Pour atténuer la forte interférence intercellulaire, les ressources, en termes de temps, fréquence et puissance d’émission, devraient être alloués efficacement. Un modèle pour chaque dimension est calculé pour permettre en particulier aux utilisateurs en bordure de cellule de bénéficier d’un débit plus élevé et d’une meilleure qualité de l’expérience. L’optimisation de tous ces paramètres peut également offrir un gain en consommation d’énergie. Dans cette thèse, 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 réseaux cellulaires LTE maximisant une fonction d’utilité du réseau qui peut être choisie de manière adéquate.Notre solution, basée sur la théorie des jeux, permet de calculer les meilleures valeurs pour l’offset individuelle par cellule (CIO) et pour les niveaux de puissance à appliquer au niveau temporel et fréquentiel pour chaque cellule. Nous présentons des résultats des simulations effectuées pour illustrer le gain de performance important apporté par cette optimisation. Nous obtenons une significative hausse dans le débit moyen et le débit des utilisateurs en bordure de cellule avec 40 % et 55 % de gains respectivement. En outre, on obtient un gain important en énergie. Ce travail aborde des défis pour l’industrie des télécoms et en tant que tel, un prototype de l’optimiseur a été implémenté en se basant sur un trafic HetNets émulé
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

La croissance exponentielle du nombre de dispositifs communicants et des services sans fils émergents fixe des objectifs toujours plus haut pour répondre à la demande de capacité sans cesse croissante des utilisateurs. Cela pose des défis constants pour atteindre les objectifs envisagés. La réutilisation spectrale élevée (High efficiency spectral reuse) a été adopté, cependant, elle conduit à des interférences accrues sur le réseau, ce qui dégrade les performances. L'OFDM (Orthogonal Frequency Division Multiplexing) est utilisé comme solution dans les réseaux de 4 G. Grâce à son orthogonalité, l'OFDM élimine l'interférence intra-cellulaire, mais l'interférence inter-cellule reste importante. Plusieurs méthodes connues sous le nom d'Inter-Cell interférences coordination (ICIC) ont été proposées pour les diminuer. L'ICIC permet la gestion des ressources radio coordonnée entre plusieurs cellules appelées ENodeB. Ces eNodeB peuvent partager les informations nécessaires grâce à l'interface X2 qui les relient, ces informations sont transmises par des messages LTE normalisés. Lorsque les ENodeBs sélectionnent égoïstement les ressources, la théorie de jeux non-coopératifs est largement appliquée pour trouver un juste équilibre. Dans cette thèse, nous mettons l'accent sur l'ICIC pour la liaison descendante d'un système OFDMA cellulaire dans le contexte du projet SOAPS (Spectrum opportuniste accès à la Sécurité publique). Ce projet a pour but l'amélioration de la planification des ressources de fréquences pour fournir des services à large bande dans les systèmes PMR (radiocommunications mobiles privées) en utilisant les technologies LTE. Nous adressons le problème d'ICIC en proposant quatre solutions différentes sous forme d'algorithmes entièrement décentralisés, ces algorithmes se basent sur la théorie des jeux non-coopératifs avec des équilibres de Nash purs des jeux considérés
The exponential growth in the number of communications devices has set out new ambitious targets to meet the ever-increasing demand for user capacity in emerging wireless systems. However, the inherent impairments of communication channels in cellular systems pose constant challenges to meet the envisioned targets. High spectral reuse efficiency was adopted as a solution to higher data rates. Despite its benefits, high spectral reuse leads to increased interference over the network, which degrades performances of mobile users with bad channel quality. To face this added interfence, OFDM (Orthogonal Frequency Division Multiplexing) is used for the new 4th generation network. Thanks to its orthogonality OFDM eliminates the intra-cellular interference, but when the same resources are used in two adjacents cells, the inter-cell interference becomes severe. To get rid of the latter, several methods for Inter-Cell Interference Coordination (ICIC) have been proposed. ICIC allows coordinated radio resources management between multiple cells. The eNodeBs can share resource usage information and interference levels over the X2 interface through LTE-normalized messages. Non-cooperative game theory was largely applied were eNodeBs selfishly selects resource blocks (RBs) in order to minimize interference. In this thesis, we stress on ICIC for the downlink of a cellular OFDMA system in the context of the SOAPS (Spectrum Opportunistic Access in Public Safety) project. This project focuses on the improvement of frequency resource scheduling for Broadband Services provision by PMR (Private Mobile Radio) systems using LTE technologies. We addressed this problem with four different solutions based on Non-cooperative game theory, three algorithms are devoted to RB selection in order to manage the interference, while the last one is a power control scheme with power economy and enhanced system performances

博士
國立中央大學
資訊工程學系
104
The Long Term Evolution (LTE) Heterogeneous Networks (HetNet) consists of several different type of base station for providing different coverage and capacity and increasing network capacity continuously. In LTE HetNet, the mass deployment and frequently on/off of small cells, such as femtocells, causes severe inter-cell interference problem due to the nature of user deployment without X2 interface, especially in Closed Subscriber Group (CSG) mode. The concept of Inter-Cell Interference Coordination proposed by The 3rd Generation Partnership Project (3GPP) can be achieved by using power restriction or resource restriction methods. In this article, we proposed two distributed fuzzy-based Inter-Cell Interference Coordination (ICIC) algorithms based on the concept of the power restriction and resource restriction. The low complexity and high flexibility of the proposed algorithms is benefited from the fuzzy Multi-Attributes Decision Making (MADM). Fuzzy theory can provide means to make approximate decisions with low complexity and high flexibility, especially in current multi-parameters communication systems, such as LTE system, in which the diversity of network metrics can help fuzzy system to make better decision. The proposed adaptive power restriction algorithm provides an appropriate serving range for femtocells, determining center zone and separating UEs into cell center and cell edge for frequency-reused algorithms, such as Soft Frequency Reuse (SFR) and Fractional Frequency Reuse (FFR), without complicated negotiation among cells. The proposed adaptive radio restriction algorithm weighs the trade-off between coverage and capacity by leveraging three system metrics to make an appropriate scheduling decision to avoid the conflict in radio resource used among cells. In particular, there are no fixed fuzzy logic rules and shaped fuzzy membership model compared to conventional fuzzy-based algorithms. The simulation results show that proposed algorithms provide about 49 % data rate improvement for femtocell and about 18 % data rate improvement for macrocell compared to current link adaptation algorithm. In addition, it can achieve up to 56 % data rate and 89 % radio resource efficiency of the up bound case.

碩士
國立中央大學
通訊工程學系
103
Inter-cell Interference coordination (ICIC) has been more and more important in the 3rd Generation Partnership Project’s (3GPP’s) Long Term Evolution –Advanced (LTE-A) standardization since the Frequency Reuse Factor (FRF) has already been 1 which means we utilized whole frequency without partition into several segmentations. Meanwhile, with radio access networks in LTE/LTE-A are flatter, decentralized ICIC algorithm has become more suitable than the centralized algorithm. Because of the import of the Load Information (LI) through X2 interface, ICIC could be effectively used to reduce the interference of edge users in LTE/LTE-A system. In the multi-cell radio resource management of LTE/LTE-A system, ICIC plays a significant role in enhancing cell edge spectrum efficiency. In this thesis, we propose a decentralized ICIC method, named relative throughput based resource block coordination (RTRBC), to coordinate the interference between eNBs. By comparing the relative gain and loss in heuristic manner, the proposed scheme negotiates the RB usage between adjacent eNBs to achieve higher throughput. The simulation results also demonstrate the effectiveness of the proposed scheme.

碩士
國立交通大學
網路工程研究所
99
In recent year, people who need radio network are increasing, especially for the multimedia communication. To reach such demand, 4G cellular wireless network is working on. Long Term Evolution (LTE) is one of the 4G standards proposed by 3GPP. LTE is a cellular network system; this kind of system suffers from interference problem between cells. If we do not handle interference well, we cannot reach the goal of high transmission rate and high cell coverage. In traditional static interference avoidance scheme, different user distribution will cause wasting of resource. In this thesis we propose a fractional frequency based dynamic interference coordination scheme. By the scheme we can dynamic adjust the high power frequency band and normal power frequency band according to user distribution. Adjusting frequency band through this scheme can efficiently eliminate the resource wasting problem.

碩士
國立臺灣海洋大學
通訊與導航工程學系
101
Because of the increasing demand of the transmission data rate for a wireless access service, the development of the fourth generation (4G) wireless communication system becomes more and more urgent and important. The Long Term Evolution Advanced (LTE-A) is the most popular candidate for the future 4G system, and it has some issues need to be investigated, such as Synchronization, Inter-cell interference, Channel Estimation (CE), etc. In this thesis, the synchronization and inter-cell interference problems are discussed. LTE-A adopts the PSSs and SSSs that transmit every 5ms for the synchronization. Several low-complexity schemes are provided to conduct the Timing Offset (TO) estimation via the time-domain symmetric property of PSS and conjugated symmetric property of SSS in this thesis. Computer simulations show that the proposed synchronization methods have not only the good Mean Square Error (MSE) performance but also the low computation complexity advantage. Besides, a sectorized Coordinated Multi-Point (CoMP) resource planning method is provided to avoid the macro cell to macro cell inter-cell interference. The proposed sectorized CoMP is compared with the traditional Inter-Cell Interference Coordination (ICIC) methods and results shows that the proposed method has better performance of system frequency efficiency and user capacity. Finally, a modified greedy method is also provided to achieve the fair resource allocation purpose for the UEs in this thesis.

碩士
國立中央大學
資訊工程學系
106
In order to satisfy increasing traffic demands in 5G network. 5G provides mmWave technology. Beamforming is considered to be a promising technique to reduce the pathloss of mmWave. Beamforming is a signal processing by antenna arrays for directional signal transmission or reception. The directional signal can reduce the pathloss of mmWave very well. Besides, increasing traffic demands. 5G will also support Heterogeneous Network (HetNet). One of the key challenges is reducing the interference and maximizing the throughput. In LTE, it provides enhanced Inter-Cell Interference Coordination (eICIC) to reduce the interference of the cells. Clearly, an uniform eICIC in mmWave scenario can't fully utilize the beams capability. In this paper, we propose an non-uniform eICIC configuration algorithm to improve the throughput of the cells. Final, we use Gurobi to evaluate our performance

碩士
國立臺北科技大學
電子工程系
106
With the evolution of 5G communication, to enable users to achieve better communication quality and signal coverage, telecom operators and users may install more small cells in the indoor region. However, the small cells would suffer severe inter-cell interference due to denser deployment. The thesis explores the implementation issues of enhanced inter-cell interference (eICIC) coordination among small cells. The time-domain based eICIC, namely almost blank subframe (ABS), is utilized to avoid the concurrent transmission among the neighbor cells. According to the literature, the time synchronization requirement should be within 1$mu$s. Moreover, although the major part of each subframe, i.e., the data transmission interference through the physical downlink shared channel (PDSCH), is coordinated, the other portion of the subframe such as the synchronization signals and the physical broadcast channel (PBCH) would still interfere others. The subframe shifting among neighbor cells is further considered to improve the performance. We implement using OpenAirInterface (OAI) with universal software radio peripherals (USRP). To study the impact of time synchronization on the performance of eICIC, we utilize a packet-based protocol IEEE 1588 and compare with the clock source device OctoClock-G. In the experiments, three USRPs are installed to serve as two small cells and one user. One small cell transmits data to the user, and the other transmits as the interference source. We verified that the throughput of the time synchronization case could increase up to 28% compared to the asynchronous case, and the further consideration of subframe offset scheme will increase by 40% in total, which shows that user can get guarantee data transmission in the dense small cell.

博士
國立交通大學
資訊科學與工程研究所
104
Wireless data traffic has seen prolific growth in recent years because the use of smart handheld devices and new emerging services are widespread, such as real-time video streaming and multimedia file sharing. To handle huge wireless data traffic, LTE-A (Long Term Evolution-Advanced) has adopted heterogeneous networks (HetNets) architecture, which consists of macro eNB and pico eNB/relay node (RN), to increase the capacity of LTE-A. In LTE-A HetNets, access control for Machine-to-Machine (M2M) communications, energy saving, and inter-cell interference coordination are three important issues, which are to be resolved in this thesis. For the access control for M2M communications issue, we propose two efficient cooperative access class barring with load balancing (CACB-LB) and traffic adaptive radio resource management (TARRM) schemes for M2M communications. The proposed CACB-LB uses the percentage of the number of MTC devices that can only access one enhanced Node B (eNB) between two adjacent eNBs as a criterion to allocate those MTC devices that are located in the overlapped coverage area to each eNB. Note that an eNB is a base station of LTE-A. In this way, the proposed CACB-LB can achieve better load balancing among eNBs than CACB, which is the best available related work. The proposed CACB-LB also uses the ratio of the channel quality indication (CQI) that an MTC device received from an eNB over the number of MTC devices that attach to the eNB as a criterion to adjust the estimated number of MTC devices that may access the eNB. As a result, the proposed CACB-LB can have a better set of barring rates of access class barring than CACB and can reduce random access delay experienced by an MTC device, which is also applicable to user equipment (UE). In addition, the proposed TARRM allocates radio resources for an MTC device based on the random access rate of the MTC device and the amount of data uploaded and downloaded by the MTC device in a homogeneous MTC device network, and the priority of an MTC device in a heterogeneous MTC device network so as to effectively utilize the radio resources. For the energy saving issue, we propose a self-organizing network (SON)-based adaptive energy saving (AES) mechanism for LTE-A self-organizing HetNets. The proposed AES uses two-level multi-threshold load management for each RN under different eNBs (inter-cell level) and for each RN within the same eNB (intra-cell level) so as to reduce the congestion in hot spot eNBs and RNs. In addition, the proposed AES can dynamically switch an RN between active and sleep modes to maximize the number of sleep RNs for adaptive energy saving. It can also dynamically change an RN’s coverage area to reduce energy consumption and to increase radio resource utilization. Besides, the proposed AES adopts a neural network predictor to forecast the loading of each RN to determine whether it is appropriate to switch an RN to sleep mode. For the inter-cell interference coordination issue, we propose SON-based cell size adaption (SCSA) and traffic adaptive enhanced inter-cell interference coordination (TAeICIC) to resolve the interference problem. The proposed SCSA uses dynamic multi-threshold load management to dynamically set the transmission power of each pico eNB by adjusting the pilot power. In addition, the proposed TAeICIC utilizes a scheduling metric, proportional-fair (PF), which is the estimated throughput based on the CQI reported by a UE divided by the estimated long term average throughput achieved by the UE, to dynamically allocate an appropriate number of Almost Blank Subframes (ABSs) in each ABS period in a macro eNB so as to mitigate the interference from the macro eNB to its adjacent pico eNBs.