113 research outputs found
Improving Macrocell - Small Cell Coexistence through Adaptive Interference Draining
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
Heterogeneous network optimization using robust power-and-resource based algorithm
In order to meet the increasing mobile data-traffic, spatial densification of network with several low-power nodes, the high-power macro BS and HetNet are the major key enabling solution. However, the HetNet is unplanned in nature, causes irregularities and interferences that without any user association rules. The appropriate deployment of the femto-cell in HetNet can provide effective traffic offloading, where the alleviate mobbing in the macro-cells can decrease the power consumption therefore it optimizes the user experience. Moreover, the protection is also important for the macro and femto cell users in a network through maintaining the min-max level of interferences. In this paper, we proposed RPRA that comprises two robust approach such as robust power-controller and the robust channel-allocation approach, which can improve the spectral efficiency and user experiences at lower network coverage areas via eliminating the week coverage zones. Also provide high user rate connection by effective interference in an efficient spectrum, lowering in transmission power and cost-effectiveness via less time delay. To show the effectiveness of our proposed model we have compared with several existing techniques and we got significant improvement in throughput, also reduction in time delay and transmission power
Throughput evaluation for the downlink scenario of co-tier interference in heterogeneous network
To extend the coverage and capacity of Heterogeneous Networks (HetNets), femtocells (HeNodeBs) has been impressive to deploy in in-house or apartment. Owing to co-channel spectrum involvement these HeNodeB sources Co-Tier interference (CTI) with neighbor HeNodeBs and users of HeNodeB (HUE) in orthogonal frequency division multiplexing Access (OFDMA). As a result, CTI is occurred which causes of system throughput degradation. This paperinvestigates the OFDMA subcarrier allocation techniques and algorithms. A Genetic Algorithm based SubcarrierAllocation (GA-SA) framework is evaluated to enhanced throughput of HeNodeB and HUE. The enhancement of the system throughput and Signal to Interference Noise Ratio (SINR) is analyzed to mitigate CTI. The system level simulation is considered to evaluate the performance of the framework. The results show that the throughput is enhanced for HUE and HeNodeB, which can mitigate the CTI in OFDMA
Performances des RĂ©seaux LTE
Poussé par la demande croissante de services à haut débit sans fil, Long Term Evolution (LTE) a émergé comme une solution prometteuse pour les communications mobiles. Dans plusieurs pays à travers le monde, la mise en oeuvre de LTE est en train de se développer. LTE offre une architecture tout-IP qui fournit des débits élevés et permet une prise en charge efficace des applications de type multimédia. LTE est spécifié par le 3GPP ; cette technologie fournit une architecture capable de mettre en place des mécanismes pour traiter des classes de trafic hétérogènes comme la voix, la vidéo, les transferts de fichier, les courriers électroniques, etc. Ces classes de flux hétérogènes peuvent être gérées en fonction de la qualité de service requise mais aussi de la qualité des canaux et des conditions environnementales qui peuvent varier considérablement sur une courte échelle de temps. Les standards du 3GPP ne spécifient pas l algorithmique de l allocation des ressources du réseau d accès, dont l importance est grande pour garantir performance et qualité de service (QoS). Dans cette thèse, nous nous focalisons plus spécifiquement sur la QoS de LTE sur la voie descendante. Nous nous concentrons alors sur la gestion des ressources et l ordonnancement sur l interface radio des réseaux d accès. Dans une première partie, nous nous sommes intéressés à des contextes de macro-cellules. Le premier mécanisme proposé pour l allocation des ressources combine une méthode de jetons virtuels et des ordonnanceurs opportunistes. Les performances obtenues sont très bonnes mais n assurent pas une très bonne équité. Notre seconde proposition repose sur la théorie des jeux, et plus spécifiquement sur la valeur de Shapley, pour atteindre un haut niveau d équité entre les différentes classes de services au détriment de la qualité de service. Cela nous a poussé, dans un troisième mécanisme, à combiner les deux schémas. La deuxième partie de la thèse est consacrée aux femto-cellules (ou femtocells) qui offrent des compléments de couverture appréciables. La difficulté consiste alors à étudier et à minimiser les interférences. Notre premier mécanisme d atténuation des interférences est fondé sur le contrôle de la puissance de transmission. Il fonctionne en utilisant la théorie des jeux non coopératifs. On effectue une négociation constante entre le débit et les interférences pour trouver un niveau optimal de puissance d émission. Le second mécanisme est centralisé et utilise une approche de division de la bande passante afin d obliger les femtocells à ne pas utiliser les mêmes sous-bandes évitant ainsi les interférences. Le partage de bande passante et l allocation sont effectués en utilisant sur la théorie des jeux (valeur de Shapley) et en tenant compte du type d application. Ce schéma réduit les interférences considérablement. Tous les mécanismes proposés ont été testés et évalués dans un environnement de simulation en utilisant l outil LTE-Sim au développement duquel nous avons contribué.Driven by the growing demand for high-speed broadband wireless services, Long term Evolution (LTE) technology has emerged as a competitive alternative to mobile communications solution. In several countries around the world, the implementation of LTE has started. LTE offers an IP-based framework that provides high data rates for multimedia applications. Moreover, based on the 3GPP specifications, the technology provides a set of built in mechanisms to support heterogeneous classes of traffic including data, voice and video, etc. Supporting heterogeneous classes of services means that the traffic is highly diverse and has distinct QoS parameters, channel and environmental conditions may vary dramatically on a short time scale. The 3GPP specifications leave unstandardized the resource management and scheduling mechanisms which are crucial components to guarantee the QoS performance for the services. In this thesis, we evaluate the performance and QoS in LTE technology. Moreover, our research addresses the resource management and scheduling issues on the wireless interface. In fact, after surveying, classifying and comparing different scheduling mechanisms, we propose three QoS mechanisms for resource allocation in macrocell scenarios focused on real time services and two mechanisms for interference mitigation in femtocell scenarios taking into account the QoS of real time services. Our first proposed mechanism for resource allocation in macrocell scenarios combines the well known virtual token (or token buckets) method with opportunistic schedulers, our second scheme utilizes game theory, specifically the Shapley value in order to achieve a higher fairness level among classes of services and our third mechanism combines the first and the second proposed schemes. Our first mechanism for interference mitigation in femtocell scenarios is power control based and works by using non cooperative games. It performs a constant bargain between throughput and SINR to find out the optimal transmit power level. The second mechanism is centralised, it uses a bandwidth division approach in order to not use the same subbands to avoid interference. The bandwidth division and assignation is performed based on game theory (Shapley value) taking into account the application bitrate . This scheme reduces interference considerably and shows an improvement compared to other bandwidth division schemes. All proposed mechanism are performed in a LTE simulation environment. several constraints such as throughput, Packet Loss Ratio, delay, fairness index, SINR are used to evaluate the efficiency of our schemesTOULOUSE-INP (315552154) / SudocSudocFranceF
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Radio network management in cognitive LTE-Femtocell Systems
This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London.There is a strong uptake of femtocell deployment as small cell application
platforms in the upcoming LTE networks. In such two-tier networks of LTEfemtocell
base stations, a large portion of the assigned spectrum is used
sporadically leading to underutilisation of valuable frequency resources.
Novel spectrum access techniques are necessary to solve these current spectrum
inefficiency problems. Therefore, spectrum management solutions should have
the features to improve spectrum access in both temporal and spatial manner.
Cognitive Radio (CR) with the Dynamic Spectrum Access (DSA) is considered
to be the key technology in this research in order to increase the spectrum
efficiency. This is an effective solution to allow a group of Secondary Users
(SUs) to share the radio spectrum initially allocated to the Primary User (PUs) at
no interference.
The core aim of this thesis is to develop new cognitive LTE-femtocell systems
that offer a 4G vision, to facilitate the radio network management in order to
increase the network capacity and further improve spectrum access probabilities.
In this thesis, a new spectrum management model for cognitive radio networks is
considered to enable a seamless integration of multi-access technology with
existing networks. This involves the design of efficient resource allocation
algorithms that are able to respond to the rapid changes in the dynamic wireless
environment and primary users activities. Throughout this thesis a variety of
network upgraded functions are developed using application simulation
scenarios. Therefore, the proposed algorithms, mechanisms, methods, and system
models are not restricted in the considered networks, but rather have a wider
applicability to be used in other technologies.
This thesis mainly investigates three aspects of research issues relating to the
efficient management of cognitive networks: First, novel spectrum resource
management modules are proposed to maximise the spectrum access by rapidly
detecting the available transmission opportunities. Secondly, a developed pilot
power controlling algorithm is introduced to minimise the power consumption by
considering mobile position and application requirements. Also, there is
investigation on the impact of deploying different numbers of femtocell base
stations in LTE domain to identify the optimum cell size for future networks.
Finally, a novel call admission control mechanism for mobility management is
proposed to support seamless handover between LTE and femtocell domains.
This is performed by assigning high speed mobile users to the LTE system to
avoid unnecessary handovers.
The proposed solutions were examined by simulation and numerical analysis to
show the strength of cognitive femtocell deployment for the required
applications. The results show that the new system design based on cognitive
radio configuration enable an efficient resource management in terms of
spectrum allocation, adaptive pilot power control, and mobile handover. The
proposed framework and algorithms offer a novel spectrum management for self organised LTE-femtocell architecture.
Eventually, this research shows that certain architectures fulfilling spectrum
management requirements are implementable in practice and display good
performance in dynamic wireless environments which recommends the
consideration of CR systems in LTE and femtocell networks
Spectrum Leasing as an Incentive towards Uplink Macrocell and Femtocell Cooperation
The concept of femtocell access points underlaying existing communication
infrastructure has recently emerged as a key technology that can significantly
improve the coverage and performance of next-generation wireless networks. In
this paper, we propose a framework for macrocell-femtocell cooperation under a
closed access policy, in which a femtocell user may act as a relay for
macrocell users. In return, each cooperative macrocell user grants the
femtocell user a fraction of its superframe. We formulate a coalitional game
with macrocell and femtocell users being the players, which can take individual
and distributed decisions on whether to cooperate or not, while maximizing a
utility function that captures the cooperative gains, in terms of throughput
and delay.We show that the network can selforganize into a partition composed
of disjoint coalitions which constitutes the recursive core of the game
representing a key solution concept for coalition formation games in partition
form. Simulation results show that the proposed coalition formation algorithm
yields significant gains in terms of average rate per macrocell user, reaching
up to 239%, relative to the non-cooperative case. Moreover, the proposed
approach shows an improvement in terms of femtocell users' rate of up to 21%
when compared to the traditional closed access policy.Comment: 29 pages, 11 figures, accepted at the IEEE JSAC on Femtocell Network
Performances of LTE networks
Poussé par la demande croissante de services à haut débit sans fil, Long Term Evolution (LTE) a émergé comme une solution prometteuse pour les communications mobiles. Dans plusieurs pays à travers le monde, la mise en oeuvre de LTE est en train de se développer. LTE offre une architecture tout-IP qui fournit des débits élevés et permet une prise en charge efficace des applications de type multimédia. LTE est spécifié par le 3GPP ; cette technologie fournit une architecture capable de mettre en place des mécanismes pour traiter des classes de trafic hétérogènes comme la voix, la vidéo, les transferts de fichier, les courriers électroniques, etc. Ces classes de flux hétérogènes peuvent être gérées en fonction de la qualité de service requise mais aussi de la qualité des canaux et des conditions environnementales qui peuvent varier considérablement sur une courte échelle de temps. Les standards du 3GPP ne spécifient pas l’algorithmique de l’allocation des ressources du réseau d’accès, dont l’importance est grande pour garantir performance et qualité de service (QoS). Dans cette thèse, nous nous focalisons plus spécifiquement sur la QoS de LTE sur la voie descendante. Nous nous concentrons alors sur la gestion des ressources et l’ordonnancement sur l’interface radio des réseaux d’accès. Dans une première partie, nous nous sommes intéressés à des contextes de macro-cellules. Le premier mécanisme proposé pour l’allocation des ressources combine une méthode de jetons virtuels et des ordonnanceurs opportunistes. Les performances obtenues sont très bonnes mais n’assurent pas une très bonne équité. Notre seconde proposition repose sur la théorie des jeux, et plus spécifiquement sur la valeur de Shapley, pour atteindre un haut niveau d’équité entre les différentes classes de services au détriment de la qualité de service. Cela nous a poussé, dans un troisième mécanisme, à combiner les deux schémas. La deuxième partie de la thèse est consacrée aux femto-cellules (ou femtocells) qui offrent des compléments de couverture appréciables. La difficulté consiste alors à étudier et à minimiser les interférences. Notre premier mécanisme d’atténuation des interférences est fondé sur le contrôle de la puissance de transmission. Il fonctionne en utilisant la théorie des jeux non coopératifs. On effectue une négociation constante entre le débit et les interférences pour trouver un niveau optimal de puissance d’émission. Le second mécanisme est centralisé et utilise une approche de division de la bande passante afin d’obliger les femtocells à ne pas utiliser les mêmes sous-bandes évitant ainsi les interférences. Le partage de bande passante et l’allocation sont effectués en utilisant sur la théorie des jeux (valeur de Shapley) et en tenant compte du type d’application. Ce schéma réduit les interférences considérablement. Tous les mécanismes proposés ont été testés et évalués dans un environnement de simulation en utilisant l’outil LTE-Sim au développement duquel nous avons contribué. ABSTRACT : Driven by the growing demand for high-speed broadband wireless services, Long term Evolution (LTE) technology has emerged as a competitive alternative to mobile communications solution. In several countries around the world, the implementation of LTE has started. LTE offers an IP-based framework that provides high data rates for multimedia applications. Moreover, based on the 3GPP specifications, the technology provides a set of built in mechanisms to support heterogeneous classes of traffic including data, voice and video, etc. Supporting heterogeneous classes of services means that the traffic is highly diverse and has distinct QoS parameters, channel and environmental conditions may vary dramatically on a short time scale. The 3GPP specifications leave unstandardized the resource management and scheduling mechanisms which are crucial components to guarantee the QoS performance for the services. In this thesis, we evaluate the performance and QoS in LTE technology. Moreover, our research addresses the resource management and scheduling issues on the wireless interface. In fact, after surveying, classifying and comparing different scheduling mechanisms, we propose three QoS mechanisms for resource allocation in macrocell scenarios focused on real time services and two mechanisms for interference mitigation in femtocell scenarios taking into account the QoS of real time services. Our first proposed mechanism for resource allocation in macrocell scenarios combines the well known virtual token (or token buckets) method with opportunistic schedulers, our second scheme utilizes game theory, specifically the Shapley value in order to achieve a higher fairness level among classes of services and our third mechanism combines the first and the second proposed schemes. Our first mechanism for interference mitigation in femtocell scenarios is power control based and works by using non cooperative games. It performs a constant bargain between throughput and SINR to find out the optimal transmit power level. The second mechanism is centralised, it uses a bandwidth division approach in order to not use the same subbands to avoid interference. The bandwidth division and assignation is performed based on game theory (Shapley value) taking into account the application bitrate . This scheme reduces interference considerably and shows an improvement compared to other bandwidth division schemes. All proposed mechanism are performed in a LTE simulation environment. several constraints such as throughput, Packet Loss Ratio, delay, fairness index, SINR are used to evaluate the efficiency of our scheme
Power Minimization Based Resource Allocation for Interference Mitigation in OFDMA Femtocell Networks
[EN] With the introduction of femtocells, cellular networks are moving from the conventional centralized network architecture to a distributed one, where each network cell should make its own radio resource allocation decisions, while providing inter-cell interference mitigation. However, realizing such distributed network architecture is not a trivial task. In this paper, we first introduce a simple self-organization rule, based on minimizing cell transmit power, following which a distributed cellular network is able to converge into an efficient resource reuse pattern. Based on such self-organization rule and taking realistic resource allocation constraints into account, we also propose two novel resource allocation algorithms, being autonomous and coordinated, respectively. Performance of the proposed self-organization rule and resource allocation algorithms are evaluated using system-level simulations, and show that power efficiency is not necessarily in conflict with capacity improvements at the network level. The proposed resource allocation algorithms provide significant performance improvements in terms of user outages and network capacity over cutting-edge resource allocation algorithms proposed in the literature.This work was partially supported by the UK EPSRC Grant EP/H020268/1.LĂłpez-PĂ©rez, D.; Chu, X.; Vasilakos, AV.; Claussen, H. (2014). Power Minimization Based Resource Allocation for Interference Mitigation in OFDMA Femtocell Networks. IEEE Journal on Selected Areas in Communications. 32(2):333-344. https://doi.org/10.1109/JSAC.2014.14121333334432
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