2,397 research outputs found
Status-Seeking in Hedonic Games with Heterogeneous Players
We study hedonic games with heterogeneous player types that reflect her nationality, ethnic background, or skill type. Agents' preferences are dictated by status-seeking where status can be either local or global. The two dimensions of status define the two components of a generalized constant elasticity of substitution utility function. In this setting, we characterize the core as a function of the utility's parameter values and show that in all cases the corresponding cores are non-empty. We further discuss the core stable outcomes in terms of their segregating versus integrating properties.Coalitions, Core, Stability, Status-seeking
Distributed Caching in Small Cell Networks
The dense deployment of small cells in indoor and outdoor areas contributes mainly in increasing the capacity of cellular networks. On the other hand, the high number of deployed base stations coupled with the increasing growth of data traffic have prompted the apparition of base stations fi tted with storage capacity to avoid network saturation. The storage devices are used as caching units to overcome the limited backhaul capacity in small cells networks (SCNs). Extending the concept of storage to SCNs, gives rise to many new challenges related to the specific characteristics of these networks such as the heterogeneity of the base stations. Formulating the caching problem while taking into account all these specific characteristics with the aim to satisfy the users expectations result in combinatorial optimization problems. However, classical optimization tools do not ensure the optimality of the provided solutions or often the proposed algorithms have an exponential complexity. While most of the existing works are based on the classical optimization tools, in this thesis, we explore another approach to provide a practical solution for the caching problem. In particular, we focus on matching theory which is a game theoretic approach that provides mathematical tools to formulate, analyze and understand scenarios between sets of players. We model the caching problem as a one-to-one matching game between a set of files and a set of base stations and then, we propose an iterative extension of the deferred acceptance algorithm that needs a stable and optimal matching between the two sets. The experimental results show that the proposed algorithm reduces the backhaul load by 10-15 % compared to a random caching algorithm
The edge cloud: A holistic view of communication, computation and caching
The evolution of communication networks shows a clear shift of focus from
just improving the communications aspects to enabling new important services,
from Industry 4.0 to automated driving, virtual/augmented reality, Internet of
Things (IoT), and so on. This trend is evident in the roadmap planned for the
deployment of the fifth generation (5G) communication networks. This ambitious
goal requires a paradigm shift towards a vision that looks at communication,
computation and caching (3C) resources as three components of a single holistic
system. The further step is to bring these 3C resources closer to the mobile
user, at the edge of the network, to enable very low latency and high
reliability services. The scope of this chapter is to show that signal
processing techniques can play a key role in this new vision. In particular, we
motivate the joint optimization of 3C resources. Then we show how graph-based
representations can play a key role in building effective learning methods and
devising innovative resource allocation techniques.Comment: to appear in the book "Cooperative and Graph Signal Pocessing:
Principles and Applications", P. Djuric and C. Richard Eds., Academic Press,
Elsevier, 201
Allocations de ressources dans les réseaux sans fils énergétiquement efficaces.
In this thesis, we investigate two techniques used for enhancing the energy orspectral efficiency of the network. In the first part of the thesis, we propose tocombine the network future context prediction capabilities with the well-knownlatency vs. energy efficiency tradeoff. In that sense, we consider a proactivedelay-tolerant scheduling problem. In this problem, the objective consists ofdefining the optimal power strategies of a set of competing users, which minimizesthe individual power consumption, while ensuring a complete requestedtransmission before a given deadline. We first investigate the single user versionof the problem, which serves as a preliminary to the concepts of delay tolerance,proactive scheduling, power control and optimization, used through the first halfof this thesis. We then investigate the extension of the problem to a multiusercontext. The conducted analysis of the multiuser optimization problem leads toa non-cooperative dynamic game, which has an inherent mathematical complexity.In order to address this complexity issue, we propose to exploit the recenttheoretical results from the Mean Field Game theory, in order to transitionto a more tractable game with lower complexity. The numerical simulationsprovided demonstrate that the power strategies returned by the Mean FieldGame closely approach the optimal power strategies when it can be computed(e.g. in constant channels scenarios), and outperform the reference heuristicsin more complex scenarios where the optimal power strategies can not be easilycomputed.In the second half of the thesis, we investigate a dual problem to the previousoptimization problem, namely, we seek to optimize the total spectral efficiencyof the system, in a constant short-term power configuration. To do so, we proposeto exploit the recent advances in interference classification. the conductedanalysis reveals that the system benefits from adapting the interference processingtechniques and spectral efficiencies used by each pair of Access Point (AP) and User Equipment (UE). The performance gains offered by interferenceclassification can also be enhanced by considering two improvements. First, wepropose to define the optimal groups of interferers: the interferers in a samegroup transmit over the same spectral resources and thus interfere, but can processinterference according to interference classification. Second, we define theconcept of âVirtual Handoverâ: when interference classification is considered,the optimal Access Point for a user is not necessarily the one providing themaximal SNR. For this reason, defining the AP-UE assignments makes sensewhen interference classification is considered. The optimization process is thenthreefold: we must define the optimal i) interference processing technique andspectral efficiencies used by each AP-UE pair in the system; ii) the matching ofinterferers transmitting over the same spectral resources; and iii) define the optimalAP-UE assignments. Matching and interference classification algorithmsare extensively detailed in this thesis and numerical simulations are also provided,demonstrating the performance gain offered by the threefold optimizationprocedure compared to reference scenarios where interference is either avoidedwith orthogonalization or treated as noise exclusively.Dans le cadre de cette thĂšse, nous nous intĂ©ressons plus particuliĂšrement Ă deux techniques permettant dâamĂ©liorer lâefficacitĂ© Ă©nergĂ©tique ou spectrale desrĂ©seaux sans fil. Dans la premiĂšre partie de cette thĂšse, nous proposons de combinerles capacitĂ©s de prĂ©dictions du contexte futur de transmission au classiqueet connu tradeoff latence - efficacitĂ© Ă©nergĂ©tique, amenant Ă ce que lâon nommeraun rĂ©seau proactif tolĂ©rant Ă la latence. Lâobjectif dans ce genre de problĂšmesconsiste Ă dĂ©finir des politiques de transmissions optimales pour un ensembledâutilisateur, qui garantissent Ă chacun de pouvoir accomplir une transmissionavant un certain dĂ©lai, tout en minimisant la puissance totale consommĂ©e auniveau de chaque utilisateur. Nous considĂ©rons dans un premier temps le problĂšmemono-utilisateur, qui permet alors dâintroduire les concepts de tolĂ©rance Ă la latence, dâoptimisation et de contrĂÂŽle de puissance qui sont utilisĂ©s dans lapremiĂšre partie de cette thĂšse. Lâextension Ă un systĂšme multi-utilisateurs estensuite considĂ©rĂ©e. Lâanalyse rĂ©vĂšle alors que lâoptimisation multi-utilisateurpose problĂšme du fait de sa complexitĂ© mathĂ©matique. Mais cette complexitĂ©peut nĂ©anmoins ĂȘtre contournĂ©e grĂące aux rĂ©centes avancĂ©es dans le domainede la thĂ©orie des jeux Ă champs moyens, thĂ©orie qui permet de transiter dâunjeu multi-utilisateur, vers un jeu Ă champ moyen, Ă plus faible complexitĂ©. Lessimulations numĂ©riques dĂ©montrent que les stratĂ©gies de puissance retournĂ©espar lâapproche jeu Ă champ moyen approchent notablement les stratĂ©gies optimaleslorsquâelles peuvent ĂȘtre calculĂ©es, et dĂ©passent les performances desheuristiques communes, lorsque lâoptimum nâest plus calculable, comme câest lecas lorsque le canal varie au cours du temps.Dans la seconde partie de cettethĂšse, nous investiguons un possible problĂšme dual au problĂšme prĂ©cĂ©dent. PlusspĂ©cifiquement, nous considĂ©rons une approche dâoptimisation dâefficacitĂ© spectrale,Ă configuration de puissance constante. Pour ce faire, nous proposonsalors dâĂ©tudier lâimpact sur le rĂ©seau des rĂ©centes avancĂ©es en classification dâinterfĂ©rence.Lâanalyse conduite rĂ©vĂšle que le systĂšme peut bĂ©nĂ©ficier dâuneadaptation des traitements dâinterfĂ©rence faits Ă chaque rĂ©cepteur. Ces gainsobservĂ©s peuvent Ă©galement ĂȘtre amĂ©liorĂ©s par deux altĂ©rations de la dĂ©marchedâoptimisation. La premiĂšre propose de redĂ©finir les groupes dâinterfĂ©reurs decellules concurrentes, supposĂ©s transmettre sur les mĂȘmes ressources spectrales.Lâobjectif Ă©tant alors de former des paires dâinterfĂ©reurs âamisâ, capables detraiter efficacement leurs interfĂ©rences rĂ©ciproques. La seconde altĂ©ration portele nom de âVirtual Handoverâ : lorsque la classification dâinterfĂ©rence est considĂ©rĂ©e,lâaccess point offrant le meilleur SNR nâest plus nĂ©cessairement le meilleuraccess point auquel assigner un utilisateur. Pour cette raison, il est donc nĂ©cessairede laisser la possibilitĂ© au systĂšme de pouvoir choisir par lui-mĂȘme la façondont il procĂšde aux assignations des utilisateurs. Le processus dâoptimisationse dĂ©compose donc en trois parties : i) DĂ©finir les coalitions dâutilisateurs assignĂ©sĂ chaque access point ; ii) DĂ©finir les groupes dâinterfĂ©reurs transmettantsur chaque ressource spectrale ; et iii) DĂ©finir les stratĂ©gies de transmissionet les traitements dâinterfĂ©rences optimaux. Lâobjectif de lâoptimisationest alors de maximiser lâefficacitĂ© spectrale totale du systĂšme aprĂšs traitementde lâinterfĂ©rence. Les diffĂ©rents algorithmes utilisĂ©s pour rĂ©soudre, Ă©tape parĂ©tape, lâoptimisation globale du systĂšme sont dĂ©taillĂ©s. Enfin, des simulationsnumĂ©riques permettent de mettre en Ă©vidence les gains de performance potentielsofferts par notre dĂ©marche dâoptimisation
Joint Optimization of Resource Allocation and User Association in Multi-Frequency Cellular Networks Assisted by RIS
Due to the development of communication technology and the rise of user
network demand, a reasonable resource allocation for wireless networks is the
key to guaranteeing regular operation and improving system performance. Various
frequency bands exist in the natural network environment, and heterogeneous
cellular network (HCN) has become a hot topic for current research. Meanwhile,
Reconfigurable Intelligent Surface (RIS) has become a key technology for
developing next-generation wireless networks. By modifying the phase of the
incident signal arriving at the RIS surface, RIS can improve the signal quality
at the receiver and reduce co-channel interference. In this paper, we develop a
RIS-assisted HCN model for a multi-base station (BS) multi-frequency network,
which includes 4G, 5G, millimeter wave (mmwave), and terahertz networks, and
considers the case of multiple network coverage users, which is more in line
with the realistic network characteristics and the concept of 6G networks. We
propose the optimization objective of maximizing the system sum rate, which is
decomposed into two subproblems, i.e., the user resource allocation and the
phase shift optimization problem of RIS components. Due to the NP-hard and
coupling relationship, we use the block coordinate descent (BCD) method to
alternately optimize the local solutions of the coalition game and the local
discrete phase search algorithm to obtain the global solution. In contrast,
most previous studies have used the coalition game algorithm to solve the
resource allocation problem alone. Simulation results show that the algorithm
performs better than the rest of the algorithms, effectively improves the
system sum rate, and achieves performance close to the optimal solution of the
traversal algorithm with low complexity.Comment: 18 page
- âŠ