Showing papers by "Bernard Cousin published in 2015"

A Network-Assisted Approach for RAT Selection in Heterogeneous Cellular Networks

Abstract: When several radio access technologies (e.g., HSPA, LTE, WiFi, and WiMAX) cover the same region, deciding to which one mobiles connect is known as the Radio Access Technology (RAT) selection problem. To reduce network signaling and processing load, decisions are generally delegated to mobile users. Mobile users aim to selfishly maximize their utility. However, as they do not cooperate, their decisions may lead to performance inefficiency. In this paper, to overcome this limitation, we propose a network-assisted approach. The network provides information for the mobiles to make more accurate decisions. By appropriately tuning network information, user decisions are globally expected to meet operator objectives, avoiding undesirable network states. Deriving network information is formulated as a semi-Markov decision process (SMDP), and optimal policies are computed using the Policy Iteration algorithm. Also, and since network parameters may not be easily obtained, a reinforcement learning approach is introduced to derive what to signal to mobiles. The performances of optimal, learning-based, and heuristic policies, such as blocking probability and average throughput, are analyzed. When tuning thresholds are pertinently set, our heuristic achieves performance very close to the optimal solution. Moreover, although it provides lower performance, our learning-based algorithm has the crucial advantage of requiring no prior parameterization.

Leveraging Light Forest With Rateless Network Coding to Design Efficient All-Optical Multicast Schemes for Elastic Optical Networks

Abstract: In this paper, we study the multicast-capable routing, modulation, and spectrum assignment (MC-RMSA) schemes that consider the physical impairments from both the transmission and light splitting in elastic optical networks (EONs). Specifically, we propose to provision each multicast request with a light forest, which consists of one or more light trees to avoid the dilemma that because of the accumulated physical impairments, a relatively large light tree may have to use the lowest modulation level, and, hence, consume too many frequency slots (FS'). In order to further improve the spectral efficiency and compensate for the differential delays among the light trees, we incorporate the rateless network coding (R-NC) in the multicast system. We first formulate an integer linear programming (ILP) model to solve the problem for static network planning. Then, we propose three time-efficient heuristics that leverage the set-cover problem and utilize layered auxiliary graphs. The simulation results indicate that in both the ILP and heuristics, the MC-RMSA with R-NC can achieve better performance on the maximum index of used FS' than that without. After that we evaluate the heuristics in a dynamic network provisioning. The results show that the MC-RMSA with R-NC can effectively improve the performance of all-optical multicast in EONs to reduce the blocking probability.

A multipath energy-conserving routing protocol for wireless ad hoc networks lifetime improvement

Abstract: Ad hoc networks are wireless mobile networks that can operate without infrastructure and without centralized network management. Traditional techniques of routing are not well adapted. Indeed, their lack of reactivity with respect to the variability of network changes makes them difficult to use. Moreover, conserving energy is a critical concern in the design of routing protocols for ad hoc networks, because most mobile nodes operate with limited battery capacity, and the energy depletion of a node affects not only the node itself but also the overall network lifetime. In all proposed single-path routing schemes a new path-discovery process is required once a path failure is detected, and this process causes delay and wastage of node resources. A multipath routing scheme is an alternative to maximize the network lifetime. In this paper, we propose an energy-efficient multipath routing protocol, called AOMR-LM (Ad hoc On-demand Multipath Routing with Lifetime Maximization), which preserves the residual energy of nodes and balances the consumed energy to increase the network lifetime. To achieve this goal, we used the residual energy of nodes for calculating the node energy level. The multipath selection mechanism uses this energy level to classify the paths. Two parameters are analyzed: the energy threshold beta and the coefficient alpha. These parameters are required to classify the nodes and to ensure the preservation of node energy. Our protocol improves the performance of mobile ad hoc networks by prolonging the lifetime of the network. This novel protocol has been compared with other protocols: AOMDV and ZD-AOMDV. The protocol performance has been evaluated in terms of network lifetime, energy consumption, and end-to-end delay.

Classification and comparative analysis of inter-cell interference coordination techniques in LTE networks

Abstract: Frequency reuse-1 model is required to satisfy the exponential increase of data demands in mobile networks, such as the Long Term Evolution (LTE) of Universal Mobile Terrestrial radio access System (UMTS). However, the simultaneous usage of the same frequency resources in adjacent LTE cells creates inter-cell interference problems, that mainly affect cell-edge users. Inter-Cell Interference Coordination (ICIC) techniques are proposed to avoid the negative impact of interference on system performance. They establish restrictions on resource usage, such as Fractional Frequency Reuse (FFR), and on power allocation such as Soft Frequency Reuse (SFR). In this paper, we classify the existing ICIC techniques, and investigate the performance of reuse-1, reuse-3, FFR, and SFR schemes under various user distributions, and for various network loads. Performance of cell-center and cell-edge users are inspected, as well as the overall spectral efficiency. System level simulations show the advantages and limitations of each of the examined techniques compared to frequency reuse-1 model under different network loads and user distributions, which helps us to determine the most suitable ICIC technique to be used.

On the legacy amplifier limitation in flexgrid optical networks

Abstract: Flexgrid technology is an interesting solution to improve network capacity. However, for a given spectral band, it gives rise to the increase of the number of channels, requiring more amplification power in respect with the conventional fixed grid technology. In this work, we demonstrate that re-engineering the link margins allows supporting this increase while keeping in use legacy amplifiers.

Non-Cooperative Inter-Cell Interference Coordination Technique for Increasing Throughput Fairness in LTE Networks

Abstract: One major concern for operators of Long Term Evolution (LTE) networks is mitigating inter-cell interference problems. Inter-Cell Interference Coordination (ICIC) techniques are proposed to reduce performance degradation and to maximize system capacity. It is a joint resource allocation and power allocation problem that aims at controlling the trade-off between resource efficiency and user fairness. Traditional interference mitigation techniques are Fractional Frequency Reuse (FFR) and Soft Frequency Reuse (SFR). FFR statically divides the available spectrum into reuse-1 and reuse-3 portions in order to protect cell-edge users, while SFR reduces downlink transmission power allocated for cell-center resources to protect vulnerable users in the neighboring cells. However, these static techniques are not adapted to non-uniform user distribution scenarios, and they do not provide guarantees on throughput fairness between user equipments. In this paper, we introduce a non-cooperative dynamic ICIC technique that dynamically adjusts resource block allocation according to user demands in each zone. We investigate the impact of this technique on throughput distribution and user fairness under non-uniform user distributions, using an LTE downlink system level simulator. Simulation results show that the proposed technique improves system capacity, and increases throughput fairness in comparison with reuse-1 model, FFR and SFR. It does not require any cooperation between base stations of the LTE network.

Evaluation of gateway-based shaping methods for HTTP Adaptive Streaming

Abstract: HTTP Adaptive Streaming (HAS) is a streaming video technique commonly employed over best-effort networks. However, it is characterized by some issues that harm its quality of experience (QoE) in cases of daily use. The main use case of the present investigation involves HAS clients competing for bandwidth inside the same home network. Based on related work, we found that one of the most convenient solutions for this use case is to define a bandwidth manager, on the gateway side, that divides the available home bandwidth between HAS clients. Two main methods have previously been proposed to shape the HAS streams in accordance with the bandwidth manager's direction and are referred to as gateway-based shaping methods: a highly renowned method, Hierarchical Token Bucket Method (HTBM), that uses the hierarchical token bucket queuing discipline, and another method, Receive Window Tuning Method (RWTM), that employs TCP flow control by handling only acknowledgment TCP packets. In this paper, we compare these two shaping methods. Results indicate that RWTM improves the QoE better than HTBM and does not add queuing delay. Results were validated through experimentation and objective QoE analytical criteria.

A heuristic algorithm for joint power-delay minimization in green wireless access networks

Abstract: In this paper, we seek to jointly minimize the network power consumption and the user transmission delays in green wireless access networks. We recently studied the case of a WLAN, where we evaluated the tradeoffs between these two minimization objectives using a Mixed Integer Linear Programming (MILP) formulation. However, the MILP formulation could not deliver solutions in a reasonable amount of time due to computational complexity issues. As a result, we propose here a heuristic algorithm for the power-delay minimization problem. The proposed heuristic aims to compute the transmit power level of the Access Points (APs) deployed in the network and associate users with these APs in a way that jointly minimizes the total network power and the total network delay. The simulation results show that the proposed algorithm has a low computational complexity, which makes it advantageous compared with the optimal scheme, particularly in dense networks. Moreover, the heuristic algorithm performs close to optimally and provides power savings of up to 45% compared with legacy networks.

Pricing strategies in multi-operator heterogeneous wireless networks

Abstract: In this paper, three pricing scenarios are proposed to set the transaction cost of the inter-operators agreement in a multi-operator cooperative environment. An analysis, of the operators' profits, is performed for these cooperation scenarios and different price sharing models are investigated for comparison. First, we describe the proposed pricing scenarios, the motivation behind and the points of evaluation for each scenario. Then, we present the hybrid decision algorithm for the selection of the access in a multioperator wireless networks environment. Next, we present two business models made for the simulation, in order to highlight how network conditions and operator's strategy for service price may affect the profitability of the cooperation. Simulation results show that proposed pricing models guarantee profit gain for the cooperating operators, and are suitable in a multi-operator sharing environment. A best pricing scenario can be decided depending on the deployed capacity for sharing and the user's service price settings.

Comparison between access selection algorithms in multi-operator wireless networks

Abstract: In fifth generation mobile network, Radio Access Network sharing is an attractive solution for operators to counter the traffic growth and build cost-effective networks in order to improve coverage and capacity at reasonable investments and operational costs. It consists of sharing radio access resources between two or more operators. In such multi-operator environment access selection decision is an important issue for the mobile user and his home operator which the user has contract with. In literature, the majority of access selection algorithms are based on game theory which is very complex for implementation and the decision is slower in comparison with Multiple Attributes Decision Making (MADM) methods. In this paper, we apply Simple Additive Weighting (SAW) methods and Nearest Performance Handover (NPH) algorithm for the access selection in a multi-operator environment. These algorithms based on MADM were initially conceived for the selection decision in a single operator environment. In addition, we compare the performance of these algorithms with our previously proposed cost function for the access selection in a multi-operator sharing network. Performance analyses are made in terms of user blocking percentages and global achieved profit. Simulation results showed that our decision algorithm guarantee the lowest blocking probability for all operators, it prevents overloading operator's with high numbers of guest users which affect own clients acceptance. In addition, it improves global achieved profits for all cooperating operators. However, SAW methods showed better performance than NPH concerning users blocking percentages, but NPH guarantees higher profits than SAW methods for the operators with limited capacity.

Access selection and joint pricing in multi-operator wireless networks: A Stackelberg game

Abstract: We investigate in this paper the access selection and joint pricing problem in multi-operator wireless networks. The problem is formulated as a Stackelberg game, where cooperating service operators first set the service price to maximize their revenue. Then, the home operator of the mobile user performs the access selection process among the service operators, in order to maximize its own profits and its client satisfaction, in terms of perceived QoS. Competing operators decide the service price following a number of defined pricing schemes, and the home operator uses a hybrid utility function for the selection decision. We consider the Nash equilibrium as a solution of the service price setting game, where the best response is presented in function of the adopted pricing scheme. Simulation results show the efficiency of this multi-leader follower game for the access selection in a multi-operator environment, and illustrate how operators' cooperation enhances network performance and improves operators' revenue.

Energy-Aware Forwarding Strategy for Metro Ethernet Networks

Abstract: Energy optimization has become a crucial issue in the realm of ICT. This paper addresses the problem of energy consumption in a Metro Ethernet network. Ethernet technology deployments have been increasing tremendously because of their simplicity and low cost. However, much research remains to be conducted to address energy efficiency in Ethernet networks. In this paper, we propose a novel Energy Aware Forwarding Strategy for Metro Ethernet networks based on a modification of the Internet Energy Aware Routing (EAR) algorithm. Our contribution identifies the set of links to turn off and maintain links with minimum energy impact on the active state. Our proposed algorithm could be a superior choice for use in networks with low saturation, as it involves a tradeoff between maintaining good network performance and minimizing the active links in the network. Performance evaluation shows that, at medium load traffic, energy savings of 60% can be achieved. At high loads, energy savings of 40% can be achieved without affecting the network performance.

Coopération dans les réseaux d'accès 5G multi-Opérateurs

Abstract: La cinquieme generation de reseaux mobiles (5G) doit surmonter les nouveaux defis qui sont apparus avec la croissance explosive de la demande de trafic mobile. En fait, le trafic mondial de donnees mobiles a augmente de 69% en 2014, et il est prevu d'augmenter de pres de dix fois entre 2014 et 2019 [1]. Cette croissance de trafic est accompagnee par l'augmentation du nombre de peripheriques mobiles connectes et l'enorme augmentation de la demande de donnees par rapport a l'utilisation de la voix ce qui affecte negativement les revenus de l'operateur. Ainsi, les operateurs de reseaux mobiles (ORM) cherchent a ameliorer leurs reseaux afin d'elargir la couverture, augmenter la capacite, soutenir des debits plus eleves et ameliorer la qualite de service d'une maniere plus efficace concernant les couts et la consommation d'energie. Par consequent, les ORM doivent envisager de nouveaux investissements pour l'amelioration du reseau, le deploiement de nouvelle technologie et l'optimisation de couverture et capacite, tout en considerant les delais de commercialisation et la conservation d'un equilibre optimal entre les benefices et les couts. Le partage de reseaux est une approche puissante qui peut aider a accelerer l'expansion de la couverture, de reduire la periode de deploiement et d'optimiser l'utilisation des ressources. En outre, il est efficace pour des reductions supplementaires de cout de CAPEX. Dans ce travail, nous considerons un environnement multi-operateurs ou plusieurs OMR partagent leurs acces radio, de sorte qu'un utilisateur mobile peut etre servi dans le reseau de son operateur de domicile (avec lequel il a fait un contrat) ou dans le reseau d'un operateur de service partenaire. Dans un tel environnement, nous etudions la selection d'acces et la tarification de service entre les operateurs dans l'objectif de montrer les benefices de la cooperation entre les operateurs dans un partage de reseaux, offrir de differentes approches pour aider les operateurs a la selection d'acces. Dans ce contexte, nous avons propose deux algorithmes de selection d'acces : le premier exploite la simplicite des algorithmes MADM (Multiple Attribute Decision Making) et specifiquement SAW (Simple Additive Weighting) [2-4], pour construire une fonction de cout adoptee pour la selection de l'operateur de service. Cet algorithme est appele NP-BPA (Nearest Performance and Best Profit Algorithm), il adopte une decision hybride pour la selection de l'acces afin de garantir la satisfaction de l'utilisateur ainsi que le gain global pour tous les operateurs concernes. La fonction de cout combine les exigences de la demande de l'utilisateur mobile et le profit resultant de l'operation de l'utilisateur. En outre, cette fonction tient compte de la strategie de l'operateur pour la decision de selection, en l’exprimant explicitement par deux coefficients. La comparaison de performance de notre algorithme avec d’autre methode MADM specifiquement SAW et NPH a montrer l’efficacite de notre methode de selection en terme de probabilite de blocage et de profit global realise. Les resultats des simulations ont montre que notre algorithme de decision garantit la plus faible probabilite de blocage pour tous les operateurs comme il evite les surcharges des reseaux. En outre, il ameliore les benefices globaux obtenus pour tous les operateurs concernes. De plus, les resultats montrent que l'algorithme de selection propose satisfait les preferences de l'utilisateur pour la qualite de service percue et le prix paye, et donne aux operateurs la possibilite d'exprimer leur strategie lors de l'execution de la decision, et de controler ainsi la selection d'acces en variant les deux coefficients de la strategie dans la fonction de cout.