Sana Ben Jemaa

Orange Labs, Rhône-Alpes, France

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Publications (21)2.06 Total impact

  • X. Gelabert, B. Sayrac, S. Ben Jemaa
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    ABSTRACT: A self-organizing network (SON) is effectively realized by means of specific SON mechanisms $(hbox{SON}_{rm m})$, which relate to particular SON use cases $(hbox{SON}_{rm uc})$, these being defined by the Third-Generation Partnership Project (3GPP) and Next Generation Mobile Networks (NGMN). Typically, $hbox{SON}_{rm uc}$ are grouped into self-configuration, self-optimization, and self-healing functions. Focusing on self-optimization, $ hbox{SON}_{rm m}$ therein aim at maintaining relevant key performance indicators (KPIs) above/below a specific target by actuating over an appropriate set of input parameters to achieve predefined network objectives. Typically, this problem is represented by several control loops where controllable input parameters are dynamically adjusted according to output measurable metrics and their corresponding target requirements. From an implementation viewpoint, the concept of a single SON “black box,” integrating multiple $hbox{SON}_{rm m}$, is very appealing. However, this approach may threaten the control that network operators (NOPs) have over their own network. As a result, a coordinated framework involving stand-alone $hbox{SON}_{rm m}$ is proposed. Here, a SON controller $(hbox{SON}_{rm c})$ may be implemented responding to strategies, deciding at a given time which $hbox{SON}_{rm m}$ actions have higher priority with respect to others. In the context of a heterogeneous network (Het- et) scenario, we propose and develop a simplified framework where stand-alone $hbox{SON}_{rm m}$ react to either overshot or undershot KPI events by deciding to either increase or decrease corresponding influential parameter(s). By inspecting the arising interactions and possible conflicts between several $hbox{SON}_{rm m}$, we provide, for a specific evaluation scenario, a heuristic strategy-based solution for SON coordination, which may eventually trade off high-level NOP goals.
    IEEE Transactions on Vehicular Technology 01/2014; 63(3):1320-1334. · 2.06 Impact Factor
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    ABSTRACT: Coverage prediction is one of the most important aspects of cellular network optimisation for mobile operators due to the highly competitive market conditions and the obligations towards the regulatory authorities. Although wireless communications research is considerably diversifying, including new areas, problems and concepts with a notable pace, cellular coverage still remains as a core subject of research for operators because of the obligation to adapt to the continuously evolving wireless ecosystem, with new radio access technologies/architectures, emerging applications and innovative cellular concepts. This paper presents the application of a powerful mathematical tool coming from spatial statistics, Bayesian kriging, to construct a radio environment map (REM) for the purpose of cellular coverage prediction as an emerging application of cognitive radio techniques in cellular networks. The proposed approach provides an efficient alternative to the conventional manual coverage prediction on the basis of drive tests, which are expensive, polluting and slow solutions for obtaining the ‘ground-truth’ information. Bayesian kriging-based REMs allow to estimate the coverage situation in those regions where the operator lacks direct information. Our approach can be directly used by operators for the cellular network coverage optimisation. We evaluate the accuracy of the proposed REM construction approach for a long term evolution network with two mesh sizes using highly realistic data sets. Results show that the Bayesian kriging interpolation technique has a good accuracy for cellular coverage prediction, and this accuracy is directly related with the mesh size. Copyright © 2013 John Wiley & Sons, Ltd.
    Transactions on Emerging Telecommunications Technologies. 11/2013; 24(7-8).
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    ABSTRACT: Despite the remarkable progress in radio access technology to support the rapidly increasing wireless data demand, coverage analysis remains as one of the indispensable topics on which mobile operators still need innovations, above all, in terms of operational efficiency together with performance. Manual coverage detection and prediction is an inefficient and costly task. In this paper we show how Radio Environment Maps (REMs) developed as part of the research on cognitive wireless networks can be used as a basis for a powerful coverage estimation and prediction solution for present-day cellular networks. Applying powerful spatial interpolation techniques on the information coming from location-aware devices, REMs provide a realistic and remote representation of the ground-truth. The proposed approach automatically identifies the number, location and shape of the existing coverage holes and therefore constitutes a perfect example of a novel application of the Cognitive Radio concept on next generation cellular networks. Results on urban and rural environments show that the use of REM brings promising gains in coverage hole detection and prediction with respect to the case where only measurements are used.
    Cognitive Radio Oriented Wireless Networks (CROWNCOM), 2013 8th International Conference on; 01/2013
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    ABSTRACT: The existence of coverage holes in cellular networks is a common problem for mobile operators. Traditionally, the cellular coverage is computed using sophisticated planning tools, and then optimized through drive tests. With the drive tests information, the operators detect the poorly covered areas and take actions to eliminate them. The introduction of self-organized or “cognitive” techniques, would allow the operators to maximize the network's information obtained through drive tests or reported by the mobile users. In this paper we propose the use of spatial Bayesian geo-statistics to build a Radio Environment Map (REM) for real coverage hole detection purposes. Results show that the number of pixels forming the coverage holes, as well as the probability of detecting them, can be significantly increased with the use of REMs, compared to the case where only network measurements are used.
    Modeling & Optimization in Mobile, Ad Hoc & Wireless Networks (WiOpt), 2013 11th International Symposium on; 01/2013
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    ABSTRACT: Cellular operators routinely use sophisticated planning tools to estimate the coverage of the network based on building and terrain data combined with detailed propagation modeling. Nevertheless, coverage holes still emerge due to equipment failures, or unforeseen changes in the propagation environment. For detecting these coverage holes, drive tests are typically used. Since carrying out drive tests is expensive and time consuming, there is significant interest in both improving the quality of the coverage estimates obtained from a limited number of drive test measurements, as well as enabling the incorporation of measurements from mobile terminals. In this paper we introduce a spatial Bayesian prediction framework that can be used for both of these purposes. We show that using techniques from modern spatial statistics we can significantly increase the accuracy of coverage predictions from drive test data. Further, we carry out a detailed evaluation of our framework in urban and rural environments, using realistic coverage data obtained from an operator planning tool for an operational cellular network. Our results indicate that using spatial prediction techniques can more than double the likelihood of detecting coverage holes, while retaining a highly acceptable false alarm probability.
    01/2012;
  • S. Grimoud, S. Ben Jemaa, B. Sayrac, E. Moulines
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    ABSTRACT: Optimizing the network performance is a key objective for cellular operators as over-provisioning a network is definitely not a cost-effective solution. However the trend for the upcoming 4G networks is to simplify the planning procedure and to improve the spectral efficiency by using agressive frequency reuse schemes, e.g reuse-1, in the downlink. In this paper, we show that this is not a suitable configuration in terms of network performance and describe a simple Radio Environment Map (REM) enabled soft frequency reuse (SFR) scheme which improves the user throughput of about 14%.
    GLOBECOM Workshops (GC Wkshps), 2010 IEEE; 01/2011
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    ABSTRACT: The Radio Environment Map (REM) stores radio envi- ronmental information that can be used to enhance cognitive radio resource management in wireless networks. In this paper, we propose an iterative REM building process based on Kriging interpolation technique that builds the REM using geolocated measurements per- formed by mobile terminals. As terminal measurements are costly in terms of signalling and battery consumption, we propose an algorithm that chooses the most appropriate measurements to be requested to the mobiles. We compare the performance of this algorithm with a random choice of measurements and show that our algorithm reduces the squared error of the power map by 16%. The proposed algorithm has also the merit of being fast enough to be implemented in an online fashion.
    01/2011;
  • Xavier Gelabert, Berna Sayraç, Sana Ben Jemaa
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    ABSTRACT: The Self Organizing Network (SON) concept is a promising paradigm aiming to reduce both the capital and operational expenditures (CAPEX/OPEX) in future wireless networks through efficient self-configuration, self-optimization and self-healing functionalities. As for self-optimization, much effort has been devoted to standalone SON control loops, which, upon network metric observation, dynamically adjust the appropriate network parameters to enhance the overall network performance. However, less explored simultaneous operation of several SON control loops may cause conflicts between parameter adjustment and/or metric performance outcome. This paper focuses on SON mechanism interactions, providing a framework for further understanding and analysis. A basic two-SON mechanism interaction scenario will be provided along with an initial assessment of a simple SON interaction control.
    IEEE 22nd International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2011, Toronto, ON, Canada, September 11-14, 2011; 01/2011
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    ABSTRACT: Abstract-In this paper we propose a Bayesian approach for estimating parameters of the radio propagation model, and an iterative Kriging interpolation algorithm for choosing the best candidate measurement to be retrieved into the Radio Environment Map (REM). We compare the performance with a random choice of the candidate measurement and show that our algorithm reduces the amount of measurement needed by 33%. The proposed algorithm has also the merit of being fast enough to be implemented in an online fashion for REMs with a grid size of 25m and for pedestrian mobile speeds.
    Proceedings of the 74th IEEE Vehicular Technology Conference, VTC Fall 2011, 5-8 September 2011, San Francisco, CA, USA; 01/2011
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    ABSTRACT: This paper deals with mobile-centered decision making in heterogeneous networks, where intelligent mobile terminals take autonomous decisions about the JRRM actions, consisting to connect to one of the available systems. This distributed decision-making is possible due to Q-learning algorithms implemented within the mobile terminals that enable them to profit from their past experience in order to enhance their subsequent decisions. We develop an original Markovian model that allows analyzing analytically the evolution of the Q-learning process and show how the the performance is enhanced until convergence.
    Proceedings of the IEEE 21st International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2010, 26-29 September 2010, Istanbul, Turkey; 01/2010
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    ABSTRACT: In this paper, we focus on mobile-centered decision making in heterogeneous networks. We study the case where the JRRM decision is completely distributed so that mobile users have to decide to which of the available systems it is best to connect. To optimize their decision over the time, the mobiles implement a Q-learning algorithm that enables them to profit from their past experience. We study the performance of this decision-making framework in the case of a WiMAX/HSDPA heterogeneous network and show that the mobile decision is progressively enhanced until convergence.
    Wireless Communications and Networking Conference, 2009. WCNC 2009. IEEE; 01/2009
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    ABSTRACT: This paper describes a simple but effective concept in cognitive networks that provides awareness on the radio environment through geo-localized interference measurements: the interference cartography. The purpose of this novel concept is to combine location information with radio measurements carried out over the heterogeneous radio environment, and to provide a complete view of the environment to be used in autonomous decision making in a cognitive context. This is achieved by aggregating the already existing radio measurements that circulate in wireless networks forming the heterogeneous network panorama, combining this aggregated information with geo-localization information, performing advanced signal processing techniques to render the information complete and reliable, and updating the information to provide a viable picture of the environment for efficient detection, analysis and decision. Our focus is on hierarchical access models where licensed spectrum can be accessed by secondary users without creating harmful interference on the primaries. A complete description of a possible network implementation in a hierarchical access scheme is given, with a centralized architecture and a protocol structure that complies with the utilization of interference cartography. A case study of the proposed scheme is also given, demonstrating the utility of the notion of interference cartography.
    New Frontiers in Dynamic Spectrum Access Networks, 2008. DySPAN 2008. 3rd IEEE Symposium on; 11/2008
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    ABSTRACT: In this paper, we focus on the joint radio resource management (RRM) for HSDPA/WiMAX cooperation. We use a generic Markovian model to model the evolution of data calls in a multi-cell and multi-access context. We apply this model to a cooperative WiMAX/HSDPA network considering both inter-cell and vertical handovers and calculate the steady-state probabilities and the performance indicators taking into account intra-cell and inter-cell mobility. Then, we detail two RRM approaches: a game-theory based RRM approach and a RRM approach based on the maximization of the global network utility. In the first approach, the RRM decision is taken by the mobile terminals (MTs) but the network takes over if necessary, while the second approach is completely network-centric. Finally, we compare both RRM approaches on the basis of the defined performance indicators. The main results show that the game-theoretic method achieves better performances than the global-utility maximization method.
    Proceedings of IEEE International Conference on Communications, ICC 2008, Beijing, China, 19-23 May 2008; 01/2008
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    ABSTRACT: This paper introduces interference cartography, a simple and effective concept that helps detect, identify and use spectrum opportunities in a secondary spectrum usage context. Interference cartography combines measurements performed by different network entities (mobile terminals, base stations, access points) with the geo-location information and applies simple and effective spatial interpolation techniques to achieve a map which indicates the level of interference experienced at each mesh over the area of interest. Using this information, a secondary network can detect the presence of a primary network (or of other secondary networks) and can use spectrum opportunities without causing harmful interference to them. As an example, a reliable spatial interpolation technique, kriging, is applied to interference data obtained from a radio network simulator. Obtained results demonstrate that interference cartography is a promising concept that can enhance the performance of secondary spectrum usage.
    Proceedings of the IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2008, 15-18 September 2008, Cannes, French Riviera, France; 01/2008
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    ABSTRACT: In this paper, we develop a generic Markovian model to study the dynamics of data service in a multi-cell context, and apply it to cells served by HSDPA and WiMAX access networks. We first present analytical models for interference and throughputs in WiMAX and HSDPA. Then, we consider a cooperative WiMAX/HSDPA network considering both inter-cell and vertical handovers and show how to calculate the steady-state probabilities and the performance indicators. Our calculations take into account mobility within the cell and between different cells and make us able to calculate intra and inter-cell dropping. We compare the performances of three joint Radio Resource Management (RRM) policies: HSDPA/WiMAX traffic distribution policy, HSDPA filling policy and WiMAX filling policy. Our numerical results show that the policy favoring WiMAX access and considering HSDPA as a rescue system (WiMAX filling policy) offers the best performances.
    WCNC 2008, IEEE Wireless Communications & Networking Conference, March 31 2008 - April 3 2008, Las Vegas, Nevada, USA, Conference Proceedings; 01/2008
  • S. Horrich, S. Ben Jemaa, P. Houze
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    ABSTRACT: This paper presents a policy-based radio resource management model for decision sharing between the network and the mobile terminals in composite networks. One of the key issues discussed in this paper is the distribution of RRM decision making between the network and the mobile terminal. IEEE P1900.4 standard project proposes a policy-based radio resource usage scheme where the network orients the mobile terminals decisions by sending rules and constraints. Mobile terminals choose the most appropriate action to their own QoS objectives, within the action set allowed by the network. We propose a joint RRM framework based on this standard project and we discuss both policies definition on the network side and decision making on the mobile terminal side. We propose a model where policies are chosen automatically according to the variations of the environment conditions and the operator strategy. On the mobile terminal side, we propose to introduce a time constraint imposed by the network for policy execution in order to coordinate the resulting terminals' actions execution over time. Moreover, as final decisions are made by MTs in a distributed way, we discuss the modeling of this problem using cooperative and non cooperative games approaches.
    Personal, Indoor and Mobile Radio Communications, 2007. PIMRC 2007. IEEE 18th International Symposium on; 10/2007
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    ABSTRACT: For cognitive radio one of the most challenging issue is how to get the intelligence necessary to make the best possible allocation decision. Techniques such as sensing to get the information on the occupancy of the radio environment are being discussed. And designing terminals with scanning/sensing capabilities is a vibrant research topic; such terminals, and the sensing principles, can be very helpful when limited parts of spectrum are to be scanned. But in cases where there is no knowledge about the amount of spectrum to be scanned, this can result in time-and power-consuming operations. An alternative approach, described in this paper, consists of a "Cognition supporting Pilot Channel" (CPC) which directly provides relevant information to the terminal. This paper looks at the concept of this CPC, it initially describes the expected functionality and discusses the regulatory implications such a cognition supporting pilot channel, in the context of flexible spectrum management faces.
    Mobile and Wireless Communications Summit, 2007. 16th IST; 08/2007
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    ABSTRACT: An important emerging capability is for mobile terminals to be dynamically reconfigured. Through ongoing advances in technology such as software defined radio, reconfiguration of mobile terminals will in the near future be achievable across all layers of the protocol stack. However, along with the capability for such wide-ranging reconfiguration comes the need to manage reconfiguration procedures. This is necessary to coordinate reconfigurations, to ensure that there are no negative effects (e.g. interference to other RATs) as a result of reconfigurations, and to leverage maximal potential benefits of reconfiguration and ensuing technologies such as those involving dynamic spectrum access. The IEEE P1900.4 working group is therefore defining three building blocks for reconfiguration management: network reconfiguration management (NRM), terminal reconfiguration management (TRM), and a radio enabler to provide connectivity between the NRM and TRMs. In this paper we concentrate on aspects of the radio enabler, highlighting its relevance in heterogeneous radio access scenarios, its advantages, and some aspects of its technical realization.
    New Frontiers in Dynamic Spectrum Access Networks, 2007. DySPAN 2007. 2nd IEEE International Symposium on; 05/2007
  • P. Houze, D. Ruiz, S. Ben Jemaa, P. Cordier
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    ABSTRACT: Future wireless communications will benefit from cognitive functionalities, operated by reconfigurable networks and terminals. In a context where any parameter could be adapted dynamically in an "always best connected" perspective, the spectrum allocation flexibility would be a powerful feature. In this paper, we study the technical feasibility of dynamic spectrum allocation in a multi-technology and multi-operator context. Firstly, the generic technical approach will be described; secondly, an algorithm, inspired by the cognitive radio cycle will then be proposed. An example of DSA simulation with legacy systems will be presented, in order to underline the algorithm validity.
    Wireless and Mobile Communications, 2007. ICWMC '07. Third International Conference on; 04/2007
  • P. Houze, S. Ben Jemaa, P. Cordier
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    ABSTRACT: The global beyond 3G system consists of several coexisting and cooperating access technologies. One of the key concepts of this global technology is the reconfigurability, that allows different network elements to dynamically adapt their configuration to the new conditions encountered in specific service areas and time. Reconfigurability may comprise dynamic spectrum allocation: a technique that varies spectrum allocation of different systems in order to meet changing demands. In this context of multiple access techniques and changing spectrum allocation, when a mobile is switched on, it has no information about the available systems in its area nor on the current spectrum allocation to these systems. In order to avoid the scanning of all the spectrum range and to facilitate the initial connection to the network, this paper proposes that the mobile listens first to a broadcast radio channel containing the necessary information to initiate its connection. The paper defines the content of this broadcast channel, denoted common pilot channel, and proposes a technical implementation
    Vehicular Technology Conference, 2006. VTC 2006-Spring. IEEE 63rd; 06/2006