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  • Grup de Recerca de Comunicacions Mòbils (GRCM)

     Casadevall Palacio, Fernando-jose; Sallent Roig, Jose Oriol; Pérez Romero, Jordi; Ferrús Ferré, Ramon; Umbert Juliana, Anna; Sanchez Gonzalez, Juan; Koutlia, Aikaterini; Raschella, Alessandro; Lu, Chengsui; Agusti Comes, Ramon
    Competitive project

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  • Redes móviles eficientes para la ampliación de servicios a nuevos sectores profesionales

     Agusti Comes, Ramon; Casadevall Palacio, Fernando-jose; Umbert Juliana, Anna; Sanchez Gonzalez, Juan; Pérez Romero, Jordi; Ferrús Ferré, Ramon; Sallent Roig, Jose Oriol
    Competitive project

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  • Spectrum Usage in Cognitive Radio Networks: From Field Measurements to Empirical Models

     López Benítez, Miguel; Casadevall Palacio, Fernando-jose
    IEICE transactions on communications
    Vol. E97-B, num. 2, p. 242-250
    DOI: 10.1587/transcom.E97.B.242
    Date of publication: 2014-02-01
    Journal article

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    Cognitive Radio (CR) is aimed at increasing the efficiency of spectrum utilization by allowing unlicensed users to access, in an opportunistic and non-interfering manner, some licensed bands temporarily and/or spatially unoccupied by the licensed users. The analysis of CR systems usually requires the spectral activity of the licensed system to be represented and characterized in a simple and tractable, yet accurate manner, which is accomplished by means of spectrum models. In order to guarantee the realism and accuracy of such models, the use of empirical spectrum occupancy data is essential. In this context, this paper explains the complete process of spectrum modeling, from the realization of field measurements to the obtainment of the final validated model, and highlights the main relevant aspects to be taken into account when developing spectrum usage models for their application in the context of the CR technology.

  • Fairness-based dynamic sub-carrier assignment for real time services in OFDMA networks

     Casadevall Palacio, Fernando-jose; Rodrigues, Emanuel B.
    European Wireless
    Presentation's date: 2014-05-16
    Presentation of work at congresses

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    Fairness is a crucial aspect for resource allocation in wireless systems, particularly in the downlink of 4G Orthogonal Frequency Division Multiple Access (OFDMA)-based systems. Therefore, it would be interesting for network operators to have tools to manage fairness in their systems. This work describes the utility-based ß-rule, which is a flexible resource allocation framework based on utility theory that is able to control delaybased fairness in a scenario with real time services in an OFDMAbased system. Not only can this framework be designed to work as well-known classical policies found in the literature, but also as an adaptive policy, which is able to meet a desired system fairness target. System-level simulations demonstrate that the adaptive policy is able to guarantee a fairness requirement by dynamically adapting a fairness-controlling parameter in the subcarrier assignment algorithm. It also presents better results than the classical policies in terms of cell capacity and user satisfaction.

  • A framework for multidimensional modelling of spectrum occupancy in the simulation of cognitive radio systems

     López Benítez, Miguel; Casadevall Palacio, Fernando-jose
    IEEE/IET International Symposium on Communication Systems, Networks & Digital Signal Processing
    p. 1-6
    Presentation's date: 2014-06-24
    Presentation of work at congresses

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    Spectrum models play a key role in the research of Dynamic Spectrum Access/Cognitive Radio (DSA/CR) systems. Models existing to date are able to characterise the statistical properties of spectrum occupancy in only one of its dimensions (time, frequency or space). However, to the best of the authors¿ knowledge, there is no model capable to account for the properties of spectrum occupancy in all its dimensions simultaneously. Since the development of a single model to characterise spectrum occupancy in such a holistic manner constitutes an extremely challenging task, this work explores an alternative based on the combination of existing dimension-specific models into a unified modelling approach. In particular, a framework is proposed for the integration of spectrum models that have been designed independently for a specific dimension of spectrum occupancy (time, frequency or space), thus enabling the multidimensional modelling of spectrum occupancy. A sophisticated simulation tool implementing state-of-the-art time, frequency and space dimension models is developed according to the proposed framework and used to generate synthetic spectrum data that simultaneously accounts for the properties of spectrum occupancy in all its dimensions. The use of such modelling framework in the contextof the simulation of DSA/CR systems is illustrated as well.

    Spectrum models play a key role in the research of Dynamic Spectrum Access/Cognitive Radio (DSA/CR) systems. Models existing to date are able to characterise the statistical properties of spectrum occupancy in only one of its dimensions (time, frequency or space). However, to the best of the authors’ knowledge, there is no model capable to account for the properties of spectrum occupancy in all its dimensions simultaneously. Since the development of a single model to characterise spectrum occupancy in such a holistic manner constitutes an extremely challenging task, this work explores an alternative based on the combination of existing dimension-specific models into a unified modelling approach. In particular, a framework is proposed for the integration of spectrum models that have been designed independently for a specific dimension of spectrum occupancy (time, frequency or space), thus enabling the multidimensional modelling of spectrum occupancy. A sophisticated simulation tool implementing state-of-the-art time, frequency and space dimension models is developed according to the proposed framework and used to generate synthetic spectrum data that simultaneously accounts for the properties of spectrum occupancy in all its dimensions. The use of such modelling framework in the contextof the simulation of DSA/CR systems is illustrated as well.

  • Capacity, fairness, and QoS trade-offs in wireless networks with applications to LTE

     Bezerra Rodrigues, Emanuel; Lima, Francisco J. M.; Casadevall Palacio, Fernando-jose; Porto Cavalcanti, Francisco Rodrigo
    DOI: 10.1007/978-1-4614-8057-0_4
    Date of publication: 2013-11-01
    Book chapter

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    Wireless mobile network optimization is a complex task that consists in achieving different design objectives such as spectral efficiency, energy efficiency, fairness, and quality of service. Radio resource allocation is responsible for managing the available resources in the radio access interface and, therefore, is an important tool for optimizing networks and achieving the designed objectives mentioned previously. However, in general all these network design objectives cannot be achieved at the same time by resource allocation strategies. In fact, different resource allocation strategies can be designed to maximize one objective in detriment of the other as well as to balance the objectives. In this chapter we deal with important trade-offs between contradicting objectives in modern wireless mobile networks: capacity versus fairness and capacity versus satisfaction. We present resource allocation strategies that can achieve static and adaptive performances when the previously mentioned trade-offs are considered. In order to design the resource allocation strategies we consider heuristics and utility-based solutions. System-level simulations show that the proposed techniques are powerful tools to the network operator, since they can decide in which trade-off point of the capacity-fairness or capacity-satisfaction planes they want to operate the system.

    Postprint (author’s final draft)

  • Energy and spectral efficiencies tradeoff with filter optimization in multiple access interference-aware networks

     Souza, Alvaro R.C.; Abrao, Taufik; Sampaio, Lucas H.; Jeszensky, Paul Jean E.; Pérez Romero, Jordi; Casadevall Palacio, Fernando-jose
    European transactions on telecommunications
    DOI: 10.1002/ett.2698
    Date of publication: 2013-08
    Journal article

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    In this contribution, the optimised deployment of both spectrum and energy resources scarcely available in the mobile multiple access systems has been analysed, with special attention to the impact of the filter design on the energy efficiency (EE) of code division multiple access networks. Putting into perspective two conflicting metrics, namely throughput maximisation and power consumption minimisation, the distributed EE utility function is formulated. We also show that the best EE versus spectral efficiency trade-off is achievable when each node allocates exactly the power necessary to attain the maximum EE. In order to demonstrate the validity of our analysis, a low-complexity energy-spectral-efficient algorithm based on distributed instantaneous signal-to-interference-plus-noise ratio level is developed, and the impact of single and multi-user detection filters on the EE¿spectral efficiency trade-off is extensively analysed by numerical simulation.

    In this contribution, the optimised deployment of both spectrum and energy resources scarcely available in the mobile multiple access systems has been analysed, with special attention to the impact of the filter design on the energy efficiency (EE) of code division multiple access networks. Putting into perspective two conflicting metrics, namely throughput maximisation and power consumption minimisation, the distributed EE utility function is formulated. We also show that the best EE versus spectral efficiency trade-off is achievable when each node allocates exactly the power necessary to attain the maximum EE. In order to demonstrate the validity of our analysis, a low-complexity energy-spectral-efficient algorithm based on distributed instantaneous signal-to-interference-plus-noise ratio level is developed, and the impact of single and multi-user detection filters on the EE–spectral efficiency trade-off is extensively analysed by numerical simulation.

  • Time-dimension models of spectrum usage for the analysis, design, and simulation of cognitive radio networks

     López Benítez, Miguel; Casadevall Palacio, Fernando-jose
    IEEE transactions on vehicular technology
    Vol. 62, num. 5, p. 2091-2104
    DOI: 10.1109/TVT.2013.2238960
    Date of publication: 2013-06
    Journal article

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    This paper addresses the problem of accurately modeling the spectrum occupancy patterns of real radio communication systems, which is an essential aspect in the study of cognitive radio (CR) networks. The main drawbacks and limitations of previous works are identified, and the methodological procedures on which they rely are improved and extended. Two sophisticated measurement platforms, providing low and high time resolutions, are used to obtain extensive real-world data from a multiband spectrum measurement campaign, embracing a wide variety of spectrum bands of practical interest for CR applications. A comprehensive, systematical, and rigorous analysis of the statistical properties observed in the measurement data is then performed to find accurate models capable of capturing and reproducing, within reasonable complexity limits, the statistical properties of temporal patterns, at both short and long timescales, in real wireless systems. Innovative modeling approaches capable of simultaneously describing statistical properties at both timescales are developed as well. In summary, this paper contributes realistic and accurate time-dimension spectrum usage models for their application to the study and development of CR.

    This paper addresses the problem of accurately modeling the spectrum occupancy patterns of real radio communication systems, which is an essential aspect in the study of cognitive radio (CR) networks. The main drawbacks and limitations of previous works are identified, and the methodological procedures on which they rely are improved and extended. Two sophisticated measurement platforms, providing low and high time resolutions, are used to obtain extensive real-world data from a multiband spectrum measurement campaign, embracing a wide variety of spectrum bands of practical interest for CR applications. A comprehensive, systematical, and rigorous analysis of the statistical properties observed in the measurement data is then performed to find accurate models capable of capturing and reproducing, within reasonable complexity limits, the statistical properties of temporal patterns, at both short and long timescales, in real wireless systems. Innovative modeling approaches capable of simultaneously describing statistical properties at both timescales are developed as well. In summary, this paper contributes realistic and accurate time-dimension spectrum usage models for their application to the study and development of CR

  • Signal uncertainty in spectrum sensing for cognitive radio

     López Benítez, Miguel; Casadevall Palacio, Fernando-jose
    IEEE transactions on communications
    Vol. 61, num. 4, p. 1231-1241
    DOI: 10.1109/TCOMM.2013.021413.110807
    Date of publication: 2013-05
    Journal article

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    The inability to perfectly know the system noise properties to infinite precision, referred to as noise uncertainty, results in noise power calibration errors that have been proven to impose fundamental limitations on the detection performance of any spectrum sensing (signal detection) method in cognitive radio networks. In this work we argue that the inability of cognitive radio users to perfectly know beforehand the primary signals that might be present in the sensed band and their properties, referred to as signal uncertainty in this work, also results in an additional detection performance degradation. The noise uncertainty consequences have widely been studied, verified experimentally and distilled into tractable mathematical models. However, the potential effects of the particular primary signal properties on the resulting detection probability of generic spectrum sensing algorithms, such as energy detection, have not been taken into account in the analysis and performance evaluation of spectrum sensing in cognitive radio networks. In this context, this work develops a mathematical model for signal uncertainty and, based on such model, analyzes the impact of signal uncertainty on the resulting detection performance of spectrum sensing, with and without noise uncertainty, and compares the practical consequences of both degrading effects.

    The inability to perfectly know the system noise properties to infinite precision, referred to as noise uncertainty, results in noise power calibration errors that have been proven to impose fundamental limitations on the detection performance of any spectrum sensing (signal detection) method in cognitive radio networks. In this work we argue that the inability of cognitive radio users to perfectly know beforehand the primary signals that might be present in the sensed band and their properties, referred to as signal uncertainty in this work, also results in an additional detection performance degradation. The noise uncertainty consequences have widely been studied, verified experimentally and distilled into tractable mathematical models. However, the potential effects of the particular primary signal properties on the resulting detection probability of generic spectrum sensing algorithms, such as energy detection, have not been taken into account in the analysis and performance evaluation of spectrum sensing in cognitive radio networks. In this context, this work develops a mathematical model for signal uncertainty and, based on such model, analyzes the impact of signal uncertainty on the resulting detection performance of spectrum sensing, with and without noise uncertainty, and compares the practical consequences of both degrading effects

  • REM-based real time testbed: a proof of concept on the benefits of using REM for improving radio resource management capabilities

     Casadevall Palacio, Fernando-jose; Umbert Juliana, Anna
    International Conference on Telecommunications
    p. 1-5
    DOI: 10.1109/ICTEL.2013.6632148
    Presentation's date: 2013-05
    Presentation of work at congresses

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    The knowledge of the statistical characterization of the primary user activity can make more efficient the spectrum selection techniques, which are a key technology to improve the Cognitive Radio (CR) systems performance. In order to provide this kind of primary user information, Radio Environment Maps (REM) data bases has been proposed. This paper presents a REM-based Real Time Testbed designed to validate and exploit the dynamicity of the REM data base to improve the performances of the Radio Resource Management (RRM) algorithms in the context of cognitive radio. The implemented testbed is a flexible HW/SW tool able to use spectrum measurements in licensed bands and validate the Cognitive Radio performance of the secondary users, without causing any interference on these primary users. In particular, the RRM strategy under study in the testbed envisages the optimization of the spectrum selection policy when secondary users, with different service profiles, access opportunistically a set of channels during the inactivity periods of primary users. The selection is done taking as input the statistical characterization of the primary user activity, which will be stored in the REM data base, and the secondary user service profiles.

  • Spectrum occupancy in big cities - comparative study: measurement campaigns in Barcelona and Poznan

     Kliks, Adrian; Kryszkiewicz, Pawel; Pérez Romero, Jordi; Umbert Juliana, Anna; Casadevall Palacio, Fernando-jose
    International Symposium of Wireless Communication Systems
    p. 125-129
    Presentation's date: 2013-08
    Presentation of work at congresses

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    In this paper a comparative study of two measurement campaigns carried out in Barcelona, Spain, and Pozna, Poland, to identify spectrum occupancy in different bands, is presented. In both cases the measurement setup was harmonized to obtain comparable results. The problem of efficient noise floor estimation was also considered and a pragmatic approach that takes into account both internal and ambient noise has been proposed. Obtained results show significant amount of unused spectrum, with similar results for both sites when analyzed globally (average spectrum occupancy of 27% in Pozna¿ and 22% in Barcelona). On the contrary, when going to the detailed analysis of some specific bands, more relevant differences are obtained. These differences have been observed mainly in the Terrestrial TRunked RAdio (TETRA) bands that in Poland are also used by Code Division Multiple Access (CDMA) 450, as well as in the bands of theGlobal System for Mobile communications (GSM) due to the effects of Universal Mobile Telecommunications System (UMTS) refarming in the 900 MHz band.

  • Optimal distributed frequency planning for OFDMA femtocell networks

     Bezerra Rodrigues, Emanuel; Casadevall Palacio, Fernando-jose
    IEEE International Symposium on Personal Indoor and Mobile Radio Communications
    p. 2929-2933
    DOI: 10.1109/PIMRC.2013.6666645
    Presentation's date: 2013-09-08
    Presentation of work at congresses

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    Femtocell networks have gained momentum due to their important benefits, such as improved indoor coverage, higher areal spectral efficiency, enhanced signal quality, among others. Those benefits are only achievable if adequate deployment decisions and efficient resource allocation techniques are able to assure the seamless co-existence among Femtocell Access Points (FAPs) within the femtocell tier and between FAPs and macrocell users. In this work, we study the frequency planning problem on the femtocell tier deployed on a closed access mode and using a dedicated spectrum. A novel radio resource allocation technique that performs a mid/long-term requency planning for the FAPs in the femtocell tier is proposed. It is concluded in this paper that the Dynamic Frequency Planning (DFP) algorithm based on the Branch and Bound technique is able to find the optimal frequency planning according to any desired criterion and that the proposed algorithm is suitable for implementation in a distributed 4G femtocell network regarding signaling overhead and latency aspects.

  • Spectrum usage models for the analysis, design and simulation of cognitive radio networks

     López Benítez, Miguel; Casadevall Palacio, Fernando-jose
    DOI: 10.1007/978-94-007-1827-2_2
    Date of publication: 2012-05-01
    Book chapter

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    This chapter presents a comprehensive set of spectrum occupancy models specifically envisaged for the analysis, design and simulation of cognitive radio systems. The presented models have been proven to accurately capture and reproduce the statistical properties of spectrum occupancy patterns in real systems. The chapter begins with the description of various time-dimension modeling approaches (in discrete and continuous time) along with models for time-correlation properties. Subsequently, joint time-frequency models as well as space-dimension models are explained in detail. Finally, the chapter concludes with a discussion on the combination and integration of the presented models into a unified modeling approach where the time, frequency and space dimensions of spectrum usage can be modeled simultaneously.

  • Network of Excellence in Wireless COMmunications #

     Pascual Iserte, Antonio; Pérez Neira, Ana Isabel; Najar Marton, Montserrat; Agusti Comes, Ramon; Umbert Juliana, Anna; Casadevall Palacio, Fernando-jose; Sanchez Gonzalez, Juan; Pérez Romero, Jordi
    Competitive project

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    D6.2 - Prototype description and field trial results  Open access

     Casadevall Palacio, Fernando-jose; Pérez Romero, Jordi; Gavrilovska, Liljana; Atanasovski, Vladimir; Denkovski, Daniel; Rakovic, Valentin; Pavloski, Mihajlo; Iacobelli, Lorenzo; Fouillot, Pascale; Dagres, Ioannis; Polydoros, Andreas; van de Beek, Jaap; Lidström, Erik; Cai, Tao; Dejonghe, Antoine; Farnham, Tim; Hau Chin, Woon; Ramos, Filipe; Faies, Mohammed; Sayrac, Berna; Ansari, Junaid; Meshkova, Elena; Mähönen, Petri; Nasreddine, Jad; Riihijärvi, Janne; Wang, Peng
    Date: 2012-06
    Report

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    Deliverable D6.2 del projecte FARAMIR

  • Improved energy detection spectrum sensing for cognitive radio

     López Benítez, Miguel; Casadevall Palacio, Fernando-jose
    IET communications
    Vol. 6, num. 8, p. 785-796
    DOI: 10.1049/iet-com.2010.0571
    Date of publication: 2012-05-22
    Journal article

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  • Rate adaptive resource allocation with fairness control for OFDMA networks

     Bezerra Rodrigues, Emanuel; Casadevall Palacio, Fernando-jose
    European Wireless
    p. 1-8
    Presentation's date: 2012-04-18
    Presentation of work at congresses

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    The use of opportunistic radio resource allocation techniques in order to efficiently manage the resources generates a low fairness among the users in a cellular system due to uneven Quality of Service (QoS) distribution. Some classic rate adaptive policies tried to tackle this problem for OFDMA systems by proposing solutions to maximize capacity, maximize fairness, or find a static trade-off between these two objectives. This work generalizes these classic policies and propose a dynamic fairness/rate adaptive technique based on dynamic sub-carrier assignment and equal power allocation that considers a new fairness constraint in the optimization problem. By means of extensive system-level simulations, it is demonstrated that the proposed technique is able to provide an instantaneous (short-term) fairness control, which provides to the network operator the flexibility to operate on any desired trade-off point.

  • SPECTRUM USAGE MODELS FOR THE ANALYSIS, DESIGN AND SIMULATION OF COGNITIVE RADIO NETWORKS  Open access  awarded activity

     López Benítez, Miguel
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    The owned spectrum allocation policy, in use since the early days of modern radio communications, has been proven to effectively control interference among radio communication systems. However, the overwhelming proliferation of new operators, innovative services and wireless technologies during the last years has resulted, under this static regulatory regime, in the depletion of spectrum bands with commercially attractive radio propagation characteristics. An important number of spectrum measurements, however, have shown that spectrum is mostly underutilized, thus indicating that the virtual spectrum scarcity problem actually results from static and inflexible spectrum management policies rather than the physical scarcity of radio resources. This situation has motivated the emergence of Dynamic Spectrum Access (DSA) methods based on the Cognitive Radio (CR) paradigm, which has gained popularity as a promising solution to conciliate the existing conflicts between spectrum demand growth and spectrum underutilization. The basic underlying idea of DSA/CR is to allow unlicensed (secondary) users to access in an opportunistic and non-interfering manner some licensed bands temporarily unoccupied by the licensed (primary) users. Due to the opportunistic nature of this principle, the behavior and performance of a DSA/CR network depends on the spectrum occupancy patterns of the primary system. A realistic and accurate modeling of such patterns becomes therefore essential and extremely useful in the domain of DSA/CR research. The potential applicability of spectrum usage models ranges from analytical studies to the design and dimensioning of secondary networks as well as the development of innovative simulation tools and more efficient DSA/CR techniques. Spectrum occupancy modeling in the context of DSA/CR constitutes a rather unexplored research area. This dissertation addresses the problem of modeling spectrum usage in the context of DSA/CR by contributing a comprehensive and holistic set of realistic models capable to accurately capture and reproduce the statistical properties of spectrum usage in real radio communication systems in the time, frequency and space dimensions. The first part of this dissertation addresses the development of a unified methodological framework for spectrum measurements in the context of DSA/CR and presents the results of an extensive spectrum measurement campaign performed over a wide variety of locations and scenarios in the metropolitan area of Barcelona, Spain, to identify potential bands of interest for future DSA/CR deployments. To the best of the author's knowledge, this is the first study of these characteristics performed under the scope of the Spanish spectrum regulation and one of the earliest studies in Europe. The second part deals with various specific aspects related to the processing of measurements to extract spectrum occupancy patterns, which is largely similar to the problem of spectrum sensing in DSA/CR. The performance of energy detection, the most widely employed spectrum sensing technique in DSA/CR, is first assessed empirically. The outcome of this study motivates the development of a more accurate theoretical-empirical performance model as well as an improved energy detection scheme capable to outperform the conventional method while preserving a similar level of complexity, computational cost and application. The findings of these studies are finally applied in the third part of the dissertation to the development of innovative spectrum usage models for the time (in discrete- and continuous-time versions), frequency and space domains. The proposed models can been combined and integrated into a unified modeling approach where the time, frequency and space dimensions of spectrum usage can simultaneously be reproduced, thus providing a complete and holistic characterization of spectrum usage in real systems for the analysis, design and simulation of the future DSA/CR networks.

  • Acceso radio cognitivo y oportunista

     Raschella, Alessandro; Bouali, Faouzi; Bolea, Liliana; Sanchez Gonzalez, Juan; Umbert Juliana, Anna; Ferrús Ferré, Ramon; Casadevall Palacio, Fernando-jose; Agusti Comes, Ramon; Pérez Romero, Jordi; Sallent Roig, Jose Oriol
    Competitive project

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  • Prototype requirement analysis. Document Number D6.1

     Gavrilovska, Liljana; Atanasovski, Vladimir; Denkovski, Daniel; Rakovic, Valentin; Pavloski, Mihajlo; van de Beek, Jaap; Iacobelli, Lorenzo; Van Wesemael, Peter; Sayrac, Berna; López Benítez, Miguel; Casadevall Palacio, Fernando-jose; Agusti Comes, Ramon; Pérez Romero, Jordi; Mähönen, Petri; Riihijärvi, Janne
    Date: 2011-02-28
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    Radio environmental maps: information models and reference model. Document number D4.1  Open access

     Dagres, Ioannis; Polydoros, Andreas; Riihijärvi, Janne; Nasreddine, Jad; Mähönen, Petri; Gavrilovska, Liljana; Atanasovski, Vladimir; van de Beek, Jaap; Sayrac, Berna; Grimoud, Sebastien; López Benítez, Miguel; Pérez Romero, Jordi; Agusti Comes, Ramon; Casadevall Palacio, Fernando-jose
    Date: 2011-04-30
    Report

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    We describe herein the envisioned improvements of the REMs due to advanced sensing and processing. In relation to that, we also discuss the underlying modelling assumptions. Finally, we comment on how REMs can be of use in different scenarios as established in WP2.

    Deliverable D4.1 del projecte Europeu FARAMIR (248351)

  • Reduced cluster search ML decoding for QO-STBC M-QAM MIMO systems

     Abrao, Taufik; Suzuki, Isaque; Angelico, Bruno A.; Ciriaco, Fernando; Jeszensky, Paul Jean E.; Casadevall Palacio, Fernando-jose
    International Journal of Satellite Communications Policy and Management
    Vol. 1, num. 1, p. 15-30
    DOI: 10.1504/IJSCPM.2011.039738
    Date of publication: 2011
    Journal article

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    Since the maximum likelihood (ML) decoding for quasi-orthogonal space-time block codes (QO-STBC) with inner and outer codes multipleinputmultiple- output (MIMO) antenna systems results too complex when the modulation order index and the number of receive antennas increases, an efficient reduced complexity ML-based decoding scheme is proposed in this contribution, aiming to reach promising QO-STBC coded MIMO system throughput × complexity trade-off. Under high-order modulation indexes (16 ≤ M)-QAM, 4 × nR antennas, with nR ≥ 1, this work proposes a reduced cluster search ML decoder (RCS-ML) and compares the performancecomplexity with the ML decoding approach. Numerical results have indicated no degradation in performance and an increasing reduction in the complexity of RCS-ML decoder when the modulation order increases, been 12.5% of ML decoding complexity for 16-QAM, and <1% for 256-QAM.

  • Access to the full text
    Towards a more efficient spectrum usage: spectrum sensing and cognitive radio techniques  Open access

     Pérez Romero, Jordi; Noguet, Dominique; López Benítez, Miguel; Casadevall Palacio, Fernando-jose
    Radio Science Bulletin
    num. 336, p. 59-74
    Date of publication: 2011-03
    Journal article

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    The traditional approach of dealing with spectrum management in wireless communications has been through the definition on a license user granted exclusive exploitation rights for a specific frequency.

  • Control of the trade-off between resource efficiency and user fairness in wireless networks using utility-based adaptive resource allocation

     Rodrigues, Emanuel B.; Casadevall Palacio, Fernando-jose
    IEEE communications magazine
    Vol. 49, num. 9, p. 90-98
    DOI: 10.1109/MCOM.2011.6011739
    Date of publication: 2011-09
    Journal article

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    This work addresses the fundamental problem of the trade-off between resource efficiency and user fairness in wireless networks that use opportunistic radio resource allocation. The concept of managing the trade-off by controlling the system fairness index is applied. In order to do that, two adaptive utility-based resource allocation frameworks consisting of subcarrier assignment and power allocation algorithms are proposed. These frameworks are named utility-based alpha-rule and beta-rule, and are suitable for non-real-time and real-time services, respectively. Not only can both frameworks be designed to work as wellknown classic policies found in the literature, but also as adaptive policies, which are able to meet a desired system fairness target. System level simulations show that the proposed frameworks are powerful tools to the network operator, since they can decide in which trade-off point of the efficiency-fairness plane they want to operate the system.

  • Empirical Time-Dimension Model of Spectrum Use Based on a Discrete-Time Markov Chain With Deterministic and Stochastic Duty Cycle Models

     López Benítez, Miguel; Casadevall Palacio, Fernando-jose
    IEEE transactions on vehicular technology
    Vol. 60, num. 6, p. 2519-2533
    DOI: 10.1109/TVT.2011.2157372
    Date of publication: 2011-07
    Journal article

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    The spectrum occupancy models widely used to date in dynamic spectrum access/cognitive radio (DSA/CR) research frequently rely on assumptions and oversimplifications that have not been validated with empirical measurement data. In this context, this paper presents an empirical time-dimension model of spectrum use that is appropriate for DSA/CR studies. Concretely, a two-state discrete-time Markov chain with novel deterministic and stochastic duty cycle models is proposed as an adequate mean to accurately describe spectrum occupancy in the time domain. The validity and accuracy of the proposed modeling approach is evaluated and corroborated with extensive empirical data from a multiband spectrum measurement campaign. The obtained results demonstrate that the proposed approach is able to accurately capture and reproduce the relevant statistical properties of spectrum use observed in real-world channels of various radio technologies. The importance of accurately modeling spectrum use in the design and evaluation of novel DSA/CR techniques is highlighted with a practical case study.

  • Versatile, accurate and analytically tractable approximation for the Gaussian Q-Function

     López Benítez, Miguel; Casadevall Palacio, Fernando-jose
    IEEE transactions on communications
    Vol. 59, num. 4, p. 917-922
    DOI: 10.1109/TCOMM.2011.012711.100105
    Date of publication: 2011-04
    Journal article

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  • ADAPTIVE RADIO RESOURCE MANAGEMENT FOR OFDMA-BASED MACRO- AND FEMTOCELL NETWORKS  Open access

     Bezerra Rodrigues, Emanuel
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    Las demandas y expectativas de los usuarios y operadores móviles crecen sin parar y, consecuentemente, los nuevos estándares han incorporado tecnologías de acceso de radio cada vez más eficientes. Las especificaciones IMT-Advanced para la cuarta generación (4G) de redes móviles de banda ancha requieren, entre otras cosas, tasas más altas de transmisión de datos, del orden de 100 Mbps a 1 Gbps, dependiendo del nivel de movilidad. Para conseguir éstas tasas se ha escogido como tecnología de acceso el Acceso Múltiple por División de Frecuencias Ortogonal (OFDMA), y se han considerado femtoceldas para mejorar la cobertura de espacios interiores. Para explorar completamente la flexibilidad de estas tecnologías y utilizar los escasos recursos radio de la manera más eficiente posible se requieren técnicas de Gestión de Recursos Radio (RRM) adaptativas e inteligentes. En el ámbito de los sistemas celulares basados en OFDMA, uno de los problemas todavía no resuelto es el compromiso que existe entre la eficiencia en la utilización de los recursos y la equidad en su distribución entre los usuarios de la red. El compromiso entre eficiencia y equidad aparece cuando los recursos radio asignados dan lugar a diferentes indicadores de eficiencia con respecto a los distintos usuarios de red (diversidad multi-usuario). El uso de una asignación de recursos oportunista, para explorar estas diversidades y maximizar la capacidad, causa situaciones de desigualdad en la distribución de los recursos. Por otro lado, los esquemas de RRM que propician equidad absoluta consideran un escenario de peor caso, penalizando a los usuarios con mejores condiciones y reduciendo la capacidad del sistema. En esta tesis, se han propuesto varias políticas y técnicas de RRM para balancear este compromiso en el contexto de redes macrocelulares y femtocelulares. En el caso particular de sistemas macrocelulares, proponemos un nuevo paradigma de gestión de red basado en el control del índice de equidad de la celda en escenarios con servicios de tiempo no-real y de tiempo real. Se han estudiado dos enfoques para el control de la equidad: control instantáneo (a corto plazo) utilizando técnicas de RRM de adaptación de tasa y equidad, y control promediado (a mediano plazo) utilizando estructuras de RRM basadas en la Teoría de la Utilidad. En el caso de las femtoceldas, se ha formulado una nueva técnica para evitar la interferencia capaz de balancear el compromiso entre eficiencia espectral y la equidad entre los puntos de acceso de las femtoceldas. Esta estrategia de RRM se basa en una planificación a mediano/largo plazo de las frecuencias disponibles, que toma en consideración la topología de interferencia de grupos de femtoceldas vecinas. Las técnicas de RRM consideradas en esta tesis se han evaluada utilizando de forma sistemática técnicas de simulación numéricas a nivel de sistema. En el caso del escenario macrocelular, se demuestra que las técnicas adaptativas de RRM propuestas son, para los operadores móviles una, herramienta valiosa porqué, además de ser una generalización de estrategias clásicas bien conocidas, son capaces de garantizar de forma eficiente diferentes niveles de equidad en el sistema, y controlar el compromiso entre eficiencia y equidad. Además, se concluye que las estrategias basadas en la teoría de utilidad, que hacen un control promedio de la equidad, muestran resultados tan buenos ó incluso mejores que los presentados por las técnicas basadas en optimización instantánea de la adaptación de la tasa y la equidad, utilizando menores recursos computacionales. Finalmente, se demuestra que la técnica propuesta para evitar interferencia en redes de femtoceldas puede garantizar una coexistencia sin degradaciones entre punto de acceso vecinos para cualquier topología de interferencia. Esta técnica puede ser implementada mediante arquitecturas de red distribuidas ó centralizadas, presentando en ambos casos unos requisitos de señalización muy bajos.

    User and cellular operator requirements and expectations have been continuously evolving, and consequently, advanced radio access technologies have emerged. The International Mobile Telecommunications - Advanced (IMT-Advanced) specifications for mobile broadband Fourth Generation (4G) networks state, among other requirements, that enhanced peak data rates of 100 Mbps and 1 Gbps for high and low mobility should be provided. In order to achieve this challenging performance, Orthogonal Frequency Division Multiple Access (OFDMA) has been chosen as the access technology, and femtocells have been considered for improving indoor coverage. In order to fully explore the flexibility of these technologies and use the scarce radio resources in the most efficient way possible, intelligent and adaptive Radio Resource Management (RRM) techniques are crucial. There are many open RRM problems in wireless networks in general and OFDMA-based cellular systems in particular. One of such problems is the fundamental trade-off that exists between efficiency in the resource usage and fairness in the resource distribution among network players. Several opportunistic RRM algorithms, which dynamically allocate the resources to the network players that present the highest efficiency indicator with regard to these resources, have been proposed to maximize the efficiency in the resource usage. The trade-off between efficiency and fairness appears when the resources have different efficiency indicators to different network players (multi-user or multi-cell diversity). The use of opportunistic resource allocation to explore these diversities causes unfair situations in the resource distribution. On the other hand, schemes that provide absolute fairness deal with the worst case scenario, penalizing players with better condition and reducing the system capacity. In this thesis, several RRM policies and techniques are proposed to balance this compromise in macrocell and femtocell networks. In the particular case of macrocell systems, we propound a new network management paradigm based on the control of a cell fairness index in scenarios with Non-Real Time (NRT) or Real Time (RT) services. Two fairness control approaches are studied: instantaneous (short-term) control by means of generalized fairness/rate adaptive RRM techniques and average (mid-term) control using utility-based frameworks. For femtocell networks, a novel interference avoidance technique able to balance the trade-off between spectral efficiency in the femtocell tier and fairness among the Femtocell Access Points (FAPs) is formulated. This RRM strategy is based on a high-level, mid/long-term frequency planning that takes into account the topology of groups of neighboring FAPs. The RRM techniques considered in this thesis are evaluated by means of extensive system-level and/or numerical simulations. Regarding the macrocell scenario, it is shown that the proposed adaptive RRM techniques are valuable tools for the mobile operators, because they are generalizations of well-known classic strategies found in the literature and they can effectively guarantee different fairness levels in the system and control the trade-off between efficiency and fairness. Furthermore, it is concluded that the utility-based strategies that perform an average fairness control can provide performance results as good as the fairness/rate adaptive techniques, which are based on instantaneous optimization, using less computational resources. Finally, it is demonstrated that the proposed interference avoidance technique for femtocell networks can guarantee a seamless coexistence between neighboring FAPs in any interference topology. Furthermore, this technique can be implemented in both centralized and distributed network architectures and generates very low signaling overhead.

  • Modeling and simulation of joint time-frequency properties of spectrum usage in cognitive radio

     Casadevall Palacio, Fernando-jose; López Benítez, Miguel; López Pérez, David; Vasilakos, Athanasios V.
    International Conference on Cognitive Radio and Advanced Spectrum Management
    p. 1-5
    Presentation's date: 2011-10
    Presentation of work at congresses

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    The development of the Dynamic Spectrum Access/Cogni- tive Radio (DSA/CR) technology can signi cantly bene t from the availability of realistic models able to accurately capture and reproduce the statistical properties of spectrum usage in real wireless communication systems. Relying on eld measurements of real systems, this paper analyzes the joint time-frequency statistical properties of spectrum usage and develops adequate models describing the observed char- acteristics. Based on such models, a sophisticated method is also proposed to generate arti cial spectrum data for simulation or other purposes. The proposed method is able to accurately reproduce the statistical time-frequency characteristics of spectrum usage in real systems.

  • An overview of spectrum occupancy models for cognitive radio networks

     Casadevall Palacio, Fernando-jose; López Benítez, Miguel
    IFIP International Workshop on Performance Evaluation of Cognitive Radio Networks
    p. 1-10
    Presentation's date: 2011-05
    Presentation of work at congresses

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  • Modeling and simulation of time-correlation properties of spectrum use in cognitive radio

     López Benítez, Miguel; Casadevall Palacio, Fernando-jose
    International ICST Conference on Cognitive Radio Oriented Wireless Networks
    p. 1-5
    Presentation's date: 2011-06
    Presentation of work at congresses

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    The development of the cognitive radio technology can enormously benefit from the availability of realistic and accurate spectrum occupancy models. Time-dimension models of spectrum use proposed in the literature so far are able to capture and reproduce essential temporal characteristics such as the mean occupancy level (duty cycle) and the statistical distribution of busy/idle-period lengths. However, more sophisticated aspects of spectrum use, such as time-correlation properties, have not been properly addressed yet. In this context, this paper studies and analyzes, based on field measurements of various radio technologies, the time-correlation properties of spectrum use. Appropriate models and simulation techniques are proposed in order to accurately capture and reproduce such features.

  • A radio spectrum measurement platform for spectrum surveying in cognitive radio

     López Benítez, Miguel; Casadevall Palacio, Fernando-jose
    International ICST Conference on Testbeds and Research Infrastructures for the Development of Networks and Communities
    p. 1-16
    Presentation's date: 2011-04
    Presentation of work at congresses

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    This paper presents a sophisticated radio spectrum measurement platform specifically envisaged and designed for spectrum occupancy surveys in the context of Dynamic Spectrum Access/Cognitive Radio (DSA/CR). The presented tool is a very flexible computer-controlled radio measurement system, which has successfully been used in extensive spectrum measurement campaigns and empirical studies in the context of the DSA/CR technology. An exhaustive and in-depth description of the developed measurement platform is provided, with a special emphasis on implementation details and lessons learned during the development of the tool that may result helpful to other researchers and engineers in the development of similar radio spectrum measurement tools.

  • Discrete-time spectrum occupancy model based on Markov chain and duty cycle models

     Casadevall Palacio, Fernando-jose; López Benítez, Miguel
    IEEE International Dynamic Spectrum Access Networks symposium
    p. 90-99
    DOI: 10.1109/DYSPAN.2011.5936273
    Presentation's date: 2011-05
    Presentation of work at congresses

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    This paper presents an empirical time-dimension model of spectrum use in the context of dynamic spectrum access. Concretely, a discrete-time two-state Markov chain with novel duty cycle models is proposed as an adequate mean to accurately describe spectrum occupancy in the time domain. The validity and accuracy of the proposed model is assessed and corroborated with extensive empirical data from a multiband spectrum measurement campaign. The obtained results demonstrate that the proposed approach is able to capture and reproduce with significant accuracy the statistical properties of spectrum use observed in real channels of various technologies.

  • Statistical prediction of spectrum occupancy perception in dynamic spectrum access networks

     Casadevall Palacio, Fernando-jose; López Benítez, Miguel
    IEEE International Conference on Communications
    p. 1-6
    DOI: 10.1109/icc.2011.5963505
    Presentation's date: 2011-06
    Presentation of work at congresses

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    Cognitive radio nodes of a dynamic spectrum access network monitor the spectrum around them in order to detect and opportunistically exploit temporarily unoccupied spectrum gaps. The overall behavior of the whole network depends on the spectrum occupancy perceived by each node at its local environment. An appropriate understanding of the local perception of cognitive radio nodes in various scenarios and locations as well as its dependence on the propagation environment can provide valuable information for the design, dimensioning and performance evaluation of dynamic spectrum access networks. In this context, this work presents a novel and practical approach to predict the spectrum occupancy that would be perceived by cognitive radio nodes in realistic scenarios. Based on such approach, we explore the dependence of the spectrum occupancy perception with the considered scenario and location as well as the impact of particular parameters of the radio environment.

  • LTE: nuevas tendencias en comunicaciones móviles

     Agusti Comes, Ramon; Bernardo Alvarez, Francisco; Casadevall Palacio, Fernando-jose; Ferrús Ferré, Ramon; Pérez Romero, Jordi; Sallent Roig, Jose Oriol
    Date of publication: 2010
    Book

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  • RADIO RESOURCE AND MOBILITY MANAGEMENT ISSUES IN THE FRAMEWORK OF WLAN 802.11 NETWORKS

     MAJKOWSKI, JAKUB
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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  • FLEXIBLE AND SPECTRUM-AWARE RADIO ACCESS THROUGH MEASUREMENTS AND MODELLING IN

     Raschella, Alessandro; López Benítez, Miguel; Garcia Escriche, Sergio; Umbert Juliana, Anna; Ferrús Ferré, Ramon; Sallent Roig, Jose Oriol; Bouali, Faouzi; Bolea, Liliana; Pérez Romero, Jordi; Casadevall Palacio, Fernando-jose; Agusti Comes, Ramon
    Competitive project

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  • Opportunistic networks and Cognitive Management Systems for Efficient Application Provision in the Future

     Sanchez Gonzalez, Juan; Ferrús Ferré, Ramon; Pérez Romero, Jordi; Gelonch Bosch, Antoni; Casadevall Palacio, Fernando-jose; Agusti Comes, Ramon; Umbert Juliana, Anna; Raschella, Alessandro; Bouali, Faouzi; Sallent Roig, Jose Oriol
    Competitive project

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    DR9.3 Final report of the JRRM and ASM activities  Open access

     Pérez Romero, Jordi; Serrador, António; Caeiro, Luisa; Correia, Luis; Moretti, Marco; Bezerra Rodrigues, Emanuel; Sroka, Pawel; Bogucka, Hanna; López Benítez, Miguel; Umbert Juliana, Anna; Casadevall Palacio, Fernando-jose; Jouini, Wassim; Palicot, Jacques; Moy, Christophe; Kliks, Adrian; Debbah, Merouane
    Date: 2010-12
    Report

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    This deliverable provides the final report with the summary of the activities carried out in NEWCOM++ WPR9, with a particular focus on those obtained during the last year. They address on the one hand RRM and JRRM strategies in heterogeneous scenarios and, on the other hand, spectrum management and opportunistic spectrum access to achieve an efficient spectrum usage. Main outcomes of the workpackage as well as integration indicators are also summarised.

    Deliverable del projecte europeu NEWCOM++

  • State of the art review

     López Benítez, Miguel; Akyildiz, Ian F.; Agusti Comes, Ramon; Casadevall Palacio, Fernando-jose
    Date: 2010-04
    Report

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    Deffinition and evaluation of JRRM and ASM algorithms  Open access

     López Benítez, Miguel; Umbert Juliana, Anna; Casadevall Palacio, Fernando-jose; Pérez Romero, Jordi
    Date: 2010-01
    Report

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    This deliverable (DR9.2) describes the radio resource management, joint radio resource management and advanced spectrum management strategies developed in each of the tasks of WPR.9 during the second year of study. The proposed algorithms together with the results of evaluation in scenarios identified in the deliverable DR9.1 are presented. A special attention is given to JRRM in heterogeneous networks, OFDMA spectrum management and measurements, and game-theoretical optimization of cognitive networks.

  • Methodological aspects of spectrum occupancy evaluation in the context of cognitive radio

     López Benítez, Miguel; Casadevall Palacio, Fernando-jose
    European transactions on telecommunications
    Vol. 21, num. 8, p. 680-693
    DOI: 10.1002/ett.1453
    Date of publication: 2010-12
    Journal article

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    Spectrum occupancy in realistic scenarios and duty cycle model for cognitive radio  Open access

     López Benítez, Miguel; Casadevall Palacio, Fernando-jose
    Advances in Electronics and Telecommunications, Special Issue on Radio Communication Series: Recent Advances and Future Trends in Wireless Communication
    Vol. 1, num. 1, p. 1-9
    Date of publication: 2010-04
    Journal article

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    Most of the spectrum occupancy measurement campaigns performed to the date in the context of cognitive radio are based on measurements in outdoor high points such as building roofs, balconies and towers. Although these measurement scenarios enable a more accurate estimation of the primary transmitters’ spectral activity, they may not be representative of the spectrum occupancy perceived by a cognitive radio user in many other interesting practical situations where users are not placed in a static high point. In this context, this work presents the results obtained in a spectrum measurement campaign performed over a rich diversity of measurement scenarios of practical interest. The considered scenarios include not only high points but also indoor environments as well as outdoor locations at the ground level in open areas and between buildings. The variety of considered measurement scenarios provides a broader view and understanding of dynamic spectrum occupancy under different practical scenarios of interest. The impact of considering various locations on the spectral activity perceived by a cognitive radio user is determined, analyzed and quantified. Moreover, a theoretical model for the occupancy levels observed at different locations is developed and verified with the obtained results.

  • S/MIMO MC-CDMA Heuristic Multiuser Detectors Based on Single-Objective Optimization

     Abrao, Taufik; de Oliveira, Leonardo D.; Ciriaco, Fernando; Angelico, Bruno A.; Jeszensky, Paul Jean E.; Casadevall Palacio, Fernando-jose
    Wireless personal communications
    Vol. 53, num. 4, p. 529-553
    DOI: 10.1007/s11277-009-9701-8
    Date of publication: 2010-06
    Journal article

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    ETSI reconfigurable radio systems: status and future directions on software defined radio and cognitive radio standards  Open access

     Mueck, Markus; Piiponen, Antti; Kalliojarvi, Kari; Dimitrakopoulos, George; Demestichas, Panagiotis; Casadevall Palacio, Fernando-jose; Pérez Romero, Jordi; Sallent Roig, Jose Oriol; Baldini, Gianmarco; Filin, Stanislav; Harada, Hiroshi; Debbah, Merouane; Haustein, Thomas; Gebert, Jens; Deschamps, Benoist; Bender, Paul; Street, Michael; Kandeepan, Sithamparanathan; Lota, Jaswinder; Hayar, Aawatif; Tsagkaris, Kostas
    IEEE communications magazine
    Vol. 48, num. 9, p. 78-86
    DOI: 10.1109/MCOM.2010.5560591
    Date of publication: 2010-09
    Journal article

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    This article details the current work status of the ETSI Reconfigurable Radio Systems Technical Committee, positions the ETSI work with respect to other standards efforts (IEEE 802, IEEE SCC41) as well as the European Regulatory Framework, and gives an outlook on the future evolution. In particular, software defined radio related study results are presented with a focus on SDR architectures for mobile devices such as mobile phones. For MDs, a novel architecture and inherent interfaces are presented enabling the usage of SDR principles in a mass market context. Cognitive radio principles within ETSI RRS are concentrated on two topics, a cognitive pilot channel proposal and a Functional Architecture for Management and control of reconfigurable radio systems, including dynamic self-organizing planning and management, dynamic spectrum management, joint radio resource management. Finally, study results are indicated that are targeting a SDR/CR security framework.

  • Performance of spectrum sensing for cognitive radio based on field measurements of various radio technologies

     López Benítez, Miguel; Casadevall Palacio, Fernando-jose; Martella, Corrado
    European Wireless
    p. 969-977
    DOI: 10.1109/EW.2010.5483510
    Presentation's date: 2010-04-12
    Presentation of work at congresses

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    Despite its practical performance limitations, energy detection has gained popularity during the last years as a spectrum sensing technique for dynamic spectrum access in cognitive radio networks. The main advantages of energy detectionbased spectrum sensing are its simplicity, low computational and implementation costs as well as its ability to work irrespective of the actual signal to be detected. Since no prior knowledge is required, energy detection can be employed when the secondary receiver cannot gather sufficient information about the primary user signal. Due to the generality of its operating principle, the energy detector performance would not be expected to depend on the type of primary signal being detected. In this context, this paper evaluates the performance of energy detectionbased spectrum sensing for several real-world primary signals of various radio technologies. The obtained results indicate that the detection performances may vary notably with the considered primary signal but converge under certain conditions. The practical consequences of the different observed performances for several primary radio technologies are illustrated and discussed.

  • Spatial duty cycle model for cognitive radio

     López Benítez, Miguel; Casadevall Palacio, Fernando-jose
    IEEE International Symposium on Personal Indoor and Mobile Radio Communications
    p. 1631-1636
    DOI: 10.1109/PIMRC.2010.5671939
    Presentation's date: 2010-09
    Presentation of work at congresses

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    Spectrum occupancy modeling in the context of Dynamic Spectrum Access/Cognitive Radio (DSA/CR) constitutes a rather unexplored research area that still requires much more effort. This paper addresses the problem of modeling spectrum occupancy in the spatial domain by proposing a novel theoretical approach that enables modeling the occupancy level perceived at any geographical location based on the knowledge of some simple primary signal parameters. The validity of the theoretical model is verified with extensive empirical measurement results. Some examples of its potential applicability are discussed as well.

  • On the spectrum occupancy perception of cognitive radio terminals in realistic scenarios

     López Benítez, Miguel; Casadevall Palacio, Fernando-jose
    International Workshop on Cognitive Information Processing
    p. 99-104
    DOI: 10.1109/CIP.2010.5604131
    Presentation's date: 2010-06-14
    Presentation of work at congresses

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    Cognitive radio terminals sense the spectrum to detect temporarily unoccupied spectrum gaps and transmit. The behavior of a network of cognitive radio terminals therefore depends on the spectrum occupancy perceived by each terminal at its local environment. In this context, this work explores (via empirical measurements) the spectrum occupancy that would be perceived by a cognitive radio terminal over a rich diversity of practical scenarios, including indoor environments as well as outdoor locations in high points and at the ground level (in open areas and between buildings). The impact of considering various locations on the spectral activity perceived by a cognitive radio terminal is determined, analyzed and quantified. The variety of considered scenarios provides a broader view and understanding of dynamic spectrum occupancy under different realistic scenarios of practical interest.

  • GRUP DE RECERCA EN COMUNICACIONS MÒBILS

     Bolea, Liliana; Pérez Romero, Jordi; Gelonch Bosch, Antoni; Casadevall Palacio, Fernando-jose; Umbert Juliana, Anna; Sanchez Gonzalez, Juan; Marojevic, Vuk; Ferrús Ferré, Ramon; Sallent Roig, Jose Oriol; Bouali, Faouzi; Agusti Comes, Ramon
    Competitive project

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    On concurrent multipath transfer in SCTP-based handover scenarios  Open access

     Budzisz, Lukasz; Ferrús Ferré, Ramon; Casadevall Palacio, Fernando-jose; Amer, Paul
    IEEE International Conference on Communications
    p. 1-6
    DOI: 10.1109/ICC.2009.5199237
    Presentation's date: 2009-06
    Presentation of work at congresses

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    Abstract—Handling mobility at the transport layer is a promising approach to achieve seamless handover in the context of heterogeneous wireless access networks. In particular, features such as multihoming and dynamic address reconfiguration provided by mobile SCTP (mSCTP) protocol are among the key enablers for handover support at the transport layer. This paper investigates the applicability of Concurrent Multipath Transfer (CMT) to distribute data among two end-to-end paths of an mSCTP association during the handover transition process. To that end, the principles of the mSCTP-CMT design are given, emphasizing the consequences of a sender-introduced reordering and its effect on congestion control. The proposed mSCTPCMT handover scheme is benchmarked with two other handover schemes, namely mSCTP and SCTP failover-based. Provided analysis indicates the possible application area of mSCTP-CMT, taking into account not only handover scenario parameters (dwelling time, available bandwidth ratio and round-trip time), but also an important design constraint: receiver buffer (rbuf) size. Rbuf size proves to be a major limiting factor shrinking significantly, yet not excluding mSCTP-CMT’s application scope