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  • Characterizing user behavior in a european academic WiFi network

     Zola, Enrica Valeria; Barceló Arroyo, Francisco
    International Journal of Handheld Computing Research (IJHCR)
    Date of publication: 2013
    Journal article

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    Wireless local area networks (WLANs) are commonplace in many universities. Understanding the trends in the usage of these networks is becoming more important. Interesting results can be extracted about association patterns by analyzing WLAN traces from real scenarios. In this work, the library in the main campus of the Technical University of Catalonia (UPC) in Barcelona has been studied. Daily and weekly patterns of the WLAN connections are shown. The population accessing the network is mostly composed of infrequent users: half of the population accesses the WLAN once during each month. Many users associate to only one of the twelve possible access points, which means that, despite the widespread use of lightweight devices, many users are static. The results of this analysis provide general tools for characterizing campus-wide WLAN and a better understanding of usage and performance issues in a mature wireless network.

  • Robust association for multi-radio devices under coverage of multiple networks

     Zola, Enrica Valeria; Dely, Peter; Kassler, Andreas; Barceló Arroyo, Francisco
    International Conference on Wired/Wireless Internet Communications
    Presentation's date: 2013-06-05
    Presentation of work at congresses

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    Many devices are nowadays equipped with multiple wireless network interfaces such as GSM, HSPA+ and WLAN. This requires a mechanism for identifying which access network to use at a given time so to provide best user experience. Such decision is typically made using past information available at the user (e.g. history of signal strength measurements), or using a prediction of the future status of the parameters of interest. The key problem is that the parameter estimation is difficult and that the predictions may be inaccurate. In this paper, we develop a mathematical model for the access network selection problem, which is solved using robust optimization techniques. The objective is to maximize the download rate the user can achieve during a certain period in the future. The model provides guidelines for selecting the access network which guarantees, within a given probability bound, a minimum download rate for a given rate uncertainty.

  • Software based measurement of round trip time observables for location in IEEE 802.11 networks

     Martin Escalona, Israel; Barceló Arroyo, Francisco; Zola, Enrica Valeria
    International Conference on Telecommunications
    Presentation's date: 2013-07
    Presentation of work at congresses

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    Time-based multilateration in IEEE 802.11 networks usually involves custom hardware designs, which tend to slow down the implementation and deployment of the location system. This paper presents software for calculating time-based location observables. This software enhances the SoftMAC layer of the Linux operating system by adding location-related measuring capabilities. A plugin for calculating the round trip time between two network entities is included in the software definition. Real data have been collected to test the performance of the proposed system. Despite the relevant noise present in the measurements, the results prove that the round trip time measurements achieved are useful to estimate distances achieving estimates with RMS of the error close to 2 meters.

    Time-based multilateration in IEEE 802.11 networks usually involves custom hardware designs, which tend to slow down the implementation and deployment of the location system. This paper presents software for calculating time-based location observables. This software enhances the SoftMAC layer of the Linux operating system by adding location-related measuring capabilities. A plugin for calculating the round trip time between two network entities is included in the software definition. Real data have been collected to test the performance of the proposed system. Despite the relevant noise present in the measurements, the results prove that the round trip time measurements achieved are useful to estimate distances achieving estimates with RMS of the error close to 2 meters.

  • Linux-based measuring platform for time-based location observables in IEEE 802.11 networks

     Martin Escalona, Israel; Barceló Arroyo, Francisco; Zola, Enrica Valeria
    Joint ERCIM eMobility and MobiSense Workshop
    Presentation's date: 2013-06-04
    Presentation of work at congresses

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    Positioning has been a hot topic in research for several years. GPS is accepted as a global solution for positioning outdoors, but indoor positioning still remains an open issue. Time-based multilateration techniques are presented as a good trade-off between performance and complexity for indoor positioning. Although several proposals for time-based multilateration has been presented, only some of them has been really implemented and of them, only few can be reproduced by other researchers (mainly due to hardware customization). This work presents a system for measuring time-based location observables in IEEE 802.11 networks. This measuring system has been implemented in Linux, so it can be deployed easily by any researcher. The current implementation supports the measurement of two kind of observables: round trip times (for two-way time-of-arrival techniques) and passive TDOAs (for the passive TDOA location technique). First experiments, presented in this paper, are focused on demonstrating the feasibility of the system for measuring these two location observables.

    Positioning has been a hot topic in research for several years. GPS is accepted as a global solution for positioning outdoors, but indoor positioning still remains an open issue. Time-based multilateration techniques are presented as a good trade-off between performance and complexity for indoor positioning. Although several proposals for time-based multilateration has been presented, only some of them has been really implemented and of them, only few can be reproduced by other researchers (mainly due to hardware customization). This work presents a system for measuring time-based location observables in IEEE 802.11 networks. This measuring system has been implemented in Linux, so it can be deployed easily by any researcher. The current implementation supports the measurement of two kind of observables: round trip times (for two-way time-of-arrival techniques) and passive TDOAs (for the passive TDOA location technique). First experiments, presented in this paper, are focused on demonstrating the feasibility of the system for measuring these two location observables.

  • The introduction of a topic on accessibility in several engineering degrees

     Martin Escalona, Israel; Barceló Arroyo, Francisco; Zola, Enrica Valeria
    IEEE Global Engineering Education Conference
    Presentation's date: 2013-03-13
    Presentation of work at congresses

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    Together with the trend towards engineering designs more accessible to handicapped people there is an increasing concern at the engineering faculties to include topics related to accessibility in their programs. Engineers must be aware that handicapped people use technology and designs must take into account this fact. This paper explains how a topic on accessibility was started at a technical faculty as a cross topic to five different engineering degrees: Electrical, Electronics and Automatic Control, Industrial Product Design, Electronic Systems and Computer Science. The introduction process is explained along with the teaching methodology. Results after the first two courses are good in general but present some issues. The main issue to be corrected is that students from different branches achieve different academic performances.

    Together with the trend towards engineering designs more accessible to handicapped people there is an increasing concern at the engineering faculties to include topics related to accessibility in their programs. Engineers must be aware that handicapped people use technology and designs must take into account this fact. This paper explains how a topic on accessibility was started at a technical faculty as a cross topic to five different engineering degrees: Electrical, Electronics and Automatic Control, Industrial Product Design, Electronic Systems and Computer Science. The introduction process is explained along with the teaching methodology. Results after the first two courses are good in general but present some issues. The main issue to be corrected is that students from different branches achieve different academic performances.

  • From integrated to international masters in engineering: the increase of heterogeneity

     Barceló Arroyo, Francisco; Martin Escalona, Israel; Zola, Enrica Valeria
    International Conference on Education and New Learning Technologies
    Presentation's date: 2013-07-01
    Presentation of work at congresses

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    This paper analyses the difficulties found in some countries in Europe were the traditional integrated masters of five or six academic years were split into degree plus master after the Bologna process. Often, the master years of the former integrated master are oriented to international students and the lecturers find a high degree of diversity not present in the degree (this latter in local language and targeted to local students, close to the former first years of the integrated master). A case belonging to a master in computer networks is discussed together with some facts, difficulties found during the first years, discussion and possible ways to solve some of the detected issues.

  • Expected bit rate for terminals moving according to the random waypoint model in a WLAN cell

     Zola, Enrica Valeria; Barceló Arroyo, Francisco; Kassler, Andreas; Dely, Peter
    Wireless and Mobile Networking Conference
    Presentation's date: 2013-04-24
    Presentation of work at congresses

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    The IEEE 802.11 standard defines the different bit rates and modulation schemes to which a WLAN device may adapt according to the channel quality. User mobility may also have an impact on the available bit rate. This paper presents a study of the bit rate evolution along time for devices that move according to the Random Waypoint mobility pattern in WLAN cells. Simulation has been applied in order to obtain statistical results that permit to characterize the evolution of the bit rate behavior along time and to compute average results in the ideal case (without interference) and in the presence of interfering devices. Our results can be useful in the solution of optimization problems in which decision on where to connect must be taken based on some minimum guaranteed bit rate. They also can be useful in the design of inter and intra-cell handover methods and load balancing schemes.

  • A software platform for measuring distances through round trip time in IEEE 802.11

     Martin Escalona, Israel; Barceló Arroyo, Francisco; Zola, Enrica Valeria
    Wireless and Mobile Networking Conference
    Presentation's date: 2013-04-23
    Presentation of work at congresses

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    Indoor positioning has focused the interest of researchers for years. Although there are several techniques proposed, they are difficult to reproduce and consequently to contrast and improve. This paper presents a modular location platform, which enhances the SoftMAC implementation in Linux with positioning capabilities. This platform can be deployed in any device running Linux kernel 2.6 or higher. The core of the platform is its software-based measuring system. This measuring system supports the 2-way TOA technique, but any time-based multilateration technique (e.g. passive TDOA) can be incorporated with minimum changes. Real data have been gathered to assess the performance of the measuring system. The RTTs estimated grow with the distance, which demonstrates the feasibility of the system.

    Indoor positioning has focused the interest of researchers for years. Although there are several techniques proposed, they are difficult to reproduce and consequently to contrast and improve. This paper presents a modular location platform, which enhances the SoftMAC implementation in Linux with positioning capabilities. This platform can be deployed in any device running Linux kernel 2.6 or higher. The core of the platform is its software-based measuring system. This measuring system supports the 2-way TOA technique, but any time-based multilateration technique (e.g. passive TDOA) can be incorporated with minimum changes. Real data have been gathered to assess the performance of the measuring system. The RTTs estimated grow with the distance, which demonstrates the feasibility of the system.

  • Software-based system for measuring location observables in IEEE 802.11 networks

     Martin Escalona, Israel; Barceló Arroyo, Francisco; Zola, Enrica Valeria
    IEEE IFIP Annual Mediterranean Ad Hoc Networking Workshop
    Presentation's date: 2013-06-26
    Presentation of work at congresses

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    Several techniques have been proposed for positioning nodes over IEEE 802.11 networks, but only few consist in time-based multilateration, mainly due to the protocol stack not supporting accurate timestamps. One frequent solution is to develop the hardware required for providing accurate timestamps. However, this approach tends to slow down the research and the ulterior deployment of the location techniques, since the performance of these techniques is bounded to a specific hardware design. This paper presents a measuring system aimed at providing location observables that can be used in time-based multilateration techniques. The system, which follows a software approach, is based on enhancing the SoftMAC layer of Linux with location-measuring capabilities. The system is conceived for supporting any kind of time-based measurements, by adding as many plugins as measured observables. Two plugins have been initially developed. The first one computes the round trip time of a message from a station to an access point and back again to the station. The second plugin calculates time-differences of arrival suitable for being used in the passive TDOA technique. This work provides the definition of the measuring system. Real data has been collected to test the system. The results indicate that the measurements provided by the system can be used for location purposes, i.e. they follow the physical laws in which metrics are based (e.g. they grow along with the distance between the nodes).

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    Positioning terminals in mobile computing networks  Open access

     Barceló Arroyo, Francisco; Martin Escalona, Israel; Ciurana Adell, Marc
    ERCIM news
    Date of publication: 2013-03-27
    Journal article

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  • Forecasting the next handoff for users moving with the Random Waypoint mobility model

     Zola, Enrica Valeria; Barceló Arroyo, Francisco; Martin Escalona, Israel
    Eurasip journal on wireless communication and networking
    Date of publication: 2013-01-25
    Journal article

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    Users in a cellular network can move while their connections are handed off to different access points. Studies prove that the mobility pattern followed have a strong impact on performance metrics (i.e., handoff (HO) rate, cell residence time). Recently, some key aspects of the Random Waypoint mobility model have been studied in depth, but relating those studies with different cellular layouts has not been reported. Interest in forecasting the cell to which a device may be handed off depending on the movement pattern is twofold. First, it gives insight into properties and statistics of the mobility model. Second, and from a more practical perspective, it is useful to manage resource allocation and reservation strategies in order to smooth the HO process. The goal of this article is to provide an analytical framework for these predictions in a simple layout. Given a node's current location and the timestamp and location of the last waypoint, an approximation for HO during time Delta t is derived. The analysis is provided along with numerical examples and simulations for a symmetrical layout and uniform speed distribution. Results shed light on how useful more advanced strategies can be.

  • Probability of handoff to neighbor cells for random waypoint mobility and non-ideal conditions

     Zola, Enrica Valeria; Barceló Arroyo, Francisco
    Baltic Congress on Future Internet Communications
    Presentation's date: 2012-04-26
    Presentation of work at congresses

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    The handoff process allows users to move while their communication is handled by different antennas in the network. A proper configuration of network's parameters is required in order to guarantee a given QoS for both moving and static users. Prediction of the next cell to which a user may need to connect in the near future may help to better allocate resources in the network and to guarantee the continuity of the communication. In previous works, analytical results for these predictions for nodes moving according to the Random Waypoint mobility model have been presented. However, the mathematical analysis is only possible for simple cases with ideal conditions of propagation and handoff strategy. In this paper, simulation results for the proposed model are presented under different radio channel conditions and handoff strategies. First, the study validates the existing analytical model for ideal conditions. Second, the results prove that the probability of handoff increases under non-ideal radio channel conditions. Moreover, a different handoff strategy may lead to relevant differences in the prediction, thus proving that the handoff strategy has a strong impact on the network performance.

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    DYMO routing protocol with knowledge of nodes¿ position  Open access

     Zola, Enrica Valeria; Barceló Arroyo, Francisco
    Joint ERCIM eMobility and MobiSense Workshop
    Presentation's date: 2012-06-08
    Presentation of work at congresses

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    We present a system that selects the optimal route between two points for vehicles moving in an urban environment. Our approach uses location data gathered from smartphones, which includes route segments and their corresponding travel time. The system can be used as a standalone application with a user interface for path visualization. Additionally, route selection and location prediction can be used for improving streaming video applications and for scheduling delay tolerant data transfers to achieve mobile data offloading.

  • Performance evaluation of the passive TDOA algorithm in dark areas

     Martin Escalona, Israel; Malpartida, Marta; Barceló Arroyo, Francisco
    International Conference and Exhibition on Ubiquitous Positioning, Indoor Navigation and Location Based Services
    Presentation's date: 2012-10-04
    Presentation of work at congresses

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    Positioning in wireless networks has recently concentrated the interest of the research community. Outdoor positioning has been addressed successfully, but location indoors poses some open issues. Time-based ranging techniques, such as 2-way time-of-arrival (TOA), are promising for indoor positioning but present issues such as scalability and landmark dependency. Handling these problems separately makes it difficult to find solutions that can be implemented over communication networks on which positioning solutions rely. The passive TDOA algorithm was proposed for overcoming both issues together. Preliminary results indicate that scalability can be improved. This work assesses the performance of the passive TDOA in scenarios where there are not enough landmarks to run a regular 2-way TOA algorithm. Results show that the accuracy provided is worse than in scenarios with enough landmarks but, depending on the power of the ranging noise, good enough for most of the location-based services indoors.

  • Study of the results in a heterogeneous group for a course on computer networks

     Barceló Arroyo, Francisco; Martin Escalona, Israel
    International Conference on Interactive Collaborative Learning
    Presentation's date: 2012-09-26
    Presentation of work at congresses

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    This paper shows statistics of a group at the Faculty of Telecommunications Engineering in Barcelona (Spain). Due to the different origin and academic background of the students, planning the course is a challenging task. This work shows the features that characterize the group as heterogeneous. Statistics about the origin and the grades of a test before the course are shown along with the existing correlation between both. The paper also analyzes the grades obtained in the final exams and relates them to the origin and initial test. In the statistics some groups can be differentiated with students belonging to each group showing a similar degree of academic progress. The results allow drawing some conclusions on how a careful observation of the countries of origin, academic background and the results of a test before starting the course can help to plan a balanced course and evaluation.

    This paper shows statistics of a group at the Faculty of Telecommunications Engineering in Barcelona (Spain). Due to the different origin and academic background of the students, planning the course is a challenging task. This work shows the features that characterize the group as heterogeneous. Statistics about the origin and the grades of a test before the course are shown along with the existing correlation between both. The paper also analyzes the grades obtained in the final exams and relates them to the origin and initial test. In the statistics some groups can be differentiated with students belonging to each group showing a similar degree of academic progress. The results allow drawing some conclusions on how a careful observation of the countries of origin, academic background and the results of a test before starting the course can help to plan a balanced course and evaluation.

  • Study of the results in a heterogenous group for a course on computer networks

     Barceló Arroyo, Francisco; Martin Escalona, Israel
    Interactive Collaborative Learning: International Conference on Interactive Collaborative Learning and International Conference on Engineering Pedagogy
    Presentation's date: 2012-09-28
    Presentation of work at congresses

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    This paper shows statistics of a group at the Faculty of Telecommunications Engineering in Barcelona (Spain). Due to the different origin and academic background of the students, planning the course is a challenging task. This work shows the features that characterize the group as heterogeneous. Statistics about the origin and the grades of a test before the course are shown along with the existing correlation between both. The paper also analyzes the grades obtained in the final exams and relates them to the origin and initial test. In the statistics some groups can be differentiated with students belonging to each group showing a similar degree of academic progress. The results allow drawing some conclusions on how a careful observation of the countries of origin, academic background and the results of a test before starting the course can help to plan a balanced course and evaluation.

  • Impact of the range and geometry estimation in the accuracy of the passive TDOA algorithm

     Martin Escalona, Israel; Barceló Arroyo, Francisco; Zola, Enrica Valeria
    Annual Mediterranean Ad Hoc Networking Workshop
    Presentation's date: 2012-06-22
    Presentation of work at congresses

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    The positioning ability is essential in mobile networks. Providing the position of entities is in general a complex task that becomes especially hard in ad hoc networks. In these networks, the topology cannot be planned and network nodes usually present restrictions in terms of computation capabilities and autonomy that constrain the network lifetime. Passive algorithms have been proposed for minimizing the impact of location services in the network, i.e. reducing the location traffic and extending the network life. However, the accuracy of passive algorithms tends to be worse than the accuracy for active approaches. This paper studies the impact of several proposals focused on improving the accuracy of the passive TDOA algorithm. Results indicate that weighing the ordinary least squares algorithm with the appropriate factors could be enough for improving the accuracy of the algorithm in some scenarios.

  • Distribution of the frequency of connections in academic WLAN networks

     Zola, Enrica Valeria; Barceló Arroyo, Francisco
    International Conference on Networking and Services
    Presentation's date: 2012-03-26
    Presentation of work at congresses

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    Understanding the trends in the use of wireless local area networks (WLANs) (i.e., how much, when and where traffic is present) is an important issue for modeling the network and for optimizing the allocated resources. Interesting results can be extracted by analyzing traces from real scenarios. In previous works, the authors studied three buildings belonging to two campuses in Barcelona (Spain) and its surroundings. Similar common trends were observed in the three buildings, despite the different amount of users, purpose of the building, geographical location and size of the campus. In this work, the fidelity of the users in accessing the WLAN in different days is analyzed in depth. The population accessing the networks is mostly composed of infrequent users: less than half of the devices access the WLAN more than four days during the studied period. Special insight is given to the underlying distribution. It is shown that, in contrast to previous studies in the same environment, the distribution of the frequency of reconnections to the WLAN is not uniform. The main difference among different buildings is the fidelity of users: users on a small campus are more likely to reappear on different days than on a large campus, where the population is more heterogeneous. The results of this analysis provide general tools for characterizing campus-wide WLAN and a better understanding of usage and performance issues in a mature wireless network in Europe.

  • Calculating distances between wireless nodes for wireless network localization

     Martin Escalona, Israel; Barceló Arroyo, Francisco; Ciurana Adell, Marc
    Recent Advances in Communications and Networking Technology
    Date of publication: 2012-12-01
    Journal article

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    This paper presents a patent targeted to obtain distance measurements between nodes belonging to a wireless network. The main motivation for this patent is the measurement of the distance between a user device and an access point (or base station). After several distance measurements to different access points at sight and assuming the position of the access points known, the device can compute its own position by trilateration. The main advantage in front of previously existing methods to obtain distance measurements is that the method presented here involves only software modifications to legacy terminals, thus allowing avoiding the need for hardware modifications at the user terminal.

  • Admission control in mobile cellular networks. Design, performance evaluation and analysis  Open access

     Vesselinova, Natalia Vassileva
    Defense's date: 2012-04-13
    Department of Telematics Engineering, Universitat Politècnica de Catalunya
    Theses

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    Key to the success of the mobile telecommunication systems is provision of mobility and more specifically, continuity of communication sessions on the move. However, from engineering point of view the cobination of scarce radio resource capacity, radio channel randomness, cellular structure, and user mobility can lead to call interruptions. The latter are regarded as highly undesirable by mobile users. One essential part of the solution to this problem is to address resource insufficiency. To this end admission control algorithms are incorporated into the system. In this thesis we concentrate on admission control as a means of guaranteeing uninterrupted service to users with active calls on the move.The research work reported in the monograph can be briefly summarised as follows. We explored the extensive empirical, analytical, and simulation results concerning teletraffic random variables of mobile cellular systems from the perspective of admission control. We proposed a conceptually different from prior work admission control solution based on the scientific evidence about the statistical nature of system variables and on the main result of renewal theory namely, decision making based on estimated system behaviour. In particular, we proposed a new admission control metric that uses statistical estimates. We evaluated the performance of the devised admission control strategy, which we named MRT (Mean Remaining Time) after the admission control condition, using both analytical and simulation approaches. We mathematically modelled system performance for traditional exponential conditions through a Markov chain. To study the MRT performance for non-conventional teletraffic scenarios we developed a simulation pure performance model. We examined the MRT for conditions that matched measured data from real, live mobile cellular networks. The results show that the scheme can guarantee call continuity and that it achieves a continuous working interval in contrast to the discrete one of the common cut-off scheme, yet the MRT strategy meets the important practical requirement for simplicity. We proposed an approximation to the MRT strategy for the case when not all of the required statistical information is readily available. Next, we studied in-depth the implications of novel techniques introduced in advanced mobile telecommunication systems. In particular, we examined the effect of the adaptive modulation and coding (AMC) technique on system performance and consequently on admission control design in mobile WiMAX. The dynamic tuning to time-varying radio link conditions introduces new random variables that drastically change the traditional mobile cellular system model. In particular, cell capacity and call resource demands are not constant but random, determined by wireless link quality. We analytically modelled the radio channel randomness and the consequent non-deterministic resource demand for a streaming service with constant bit rate and strict delay requirements through a zone-based cell model. Furthermore, we examined system-level fairness, which metric had not been explored in previous studies on mobile WiMAX. Additionally, we studied the effect of AMC on system performance under the two basic admission control approaches proposed in the literature by incorporating them in the analytical model. The results show that the total new call blocking probability and forced call termination probability of a constant bit rate calls deteriorate when the radio channel conditions are quickly varying and the offered load is moderate to heavy. Furthermore, the results show important differences in blocking and dropping probabilities of calls belonging to the same service (voice) and call (either new or handoff) class but being served in different modulation and coding zones. The results also indicate that if the admission control is not adapted to the actual environment (non-deterministic) the system performance is considerably worsened.

  • Middleware for positioning in cellular networks

     Martin Escalona, Israel; Barceló Arroyo, Francisco; Ciurana Adell, Marc
    Date of publication: 2011-04-23
    Book chapter

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  • Fusion of WLAN and GNSS observables for positioning in urban areas: the position ambiguity

     Fernández, Daniel; Barceló Arroyo, Francisco; Martin Escalona, Israel; Ciurana Adell, Marc; Jofre, Martí; Gutiérrez, Esteban
    IEEE Symposium on Computers and Communications
    Presentation's date: 2011
    Presentation of work at congresses

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    This paper proposes a positioning method that combines GPS pseudoranges and WLAN ranges when less than four GPS satellites are within sight. To enhance the positioning availability, a tight hybridization approach with both technologies is considered. Although the work has been performed considering WLAN and GPS, most of the presented ideas, procedures and results are also valid for generic tight non-synchronized fusion of GNSS with terrestrial signals. Special emphasis is placed on the phenomenon of positioning ambiguity that appears due to the combination of measurements with different characteristics. To solve this ambiguity, a method is proposed and studied. The availability and accuracy of the system are tested considering different satellite and terrestrial geometries. The results show that the proposed system is able to improve the availability while maintaining the accuracy of GPS as a standalone.

  • Probability of handoff for users moving with the random waypoint mobility model

     Zola, Enrica Valeria; Barceló Arroyo, Francisco
    IEEE Conference on Local Computer Networks
    Presentation's date: 2011-10-05
    Presentation of work at congresses

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  • Analysis of a heterogeneous group belonging to an international master course on computer networks

     Barceló Arroyo, Francisco; Cruz Llopis, Luis Javier de La; Martin Escalona, Israel
    International Conference on Engineering and Computer Education
    Presentation's date: 2011-09-25
    Presentation of work at congresses

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  • A comparative analysis of the user behavior in academic WiFi networks

     Zola, Enrica Valeria; Barceló Arroyo, Francisco
    ACM Performance Monitoring, Measurement, and Evaluation of Heterogeneous Wireless and Wired Networks
    Presentation's date: 2011-10-31
    Presentation of work at congresses

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  • How students use WLAN inside the classrooms: patterns and behavior

     Zola, Enrica Valeria; Barceló Arroyo, Francisco
    IADIS International Conference on Mobile Learning
    Presentation's date: 2011-03-10
    Presentation of work at congresses

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  • Comparative performance evaluation of IEEE 802.11v for positioning with time of arrival

     Ciurana Adell, Marc; Barceló Arroyo, Francisco; Martin Escalona, Israel
    Computer Standards & Interfaces
    Date of publication: 2011-03
    Journal article

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    Time of Arrival (TOA) based techniques are expected to overcome performance limitations of existing WLAN positioning approaches. The upcoming IEEE 802.11v standard is expected to play a key role because it will include new specific mechanisms for TOA-based positioning with WLAN. This article analyzes some of these new capabilities and evaluates the performance enhancement that they can provide in practice. To this end, a comparative assessment between an existing WLAN TOA-based approach that uses IEEE 802.11 b/g and an analogous solution employing IEEE 802.11v is performed.

  • Contributions to the Planning of the Layout and Handover in Cellular Networks

     Zola, Enrica Valeria
    Defense's date: 2011-10-20
    Department of Telematics Engineering, Universitat Politècnica de Catalunya
    Theses

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  • Sistema de localització de terminals sense fils WLAN a l' interior d'edificis

     Barceló Arroyo, Francisco; Martin Escalona, Israel
    Participation in a competitive project

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  • Passive TDOA location in mobile ad-hoc networks

     Martin Escalona, Israel; Barceló Arroyo, Francisco
    International Conference on Ultra Modern Telecommunications
    Presentation's date: 2010-10
    Presentation of work at congresses

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  • On the Resolution of position ambiguity when integrating GNSS and WLAN observables

     Fernández, Daniel; Ciurana Adell, Marc; Jofre, Martí; Gutiérrez, Esteban; Chester, Edward Ian; Barceló Arroyo, Francisco; Martin Escalona, Israel
    European Navigation Conference on Global Navigation Satellite Systems
    Presentation's date: 2010-10-20
    Presentation of work at congresses

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  • Performance stability of software ToA-based ranging in WLAN

     Ciurana Adell, Marc; Giustiniano, Domenico; Neira, Albert; Barceló Arroyo, Francisco; Martin Escalona, Israel
    International Conference on Indoor Positioning and Indoor Navigation
    Presentation's date: 2010-09
    Presentation of work at congresses

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    This article proposes a set of strategies to improve the performance stability and reliability of purely software ToA-based ranging with off-the-shelf WLAN equipment. Taking as starting point the core design lines proposed in (1), where timing measurements were taken at OS level using the CPU clock of the client device, we optimize the OS configuration and the capture of the time-stamps. Results obtained with a prototype demonstrate that the proposed enhancements improve the performance stability by a factor four. The interest in this kind of ranging methods is because they enable cost-effective and accurate positioning in GNSSless environments.

  • A Field Study on Satellite and Cellular Signals as Sources for Location

     Gete-Alonso Roldan, Oscar; Martin Escalona, Israel; Barceló Arroyo, Francisco
    International Conference on Computer Engineering and Applications
    Presentation's date: 2010-03-20
    Presentation of work at congresses

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    This article presents a statistical study on the availability of location sources. In particular, it rates the availability of cellular network base stations and GPS satellites in urban scenarios. Individual and joint availability density functions have been obtained for both types of signal sources, as well as statistical information that complements these functions. This information is of great importance due to the growing interest in fusion (i.e., combination) of location techniques. The results indicate that the improvements in coverage from fusion techniques depend both on the fusion mechanism and the scenario, obtaining noticeable benefits in constrained situations.

  • Access to the full text
    Impacto del modelo de error en distancia en la simulación de sistemas de localización  Open access

     Guardiola, Salvador; Martin Escalona, Israel; Barceló Arroyo, Francisco; Ciurana Adell, Marc
    Jornadas de Ingeniería Telemática1
    Presentation's date: 2010-09
    Presentation of work at congresses

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    Las redes inalámbricas han favorecido enormemente el interés de los usuarios, proveedores de servicio y operadores de red en el posicionamiento geográfico. Como consecuencia, se han propuesto mecanismos en la mayor parte de tecnologías de red inalámbrica con los que soportar la localización de usuarios. La evaluación de calidad ofrecida por dichas técnicas de localización, normalmente en términos de precisión, latencia y escalabilidad, recae en herramientas de simulación. Es esencial por tanto, que los modelos de error empleados en estas herramientas estén acordes a la realidad. Este hecho es si cabe más importante en el caso de emplear técnicas de localización basadas en medida de la distancia a partir de métricas temporales, como son el tiempo de llegada (TOA) o la diferencia entre tiempos de llegada (TDOA). Estas técnicas son especialmente sensibles a no disponer de visión directa entre los distintos elementos involucrados en la localización, por lo que la evaluación de sus capacidades suele hacerse bajo esas condiciones. El presente artículo compara bajo un mismo escenario, diversos modelos de error para las métricas empleadas en técnicas como TOA o TDOA. Los resultados concluyen que los modelos que no tienen en cuenta las distancias reales (que son los más habituales) tienden a proporcionar una estimación optimista el error de posicionamiento, cosa que no ocurre en el caso de modelos más complejos que sí tienen en cuenta esa información.

  • WLAN User Behavior: Opportunities for m-Learning

     Zola, Enrica Valeria; Barceló Arroyo, Francisco
    IADIS International Conference on Mobile Learning
    Presentation's date: 2010-03-19
    Presentation of work at congresses

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  • A field study on the fusion of terrestrial and satellite location methods in urban cellular networks

     Barceló Arroyo, Francisco; Martin Escalona, Israel; Manente, Cyrille
    European transactions on telecommunications
    Date of publication: 2010-05-01
    Journal article

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    This work studies the improvement in service coverage obtained by three different approaches to combining two triangulation (terrestrial and satellite) location methods for cellular networks in an urban environment. The paper assumes that the terrestrial cellular network uses enhanced observed time difference (E-OTD) in 2G or observed time difference of arrival (OTDOA) in 3G, while the satellite GNSS uses the assisted global positioning system (A-GPS), but the analysis can be easily generalised to other triangulation methods. A straightforward analytical model is presented to evaluate the service coverage resulting from each of the three approaches. The model is fed with actual coverage figures, gathered from test measurements carried out in Paris (France) for several urban scenarios. Numerical results show that the three approaches lead to improvements in all the tested scenarios, and that the improvement obtained by the increasing complexity of the fusion approach depends highly on the coverage of each individual method and on the joint probability function of individual performances

  • A robust to multi-path ranging technique over IEEE 802.11 networks

     Ciurana Adell, Marc; Barceló Arroyo, Francisco; Cugno, Sebastiano
    Wireless networks
    Date of publication: 2010-05
    Journal article

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  • Location in wireless Local Area Networks

     Ciurana Adell, Marc; Martin Escalona, Israel; Barceló Arroyo, Francisco
    Date of publication: 2010-07-01
    Book chapter

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  • Access to the full text
    Discrete event simulation of wireless cellular networks  Open access

     Zola, Enrica Valeria; Martin Escalona, Israel; Barceló Arroyo, Francisco
    Date of publication: 2010-09
    Book chapter

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    Location in ad-hoc networks  Open access

     Martin Escalona, Israel; Ciurana Adell, Marc; Barceló Arroyo, Francisco
    Date of publication: 2010
    Book chapter

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  • Contributions to location in cellular networks

     Martin Escalona, Israel
    Defense's date: 2010-05-10
    Department of Telematics Engineering, Universitat Politècnica de Catalunya
    Theses

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  • Contributions to TOA-based location with WLAN  Open access

     Ciurana Adell, Marc
    Defense's date: 2010-07-15
    Department of Telematics Engineering, Universitat Politècnica de Catalunya
    Theses

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    Location techniques that satisfy the requirements of advanced Location-Based Services (LBS) in environments where GPS fails are needed, therefore accurate indoor positioning is becoming increasingly important. This PhD Thesis is devoted to the research on location of mobile devices employing WLAN (IEEE 802.11). The use of this kind of wireless networks infrastructures for positioning enables a powerful synergy between communications and location and allows solutions with good performances at moderated costs. However the adopted WLAN location methods suffer from important limitations that prevents from applying them to some fields that need more flexible and robust solutions. The main objective of this PhD is exploring precise WLAN location methods that allow overcoming these limitations. The researched methods here are based on measuring the Time Of Arrival (TOA), which is the time that takes the signal propagating from the transmitter to the receiver. TOA-based location works in two stages: ranging and positioning. The ranging consists of estimating the distances between the targeted terminal and several WLAN access points, each distance obtained measuring the TOA and then multiplying it by the speed of the WLAN signal. After that, the positioning takes as inputs the estimated distances and the known coordinates of the involved access points and calculates the position of the terminal by means of a trilateration or tracking algorithm. The key problem is that the characteristics of the IEEE 802.11 protocols difficult to perform accurate TOA measurements. The main challenge that faces the research work reported here is demonstrating the feasibility of achieving this while keeping the modifications over standard WLAN consumer equipment at minimum. The objective of this work can be understood as exploring the current limits of TOA-based methods over WLAN, making contributions that form a complete TOA-based location method that goes a step forward with respect to the other existing proposals. First, research on TOA-based ranging -the key component of TOA-based location methods- is reported. The general adopted approach consists of performing Round Trip Time (RTT) measurements employing IEEE 802.11 MAC frames, taking the maximum advantage of the combination of IEEE 802.11 protocol and WLAN consumer devices mechanisms. After that, the performed research on trilateration/tracking -the second stage of TOA-based location methods- is explained. Finally some performed studies about the achieved location method are presented. Lloc i data Signatura

    Actualment existeix la necessitat de disposar de tècniques de localització que satisfacin els requeriments de serveis avançats basats en localització en entorns on GPS no està disponible, de manera que el posicionament precís en interiors d’edificis és cada vegada més important. Aquesta tesi doctoral està dedicada a la investigació sobre la localització de dispositius mòbils que utilitzen WLAN (IEEE 802.11). L'ús d'aquest tipus de xarxes sense fils per al posicionament permet una profitosa sinèrgia entre les comunicacions i la localització i permet solucions amb un bon rendiment a un cost moderat. No obstant això, els mètodes basats WLAN proposats fins el moment pateixen de limitacions importants que impedeix la seva aplicació a alguns camps que requereixen solucions més flexibles i robustes. L'objectiu principal d'aquesta tesi és explorar mètodes de localització precisa WLAN que permetin superar aquestes limitacions. Els mètodes que s’han investigat durant la tesi es basen en la mesura del time of arrival (TOA), que és el temps que tarda el senyal en propagar-se des del transmissor fins al receptor. En les tècniques de posicionament basades en TOA s’hi poden diferenciar dues fases: ranging i posicionament. El ranging consisteix en l’estimació de distàncies entre el terminal a localitzar i diversos punts d'accés WLAN; cada estimació de distància s’obté mesurant el TOA i multiplicant-lo després per la velocitat de propagació del senyal IEEE 802.11. Un cop fet això, el posicionament pren com a inputs les distàncies estimades per a, conegudes les coordenades dels punts d'accés involucrats, calcular la posició del terminal per mitjà d'un algoritme de tracking o trilateració. El problema clau és que les característiques dels protocols IEEE 802.11 a dia d’avui fan difícil la realització de mesures precises de TOA d’una manera senzilla. El principal repte que afronta el present treball de recerca és demostrar la viabilitat d’això darrer, minimitzant en la major mesura possible les modificacions sobre els equips WLAN comercials. L'objectiu d'aquest treball pot ser entesa com l'exploració dels límits actuals dels mètodes de posicionament basats en TOA sobre WLAN, realitzant contribucions que conformen un mètode complet de localització basat en TOA que pretén anar un pas endavant respecte a les propostes existents. En primer lloc, la investigació sobre ranging basat en TOA -el component clau dels mètode de localització TOA- és explicada en detall. El mètode general adoptat per a calcular el TOA consisteix en la mesura del temps d'anada i tornada del senyal, round trip time (RTT), utilitzant trames MAC IEEE 802.11 per tal de treure el màxim profit de la combinació del protocol IEEE 802.11 i els mecanismes dels dispositius WLAN comercials. Després d'això, es detalla la investigació realitzada sobre trilateració i tracking, la segona etapa dels mètodes de localització basats en TOA. Finalment es descriuen alguns estudis realitzats sobre les prestacions, possibles millores i encaix en futurs estàndars del mètode de localització explorat.

  • ENCAMINAMIENTO PARA REDES AD-HOC BASADO EN LOCALIZACION DE TERMINALES. APLICACIONES Y SINERGIAS CON

     Rojas Espinosa, Alfonso; Martin Escalona, Israel; Zola, Enrica Valeria; Ciurana Adell, Marc; Barceló Arroyo, Francisco
    Participation in a competitive project

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  • Process and system for calculating distances between wireless node

     Martin Escalona, Israel; Barceló Arroyo, Francisco; Ciurana Adell, Marc
    Date of request: 2010-05-11
    Invention patent

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  • Procedimiento y sistema para el cálculo de distancias entre nodos inalámbricos

     Martin Escalona, Israel; Barceló Arroyo, Francisco; Ciurana Adell, Marc
    Date of request: 2010-04-16
    Invention patent

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  • On the impact of ranging-error models for simulating indoors location systems

     Guardiola, Salvador; Martin Escalona, Israel; Barceló Arroyo, Francisco
    IEEE International Symposium on Personal, Indoor, and Mobile Radio Communications
    Presentation of work at congresses

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  • Guard capacity implementation in OPNET modeler WiMAX suite

     Vassileva Vesselinova, Natalia; Koucheryavy, Yevgeni; Barceló Arroyo, Francisco
    International Conference on ultra Modern Telecommunications & Workshops
    Presentation's date: 2009-10-14
    Presentation of work at congresses

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    Admission Control (AC) algorithms in mobile cellular networks support continuity of active communication sessions by guaranteeing availability of free resources. In this paper, we first describe the factors that condition AC design and show that AC in broadband mobile networks presents new challenges compared to AC in telephone cellular networks. We tailor the guard channel admission control strategy to the characteristics of mobile WiMAX networks. For AC validation and performance evaluation we use OPNET Modeler WiMAX Suite. To this end, we create in the simulator a framework for AC implementation. Then, we incorporate the Guard Capacity (GC) algorithm, which is the preferred choice of telephone cellular networks’ operators as GC is simple yet efficient. The accuracy of implementation is validated through simulation.

  • Improving the performance of TOA over wireless systems to track mobile targets

     Ciurana Adell, Marc; Barceló Arroyo, Francisco; Llombart, M.
    IEEE International Conference on Communications
    Presentation's date: 2009
    Presentation of work at congresses

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  • SofTOA: software ranging for TOA-based positioning of WLAN terminals

     Ciurana Adell, Marc; López Bueno, David; Barceló Arroyo, Francisco
    International Symposium on Location and Context Awareness
    Presentation's date: 2009-05-01
    Presentation of work at congresses

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    TOA-based trilateration constitutes an interesting choice to locate terminals employing WLAN networks. A major limitation of this technique is the requirement for hardware modifications in the WLAN device in order to achieve accurate ranging. This paper presents an approach that overcomes this limitation. It is based on RTT measurements performed through time-stamping the transmission and reception of IEEE 802.11 MAC frames from the WLAN driver’s code, employing the CPU clock as time-base. Some statistical processing is needed in order to mitigate the noise of the measurements. This paper presents experimental results obtained with a prototype showing ranging errors of a few meters when applied to estimate distances up to 25 meters in both indoor and outdoor environments.

  • Validation of a traffic-based CAC method under general channel holding time

     Vassileva Vesselinova, Natalia; Barceló Arroyo, Francisco
    IEEE Conference on Computer Communications
    Presentation's date: 2009-08-06
    Presentation of work at congresses

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    We validate a call admission control (CAC) method for mobile cellular networks under more restrictive conditions than those assumed in its design. The method uses distribution and the first and second moments of the channel holding time (CHT) parameter to compute the algorithm’s main admission control metric: remaining CHT. Our goal is to generalize the handover method when only the mean and variance of CHT are known, but precise knowledge of the CHT’s complete distribution is not available. The problem is of practical interest because probability distribution fitting can be time- and CPU-intensive. To this end, we use an approximation of the expected remaining holding time instead of its exact value. We show that for a variety of traffic conditions and the general gamma distribution, the approximation yields acceptable results. For a log-normal distribution, our results also suggest that the algorithm can be defined based solely on the mean and variance of CHT.