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Now showing items 1 - 16 of 44

  • Hierarchical Slotted Wireless Random Channel Access with Power Control

    Karouit, Abdelillah   Orozco Barbosa, Luis   Ramírez-Mireles, Fernando   Haqiq, Abdelkrim  

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  • Hierarchical Slotted Wireless Random Channel Access with Power Control

    Karouit, Abdelillah   Orozco Barbosa, Luis   Ramirez-Mireles, Fernando   Haqiq, Abdelkrim  

    This paper introduces a hierarchical Wireless Random Access scheme based on power control where intelligence is split among the mobile users in order to drive the outcome of the system towards an efficient point. The hierarchical game is obtained by introducing a special user who plays the role of altruistic leader whereas the other users assume the role of followers. We define the power control scheme in such a way that the leader first chooses the lowest power to transmit its packets among.. available levels whereas the followers re-transmit by randomly choosing a power level picked from N - 1 higher distinct power levels. Using a 3D Markovian model, we compute the steady state of the system and derive the average system throughput and expected packet transmission delay. Our numerical results show that the proposed scheme considerably improves the global performance of the system avoiding the well known throughput collapse at high loads commonly characterizing most random channel access mechanisms.
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  • Calibration of Wi-Fi-Based Indoor Tracking Systems for Android-Based Smartphones

    Martinez del Horno, Miguel   Garcia-Varea, Ismael   Orozco Barbosa, Luis  

    With the growing development of smartphones equipped with Wi-Fi technology and the need of inexpensive indoor location systems, many researchers are focusing their efforts on the development of Wi-Fi-based indoor localization methods. However, due to the difficulties in characterizing the Wi-Fi radio signal propagation in such environments, the development of universal indoor localization mechanisms is still an open issue. In this paper, we focus on the calibration of Wi-Fi-based indoor tracking systems to be used by smartphones. The primary goal is to build an accurate and robust Wi-Fi signal propagation representation in indoor scenarios.We analyze the suitability of our approach in a smartphone-based indoor tracking system by introducing a novel in-motion calibration methodology using three different signal propagation characterizations supplemented with a particle filter. We compare the results obtained with each one of the three characterization in-motion calibration methodologies and those obtained using a static calibration approach, in a real-world scenario. Based on our experimental results, we show that the use of an in-motion calibration mechanism considerably improves the tracking accuracy.
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  • Modeling and Analysis of the 1-Wire Communication Protocol Using Timed Colored Petri Nets

    Emilia Cambronero, Maria   Macia, Hermenegilda   Valero, Valentin   Orozco Barbosa, Luis  

    The widespread use of sensor networks has enabled the deployment of a wide variety of services. In order to reduce maintenance costs without jeopardizing the reliability of the services, developers and researchers are exploring ways to reduce the complexity of the protocols and their underlying hardware infrastructure. However, the verification and evaluation of novel solutions must also be taken as a key design parameter in the development of reliable and cost-effective solutions. In this paper, we develop a timed colored Petri net (TCPN) model of the 1-wire protocol, which is one of the most popular and simplest protocols currently used in the implementation of sensor platforms. The use of TCPNs is justified by the fact that they provide us with the means to evaluate the qualitative and quantitative properties of the protocol. Our results include the analysis of the absence of deadlocks as well as the quantitative evaluation of the protocol. Our numerical results are also confirmed by using an event-driven simulator.
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  • Spatial statistical analysis for the design of indoor particle-filter-based localization mechanisms

    Martinez-Gomez, Jesus   Martinez del Horno, Miguel   Castillo-Cara, Manuel   Brea Lujan, Victor Manuel   Orozco Barbosa, Luis   Garcia-Varea, Ismael  

    The accurate localization of end-users and resources is seen as one of the main pillars toward the successful implementation of context-based applications. While current outdoor localization mechanisms fulfill most application requirements, the design of accurate indoor localization mechanisms is still an open issue. Most research efforts are focusing on the design of mechanisms making use of the receiver signal strength indications generated by WLAN (wireless local area network) devices. However, the accuracy and robustness of such mechanisms can be severely compromised due to the random and unpredictable nature of radio channels. In this article, we develop a methodology incorporating various algorithms capable of coping with the unpredictable nature of radio channels. Following a holistic approach, we start by identifying the wireless equipment parameter setting, better meeting the implementation requirements of a robust indoor localization mechanism. We then make use of RANdom SAmple Consensus paradigm: a robust model-fitting mechanism capable of smoothing the data captured during the space survey. Using an experimental setup, we evaluate the benefits of integrating the floor plan and an ordinary Kriging interpolation algorithm in the estimation process. Our main findings show that our proposal can greatly improve the quality of the information to be used in the development of particle-filter-based indoor localization mechanisms.
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  • A Team Study of a Multiple-Power Wireless Random Channel Access Mechanism with Capture Effect

    Karouit, Abdelillah   Sabir, Essaid   Ramirez-Mireles, Fernando   Orozco Barbosa, Luis   Haqiq, Abdelkrim  

    We present a team analysis of a slotted random wireless channel access mechanism. Under the proposed scheme, denoted wireless random access mechanism with multiple power levels (MPL-WRA), each mobile station contends for a transmission opportunity following the principles of a slotted access mechanism incorporating a random transmitting power value selected among various available power levels. In this way, a capture effect may be produced allowing the packet to be decoded whenever the signal-to-interference-plus-noise ratio is higher than a given threshold. In order to analyze the performance and optimization of the proposed setup, we build aMarkovian model integrating the wireless access mechanism supplemented by the use of multiple power levels in an attractive and simple cross-layer fashion. We follow a team problem approach allowing us to fine tune the design parameters of the overall system configuration. Throughout an extensive numerical analysis, our main results set the basis for the social optimal system configuration of the proposed mechanism taking into account the physical constraints of using multiple power levels and the actual practical implementation of a slotted access mechanism. We end the paper with concluding remarks and future research directions including guidelines for the actual implementation of our proposal.
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  • On the American concept of power.by Jose Luis Orozco

    Review by: Jules R. Benjamin  

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  • On the American concept of power.by Jose Luis Orozco

    Review by: Jules R. Benjamin  

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  • El negocio de los ilegales. Ganancias para quiénby Juan Luis Orozco

    Review by: Carlos Alba Vega  

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  • El negocio de los ilegales. Ganancias para quiénby Juan Luis Orozco

    Review by: Carlos Alba Vega  

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  • Reasons of State and Reasons of Market: Theory and Practice of American Foreign Policy.by Jose Luis Orozco

    Review by: Jules R. Benjamin  

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  • Reasons of State and Reasons of Market: Theory and Practice of American Foreign Policy.by Jose Luis Orozco

    Review by: Jules R. Benjamin  

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  • La primera bomba hidráulica novohispana: Anotaciones al texto de Luis Chávez Orozco

    Enrique Guadian  

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  • La primera bomba hidráulica novohispana: Anotaciones al texto de Luis Chávez Orozco

    Enrique Guadian  

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  • LUIS CHAVEZ OROZCO

    Luis Rublúo  

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  • LUIS CHAVEZ OROZCO

    Luis Rublúo  

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