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Software in Telecommunications and Computer Networks, 2006. SoftCOM 2006. International Conference on

Date Sept. 29 2006-Oct. 1 2006

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Displaying Results 1 - 25 of 85
  • Geometrical aspects of 3D human body exposed to extremely low frequency high voltage electric fields. A BEM approach

    Page(s): 17 - 21
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (5219 KB) |  | HTML iconHTML  

    The paper deals with the three dimensional modelling of the human body exposed to extremely low frequency (ELF) high voltage electric fields by mean of the boundary element method (BEM). Numerical results along head, neck, torso, abdomen, arms, legs and ankles are presented and discussed in the case of grounded subject standing under power distribution lines. The objective is to characterise the influence of different shape and geometrical factors on the current distribution inside the body and electric field in the near field. The inclusion of legs and arms with different orientations with respect to the incident field are considered. The main contribution is to present new results of the BEM for extremely low frequency exposure and to evaluate the relationship between degree of detail in 3D modelling and the corresponding fluctuation of results for induced currents View full abstract»

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  • Analytical model of human body when exposed to high frequency electromagnetic fields

    Page(s): 32 - 36
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (215 KB) |  | HTML iconHTML  

    Analytical model of human body is used to calculate the electric field and current density induced in human body when it is exposed to high frequency electromagnetic fields (50-200 MHz). Especially, of interest are frequencies used by radio amateurs (50-200 MHz). Formulas used in this study are derived by using a cylindrical model of human body. Tabulations and graphical representations illuminate the results. The intent of this work is to draw more attention on possible health effects that RF fields from radio amateur antennas might have on human body View full abstract»

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  • Finite element thermal model of the human exposed to electric field generated from GSM base station

    Page(s): 22 - 26
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3800 KB) |  | HTML iconHTML  

    Thermal analysis of human exposure to base station antennas radiation is presented in this article. The formulation is based on complex anatomic homogenous model of human body. The temperature rise is determined by solving the Pennes bio-heat equation using the standard finite element method, and it is found rather negligible. The advantage of the presented model is that it is fully anatomic View full abstract»

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  • A Simple Finite Element Model of Heat Transfer in the Human Eye

    Page(s): 27 - 31
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (4281 KB) |  | HTML iconHTML  

    A simple finite element 2D model of the human eye is developed to calculate the steady-state temperature distribution. The mathematical model of the eye is based on the Pennes bio-heat transfer equation. Problem is solved using the weak formulation and the Galerkin-Bubnov procedure. The study was performed to determine the effects of various values of thermal conductivity of lens on temperature distribution inside human eye and also the effects due to changes in ambient temperature and blood temperature View full abstract»

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  • Finite element model of the human head exposed to electrostatic field generated by Video Display Units

    Page(s): 12 - 16
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (4357 KB) |  | HTML iconHTML  

    The goal of this paper is to investigate interaction between electrostatic field of video display units (VDU's) and human head in front of it. Special attention is given to the field at the surface of the face. The finite element model for assessment of the electrostatic field, by solving Laplace equation for the electric potential, is implemented. The electrostatic field is calculated for two different faces and for two different types of the domain and then compared with results obtained by the finite difference method. The advantage of the presented numerical method is a high resolution and a higher accuracy View full abstract»

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  • Assessment of Human Exposure to Power Substation Electric Field

    Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (5280 KB) |  | HTML iconHTML  

    The paper deals with human exposure to extremely low frequency (ELF) electric fields generated by transformer substation. The problem is twofold, i.e. it requires the calculation of power substation electric field and current density induced inside the human body. ELF electric field generated from a power substation is assessed by solving the Scalar Potential Integral Equation (SPIE) using the Source Element Method (SEM), a variant of the Indirect Boundary Element Method (IBEM). Knowing the electric field due to the substation the current density induced within the human being exposed to such field is obtained by solving the Laplace equation variant of the continuity equation using the direct Boundary Element Method with domain decomposition (BEM-DM). Some illustrative computational results for external electric field and internal current density are presented. View full abstract»

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  • Multi-monopole model of man for SAR evaluations

    Page(s): 7 - 11
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (278 KB) |  | HTML iconHTML  

    The paper introduces a multi-element model of man exposed to a radiation field for evaluating the local specific absorption rate (SAR) distributions. Use will be made of an assembly of constitutive elements representing a postured human subject. Based on the SAR dependence on frequency, two different equivalents of the exposed human body are proposed. For frequencies below human resonance, the irradiated body is assimilated to an interconnected multi-sphere electrode structure. Conversely, above human resonance, the human equivalent is envisaged being composed by a disconnected assembly of double-cone antennas surrounded by biological media. Simple formulas for the local SAR evaluation are derived accordingly View full abstract»

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  • Modeling panel antenna in NEC

    Page(s): 61 - 65
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (4209 KB) |  | HTML iconHTML  

    The paper deals with the panel antenna modeling using NEC Win PRO v. 1.1 package. Base of antenna modeling would be wire construction. To achieve better performance and characteristics, several solutions for reflector and dipole are proposed. Antenna with best results and attributes will be compared with technical data of APX907016 RFS antenna given by producer. The challenge in the design of a suitable antenna is overcoming the inherent relationships between gain, pattern beam width, the presence of pattern side and back lobes, and also the size of the antenna View full abstract»

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  • Teaching Electromagnetic Radiation effects on Humans

    Page(s): 52 - 56
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (93 KB) |  | HTML iconHTML  

    We teach electromagnetics as part of a general education course in physics (for non science majors) in which we relate physics to societal issues. The course covers the effects of electromagnetic radiation on human beings. This discussion is limited to at most one class room period (about 50 minutes) usually less. There are several important conceptual issues that must be covered before such a presentation can be meaningful. The paper presents the arguments we use in this course View full abstract»

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  • Usage Limitations of Field Strength Probes for RADHAZ Survey

    Page(s): 43 - 47
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (256 KB) |  | HTML iconHTML  

    The radiation hazard (RADHAZ) survey is commonly done using field strength probes. These probes are inherently wideband and thus non-selective, what makes them a good choice for quick wideband surveys. On the other hand, this characteristic presents a problem when trying to discriminate signals in a multifrequency environment. The most commonly used diode-based probes have another significant drawback: some probes are very sensitive to the waveform of the measured signal. As shown by the measurement experiment described in this paper, the measurement result of such a probe can show overestimated value of the field strength, which is still usable for the worst-case RADHAZ analysis. Also, the experiment shows that such probes can show the underestimation of the field strength, which makes them unusable for RADHAZ survey. Knowing this, some guidelines on the probe usage and RADHAZ survey procedures are given View full abstract»

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  • Modeling radar antenna in NEC

    Page(s): 48 - 51
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (335 KB) |  | HTML iconHTML  

    The paper deals with the radar antenna modelling using NEC Win package. Obtaining radar antenna radiation model was necessary so one can later use it for calculation of radiation strength and estimation if there is any potential radiation damage to instruments that should be used for measuring radar antenna radiation. Model is also needed for future study radiation effects on human body exposure. Some illustrative numerical results have been presented in this work View full abstract»

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  • Electromagnetic effects on transmission lines

    Page(s): 37 - 42
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (475 KB) |  | HTML iconHTML  

    Electromagnetic fields can generate interference on intersystem wiring and cabling. Often this interconnection is in the form of cables and other forms of transmission lines. The simplest model for the system interconnections is a two wire transmission line. Even such a simple case is complex when the wavelength approaches the spacing between the conductors. In such a case one needs to use the full set of Maxwell's equations. Such calculations are computationally expensive. The general solution to this problem provides more information than is needed. A simpler approach is to compute the resonant frequency amplitudes using a modified transmission line model which includes a radiation resistance term. We have obtained a closed form solution of the modified transmission line model with radiation resistance. We compare the results of this solution with computational solutions obtained from a Maxwell equation solver. We conclude that under some conditions, the model is sufficiently accurate at wavelengths larger than 5 times the separation of the wires on the transmission line View full abstract»

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  • Electromagnetic Field Measurements In Student Microwave Laboratory

    Page(s): 57 - 60
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (765 KB) |  | HTML iconHTML  

    This paper presents the measurements of the electromagnetic fields present in the student microwave laboratory. Due to the high altitude and vulnerability to the ambient electromagnetic fields, it was interesting to see if the level of exposure to microwave frequencies in the laboratory exceeds the international and Croatian standards. The measurements were done in the frequency range from 75 MHz to 3 GHz. The highest fields were from the nearby base station, but still only 0.25 V/m, which is app. 0.5% of the reference level, while the measured radiation from the mobile phone showed peak value of 30 V/m during call, or app. 0.9% of the reference level View full abstract»

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  • Dynamic TXOP configuration for Qos enhancement in IEEE 802.11e wireless LAN

    Page(s): 66 - 70
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (210 KB) |  | HTML iconHTML  

    This paper presents a study on transmission opportunity (TXOP) mechanism of the new MAC protocol described in the IEEE 802.11e supplement to the standard. A simple algorithm for dynamic configuration of TXOP limit is proposed for the contention channel access mode, called enhanced distributed channel access (EDCA). The proposed scheme aims to define dynamic rules for TXOP duration adjustment in multimode IEEE 802.11e networks in order to improve system efficiency and provide better QoS provision View full abstract»

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  • Cross-layer design of packet scheduling algorithm

    Page(s): 76 - 80
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (156 KB) |  | HTML iconHTML  

    This paper presents a cross-layer design approach for a packet scheduling algorithm called an adaptive profile scheduling (APS) algorithm. The proposed APS takes into account different wireless channel conditions observed by subscriber stations to enhance the system throughput while it preserves the property of the long-term fairness and the guaranteed rate for users View full abstract»

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  • Comparison of WiMAX coverage at 450MHz and 3.5GHz

    Page(s): 71 - 75
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (5899 KB) |  | HTML iconHTML  

    In this paper we calculate, analyze and compare the area covered by radio signal based on WiMAX standard at two carrier frequencies, namely 450 MHz and 3.5 GHz in flat rural, hilly rural and urban environment. The channel model proposed by WiMAX forum has been applied as path loss model at 3.5 GHz for cell coverage prediction, while at 450 MHz the Longley-Rice model for rural areas and Okumura Hata channel models for urban area is used. The cell size prediction strongly suggests to limit the 3.5 GHz frequency band to urban areas, where the higher system capacity is required, while in rural areas the 450 MHz carrier frequency provide good compromise between coverage and system capacity View full abstract»

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  • Palm's Machine-Repair Model with a Generalised Poisson Input Stream and Constant Service Time

    Page(s): 81 - 85
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (334 KB) |  | HTML iconHTML  

    This model belongs to the class of queueing systems with feedback. It is M(g)/D/1/k/S queue with generalised Poisson arrival process, constant service time, single server, limited waiting positions and finite number of customers. We use the generalised input Poisson stream that can be peaked, regular or smooth. This model with quasi-random input stream and constant service time is a non-Markov process (renewal process). An algorithm for the calculation of the state probabilities, the time congestion probability, the average delay and the waiting time distributions are presented. It is shown that the variance of the input stream changes significantly the characteristics of this waiting system View full abstract»

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  • Optimizing SIP Service Provisioning in Internet Connected MANETs

    Page(s): 86 - 90
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (91 KB) |  | HTML iconHTML  

    Recently, mobile ad-hoc networks (MANETs) have gained a lot of attraction because they are flexible, self-configurable and fast to deploy. Systems beyond 4G are likely to consist of a combination of heterogeneous wireless technologies and naturally might comprise MANETs as one component. In order to provide multimedia services such as voice over IP in such environment, support for session initiation protocol (SIP) is essential. A MANET is a decentralized collection of autonomous nodes but a SIP infrastructure requires centralized proxies and registrar servers. In this paper, we first study the implications of using standard SIP architecture in Internet connected MANETs. We analyze limitations of SIP service scalability when centralized proxies/registrars located in the access network are used by MANET nodes. Finally, we present alternative approaches to provide SIP services in such environment to avoid current limitations View full abstract»

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  • Quality of Service in Mesh Mode IEEE 802.16 Networks

    Page(s): 107 - 111
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (298 KB) |  | HTML iconHTML  

    In recent years wireless metropolitan area networks have become very popular. The wireless MAN, which is defined in IEEE 802.16 standard, offers an alternative to a cabled access networks in rural and suburban areas where is slow deployment of more expensive traditional wired technologies. Wireless MAN is full-service high speed network which is developed to support various type of traffic. This paper presents service flow management which can satisfy QoS requirements for all types of traffic View full abstract»

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  • The Importance of Adaptive Applications in Mobile Wireless Networks

    Page(s): 96 - 101
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (262 KB) |  | HTML iconHTML  

    In this paper, we illustrate the importance of applications' adaptability and QoS awareness in mobile wireless networks. We utilize a "mobile QoS adaptation" strategy aiming to deal with the inconsistencies arising from mobility events in a wireless mobile environment. The performance of the specific adaptation strategy is evaluated through simulations under different traffic environments in a wireless network based on 3GPP's UMTS structure. As a result, we show that the performance of a network can be improved when adaptive applications are used by both mobile and fixed hosts View full abstract»

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  • Evaluation of QoS Support for Multimedia Traffics in IEEE 802.11e

    Page(s): 91 - 95
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (301 KB) |  | HTML iconHTML  

    The efficient delivery of multimedia over wireless LANs is strongly dependent on the requirements imposed by different traffics contending the channel resources. Mechanisms for supporting QoS are needed, especially when voice and video applications come into play with stringent constraints in terms of delay and throughput. In this paper we evaluate, through simulations, the benefits derived from the adoption of the IEEE 802.11e standard in delivering multimedia over WLANs. The adoption of fine-tuned parameters regulating the EDCA MAC scheme permits to achieve high performance in terms of goodput and delay, allowing multimedia traffics to fully satisfy their QoS requirements. Realistic assumptions have been made in our simulations, by taking into account the shadowing effects, typical of closed environments, and by adopting suitable parameters to simulate 802.11e channels as exactly as possible View full abstract»

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  • Video-streaming Transmission with QoS over Cross-Layered Ad hoc Networks

    Page(s): 102 - 106
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (240 KB) |  | HTML iconHTML  

    End-to-end quality of service (QoS) provision to video-streaming applications over mobile ad hoc networks (MANETs) poses a specially challenging problem. In this paper we propose a cross-layer (XL) network architecture design to optimize the overall performance of video-streaming services over MANETs, called ViStA-XL. The idea relies on applying several optimization strategies to different network layers in a holistic way. In our proposal, a real-time XL optimizer (XLO) collects information about the node and network states from different layers of the network's protocol stack. Then, in order to minimize the error between received and transmitted video, the XLO module takes the necessary decisions to act dynamically over different layers' parameters. In addition, our proposal exploits path diversity as a mean to reinforce QoS provision to layered-coded video-streaming applications, by protecting the most important video information packets. To show the advantages of our approach, we have developed an algorithm based on ViStA-XL. Simulation results show that our proposed network design can improve the performance of video-streaming transmissions over MANETs in spite of frequent changes in network topology and node's conditions View full abstract»

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  • A Hybrid Algorithm for Topology Optimization in Wireless Sensor Networks

    Page(s): 121 - 126
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (267 KB) |  | HTML iconHTML  

    This paper proposes a topology control algorithm for wireless sensor networks which have a large scale structure and densely distributed nodes. One of the main problems in topology control is power efficiency with consideration of connectivity. The proposed algorithm is aimed to find a topology with near optimum power consumption within reasonable convergence time. While game theory is exploited to prove convergence property of proposed algorithm, clustering concept is employed to reduce convergence time with the aid of parallel processing View full abstract»

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  • Multipath Routing for video-streaming services over IEEE 802.1le Ad hoc Networks

    Page(s): 132 - 136
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (5715 KB) |  | HTML iconHTML  

    Mobile ad hoc networks (MANETs) are nowadays being used much more than some years ago. One of the major reasons is the increasing number of devices that have risen lately capable of forming part of such networks. This situation makes feasible the development of new services. Especially, video-streaming is one of the most successful services demanded by the customers. In this paper we propose a QoS-aware multipath DSR-based (dynamic source routing) routing protocol which helps to improve the reliability of the connections while balancing the load and decreasing the end-to-end delay. Several multipath routing designs have been evaluated seeking to get better global performance of the network. Besides, we propose a QoS-aware architecture that includes a cross-layer scheme in which a network layer scheduler manages different priority traffics and operates according to the IEEE 802.11e MAC (medium access control) layer. Extensive simulations have been carried out to show the benefits of our scheme in providing different levels of QoS, including user-level QoS parameters View full abstract»

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  • Visualization of Mobile Ad-Hoc Laboratory Network (S-Net)

    Page(s): 126 - 131
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2858 KB) |  | HTML iconHTML  

    Surging mobile ad-hoc networks have become interesting from application and service delivery point of view. Since links between nodes in such infrastructureless network alternate continuously, the network's wireless topology may change rapidly and unpredictably. Thus, the visualization of the topology and routing mechanisms becomes important in testing and evaluation of the very network, as well as in understanding of its concepts and organisation. This paper reviews the most frequently used techniques in the visualization of mobile ad-hoc networks. Moreover, the visualization of S-Net, a mobile ad-hoc laboratory network developed by our research team, is described in detail View full abstract»

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