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Area Networks (area + network)

Distribution by Scientific Domains
Engineering48%
Life Sciences23%
Information Science and Computing8%
Business, Economics, Finance and Accounting8%

Kinds of Area Networks

  • local area network
  • metropolitan area network
    		•
  • wide area network
  • wireless local area network
    		•

    Selected Abstracts

    Efficient IP-multicast via Inmarsat BGAN, a 3GPP satellite network

    INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 5 2007
    Paul Febvre
    Abstract This paper outlines a number of challenges associated with supporting IP-multicast services efficiently across the Inmarsat Broadband Global Area Network (BGAN) 3GPP-based satellite network operating over the Imarsat-4 satellite constellation. The paper presents a network architecture that extends the 3GPP reference architecture to allow IP-multicast to be delivered when the Core Network is in a 3GPP Release-4 (non-MBMS compliant) configuration. This paper further extends the service and system concepts defined in 3GPP MBMS to provide improved flexibility and accountability, and improved scalability and efficiency when operating with the Inmarsat-4 BGAN TDM/TDMA air interface. This paper describes a number of radio resource management techniques that were deployed in a test system and the validation testing that was undertaken to support multimedia distribution and VoIP-based netted communications applications. The tuning of application and system behaviour to achieve acceptable performance is described in outline. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    DEA network computing in multi-stage parallel processes

    INTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 3 2003
    Toshiyuki Sueyoshi
    DEA (Data Envelopment Analysis) is a managerial method that has been widely used for performance analysis in various public and private sectors. To deal with large-scale DEA problems, this research proposes the architecture of DEA network computing (LAN: Local Area Network) that is designed to coordinate a simultaneous use of multiple personal computers. An important feature of the proposed DEA computer architecture is that it is computationally structured in multi-stage parallel processes to enhance its algorithmic efficiency. The performance of the proposed network computing approach is tested and examined in a large simulation study. [source]

    Marking high-technology market evolution through the foci of market stories: the case of local area networks

    THE JOURNAL OF PRODUCT INNOVATION MANAGEMENT, Issue 6 2002
    Vasilis Theoharakis
    Previous research suggests that changing consumer and producer knowledge structures play a role in market evolution and that the sociocognitive processes of product markets are revealed in the sensemaking stories of market actors that are rebroadcasted in commercial publications. In this article, the authors lend further support to the story-based nature of market sensemaking and the use of the sociocognitive approach in explaining the evolution of high-technology markets. They examine the content (i.e., subject matter or topic) and volume (i.e., the number) of market stories and the extent to which content and volume of market stories evolve as a technology emerges. Data were obtained from a content analysis of 10,412 article abstracts, published in key trade journals, pertaining to Local Area Network (LAN) technologies and spanning the period 1981 to 2000. Hypotheses concerning the evolving nature (content and volume) of market stories in technology evolution are tested. The analysis identified four categories of market stories,technical, product availability, product adoption, and product discontinuation. The findings show that the emerging technology passes initially through a ,technical-intensive' phase whereby technology related stories dominate, through a ,supply-push' phase, in which stories presenting products embracing the technology tend to exceed technical stories while there is a rise in the number of product adoption reference stories, to a ,product-focus' phase, with stories predominantly focusing on product availability. Overall story volume declines when a technology matures as the need for sensemaking reduces. When stories about product discontinuation surface, these signal the decline of current technology. New technologies that fail to maintain the ,product-focus' stage also reflect limited market acceptance. The article also discusses the theoretical and managerial implications of the study's findings. [source]

    Comparison between objective and subjective measurements of quality of service over an Optical Wide Area network

    EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 3 2008
    Francesco Matera
    The introduction of intelligence for management and control of the quality of service (QoS) are key issues for the evolution of the next generation IP optical network based on Ethernet technology. A test bed of a core-access network was implemented to investigate such issues and in this paper, the authors report measurements concerning the QoS of multimedia services for different traffic conditions. The network was implemented with a differentiated service over Multi-Protocol Label Switch (MPLS) architecture; it consists of a real optical network based on core routers with optical Gigabit Ethernet (GBE) interfaces connected by means of long single mode fibres (about 50\,km), contained in an installed cable between Rome and Pomezia. The network is based on different access devices, but in this paper we only refer to an access based on Fibre To The building (FTTB) architecture. The QoS was investigated both in terms of network (or objective) tests that include packet loss, jitter, one way delay and throughput measurements and perceptive (or subjective) tests that conversely are based on the evaluation of user perception. The services under test mainly consisted of video streams that circulated in the network according to the switching operations based in the IP differentiated service over MPLS technique that allowed us to guarantee the QoS for some class of service, also in the presence of network overload. Particular attention was given to the correlation between objective and subjective measurements. Furthermore, in order to have a complete analysis about QoS of real networks, measurements were performed also in the presence of restoration operations for link failures; in particular we compare the results in the case of conventional IP network restoration with a procedure proposed by us and based on a link switching activated by the loss of signal command coming from the routers. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    A Nationwide Assessment of the Biodiversity Value of Uganda's Important Bird Areas Network

    CONSERVATION BIOLOGY, Issue 1 2006
    HERBERT TUSHABE
    AIAs; complementariedad; congruencia trans-taxón; selección de sitios de conservación Abstract:,BirdLife International's Important Bird Areas (IBA) program is the most developed global system for identifying sites of conservation priority. There have been few assessments, however, of the conservation value of IBAs for nonavian taxa. We combined past data with extensive new survey results for Uganda's IBAs in the most comprehensive assessment to date of the wider biodiversity value of a tropical country's IBA network. The combined data set included more than 35,000 site × species records for birds, butterflies, and woody plants at 86 Ugandan sites (23,400 km2), including 29 of the country's 30 IBAs, with data on additional taxa for many sites. Uganda's IBAs contained at least 70% of the country's butterfly and woody plant species, 86% of its dragonflies and 97% of its birds. They also included 21 of Uganda's 22 major vegetation types. For butterflies, dragonflies, and some families of plants assessed, species of high conservation concern were well represented (less so for the latter). The IBAs successfully represented wider biodiversity largely because many have distinctive avifaunas and, as shown by high cross-taxon congruence in complementarity, such sites tended to be distinctive for other groups too. Cross-taxon congruence in overall species richness was weaker and mainly associated with differences in site size. When compared with alternative sets of sites selected using complementarity-based, area-based, or random site-selection algorithms, the IBA network was efficient in terms of the number of sites required to represent species but inefficient in terms of total area. This was mainly because IBA selection considers factors other than area, however, which probably improves both the cost-effectiveness of the network and the persistence of represented species. Resumen:,El programa de Áreas de Importancia para las Aves (AIAs) de Birdlife International es el sistema global más desarrollado para la identificación de sitios de prioridad para la conservación. Sin embargo, ha habido pocas evaluaciones del valor de conservación de las AIAs para taxa no aviares. En la evaluación más integral, hasta la fecha, del valor de la biodiversidad en general de la red de AIAs de un país tropical, combinamos datos antiguos con los resultados de muestreos extensivos recientes de las AIAs de Uganda. El conjunto de datos combinados incluyó más de 35000 registros de sitios x especies de aves, mariposas y plantas leñosas en 86 sitios en Uganda (23400 km2), incluyendo 29 de las 30 AIAs del país, con datos sobre taxa adicionales en muchos sitios. Las AIAs de Uganda contenían por lo menos un 70% de las especies de mariposas y plantas leñosas del país, 86% de sus libélulas y 97% de sus aves. También incluyeron 21 de los 22 principales tipos de vegetación. En las mariposas, libélulas y algunas de las familias de plantas evaluadas, la representación de especies de alto interés para la conservación fue buena (menor en las plantas). Las Áreas de Importancia para las Aves representaron exitosamente a la biodiversidad en general principalmente porque muchas tienen avifaunas distintivas y, como muestra la alta congruencia trans-taxón en complementariedad, tales sitios tendieron a ser distintivos para otros grupos también. La congruencia trans-taxón en la riqueza de especies total fue más débil y se asoció principalmente con diferencias en el tamaño del sitio. Cuando se compara con conjuntos alternativos de sitios seleccionados mediante algoritmos basados en complementariedad, área o selección aleatoria de sitios, la red de AIAs fue eficiente en términos del número de sitios requeridos para representar especies, pero ineficiente en términos del área total. Sin embargo, esto se debió principalmente a que la selección de AIA considera factores distintos al área que probablemente mejoran tanto la efectividad de la red como la persistencia de las especies representadas. [source]

    Wilderness and future conservation priorities in Australia

    DIVERSITY AND DISTRIBUTIONS, Issue 6 2009
    James E.M. Watson
    Abstract Aim, Most approaches to conservation prioritization are focused on biodiversity features that are already threatened. While this is necessary in the face of accelerating anthropogenic threats, there have been calls to conserve large intact landscapes, often termed ,wilderness', to ensure the long-term persistence of biodiversity. In this study, we examine the consequences of directing conservation expenditure using a threat-based framework for wilderness conservation. Location, The Australian continent. Methods, We measured the degree of congruence between the extent of wilderness and the Australian protected area network in 2000 and 2006, which was established using a threat-based systematic planning framework. We also assessed priority areas for future reserve acquisitions identified by the Australian government under the current framework. Results, In 2000, 14% of Australia's wilderness was under formal protection, while the protected area network covered only 8.5% of the continent, suggesting a historical bias towards wilderness protection. However, the expansion of the reserve system from 2000 to 2006 was biased towards non-wilderness areas. Moreover, 90% of the wilderness that was protected over this period comprised areas not primarily designated for biodiversity conservation. We found a significant (P < 0.05) negative relationship between bioregions considered to be a priority for future reserve prioritization and the amount of wilderness they contain. Main conclusions, While there is an urgent need to overcome past biases in reserve network design so as to better protect poorly represented species and habitats, prioritization approaches should not become so reactive as to ignore the role that large, intact landscapes play in conserving biodiversity, especially in a time of human-induced climate change. This can be achieved by using current or future threats rather than past threats to prioritize areas, and by incorporating key ecological processes and costs of acquisition and management within the planning framework. [source]

    Endemic species and ecosystem sensitivity to climate change in Namibia

    GLOBAL CHANGE BIOLOGY, Issue 5 2006
    WILFRIED THUILLER
    Abstract We present a first assessment of the potential impacts of anthropogenic climate change on the endemic flora of Namibia, and on its vegetation structure and function, for a projected climate in ,2050 and ,2080. We used both niche-based models (NBM) to evaluate the sensitivity of 159 endemic species to climate change (of an original 1020 plant species modeled) and a dynamic global vegetation model (DGVM) to assess the impacts of climate change on vegetation structure and ecosystem functioning. Endemic species modeled by NBM are moderately sensitive to projected climate change. Fewer than 5% are predicted to experience complete range loss by 2080, although more than 47% of the species are expected to be vulnerable (range reduction >30%) by 2080 if they are assumed unable to migrate. Disaggregation of results by life-form showed distinct patterns. Endemic species of perennial herb, geophyte and tree life-formsare predicted to be negatively impacted in Namibia, whereas annual herb and succulent endemic species remain relatively stable by 2050 and 2080. Endemic annual herb species are even predicted to extend their range north-eastward into the tree and shrub savanna with migration, and tolerance of novel substrates. The current protected area network is predicted to meet its mandate by protecting most of the current endemicity in Namibia into the future. Vegetation simulated by DGVM is projected to experience a reduction in cover, net primary productivity and leaf area index throughout much of the country by 2050, with important implications for the faunal component of Namibia's ecosystems, and the agricultural sector. The plant functional type (PFT) composition of the major biomes may be substantially affected by climate change and rising atmospheric CO2, currently widespread deciduous broad leaved trees and C4 PFTs decline, with the C4 PFT particularly negatively affected by rising atmospheric CO2 impacts by ,2080 and deciduous broad leaved trees more likely directly impacted by drying and warming. The C3 PFT may increase in prominence in the northwestern quadrant of the country by ,2080 as CO2 concentrations increase. These results suggest that substantial changes in species diversity, vegetation structure and ecosystem functioning can be expected in Namibia with anticipated climate change, although endemic plant richness may persist in the topographically diverse central escarpment region. [source]

    Performance evaluation of CSMA/ID MAC protocol for IP over WDM ring networks

    INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 11 2008
    Jih-Hsin Ho
    Abstract In this paper, a packet pre-classification media access control protocol based on a carrier sense multiple access with idle detection (CSMA/ID) scheme is investigated for supporting IP packets over all-optical WDM ring networks. The purpose of the protocol is to increase throughput and to decrease the packet transmission delay of IP packets over optical networks in a metropolitan area network. This protocol avoids both packet collision and packet fragmentation. In order to improve the utilization of the network, the packets transmitted from a local area network are first pre-classified into various class queues of an access point (AP) according to their length. After checking the available space based on the wavelength received by the receivers of the AP, the packets in the queues are transmitted. An analytical model is developed to evaluate the performance of the protocol, with simulation results showing good network efficiency. The proposed network has short-term variations that introduce unfairness conditions. This problem could be overcome by assigning a quota on individual queues to allow all queues fair access. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Explaining the global pattern of protected area coverage: relative importance of vertebrate biodiversity, human activities and agricultural suitability

    JOURNAL OF BIOGEOGRAPHY, Issue 8 2008
    Colby Loucks
    Abstract Aim, Twelve per cent of the Earth's terrestrial surface is covered by protected areas, but neither these areas nor the biodiversity they contain are evenly distributed spatially. To guide future establishment of protected areas, it is important to understand the factors that have shaped the spatial arrangement of the current protected area system. We used an information-theoretic approach to assess the ability of vertebrate biodiversity measures, resource consumption and agricultural potential to explain the global coverage pattern of protected areas. Location, Global. Methods, For each of 762 World Wildlife Fund terrestrial ecoregions of the world, we measured protected area coverage, resource consumption, terrestrial vertebrate species richness, number of endemic species, number of threatened species, net primary production, elevation and topographic heterogeneity. We combined these variables into 39 a priori models to describe protected area coverage at the global scale, and for six biogeographical realms. Using the Akaike information criterion and Akaike weights, we identified the relative importance and influence of each variable in describing protected area coverage. Results, Globally, the number of endemic species was the best variable describing protected area coverage, followed by the number of threatened species. Species richness and resource consumption were of moderate importance and agricultural potential had weak support for describing protected area coverage at a global scale. Yet, the relative importance of these factors varied among biogeographical realms. Measures of vertebrate biodiversity (species richness, endemism and threatened species) were among the most important variables in all realms, except the Indo-Malayan, but had a wide range of relative importance and influence. Resource consumption was inversely related to protected area coverage across all but one realm (the Palearctic), most strongly in the Nearctic realm. Agricultural potential, despite having little support in describing protected area coverage globally, was strongly and positively related to protection in the Palearctic and Neotropical realms, as well as in the Indo-Malayan realm. The Afrotropical, Indo-Malayan and Australasian realms showed no clear, strong relationships between protected area coverage and the independent variables. Main conclusions, Globally, the existing protected area network is more strongly related to biodiversity measures than to patterns of resource consumption or agricultural potential. However, the relative importance of these factors varies widely among the world's biogeographical realms. Understanding the biases of the current protected area system may help to correct for them as future protected areas are added to the global network. [source]

    Historical biogeography of Southeast Asia and the West Pacific, or the generality of unrooted area networks as historical biogeographic hypotheses

    JOURNAL OF BIOGEOGRAPHY, Issue 2 2003
    Peter C. van Welzen
    Abstract Aim Unrooted area networks are perhaps a general way in which different historical biogeographical patterns may be combined. Location Southeast Asia up to the West Pacific, Australia, South America. Methods Unrooted area networks based on Primary Brooks Parsimony Analysis of different data sets of Southeast Asian,West Pacific, Australian and South American clades. Results A large Brooks Parsimony historical (cladistic) biogeographic analysis of Southeast Asia and the West Pacific gave a meaningful result when all clades (representing different historical biogeographic patterns) were united into one matrix and an unrooted area network was produced. This network showed geographically adjacent areas as neighbours, which is interpreted as clades dispersing and speciating as soon as areas rafted towards each other. This pseudo-vicariance mechanism, together with the very limited, mainly linear dispersal possibilities, a few large, widespread clades with many endemic species, and the large overlap in distributions displayed by different patterns, may explain the peculiar result. When applied to examples from other areas (bird data from Australia and South America), unrooted area networks for all data perform very poorly. Main conclusions Unrooted historical general area networks are not universally applicable. In general, it is better to split historical patterns a priori and analyse them separately. [source]

    Novel planar triple band monopole antenna for WiMAX/WLAN applications

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2010
    Hsien-Wen Liu
    Abstract A coplanar waveguide (CPW)-fed planar monopole antenna with triple band operation for worldwide interoperability for microwave access (WiMAX) and wireless local area network (WLAN) applications is presented. The antenna, which occupies a small size of 25 (L) × 25 (W) × 0.8 (H) mm3, is simply composed of a pentagonal radiating patch with two bent slots. By carefully selecting the positions and lengths of these slots, good dual stopband rejection characteristic of the antenna can be obtained, so that three operating bands covering 2.14,2.85, 3.29,4.08, and 5.02,6.09 GHz can be achieved. The measured results also demonstrate that the proposed antenna has good omnidirectional radiation patterns with appreciable gain across the operating bands, and is thus suitable to be integrated within the portable devices for WiMAX/WLAN applications. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2405,2408, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25497 [source]

    Dual band-notched ultra-wideband printed antenna with two different types of slots

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2010
    Jun-Bo Jiang
    Abstract A compact wideband printed antenna with dual band-notched characteristics for wireless local area network (WLAN) (2.4 GHz/5.8 GHz) is introduced. It is demonstrated that dual band rejection characteristics at 2.4 and 5.8 GHz with desired bandwidths can be obtained by using two different types of slots, one is a folded stripline slot on the radiation patch, and the other is a pair of inverted-L-shaped slot on the ground. The proposed antenna operates over 2.2,11 GHz for VSWR <2, while providing a band-stop function in the frequency bands of 2.3,2.9 GHz and 5.5,6.3 GHz. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1930,1933, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25411 [source]

    Dual-band hybrid coupler with extended bandwidth

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2010
    King Yin Cheung
    Abstract A dual-band branch-line quadrature coupler with extended bandwidth using simple three-section branch line is presented. This proposed design exhibits larger bandwidth than existing dual-band designs reported in previous literature. A dual-band branch-line coupler was designed and measured to give 34.5 and 16.4% bandwidth in the lower band and upper band, respectively, for an amplitude imbalance less than 1 dB. The achieved bandwidth is wide enough to cover wireless local area network and wideband code division multiple access applications. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2095,2098, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25405 [source]

    Design of dual-band antenna with U-shaped open stub for WLAN/UWB applications

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2009
    Jung N. Lee
    Abstract In this article, we have proposed a dual-band antenna with U-shaped open stub for wideband local area network (WLAN)/ultra wideband (UWB) applications. The designed dual-band antenna consists of two semicircle radiating patches, a rectangular slot separating the two semicircles, one step for impedance matching, and coplanar waveguide (CPW) feeding. Two kinds of prototypes (CPW-fed UWB antenna and the dual-band antenna with U-shaped open stub) are fabricated and measured. Parametric studies and radiation characteristics for the two antennas are presented. The designed antenna has the figure-of-eight radiation pattern, wide bandwidth, and negligible dispersion over the operating frequency band. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 284,289, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24033 [source]

    Uniplanar coupled-fed printed PIFA for WWAN operation in the laptop computer

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2009
    Kin-Lu Wong
    Abstract In this article, a uniplanar printed PIFA (planar inverted-F antenna) with a coupling feed for application as an internal laptop computer antenna for penta-band WWAN (wireless wide area network) operation is presented. The proposed PIFA has a compact structure and can be easily printed on one side of a small 0.8-mm thick FR4 substrate of size 11 × 59 mm2, making it very promising to be embedded inside the casing of the laptop computer, especially for the thin-profile laptop computer. With the coplanar coupling feed, the large inductive input reactance of the PIFA at around 900 MHz is compensated, and dual-resonance excitation for the antenna's lower band at about 900 MHz is obtained, which allows it to easily cover GSM850/900 operation. A wide operating band is also achieved for the antenna's upper band at about 1900 MHz, and a bandwidth of larger than 500 MHz is obtained to cover GSM1800/1900/UMTS operation. That is, the proposed PIFA covers all the five operating bands of GSM850/900/1800/1900/UMTS for WWAN operation. Details of the proposed PIFA are presented. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 549,554, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24084 [source]

    Design of dual-band bandpass filter using diverse quarter-wavelength resonators for GPS/WLAN applications

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2008
    Hung-Wei Wu
    Abstract The novel compact dual-band bandpass filter (BPF) by using diverse quarter-wavelength (,/4) resonators for global position system (GPS)/wireless local area network (WLAN) applications is proposed for the first time. The use of two interdigital-like ,/4 resonators of the proposed BPF effectively provides the responses for GPS/WLAN at 1.575/5.7 GHz by properly arranging the ,/4 SIRs. Full-wave simulator IE3D is used to design the proposed BPF. Good agreement with responses of electromagnetic (EM) simulation and measurement is compared. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2694,2696, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23716 [source]

    Compact band-notched ultra-wideband printed antenna

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2007
    Yi Ding
    Abstract A novel and compact ultra-wideband (UWB) printed monopole antenna with extended band-notched designs is presented. The antenna with a total size of 20 mm × 35 mm operates in a band from 3 to over 11 GHz (VSWR , 2), and shows omnidirectional radiation with a low cross-polarization in the range of the operated band. Measured results indicate that the antenna presents a notched-band from 5.1 to 6 GHz for VSWR , 3:1, which covers the wireless local area network (WLAN) band. The notched-band is produced by an embedded resonant cell (ERC). Experimental results show that the band-notched function can be controlled by adjusting the length of the ERC and area of the slot. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2686,2689, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22842 [source]

    Compact meander monopole antenna for tri-band WLAN application

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2007
    Li-Na Zhang
    Abstract A novel printed meander monopole antenna for tri-band wireless local area network (WLAN) applications is presented. The antenna is composed of a meander strip and a straight strip with a gap between the ends of them, both printed on an inexpensive FR4 substrate, and is fed by a 50 , microstrip feeder with the notched ground plane. The operation bandwidth of the proposed antenna covers 2.4, 5.2, and 5.8 GHz WLAN bands with light weight and compact radiator size of only 12 × 7 mm2. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 986,988, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22314 [source]

    Printed pentagon monopole antenna with a band-notched function

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2006
    Shun-Yun Lin
    Abstract In this study, we propose a design to obtain band-notching characteristics in printed planar monopoles. An ultra-wide band was achieved by means of the beveled upper edge of the rectangular patch with dimension as small as 55 mm2. On the other hand, it is necessary to notch certain bands to avoid interference from existing wireless local area network (WLAN), such as the 5.2 GHz band (5150,5350 MHz) and 5.8 GHz band (5725,5875 MHz), in spite of the adoption of the FCC for UWB communication systems operating between 3.1 and 10.6 GHz. This feature can be easily achieved by embedding an inverted-V-shape slot with length about one-half of the guided wavelength of the expected notched frequencies and along the boundary of the beveled radiating patch. This article presents the design of the proposed slotted monopole antenna, demonstrates the UWB operation with a notched frequency band, and analyzes the effects of the dimensions of the inverted-V-shape slot on the notched frequency band. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2016,2018, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21859 [source]

    Three-antenna MIMO system for WLAN operation in a PDA phone

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2006
    Kin-Lu Wong
    Abstract A multiple input multiple output (MIMO) system using three EMC (electromagnetic compatible) chip antennas in a personal digital assistant (PDA) phone is demonstrated. The three EMC chip antennas are mounted at three corners of the system ground plane of the PDA phone and all generate a wide bandwidth covering the wireless local area network (WLAN) operation in the 2.4-GHz band (2400,2484 MHz). By adding a T-shaped shorted strip in the proposed MIMO antenna system, large improvements in the isolation (S12, S13, and S23 all less than ,20 dB) between any two antennas of the MIMO system are achieved. Detailed effects of the T-shaped shorted strip on the isolation improvement in the proposed MIMO antenna system are analyzed. Radiation characteristics of the three antennas are also studied. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1238,1242, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21665 [source]

    Narrow flat metal-plate antenna for dual-band WLAN operation

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2003
    Chi-Yin Fang
    Abstract A novel dual-band antenna made of a narrow, rectangular, flat metal plate for wireless local area network (WLAN) operation in the 2.4- and 5.2-GHz bands is presented. The antenna comprises a larger radiating arm, a smaller radiating arm, and a shorting portion. The larger and smaller radiating arms control a lower resonant mode at about 2.4 GHz and an upper resonant mode at about 5.2 GHz, respectively, and are connected to each other through the shorting portion. The antenna is easily excited by using a 50, mini coaxial line and shows good antenna performance. The proposed antenna design is described and experimentally studied. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 398,400, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11072 [source]

    Broadband circularly polarized inverted-L patch antenna

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2003
    Che-Wei Su
    Abstract An innovative design of a corner-truncated inverted-L patch antenna for achieving circular polarization (CP) operation over a wide bandwidth is presented. The antenna has a thick air-layer substrate; however, it can be easily excited using a probe feed with a short probe pin. CP operation is obtained by selecting an optimal size of the truncated corners, and good impedance matching over a wide bandwidth is obtained by using a beveling technique on the vertical portion of the inverted-L patch. For a prototype constructed for wireless local area network (WLAN) operation in the 2.4-GHz band (2.4,2.484 GHz), the obtained CP bandwidth (3-dB axial ratio) reaches about 7%, and the measured antenna gain is about 8.0 dBi across the CP bandwidth. Details of the antenna design and the experimental results are presented. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 134,136, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10995 [source]

    Analysing disruptive potential: the case of wireless local area network and mobile communications network companies

    R & D MANAGEMENT, Issue 1 2005
    Stefan Hüsig
    In this article, we analyse the prediction that wireless local area network (W-LAN) technologies will be disruptive for incumbent mobile communications network operators. For this purpose, we develop a methodology of guided interviews to assess technologies for their disruptive characteristics based on theory of disruptive technology developed by Christensen (1997) and recent extensions. The application of our comprehensive step-by-step method improves the precision of the disruptive technology concept and its usability for practitioners to make ex ante distinctions between disruptive technologies and other phenomena caused by emerging technologies. Our method predicts that contrary to common assumptions, W-LAN is not likely to represent a disruptive technology for the established mobile communications network firms in terms of Christensen's concept. This research was conducted in close collaboration with Vodafone Pilotentwicklung, an R&D and technology monitoring unit of the Vodafone Group. Vodafone provided part of the empirical data through expert interviews and market reports. [source]

    Packet OADMs for the next generation of ring networks

    BELL LABS TECHNICAL JOURNAL, Issue 4 2010
    Dominique Chiaroni
    The deployment of fiber-to-the-home (FTTH) technology in access networks is creating new demands on metropolitan area and backbone networks. The increasing bit rate per user and the simplification of access networks will make the traffic profile more bursty, requiring new flexible techniques at the metropolitan area network. This paper describes a ring network exploiting optical transparency and packet granularity. After a description of the packet optical add/drop multiplexer (POADM)-based network model motivated by specifications derived from expected needs, the paper addresses the advantages of the approach and the feasibility of the concept. © 2010 Alcatel-Lucent. [source]

    Evolution of the wide area network

    BELL LABS TECHNICAL JOURNAL, Issue 1 2000
    Harry L. Bosco
    This paper describes the dramatic changes taking place in the architecture and capabilities of the wide area network as it evolves from a collection of several service-specific networks, each typically supporting only one transport protocol, to a single multiprotocol network supporting a variety of services. The paper also discusses the technological forces driving this evolution and considers its practical implications. [source]

    Incorporating multiple criteria into the design of conservation area networks: a minireview with recommendations

    DIVERSITY AND DISTRIBUTIONS, Issue 2 2006
    Alexander Moffett
    ABSTRACT We provide a review of multicriteria decision-making (MCDM) methods that may potentially be used during systematic conservation planning for the design of conservation area networks (CANs). We review 26 methods and present the core ideas of 19 of them. We suggest that the computation of the non-dominated set (NDS) be the first stage of any such analysis. This process requires only that alternatives be qualitatively ordered by each criterion. If the criteria can also be similarly ordered, at the next stage, Regime is the most appropriate method to refine the NDS. If the alternatives can also be given quantitative values by the criteria, Goal Programming will prove useful in many contexts. If both the alternatives and the criteria can be quantitatively evaluated, and the criteria are independent of each other but may be compounded, then multi-attribute value theory (MAVT) should be used (with preferences conveniently elicited by a modified Analytic Hierarchy Process (mAHP) provided that the number of criteria is not large). [source]

    Experimental analysis of the impact of peer-to-peer applications on traffic in commercial IP networks

    EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 6 2004
    Nadia Ben Azzouna
    To evaluate the impact of peer-to-peer (P2P) applications on traffic in wide area networks, we analyze measurements from a high speed IP backbone link carrying TCP traffic towards several ADSL areas. The first observations are that the prevalent part of traffic is due to P2P applications (almost 80% of total traffic) and that the usage of network becomes symmetric in the sense that customers are not only clients but also servers. This latter point is observed by the significant proportion of long flows mainly composed of ACK segments. When analyzing the bit rate created by long flows, it turns out that the TCP connections due to P2P applications have a rather small bit rate and that there is no evidence for long range dependence. These facts are intimately related to the way P2P protocols are running. We separately analyze signaling traffic and data traffic. It turns out that by adopting a suitable level of aggregation, global traffic can be described by means of usual tele-traffic models based on M/G/, queues with Weibullian service times. Copyright © 2004 AEI [source]

    Adaptive routing algorithms and buffer management in multihop metropolitan area networks

    EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 3 2002
    Paolo Giacomazzi
    The present study is devoted to multihop Metropolitan Area Network architectures characterized by some buffer capacity at the nodes and routing algorithm slightly more complex than those already present in the literature. A new adaptive routing algorithm and a new buffer management scheme are presented, and their performance are compared to that of the best algorithms known in the literature. Both the new proposals exhibit significant improvements in throughput and delay with respect to the older ones, for various MAN topologies, sizes and buffer dimensions. These results, which in some cases are very close to the theoretical optimum, are achieved with an implementation complexity well within the limits of present day technology. [source]

    Metapopulation ecology in the sea: from Levins' model to marine ecology and fisheries science

    FISH AND FISHERIES, Issue 2 2004
    Jacob P Kritzer
    Abstract Marine and fisheries scientists are increasingly using metapopulation concepts to better understand and model their focal systems. Consequently, they are considering what defines a metapopulation. One perspective on this question emphasizes the importance of extinction probability in local populations. This view probably stems from the focus on extinction in Levins' original metapopulation model, but places unnecessary emphasis on extinction,recolonization dynamics. Metapopulation models with more complex structure than Levins' patch-occupancy model and its variants allow a broader range of population phenomena to be examined, such as changes in population size, age structure and genetic structure. Analyses along these lines are critical in fisheries science, where presence,absence resolution is far too coarse to understand stock dynamics in a meaningful way. These more detailed investigations can, but need not, aim to assess extinction risk or deal with extinction-prone local populations. Therefore, we emphasize the coupling of spatial scales as the defining feature of metapopulations. It is the degree of demographic connectivity that characterizes metapopulations, with the dynamics of local populations strongly dependent upon local demographic processes, but also influenced by a nontrivial element of external replenishment. Therefore, estimating rates of interpopulation exchange must be a research priority. We contrast metapopulations with other spatially structured populations that differ in the degree of local closure of their component populations. We conclude with consideration of the implications of metapopulation structure for spatially explicit management, particularly the design of marine protected area networks. [source]

    A terminal-controlled vertical handover decision scheme in IEEE 802.21-enabled heterogeneous wireless networks

    INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 7 2009
    Jung-Shyr Wu
    Abstract The seamless internetworking among heterogeneous networks is in great demand to provide ,always-on' connectivity services with quality of service (QoS) provision, anywhere at anytime. The integration of wireless-fidelity (Wi-Fi) and wireless metropolitan area networks (WiMAX) networks can combine their best features to provide ubiquitous access, while mediating the weakness of both networks. While it is challenging to obtain optimized handover decision-based dynamic QoS information, users can improve their perceived QoS by using the terminal-controlled handover decision in a single device equipped with multiple radio interfaces. The IEEE 802.21 aims at providing a framework that defines media-independent handover (MIH) mechanism that supports seamless handover across heterogeneous networks. In this paper, an multiple attributes decision making-based terminal-controlled vertical handover decision scheme using MIH services is proposed in the integrated Wi-Fi and WiMAX networks to provide ,always-on' connectivity QoS services. The simulation results show that the proposed scheme provides smaller handover times and lower dropping rate than the RSS-based and cost function-based vertical handover schemes. Copyright © 2009 John Wiley & Sons, Ltd. [source]