| 1. |
- Dias,, Jacklyn, et al.
(författare)
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Improving the Performance Evaluation of ADSL systems by using a Modem Diagnosis Methodology
- 2006
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Ingår i: Simpósio Brasileiro de Microondas e Optoeletrônica – Congresso Brasileiro de Eletromagnetismo.
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Konferensbidrag (refereegranskat)abstract
- This paper presents test methodologies to measure and evaluate performance of ADSL modems which take into account loss of packet rate, bit rate, and latency in transporting ADSL service scenario. This evaluation method can be used by ADSL provider (CO - Central Office) to guarantee the system quality and avoid low performance of service. In order to present this evaluation method, this paper considers a traffic generator, modems under test, a telephony local loop carring ADSL service, and DSLAM as the lab setup to perform such tests.
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| 2. |
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| 3. |
- Kivimäki, Antti, et al.
(författare)
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An energy resolved electron-ion coincidence study near the S 2p thresholds of the SF6 molecule
- 2003
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 36:4, s. 781-791
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Tidskriftsartikel (refereegranskat)abstract
- The fragmentation dynamics of the SF6 molecule following the excitations of S 2p electrons into unoccupied molecular orbitals has been studied using the energy-resolved electron-ion coincidence technique. Fragmentation patterns were found to depend on the particular excitation and on the electronic state of the molecular ion. The spectator resonant Auger decay at the 2p --> 6a(1g) resonance induces changes in the ion distributions as compared to direct photoionization. Furthermore, coincidence spectra related to the same Auger structure display different ion abundances at the 2t(2g) and 4e(g) shape resonances. Differences were also found in the Auger decay spectra. These findings give further support for the previously suggested many-electron character of the 4e(g) shape resonance.
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| 4. |
- Magesacher, Thomas, et al.
(författare)
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Limits of Ultra-Wideband Communication Over Copper
- 2006
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Ingår i: Proc. Intl. Conference on Communication Technology (ICCT) 2006. - 1424408016 ; , s. 1437-1440
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Konferensbidrag (refereegranskat)abstract
- Wireline communication using the copper plant is one of the major access techniques. The shorter the wires, the larger is the frequency band that can be exploited in an economically feasible way. Several technologies using frequency bands up to 30MHz have been standardized during the last decade. Properties of the wireline channel for frequencies above 30MHz are to a large extent unexplored. This paper investigates the limits of "ultra-wideband" communication over very short copper cables in terms of exploitable bandwidth and data rate. Extrapolations of standard cable models, whose validity has been verified by means of measurements, are used for channel modeling. The CISPR 22 standard forms the basis for the analysis of ingress and egress.
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| 5. |
- Magesacher, Thomas, et al.
(författare)
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Measurement and modeling of short copper cables for ultra-wideband communication
- 2006
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 6390, s. 39006-39006
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Konferensbidrag (refereegranskat)abstract
- High-speed communication using the copper network, originally installed for telephony, is one of the dominant Internet access techniques. Several variants of a technology referred to as digital subscriber line (DSL) have been developed, standardized and installed during the last two decades. Essentially, DSL achieves high rates by exploiting wide bands of the copper cable channel. The shorter the cable, the wider the band that can be used efficiently for communication. Current DSL standards foresee the use of bands up to 30MHz. Cable properties have been studied by means of measurements, characterization and modeling up to frequencies of 30MHz. Recent investigations have shown that it is feasible both from technical and from economical point of view to exploit very short cables (up to 200m) even further and use bands above 30MHz. A prerequisite for further evaluation and the design of such ultra-wideband copper (UWBC) systems is the extension of existing cable models to higher frequencies. This paper presents wideband measurement results of insertion loss and crosstalk coupling in a 10-pair cable of various length values for frequencies up to 200MHz. We compare the results with extrapolations of cable models that are established in the 30MHz-range.
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| 6. |
- Magesacher, Thomas, et al.
(författare)
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Modeling and measurement of short copper cables for ultra-wideband communications
- 2006
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Ingår i: Proc. SPIE OpticsEast Broadband Access Communication Technologies.
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Konferensbidrag (refereegranskat)abstract
- High-speed communication using the copper network, originally installed for telephony, is one of the dominant Internet access techniques. Several variants of a technology referred to as digital subscriber line (xDSL) have been developed, standardized and installed during the last two decades. Essentially, xDSL achieves high rates by exploiting wide bands of the copper cable channel. The shorter the cable, the wider is the band that can be used efficiently for communication. Current xDSL standards use bands up to 18MHz. Cable properties have been studied by means of measurements, characterization and modeling up to frequencies of 30MHz. Recent investigations have shown that is feasible both from technical and from economical point of view to exploit very short cable (up to 300m) even further and use bands above 30MHz. A prerequisite for further evaluation and the design of such ultra-wideband copper (UWBC) systems is the extension of existing cable models to higher frequencies. This paper presents wide-band measurement results of insertion loss and crosstalk coupling in a 10-pair cable of various length values for frequencies up to 400MHz. We compare the results to extrapolations of cable models that are established in the 30MHzrange.
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| 7. |
- Moraes, Rodrigo B., et al.
(författare)
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Semiblind Spectrum Balancing for DSL
- 2010
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Ingår i: IEEE Transactions on Signal Processing. - 1053-587X. ; 58:7, s. 3717-3727
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Tidskriftsartikel (refereegranskat)abstract
- Digital subscriber lines (DSLs) technology is vastly used for high-speed data transmission. Crosstalk is one of the main problems in DSL. The research community has done extensive work on how to optimize spectrum allocation across DSL frequencies and mitigate crosstalk, a subject that has been called dynamic spectrum management (DSM). This text presents a novel DSM solution, referred to as semiblind spectrum balancing (2SB). 2SB performs an optimization process with a virtual line, a fictitious line that represents to each user the damage it causes for all other users. With the aid of message exchanges between modems and a central agent, the method will adjust the virtual line's parameters so that it represents the real crosstalk scenario in the binder. In this paper, we provide the conditions for how such a situation can be achieved and show that it can do so with semicentralization, low complexity and limited crosstalk channel information-only the ratios between crosstalk channels are necessary. Performance is very close to optimal.
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| 13. |
- Rius i Riu, Jaume, 1973-
(författare)
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Gas phase molecular relaxation probed by synchrotron radiation experiments
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents experimental studies of gas phasemolecular relaxation after excitation with synchrotron photonsin the 15-35 eV and in the 70-350 eV regions.In the 15-35 eV region, molecular relaxation by neutraldissociation processes and nonFranck-Condon effects in N2 and O2 molecules have beenstudied by means of dispersed fluorescence and photoelectronspectroscopy experimental techniques, respectively. From thedispersed fluorescence data, excitation functions for themeasured atomic fluorescence spectra have been obtained. Fromthe recorded photoelectron spectra vibrational branching ratioshave been produced. The results obtained reveal that Rydbergseries and singly and doubly excited valence states of theappropriate symmetry energetically accessible in the studiedregion and interactions between themaccount for most of theobserved effects in these two type of experiments.In the 70-350 eV range, molecular relaxation processesresulting in fragmentation of CD4 and SF6 after absorption ofsynchrotron light have been studied by energy resolved electronion coincidence technique using a multicoincidence experimentalstation developed by our group during the last five years forsuch type of experiments. The coincidence measurements yieldedmass spectra from which information about the kinematics of thedetected fragments has been deduced by means of Monte Carlosimulations of the experimental peak shapes. The obtainedresults show completely different dissociation patternsdepending on the molecular electronic states studied. Thesepatterns reflect the bonding properties of the excited orbitalsand they permit the description and in some cases theidentification of the different molecular relaxation pathwaysobserved. The achievements presented in this thesis exemplifythe potential of the multicoincidence station used in thereported experiments.
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| 14. |
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| 15. |
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| 16. |
- Sales, Claudomiro, et al.
(författare)
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Line Topology Identification Using Multiobjective Evolutionary Computation
- 2010
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Ingår i: IEEE Transactions on Instrumentation and Measurement. - 0018-9456. ; 59:3, s. 715-729
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Tidskriftsartikel (refereegranskat)abstract
- The broadband capacity of the twisted-pair lines strongly varies within the copper access network. It is therefore important to assess the ability of a digital subscriber line (DSL) to support the DSL services prior to deployment. This task is handled by the line qualification procedures, where the identification of the line topology is an important part. This paper presents a new method, denoted topology identification via model-based evolutionary computation (TIMEC), for line topology identification, where either one-port measurements or both one-and two-port measurements are utilized. The measurements are input to a model-based multiobjective criterion that is minimized by a genetic algorithm to provide an estimate of the line topology. The inherent flexibility of TIMEC enables the incorporation of a priori information, e. g., the total line length. The performance of TIMEC is evaluated by computer simulations with varying degrees of information. Comparison with a state-of-art method indicates that TIMEC achieves better results for all the tested lines when only one-port measurements are used. The results are improved when employing both one-and two-port measurements. If a rough estimate of the total length is also used, near-perfect estimation is obtained for all the tested lines.
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| 17. |
- Skog, Robert, et al.
(författare)
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Bolstering : The last mile with multipath TCP
- 2017
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Ingår i: Ericsson Technology Review. - : Telefonaktiebolaget L.M. Ericsson. - 0014-0171. ; 94:1, s. 66-78
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Tidskriftsartikel (refereegranskat)abstract
- The rapid uptake of bandwidth-consuming services such as video on demand and linear tv has many service providers struggling to keep pace with ever increasing bandwidth demands. The problem is particularly acute on the last mile: the segment of the network that delivers broadband services to users' homes and workplaces.
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| 18. |
- Souza, Lamartine, et al.
(författare)
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Impact of Non-Stationary Noise on xDSL Systems: an Experimental Analysis
- 2007
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Ingår i: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. ; 6603
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Konferensbidrag (refereegranskat)abstract
- Broadband services require data rates that can only be achieved by using relatively high spectrum frequencies. At such high frequencies, the DSL (Digital Subscriber Line) signal is more susceptible to external noise sources, such as radio frequency interference and impulsive noise. This paper aims to characterize how the impulsive noise impacts on services and applications for a broadband system using an ADSL2+ loop. The first approach was to use the impulsive noise defined in the standards G.996.1 (Test Procedures for DSL Transceivers) from ITU-T and TR-048 (ADSL Interoperability Test Plan) from DSL Forum. In this approach we have also used a HDSL (High Bit Rate DSL) and white noise disturbers on the line. The impulsive noises c1 and c2 (defined in G.996.1) are injected into the circuit at the CO (Central Office) end and CPE (Customer Premises Equipment) end of the loop simulator. Additionally, it was analyzed the spikes of noise's impact on the ADSL2+ line. In this case, pre-defined models of NEXT (Near-end crosstalk) and white noise are injected on CO and CPE side, simultaneously. Metrics like packet rate, lost packet count, bandwidth, short-term average transfer delay, and errored seconds are used to characterize the DSL loop under the noise impairments.
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| 19. |
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| 20. |
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| 21. |
- Stankiewicz, Marek, et al.
(författare)
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Experimental station for gas phase fluorescence spectroscopy
- 2004
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 75:7, s. 2402-2408
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Tidskriftsartikel (refereegranskat)abstract
- The details of an experimental setup for gas phase atomic and molecular fluorescence measurements using synchrotron radiation are described in this article. The most significant part of the apparatus is an optical arrangement, which allows for simultaneous measurements of dispersed as well as total fluorescence intensity using an effusive gas jet and an inbuilt gas cell assembled in a convenient plug and measure configuration. The first measurements concerning fluorescence of the N-2 molecule around the N 1s edge obtained with this setup are presented.
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| 22. |
- Stankiewicz, M., et al.
(författare)
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Relaxation dynamics of SF6 studied by energy-resolved electron ion coincidence technique
- 2004
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 137-40, s. 369-375
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Tidskriftsartikel (refereegranskat)abstract
- The mass spectra from the SF6 molecule acquired by energy-resolved electron ion coincidence (EREICO) technique using (1t(1g) + [5t(1u),1t(2u)]), (3e(g) + 1t(2g)), 4t(1u), and 5a(1g) electrons after both valence and S 2p(-1) 6a(1g) core excitation reveal a strong selectivity in the dissociation from these states. From the comparison of the obtained spectra, the influence of the core-excited state in the relaxation pathway of the molecule is studied. The S 2p --> 6a(1g) core excitation does not affect the relaxation dynamics after participator Auger decay to the (1t(1g) + [5t(1u),1t(2u)])(-1) and (4t(1u))(-l) states, but it alters the relaxation dynamics after participator Auger decay to the (3e(g) + 1t(2g))(-1) and (5a(1g))(-1) states with respect to the decay processes after direct excitation of the same orbitals. These observations point to core excitation induced dissociation in the SF6 molecule.
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| 23. |
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| 24. |
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| 25. |
- Zampolo, Ronaldo de Freitas, et al.
(författare)
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Mapping The Impulse Noise Spectral Features From Waveform Domain Onto Symbol Domain
- 2006
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Ingår i: 6th International Telecommunications Symposium. - 9788589748049 ; , s. 193-197
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Konferensbidrag (refereegranskat)abstract
- In this paper the spectral features of impulse noise in DSL systems are mapped from the waveform domain onto the symbol domain, considering a QAM receiver. This work can be viewed as part of a full symbol domain model for impulse noise, which should include the amplitude and spectral aspects. Since the available models of impulse noise in DSL are generally waveform-based, this kind of mapping is justified when symbol-based simulations are intended, in order to avoid computational overhead due to demodulating noise samples generated on waveform domain. The analytical development of such mapping is provided as well as some simulation results.
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