| 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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