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  • 1. Bengtsson, Daniel
    et al.
    Deutgren, Petra
    Grip, Niklas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Isaksson, Mikael
    Olsson, Lennart
    Luleå tekniska universitet.
    Sjöberg, Frank
    Luleå tekniska universitet.
    Öhman, Hans
    Zipper performance when mixing ADSL and VDSL in terms of reach and capacity1997Rapport (Annet vitenskapelig)
    Abstract [en]

    In this contribution we have examined how the maximum reach vary at different bit rates on a VDSL system, when different numbers of ADSL and VDSL systems share the same binder. In this context it is concluded that when using the Zipper duplex scheme, VDSL can coexist with ADSL in the same binder without a significant degradation in reach. Further, it is shown that the Zipper duplex scheme secure that ADSL is not disturbed by NEXT from VDSL The Zipper performance has also been compared with both a TDD proposal and a FDD proposal. The results from this comparison shows that Zipper outperforms FDD and TDD in terms of extended reach at all studied mixes of ADSL and VDSL sharing the same binder. For example with a moderate number (5) of ADSL disturbers, the Zipper reach is 150 meters longer than for TDD, and is 350 meters longer than for FDD when studying the medium range asymmetrical bit rate (26:3.2 Mbps).

    Fulltekst (pdf)
    FULLTEXT01
  • 2.
    Carlson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sjöberg, Frank
    Luleå tekniska universitet.
    Simultaneous maximum likelihood estimation of time delay and time scaling2004Inngår i: Norsig 2004: proceedings of the 6th Nordic Signal Processing Symposium : June 9-11, 2004, Espoo, Finland, Helsinki: Helsinki University of Technology , 2004, s. 260-263Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we present a simultaneous maximum likelihood estimator (ML) for time delay and time-scaling in the presence of additive white Gaussian Noise. The Cram´er- Rao lower bound for the variance of the estimates is also derived. The performance of the estimator is evaluated for ultrasound echoes for different time-scalings and different time delays. The performance is compared to the standard cross-correlation estimator.

    Fulltekst (pdf)
    fulltext
  • 3.
    Carlson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sjöberg, Frank
    Luleå tekniska universitet.
    Martinsson, Pär-Erik
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    A noise-tolerant group delay estimator applied to dispersion measurement in gases2003Inngår i: Proceedings, 2003 IEEE Ultrasonics Symposium: October 5 - 8, 2003, Hilton Hawaiian Village, Honolulu, Hawaii ; an international symposium / / [ed] Donald E. Yuhas, Piscataway, NJ: IEEE Communications Society, 2003, s. 254-257Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we present a model-based group velocity estimator, that can be used to measure speed of sound in ultrasonic pulse-echo systems as a function of ultrasound frequency. The estimation of group velocities involves numerical differentiation of the phase difference. In the presence of noise, this becomes numerically unstable. The model-based approach presented herein, shows better tolerance to experimental noise. The performance of the estimator is evaluated with simulations as function of pulse bandwidth and SNR. Finally, the estimator applied to real data and compared with other methods for measuring speed of sound in Ethane and Oxygen.

    Fulltekst (pdf)
    fulltext
  • 4.
    Carlson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sjöberg, Frank
    Luleå tekniska universitet.
    Quieffin, Nicolas
    Laboratoire Ondes et Acoustique, Paris.
    Ing, Ros Kiri
    Laboratoire Ondes et Acoustique, Paris.
    Catheline, Stéfan
    Laboratoire Ondes et Acoustique, Paris.
    Echo-cancellation in a single-transducer ultrasonic imaging system2002Inngår i: NORSIG 2002: 5th Nordic Signal Processing Symposium, Trondheim: The Institute of Electrical and Electronics Engineers , 2002Konferansepaper (Fagfellevurdert)
    Abstract [en]

    During the last ten years, time-reversal of acoustic fields have been shown to be a very useful technique in ultrasonic imaging and testing. With the use of transducer arrays, it is possible to steer the sound beam to an arbitrary position within the medium, even if the medium is inhomogeneous or contains scatterers. The major drawback with traditional beamforming and time-reversal techniques is that they require the use of transducer arrays. Recently a new technique was presented that, with the use of a waveguide, makes it possible to focus sound arbitrarily, with only one transducer elements. A problem with the setup is that the signal-to-noise ratio (SNR) is degraded because of interfering echoes from the waveguide. In this paper, we present an echo-cancellation scheme that results in an SNR gain of approximately 33 dB. This enables the new technique to be used in pulse-echo mode, where this was not previously possible.

    Fulltekst (pdf)
    fulltext
  • 5.
    Cendrillon, Raphael
    et al.
    Marvell Hong Kong Ltd.
    Collings, Iain
    CSIRO Information Communication Technologies Center.
    Nordström, Tomas
    Telecommunications Research Center Vienna.
    Sjöberg, Frank
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Tsatsanis, Michail
    Aktino Inc., Irvine.
    Yu, Wei
    Electrical and Computer Engineering Department, University of Toronto.
    Advanced signal processing for digital subscriber lines2006Inngår i: EURASTP journal an applied signal processing, ISSN 1110-8657, E-ISSN 1687-0433Artikkel i tidsskrift (Fagfellevurdert)
  • 6.
    Edfors, Ove
    et al.
    Luleå tekniska universitet.
    Sandell, Magnus
    Luleå tekniska universitet.
    van de Beek, Jaap
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Landström, Daniel
    Luleå tekniska universitet.
    Sjöberg, Frank
    Luleå tekniska universitet.
    An introduction to orthogonal frequency-division multiplexing1997Rapport (Annet vitenskapelig)
    Abstract [en]

    This report is an introduction to orthogonal frequency-division multiplexing (OFDM). The focus is on signal processing areas pursued by our research group at Luleå University of Technology. We present an historical background and some frequently used system models. Typical areas of applications are also described, both wireless and wired. In addition to the general overview, the addressed areas include synchronization, channel estimation and channel coding. Both time and frequency synchronization are described, and the effects of synchronization errors are presented. Different types of channel estimators are described, where the focus is on low-complexity algorithms, and in this context, advantages and disadvantages of coherent and differential modulation are also discussed. Channel coding is described, both for wireless and wired systems, and pointers are included to evaluation tools and bitloading algorithms. An extensive bibliography is also included.

    Fulltekst (pdf)
    FULLTEXT01
  • 7.
    Edfors, Ove
    et al.
    Luleå tekniska universitet.
    Sandell, Magnus
    Luleå tekniska universitet.
    van de Beek, Jaap
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Landström, Daniel
    Luleå tekniska universitet.
    Sjöberg, Frank
    Luleå tekniska universitet.
    An introduction to orthogonal frequency-division multiplexing1997Rapport (Annet vitenskapelig)
    Abstract [en]

    This report is an introduction to orthogonal frequency-division multiplexing (OFDM). The focus is on signal processing areas pursued by our research group at Luleå University of Technology. We present an historical background and some frequently used system models. Typical areas of applications are also described, both wireless and wired. In addition to the general overview, the addressed areas include synchronization, channel estimation and channel coding. Both time and frequency synchronization are described, and the effects of synchronization errors are presented. Different types of channel estimators are described, where the focus is on low-complexity algorithms, and in this context, advantages and disadvantages of coherent and differential modulation are also discussed. Channel coding is described, both for wireless and wired systems, and pointers are included to evaluation tools and bitloading algorithms. An extensive bibliography is also included.

  • 8. Isaksson, Mikael
    et al.
    Bengtsson, Daniel
    Deutgren, Petra
    Sandell, Magnus
    Luleå tekniska universitet.
    Sjöberg, Frank
    Luleå tekniska universitet.
    Ödling, Per
    Öhman, Hans
    Zipper: a duplex scheme for VDSL based on DMT1997Rapport (Annet vitenskapelig)
    Abstract [en]

    A duplex scheme for DMT-based VDSL systems is presented here. It offers a solution to the problem with NEXT and near-echoes in broadband communications. The scheme has high duplex efficiency, low latency, and attractive transmit power features. However, hardware verification remains.

    Fulltekst (pdf)
    FULLTEXT01
  • 9.
    Isaksson, Mikael
    et al.
    Telia Research AB.
    Deutgren, Petra
    Luleå tekniska universitet.
    Sjöberg, Frank
    Luleå tekniska universitet.
    Wilson, Sarah Kate
    Luleå tekniska universitet.
    Ödling, Per
    Luleå tekniska universitet.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    Zipper - a flexible duplex method for VDSL1997Inngår i: Proceedings of International Conference on Copper Wire Access Systems: CWAS '97, 1997, s. 95-99Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A novel duplex scheme for DMT-based VDSL systems on copper wire pairs is introduced. This method, named Zipper, uses different subcarriers in opposite transmission directions to divide the available bandwidth between the two directions. It provides exceptional versatility when it comes to dividing capacity between up and downstream. The scheme has high duplex efficiency, low latency, and most importantly good coexistence possibilities with other systems such as ADSL.

    Fulltekst (pdf)
    fulltext
  • 10.
    Isaksson, Mikael
    et al.
    Telia Research.
    Mestdagh, Denis
    Sjöberg, Frank
    Luleå tekniska universitet.
    Nilsson, Rickard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Ödling, Per
    Bengtsson, Daniel
    Pulse shaping with zipper: spectral compatibility and asynchrony1998Rapport (Annet vitenskapelig)
    Abstract [en]

    We have investigated what the effects of adding pulse shaping and windowing to a Zipper-VDSL system would be. By adding short, pulse-shaped wings to the DMT symbol and accepting the, say, 3 % efficiency loss, the spectral sidelobes of the DMT-symbol are reduced. This provides several attractive features including the following: · The pulse shaping in the transmitter reduces the out of band power of the DMT-signal. · The spectral compatibility with other systems such as ADSL and CAP-VDSL is enhanced. · It becomes feasible to use Zipper-VDSL in a time-asynchronous mode, where a VTU-R only synchronizes itself to its VTU-O, while the VTU-R / VTU-O pair may be asynchronous to all other transceiver pairs. · The pulse shaping gives some increase in the depth of spectral notches, for HAM-bands etc. The windowing is a part of a powerful RFI-ingress suppressing method as proposed by John Bingham, Amati.

    Fulltekst (pdf)
    FULLTEXT01
  • 11.
    Isaksson, Mikael
    et al.
    Telia Research.
    Stefansson, Tomas
    Ödling, Per
    Sjöberg, Frank
    Luleå tekniska universitet.
    Wilson, Sarah Kate
    Luleå tekniska universitet.
    Option for inband POTS and ISDN1997Rapport (Annet vitenskapelig)
    Abstract [en]

    We propose an option allowing VDSL to use the spectrum now reserved for narrowband services, such as POTS and ISDN. The main motives for the proposal are: 1) This option will provide lower network complexity and maintenance costs by avoiding duplicate line cards.2) We can increase the number of customers using VDSL for rates below 15 Mbps. This is because when VDSL can use the full spectrum, the reach can be significantly extended. For example, the reach increases by up to 1000 meters for a 2 Mbps symmetric service on TP1 in a central office based scenario.

    Fulltekst (pdf)
    FULLTEXT01
  • 12.
    Nilsson, Rickard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sjöberg, Frank
    Luleå tekniska universitet.
    Edfors, Ove
    Luleå tekniska universitet.
    Ödling, Per
    Luleå tekniska universitet.
    Wilson, Sarah Kate
    Luleå tekniska universitet.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    A low complexity threshold detector making MLSD decisions in a multiuser environment1998Inngår i: Pathway to a global wireless revolution: VTC '98, 48th IEEE Vehicular Technology Conference, Westin Hotel, Ottawa, Canada, 18 - 21 May 1998, Piscataway, NJ: IEEE Communications Society, 1998, s. 333-337Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we present a pipelined implementation of an iterative threshold detector, which makes the same decisions as a maximum likelihood sequence detector (MLSD) on some, but not necessarily all, bits. We apply this as a first stage detector in a direct sequence code division multiple access (DS-CDMA) interference-limited multiuser system. In combination with the single-user matched filter (MF) detector we obtain improved performance and lower complexity than with the decorrelating receiver for a limited number of simultaneous users, e.g. up to 25 users with a spreading factor of 127.

    Fulltekst (pdf)
    fulltext
  • 13.
    Nilsson, Rickard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sjöberg, Frank
    Luleå tekniska universitet.
    Isaksson, Mikael
    Luleå tekniska universitet.
    Cioffi, J.M.
    Stanford University.
    Wilson, S.K.
    ArrayComm, San Jose.
    Self-synchronizing a DMT-based VDSL system2001Inngår i: Where minds meet: 2001 IEEE International Conference on Communications ; ICC 2001. June 11 - 14, 2001 ; Helsinki ; conference record / IEEE Communications Society / [ed] Yrjö Neuvo, Piscataway, NJ: IEEE Communications Society, 2001, s. 1249-1253Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present an algorithm for self-synchronizing all modems in a discrete multitone (DMT)-based very high-speed digital subscriber line (VDSL) system using the Zipper duplex method. This solves the problem with non-orthogonal near-end crosstalk (NEXT) that appears in systems with unsynchronized modems. The algorithm we present runs autonomously in each VDSL-modem. It uses the auto-correlation of the DMT-signal to determine the frame-offset of other users, and adjusts the own frame-timing to be better aligned with the other users. With our method all modems will be self-synchronized to within a small fraction of the total DMT frame-length. This self-synchronization suppresses the NEXT to a level far below the background noise-floor. This means that our self-synchronized system has the same performance as a system where all modems are perfectly synchronized to a master clock

  • 14.
    Nilsson, Rickard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sjöberg, Frank
    Luleå tekniska universitet.
    Isaksson, Mikael
    UpZide Labs AB, Aurorum.
    Cioffi, John
    Electrical Engineering Department, Stanford University.
    Wilson, Sarah Kate
    ArrayComm, San Jose.
    Autonomous synchronization of a DMT-VDSL system in unbundled networks2002Inngår i: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 20, nr 5, s. 1055-1063Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present an algorithm that autonomously synchronizes all DMT-Zipper based VDSL modems in an unbundled access network, solving the problem with nonorthogonal NEXT that appears in systems with unsynchronized modems. The algorithm we present runs autonomously in each VDSL-modem in the central office or in the street cabinet. We determine the other modems ' relative frame offsets by exploiting their NEXT signal using the inherent cyclic redundancy found in DMT signals. By estimating the relative frame offsets of the other users, we can adjust a given user's own frame-timing relative to the mean of the others. With our method all modems in the network will be synchronized to within a small fraction of the total DMT frame-length, suppressing the nonorthogonal NEXT to a level far below the background noise-floor. This means that we can achieve the same performance in an unbundled access network without any master clock reference as in a system where all modems are perfectly synchronized using a master clock. Index Terms-Discrete multitone, frame synchronization, subscriber loops.

    Fulltekst (pdf)
    fulltext
  • 15.
    Nilsson, Rickard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sjöberg, Frank
    Luleå tekniska universitet.
    Leblanc, James
    A narrow-band interference canceller for OFDM-based systems2001Inngår i: Proceedings EPMCC 2001, 2001Konferansepaper (Fagfellevurdert)
    Fulltekst (pdf)
    fulltext
  • 16.
    Nilsson, Rickard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sjöberg, Frank
    Luleå tekniska universitet.
    Leblanc, James
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    A rank-reduced LMMSE canceller for narrowband interference suppression in OFDM-based systems2003Inngår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 51, nr 12, s. 2126-2140Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a narrowband interference (NBI) canceller that suppresses spectral leakage in an orthogonal frequency-division multiplexing (OFDM)-based system caused by a narrowband (NB) signal. We assume that the spectrum of the NB signal is within the spectrum of the OFDM signal. This can be the case, e.g., on digital subscriber lines (DSL) and in new unlicensed frequency bands for radio transmission. The canceller makes linear minimum mean-square error estimates of the spectral leakage by measuring the NBI on a few modulated or unmodulated OFDM subcarriers. It uses a model of the NB signal's power spectral density as a priori information. Using a frequency invariant design, it is possible to cancel NBI from signals that are changing their frequency location with significantly reduced complexity overhead. The operational complexity of the canceller can be lowered by using the theory of optimal rank reduction and using the time-bandwidth product of the NB signal. Analytical performance evaluations, as well as Monte Carlo simulations, show that, without perfect a priori information, this canceller can suppress the spectral leakage from a strong NB signal (e.g., with equal power as the OFDM signal) to well below the background noise floor for typical applications where it causes negligible signal-to-noise ratio and symbol error rate degradation.

    Fulltekst (pdf)
    fulltext
  • 17.
    Sjöberg, Frank
    Luleå tekniska universitet.
    A VDSL tutorial2000Rapport (Annet vitenskapelig)
    Abstract [en]

    This report is an introduction to very high-speed digital subscriber lines (VDSL). It gives an overview of the telephone access network and describes in more detail the characteristics of twisted-pair wire-line channel. We describe the different types of noise sources that exist, especially impulse noise, radio frequency interference (RFI), and crosstalk. We also describe some methods to deal with the different types of noise. The problem with radio frequency interference is two-fold and we address both the RFI-ingress and the RFI-egress problem. The different duplex methods and modulation methods proposed for VDSL are presented in this report, with the focus on discrete multitone modulation and the Zipper duplex method. The problem with very unequal levels of far-end crosstalk for different wire lengths is also addressed and we present some different power back-off methods to deal with that problem. Compatibility issues between VDSL and other types of systems are addressed in the last section. The report also contains an extensive bibliography

    Fulltekst (pdf)
    FULLTEXT01
  • 18.
    Sjöberg, Frank
    Luleå tekniska universitet.
    High speed communication on twisted-pair wires and low complexity multiuser detectors1998Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis deals with two different topics: High speed communication on twisted pair wires (digital subscriber lines) and low complexity multiuser detectors. The major part of this thesis concerns a technique for high speed communication over the telephone network called Very high bit rate Digital Subscriber Line VDSL). VDSL is not standardized yet but it is intended to offer bit rates up to 52 Mbit per second on twisted-pair wires. An important problem in VDSL is crosstalk between wire pairs, especially Near End Cross Talk (NEXT). A novel duplex method, called Zipper, that mitigates NEXT is presented herein. Zipper is a flexible duplex method that has high duplex efficiency and offers compatibility with existing services. It is based on Discrete Multi Tone (DMT) modulation, and uses different subcarriers in the two different transmission directions. The method relies on an additional cyclic extension to ensure orthogonality between the transmission directions. Zipper achieves best performance when all transmitters in the access network are synchronized, but it can also operate in an asynchronous mode with only a small loss in performance. Another important issue for VDSL is the problem with Radio Frequency Interference (RFI). The copper wires can act as large antennas and hence can transmit and receive radio signals. Herein the problem of radio frequency signals interfering with VDSL systems (called RFI-ingress) is addressed. The proposed method for suppressing the RFI works in the frequency domain of the DMT-receiver and can be used by any DMT-based VDSL system. By modeling the RFI and measuring the disturbance on some unmodulated subcarriers we can extrapolate and subtract the disturbance on all the other subcarriers. For a typical scenario with an average Signal-to-Noise Ratio (SNR) of 30 dB without RFI, about 20 dB can be lost due to RFI, but with the presented RFI-canceller this SNR-loss is reduced to less than 1 dB. The last part of this thesis deals with low complexity multiuser detection in a direct sequence code division multiple access system. The Maximum Likelihood Sequence Detector (MLSD) gives very good performance but is known to be very computationally complex. The detector presented herein is a simple threshold detector that makes MLSD-decisions on some, but not necessarily all, bits. A pipelined structure of the detector is presented which is attractive from an implementation point of view, since it allows parallel processing of the data. Using a single-user matched filter detector as post processor, taking care of the previously undetected bits, a complete multiuser detector with very low complexity is achieved. This detector gives better performance than the decorrelator receiver for a limited number of simultaneous users, e.g. up to 25 users with a spreading factor of 127.

    Fulltekst (pdf)
    FULLTEXT01
  • 19.
    Sjöberg, Frank
    Luleå tekniska universitet.
    The Zipper duplex method in very high-speed digital subscriber lines2000Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis deals with different aspects of digital subscriber lines (DSL). Over the years several DSL techniques for high-speed communication on the telephone access network have evolved that gradually have allowed higher data rates. In this thesis we focus on the latest technique, called Very high-speed Digital Subscriber Line (VDSL), which is intended to offer bit-rates up to 50-60 Mbits/s on ordinary twisted-pair wires. The major part of this thesis concerns a novel scheme called the Zipper duplex method, which is introduced herein. Zipper has been proposed as duplex method for VDSL, and represents one of the two leading proposals in the North American (ANSI T1E1.4), the European (ETSI TM6), and in the International (ITU SG15/Q4) standardization groups. The key advantages with the Zipper duplex method are superior flexibility, high duplex efficiency and compatibility with existing services. It is based on discrete multitone (DMT) modulation and uses different DMT-tones in the up- and the downstream directions. The method relies on an additional cyclic extension, a cyclic suffix, to ensure orthogonality between signals in opposite directions. Best performance is achieved when all transmitters in the access network are synchronized, but Zipper can also operate in an asynchronous mode. However the asynchronous mode comes with some bit-rate performance loss and this performance loss tends to increase with wire-length. So we have developed a method for self-synchronizing all Zipper-modems that guarantees best possible performance for long wires. This method uses the correlation present in DMT-signals, due to the cyclic extension, to estimate the other users' frame-offset relative to their own. It then adjusts the frame-timing accordingly. Problems with near-far far-end crosstalk (FEXT) in the upstream can severely limit the performance of modems on long wires. In this thesis we propose a bandwidth efficient power allocation method called the multi-rate power back-off. This method creates a spectrally shaped transmit power spectral density (PSD) that results in higher bit-rates for all users compared to using a flat transmit PSD. By incorporating target bit-rates, a system operator can better control the bit rate distribution among the users, and the FEXT is kept at a minimum since no user is allowed to use more transmit power than necessary to achieve the desired target rate. The unshielded wires in the access network are quite susceptible to radio frequency interference (RFI). We introduce an efficient digital RFI-cancellation method that operates in the frequency domain for modems using DMT-modulation. By deriving a parameterized model of the narrowband RFI-signal and measuring the RFI-signal on a few unmodulated DMT-tones, the RFI can be extrapolated to the other tones and cancelled. Simulations show that it is sufficient with two parameters and two measurement tones to almost completely eliminate the RFI. Impulse noise that originates from telephone activity can be very harmful to VDSL. The use of a system margin together with Reed-Solomon coding and interleaving have been proposed to handle the impulse noise. In this thesis we study the effect of impulse noise on DMT-based VDSL systems, and present a robust detection and erasure scheme that can reduce the interleaving depth required to cope with the strongest impulses.

    Fulltekst (pdf)
    FULLTEXT01
  • 20.
    Sjöberg, Frank
    et al.
    Luleå tekniska universitet.
    Isaksson, Mikael
    Telia Research AB.
    Deutgren, Petra
    Telia Research AB.
    Nilsson, Rickard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Ödling, Per
    Luleå tekniska universitet.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    Performance evaluation of the Zipper duplex method1998Inngår i: New century communications: conference record / ICC '98, 1998 IEEE International Conference on Communications, 7 - 11 June 1998, Atlanta, Georgia, USA, Piscataway, NJ, 1998, s. 1035-1039Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we present performance results for a new duplex scheme, called Zipper, for DMT-based VDSL systems on copper wires. This scheme divides the available bandwidth by assigning di¤erent subcarriers for the upstream and downstream direction. It has high .exibility to divide the capacity between the up- and downstream as well as good coexistence possibilities with other systems such as ADSL. Simulation results show high bitrate performance in different environments such as mixed ADSL and VDSL traffic, under radio frequency interference, and with different background noise sources.

    Fulltekst (pdf)
    fulltext
  • 21.
    Sjöberg, Frank
    et al.
    Luleå tekniska universitet.
    Isaksson, Mikael
    Telia Research AB.
    Nilsson, Rickard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Ödling, Per
    Lunds universitet.
    Wilson, Sarah Kate
    Luleå tekniska universitet.
    Börjesson, Per-Ola
    Lunds universitet.
    Zipper - a duplex method for VDSL based on DMT1999Inngår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 47, nr 8, s. 1245-1252Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a new duplex scheme, called Zipper, for discrete multitone (DMT)-based very high bit-rate digital subscriber line (VDSL) systems on copper wires. This scheme divides the available bandwidth by assigning different subcarriers for the upstream and downstream directions. It has high flexibility to divide the capacity between the up and downstream, as well as good coexistence possibilities with other systems such as ADSL. Simulation results show the high bit-rate performance in different environments such as mixed ADSL and VDSL traffic under radio frequency interference and with different background noise sources

    Fulltekst (pdf)
    fulltext
  • 22. Sjöberg, Frank
    et al.
    Nilsson, Rickard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Börjesson, Per Ola
    Ödling, Per
    Wiese, Brian
    Bingham, John A. C.
    Digital RFI Suppression in DMT-based VDSL Systems2004Inngår i: IEEE Transactions on Circuits and Systems Part 1: Regular Papers, ISSN 1549-8328, E-ISSN 1558-0806, Vol. 51, nr 11, s. 2300-2312Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we propose a method for suppressing radio frequency interference (RFI) in discrete multitone (DMT) based very high bit rate digital subscriber line (VDSL) systems. The method operates in the frequency domain of a DMT system. First, we derive a model of how an unknown narrow-band RF signal is mapped onto the DMT carriers. Then, by measuring the RFI on a few unused DMT carriers we are able to subtract RFI estimates from every modulated subcarrier. Simulation results show that this method, applied to an RFI signal with the same average power as the VDSL signal, suppresses the RFI with 40-50 dB, which reduces the average SNR loss from about 20 to less than 0.3 dB.

    Fulltekst (pdf)
    fulltext
  • 23.
    Sjöberg, Frank
    et al.
    Luleå tekniska universitet.
    Nilsson, Rickard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Grip, Niklas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    Wilson, Sarah Kate
    Luleå tekniska universitet.
    Ödling, Per
    Luleå tekniska universitet.
    Digital RFI suppression in DMT-based VDSL systems1998Inngår i: ICT '98: International Conference on Telecommunications : bridging east & west through telecommunications : 21-25 June 1998, Porto Carras, Greece / [ed] F-N. Pavlidou, 1998, Vol. 2, s. 189-193Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we describe a method for supressing Radio Frequency Interference (RFI) in Discrete Multitone (DMT) based Very High bit rate Digital Subscriber Line systems. The method operates in the frequency domain of a DMT-system. It is based on a Taylor-expanded transfer function which maps the disturbance from the RF-signal onto the DMT-carriers. By measuring the RF-disturbance on a few unmodulated DMT-carriers we are able to subtract estimates of the disturbance from every modulated DMT-carrier. The RF-signal is assumed to be an unknown narrowband signal. Simulation results show that this method, applied to an RFI-signal with the same average power as the VDSL-signal, reduces the SNR-loss from about 20 dB to less than 1 dB.

    Fulltekst (pdf)
    fulltext
  • 24.
    Sjöberg, Frank
    et al.
    Luleå tekniska universitet.
    Nilsson, Rickard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Isaksson, Mikael
    Telia Research AB, Aurorum 6.
    Ödling, Per
    Lund Institute of Technology, Department of Applied Electronics.
    Börjesson, Per Ola
    Lund Institute of Technology, Department of Applied Electronics.
    Asynchronous Zipper: [subscriber line duplex method]1999Inngår i: IEEE International Conference on Communications: 6 - 10 June, 1999, Vancouver, British Columbia, Canada, Piscataway, Nj: IEEE Communications Society, 1999, Vol. 1, s. 231-235Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Previously the authors presented a novel duplex method for very high bit-rate digital subscriber lines (VDSL) called Zipper. With this method all VDSL-modems on different wires in the same bindergroup have to be time-synchronized to avoid near-end cross-talk (NEXT). We describe a method which enables Zipper to run in a time-asynchronous mode. By introducing pulse-shaping in the transmitter and windowing in the receiver the NEXT is almost completely suppressed even though the synchronization between modems on neighboring lines is skipped. The remaining NEXT and efficiency loss due to pulse-shaping and windowing results in only a small bit-rate performance loss, typically less than 10% compared to the time-synchronized Zipper. However, with the new freedom of optimizing the lengths of the cyclic suffices with asynchronous Zipper, there may even be a small improvement in bit-rate performance for short wires

  • 25.
    Sjöberg, Frank
    et al.
    Luleå tekniska universitet.
    Nilsson, Rickard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Wilson, Sarah Kate
    Luleå tekniska universitet.
    Bengtsson, Daniel
    Telia Research.
    Isaksson, Minkael
    Telia Research.
    Power back-off for multiple target bit rates1998Rapport (Annet vitenskapelig)
    Abstract [en]

    This contribution describes a new efficient method to perform power back-off in the upstream of a VDSL-system. The method gives higher data rates than the earlier proposals, i.e., the constant back-off method and the reference length method. One conceptual difference with this new method is that we are not using just one design parameter as with the reference frequency and reference length methods. With this new method all users are assigned a certain service class, a target bit rate. The method then performs the power back-off such that it tries to maximize the bit rate (the system margin) for all the other users. The method tries to create FEXT, at each NT, that has the same spectral shape as the background noise. Between 5% and 20% improvement in bit rates is achieved with this new method when using the FSAN models for cable, crosstalk and background noise. The larger improvements over the other methods appear when non-flat background is present. This is because the PSD of the background noise is included in the model used by method. For thinner wires, like the TP1 wire, the method can give more than 20% higher data rate for almost all users.

    Fulltekst (pdf)
    FULLTEXT01
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