Steven van Beneden

Technische Universiteit Eindhoven, Eindhoven, North Brabant, Netherlands

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Publications (15)22.72 Total impact

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    Jamal Riani, Steven van Beneden, J.W.M. Bergmans, A.H.J. Immink
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    ABSTRACT: Receivers for partial response maximum-likelihood systems typically use a linear equalizer followed by a Viterbi detector. The equalizer tries to confine the channel intersymbol interference to a short span in order to limit the implementation complexity of the Viterbi detector. Equalization is usually made adaptive in order to compensate for channel variations. Conventional adaptation techniques, e.g., LMS, are, in general, suboptimal in terms of bit-error rate (BER). In this paper, we present a new equalizer adaptation algorithm that seeks to minimize the BER at the Viterbi detector output. The algorithm extracts information from the sequenced amplitude margin (SAM) histogram and incorporates a selection mechanism that focuses adaptation on particular data and noise realizations. The selection mechanism is based on the reliability of the add compare select (ACS) operations in the Viterbi detector. From a complexity standpoint, the algorithm is essentially as simple as the conventional LMS algorithm. Moreover, we present a further simplified version of the algorithm that does not require any hardware multiplications. Simulation results, for an idealized optical storage channel, confirm a substantial performance improvement relative to existing adaptation algorithms.
    IEEE Transactions on Communications 01/2008; · 1.75 Impact Factor
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    S. Van Beneden, J. Riani, J. W. M. Bergmans
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    ABSTRACT: In digital recording systems, the total amount of data-dependent media noise increases considerably as recording densities increase. A proper noise characterization is crucial for the design of receivers for high-density storage systems. This characterization involves the selection of a proper noise model and subsequently the accurate estimation of the parameters of the selected model. The estimation algorithm proposed in this paper jointly estimates the parameters of both media and additive noise with a high accuracy. The proposed algorithm makes use of the data dependency of the media noise to distinguish between the different noise sources. The algorithm is simple and as a result can be implemented in recording systems, with only a limited amount of complexity, as an easy "add-on" to read-channel ICs. From the simulation results and the analytical derivation of the estimation algorithm, we can clearly indicate which data patterns yield near-optimal estimation performance. These patterns are the ideal test patterns in experimental systems. We propose and discuss test patterns for magnetic and optical storage systems
    IEEE Transactions on Magnetics 03/2007; · 1.42 Impact Factor
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    ABSTRACT: The trend of increasing storage densities results in growing sensitivity of system performance to variations of storage channel parameters. To counteract these variations, more adaptivity is needed in the data receiver. Accurate tracking of rapid variations is limited by latencies in the adaptation loops. These latencies are largely governed by delays of the bit detector. In two-dimensional storage systems, data are packaged in a group of adjacent tracks or rows, and for some of the rows the detection delays can increase dramatically with respect to one-dimensional systems. As a result, the effective latencies in the adaptation loops preclude the tracking of rapid variations and really limit the performance of the system. In this paper, a scheme is proposed that overcomes this problem and that can be used for timing recovery, automatic gain control, and other adaptive circuits. Rapid variations for all the rows are tracked using control information from rows for which detector latency is smallest. This works properly if rapid variations are common across the rows as is the case, for example, for the two-dimensional optical storage (TwoDOS) system. Experimental results for TwoDOS confirm that the scheme yields improved performance with respect to conventional adaptation schemes
    IEEE Transactions on Magnetics 02/2007; · 1.42 Impact Factor
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    IEEE Transactions on Communications. 01/2007; 55:2316-2327.
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    J. Riani, J.W.M. Bergmans, S. van Beneden, A. Immink
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    ABSTRACT: In high-density data storage systems, noise becomes highly correlated and data dependent as a result of media noise, channel nonlinearities, and front-end filters. In such environments, conventional timing recovery schemes will exhibit large residual timing jitter and, especially, data-dependent timing jitter. This paper presents a new data-aided timing recovery algorithm for data storage systems with data-dependent noise. We derive a maximum-likelihood timing recovery scheme based on a data-dependent Gauss-Markov model of the noise. The timing recovery algorithm incorporates data-dependent noise prediction parameters in the form of linear prediction filters and prediction error variances. Moreover, because noise can be nonstationary in practice, we propose an adaptive algorithm to estimate and track the noise prediction parameters. Simulation results, for an idealized optical storage channel incorporating a simple model of media noise, illustrate the merits of our algorithm
    IEEE Transactions on Magnetics 12/2006; · 1.42 Impact Factor
  • J. Riani, S. Van Beneden, J.W.M. Bergmans
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    ABSTRACT: Data receivers for storage systems normally operate at a fixed sampling rate 1/T<sub>S</sub> that is asynchronous to the baud rate 1/T. A sampling-rate converter (SRC) serves to convert the incoming signal from the asynchronous to the synchronous clock domain. These receivers also contain an equalizer that serves to suppress intersymbol interference and noise. To limit receiver complexity, equalization burden can be shifted towards the SRC. This possibility is not exploited in any existing SRC. This paper presents SRC design methods that combine group delay flatness and out-of-band rejection criteria with the minimum mean square error equalization criterion. Numerical examples for an idealized optical recording channel validate the design methods
    Acoustics, Speech and Signal Processing, 2006. ICASSP 2006 Proceedings. 2006 IEEE International Conference on; 06/2006
  • S. Van Beneden, J. Riani, J.W.M. Bergmans
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    ABSTRACT: In this paper a channel model is proposed for two-dimensional digital data storage systems. This channel model describes both the intersymbol interference structure and the noise structure. This noise structure is modelled as the output of a two-dimensional data-dependent autoregressive filter. The proposed model is simple, accurate and it is able to track channel variations. An experimental two-dimensional optical system is used to validate the proposed model and to illustrate the characterization process based on the model
    Acoustics, Speech and Signal Processing, 2006. ICASSP 2006 Proceedings. 2006 IEEE International Conference on; 06/2006
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    ABSTRACT: In order to reduce the implementation complexity of maximum likelihood sequence detectors (MLSD), equalized maximum likelihood receivers are often used. This consists of employing an equalizer to transform the channel response to a short target response to which the Viterbi detector is matched. Existing equalizer and target adaptation schemes are often based on the minimum mean-square error (MMSE) criterion which is not always optimal in terms of detection bit-error rate at the Viterbi detector output. In this paper we consider minimum bit-error rate joint adaptation of equalizer and target response and present a practical adaptation algorithm that achieves near minimum bit-error rate performance. Our new equalizer and target adaptation scheme shows significant performance improvements in the presence of channel nonlinearities and media noise when compared to MMSE adaptation schemes. This is very promising for high density recording systems that are mainly hampered by media noise and channel nonlinearities. Moreover, from a complexity standpoint, the proposed algorithm is comparable to the MMSE-based algorithms.
    Proceedings of the Global Telecommunications Conference, 2006. GLOBECOM '06, San Francisco, CA, USA, 27 November - 1 December 2006; 01/2006
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    ABSTRACT: In high-density recording systems performance is largely determined by noise, n general different noise sources are present, where each source has direct impact on the overall performance. Therefore the characterization of a noise source provides insightful information about the recording system. In general noise characterization involves the choice of an appropriate stochastic model for it and furthermore the estimation of the parameters of the selected stochastic model. The characterization results can be used as diagnostic information to evaluate existing recording systems and they play an important role in state of the art bit-detection techniques. In these techniques the estimated stochastic parameters are used as side information to improve the detection reliability. For this reason an accurate estimation is very important. The estimation algorithm proposed in this paper, achieves a high estimation accuracy for systems where both data-dependent media noise and correlated additive noise are present. This algorithm makes use of the difference in data-dependency between the two noise sources to jointly estimate the stochastic parameters of the two noise sources.
    Proceedings of the Global Telecommunications Conference, 2006. GLOBECOM '06, San Francisco, CA, USA, 27 November - 1 December 2006; 01/2006
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    ABSTRACT: With storage capacities increasing much faster than data rates, fast read-out of content is becoming a bottleneck for the convenient use of optical storage devices. Two-dimensional optical storage (TwoDOS) is a new concept that solves this data-rate problem by using a multi-spot parallel readout system. In addition, the storage capacity is increased with a factor of at least 2. Using the same read-out physics as in the Blu-ray disc standard, single layered 12 cm discs with capacities up to 50 GB have been read out successfully at bit-rates as high as 560 Mbit/s. Basic pillars of TwoDOS are advanced signal processing and disc mastering techniques, and a proper design of the optical path.
    Acoustics, Speech, and Signal Processing, 2005. Proceedings. (ICASSP '05). IEEE International Conference on; 04/2005
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    J. Riani, S. Van Beneden, J.W.M. Bergmans, A. Immink
    [Show abstract] [Hide abstract]
    ABSTRACT: Receivers for partial response maximum-likelihood systems typically use a linear equalizer followed by a Viterbi detector. The equalizer tries to confine the channel intersymbol interference to a short span in order to limit the implementation complexity of the Viterbi detector. Equalization is usually made adaptive in order to compensate for channel variations. Conventional adaptation techniques, e.g. LMS, are in general suboptimal in terms of bit-error rate. In this paper we present a new equalizer adaptation algorithm that seeks to minimize bit-error rate at the Viterbi detector output. The algorithm extracts information from the sequenced amplitude margin (SAM) histogram and incorporates a selection mechanism that focuses adaptation on particular data and noise realizations. From a complexity standpoint, the algorithm is as simple as the conventional LMS algorithm. Simulation results, for an idealized optical storage channel, confirm a substantial performance improvement relative to existing adaptation algorithms.
    Global Telecommunications Conference, 2005. GLOBECOM '05. IEEE; 01/2005
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    ABSTRACT: With ever increasing storage capacities, long read-out times of content are becoming a bottleneck for the convenient use of optical storage devices. Two-dimensional optical storage (TwoDOS) is a new concept that solves this data-rate problem through parallel read-out. Furthermore, an increase of at least a factor of 2 in storage capacity is achieved by exploiting a two-dimensional format. The advantages offered by TwoDOS are obtained without the need of changing the physics of the read-out system. Using Blu-ray Disc optics, single-layered 12 cm discs with capacities up to 50 GByte have been read out successfully. Signal level and error analysis show the feasibility of a further capacity increase. Also, bit-rates as high as 700 Mbit/s during read-out have been reached. All this is achieved by applying advanced signal processing and advanced disc mastering techniques and the proper design of the optical path.
    Japanese Journal of Applied Physics 01/2005; 44:3547-3553. · 1.07 Impact Factor
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    ABSTRACT: The paper introduces the concept of two-dimensional optical storage (TwoDOS). In this concept, bits are written in a broad spiral consisting of a number of bit-rows stacked together in a hexagonal packing. Bits with a value '1' are represented physically as circular pit-holes on the disc, while bits with a value '0' are characterized by the absence of such a pit-hole. A scalar diffraction model is used to calculate the signal levels for various diameters of the pits. A stripe-wise Viterbi detector is proposed to perform 2D bit-detection with a limited state complexity of the trellis. Simulation results are shown for various diameters of the pits. A 2D modulation code is applied to eliminate patterns that yield a high probability of erroneous detection.
    Global Telecommunications Conference, 2003. GLOBECOM '03. IEEE; 01/2004
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    ABSTRACT: This paper discusses several issues related to adaptation and timing recovery for two-dimensional (2D) optical storage. In the TwoDOS format bits are stored on a 2D hexagonal lattice which is formed by recording multiple bit rows with a fixed phase relation in a so-called broad spiral or meta-spiral. Besides a large increase in data rate by reading out with multiple spots, also a density increase by a factor of two compared to Blu-ray Disc is targeted. To increase the storage density, 2D signal processing is proposed including 2D PRML detection in the form of a stripe-wise Viterbi detector. This detector introduces an increasing detection delay when going from the outer rows towards the center of the broad spiral. For fast control loops in a decision-directed mode, special measures are needed to avoid instability due to this delay. Another issue is the large span of the 2D inter-symbol interference at higher densities and tilt, leading to a large 2D equalizer. Furthermore, in case the broad spiral is recorded with a multiple-pass mastering technology (e.g. for ROM TwoDOS discs), write-channel imperfections such as time-varying lattice distortion require independent timing recovery on each row within the broad spiral.
    Proc SPIE 01/2004;
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    J Riani, S Van Beneden, J W M Bergmans
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    ABSTRACT: This paper presents a new data-aided timing recovery al-gorithm for channels with data-dependent noise. Based on a data-dependent Gauss-Markov model of the noise, a maximum-likelihood timing recovery scheme is derived. The proposed timing recovery algorithm incorporates data-dependent noise prediction parameters in the form of linear prediction filters and prediction error variances. Moreover, because noise can be nonstationary in practice, an adaptive algorithm is proposed in order to estimate and track the noise prediction parameters. Simulation results, for a partial re-sponse maximum-likelihood system, show that our algorithm allows an important reduction in timing jitter whenever noise is dominantly data-dependent.