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On the application of sequence estimation algorithms in the digital compact cassette (DCC)
Abstract
In the current digital compact cassette (DCC) recorder, a
straightforward threshold detection scheme is applied which does not
exploit the distance properties of the 8-to-10 modulation (ETM) code.
More advanced detection schemes are investigated to see if they improve
system performance. Two soft decision sequence estimation algorithms are
considered: a fully-fledged Viterbi algorithm realizing maximum
likelihood sequence estimation (MISE) and a suboptimal trellis detection
algorithm. With either of the algorithms, an asymptotic gain of 3 dB
versus threshold detection level in the presence of additive white
Gaussian noise (AWGN) is expected. The suboptimal detection algorithm is
based on the running digital sum (RDS) trellis underlying the ETM code.
Performing the suboptimal algorithm requires a minimum of 48 additions,
19 comparisons, and a single table look-up for both detection and
decoding of an ETM codeword, versus a minimum of 4234 additions, 421
comparisons, and 423 table look-ups for the fully-fledged algorithm.
Compared to the fully-fledged scheme, the suboptimal algorithm leads to
a large reduction in computational complexity. The performance of either
of the algorithms in the presence of AWGN is determined by means of a
computer simulation. The fully-fledged Viterbi algorithm achieves a gain
of about 2.3 dB versus threshold detection level for symbol error rates
in the order of 10<sup>-4</sup> to 10<sup>-5</sup>
... For analytical and experimental results pertaining to a rate , MSN-coded PR4 system, the reader is referred to [164] and [169]. Experimental evaluation of a spectral-null coded-tape system is described in [27]. For these examples of MSN-constrained PR channels, the error event characterization discussed above provides another confirmation, and a refinement, of the coding gain bounds. ...
... Based upon these techniques, a number of proposals for performance-improving codes for the PR4 channel have been made, and VLSI prototypes of MSN codes, in particular, have been experimentally evaluated [46], [13]. However, none has yet been incorporated widely into commercial magneticrecording systems. ...
Partial-response (PR) signaling is used to model communications
channels with intersymbol interference (ISI) such as the magnetic
recording channel and the copper-wire channel for digital subscriber
lines. Coding for improving noise immunity in higher order
partial-response channels, such as the “extended” class-4
channels denoted EPR4, E<sup>2</sup>PR4, E<sup>3</sup>PR4, has become an
important subject as the linear densities in magnetic recording approach
those at which these partial-response channels are the best models of
real channels. In this paper, we consider partial-response channels for
which ISI is so severe that the channels fail to achieve the
matched-filter bound (MFB) for symbol error rate, assuming
maximum-likelihood decoding. We show that their performance can be
improved to the MFB by high-rate codes based on constrained systems,
some of which may even simplify the Viterbi (1979) detectors relative to
the uncoded channels. We present several examples of high-rate
constrained codes for E<sup>2</sup>PR4 and E<sup>3</sup>PR4 channels and
evaluate their performance by simulation
... For analytical and experimental results pertaining to a rate , MSN-coded PR4 system, the reader is referred to [164] and [169]. Experimental evaluation of a spectral-null coded-tape system is described in [27]. For these examples of MSN-constrained PR channels, the error event characterization discussed above provides another confirmation, and a refinement, of the coding gain bounds. ...
Constrained codes are a key component in digital recording devices
that have become ubiquitous in computer data storage and electronic
entertainment applications. This paper surveys the theory and practice
of constrained coding, tracing the evolution of the subject from its
origins in Shannon's classic 1948 paper to present-day applications in
high-density digital recorders. Open problems and future research
directions are also addressed
Constrained codes are a kev component in the digital recording devices that have become ubiquitous in computer data storage and electronic entertainment applications. This paper surveys the theory and practice of constrained coding, tracing the evolution of the subject from its origins in Shannon's classic 1948 paper to present-day applications in high-density digital recorders. Open problems and future research directions are also addressed.
We present a new insertion/deletion detection and correcting decoding scheme for convolutional codes that is based on the Viterbi decoding algorithm. Firstly, we show that, when using a coding scheme that utilises a standard rate, R=k/n, convolutional code and n Viterbi decoders in parallel, it is possible to correct up to n-1 consecutive deletions or insertions. Our results show the effectiveness of this scheme to re-establish bit-synchronisation after the deletion of bits. Further, we investigate the correction of multiple deletions or insertions using standard concatenated coding schemes employing convolutional inner codes, and Reed-Solomon outer codes.
We report on the design considerations of stationary-head multi-track magnetic recorders. We focus on the particular reasons for adopting the rate 8/10, DC-free recording code, the full-response detection method, and the clock recovery circuitry. Implementation issues of the channel chip, particularly related to cost and power consumption, are addressed. A new multi-track phase-lock loop (PLL) has been developed, in order to improve the recorder's robustness against time-base variations.< >
The authors present the application and performance of a rate 8/10
matched-spectral null (MSN) trellis code in conjunction with class-4
partial response (PR4) signaling. Details of the encoder and decoder
functions are presented, as well as the reduced-complexity trellis
structure underlying the Viterbi detector for the coded system.
Implementation issues involved in the design of a VLSI chip embodying
the encoder, decoder, and Viterbi detector for the trellis-coded system
are discussed. Results of experiments using synthesized PR4 waveforms
are presented, and it is shown that the rate 8/10 code can provide about
a 3-dB advantage relative to the class-4 partial response maximum
likelihood detection in the presence of additive white Gaussian noise as
well as additive synthesized adjacent track interference
Many of the types of modulation codes designed for use in storage devices using magnetic recording are discussed. The codes are intended to minimize the negative effects of intersymbol interference. The channel model is first presented. The peak detection systems used in most commercial disk drives are described, as are the run length-limited (d,k) codes they use. Recently introduced recording channel technology based on sampling detection-partial-response (or PRML) is then considered. Several examples are given to illustrate that the introduction of partial response equalization, sampling detection, and digital signal processing has set the stage for the invention and application of advanced modulation and coding techniques in future storage products.< >
Precision adaptive subband coding is an audio coding method that
allows a high-quality audio signal to be coded at a low bit rate. Basic
design considerations, subjective testing for system improvement, a
performance comparison, and the final implementation in integrated
electronics are described
The design philosophy of the DCC is described. The DCC system is a
digital extension of the well-known compact cassette system. The main
differences are: highly efficient source coding of the audio signal,
called precision adaptive subband coding (PASC), resulting in excellent
sound quality; digital multitrack recording, including error correction
techniques; thin film techniques for head production; autoreverse
feature in all players; and new features (e.g., text display). The
system performance, the cassette, the tape format, and the PASC are
discussed
In pulse-amplitude modulation (PAM) digital transmission systems line encoding is used for shaping the spectrum of the encoded symbol sequence to suit the frequency characteristics of the transmission channel. In particular, it is often required that the encoded symbol sequence have a zero mean and spectral density vanishing at zero frequency. We show that the finite running digital sum condition is a necessary and sufficient condition for this to occur. The result holds in particular for alphabetic codes, which are the most widely used line codes.
Viterbi Reception of Miller-Squared Code on a Tape Channel
- R Wood
R. Wood, " Viterbi Reception of Miller-Squared Code on a Tape Channel, " Proc. of the Fourth Intern. Conf. on Video and Data Recording, pp. 333-343, Southampton, April 1982.
Optimal Bit-Level Synchronization Strategy for Digital Magnetic Recorders
- [ A Si M
[SI M.A. Ribeiro, " Optimal Bit-Level Synchronization Strategy for Digital Magnetic Recorders, " Proc. of the Fourteenth Sympo-rium on Information Theory in the Benekz, pp. 222-227, May 1993.
Codes for Zero Spectral Density at Zero fie-quency Modulation and Coding for Infor-mation Storage
- G L Pierobonsi
- P H Siegel
- J K Wolf
G.L. Pierobon, " Codes for Zero Spectral Density at Zero fie-quency, " IEEE Trans. Inform. Theory, vol. IT-30, no. 2, pp. [SI P.H. Siegel, and J.K. Wolf, " Modulation and Coding for Infor-mation Storage, " ZEEE Comm. Magazine, vol. 29, no. 12, pp. 68-86, December 1991.