Coding for improving noise immunity in multi-track, multi-head recording systems /
The goal to increase the amount of information that can be
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| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1994.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=741966151&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The goal to increase the amount of information that can be stored per disk unit area in digital recording systems continues to be important, together with the tendency to make recording systems physically smaller. An obvious way to increase information density in existing systems is to increase the number of bits per track and the number of tracks per unit area. Several detection schemes proposed for multi-track, multi-head, digital recording systems as well as theoretical studies about achievable radial information densities in these systems suggest that, if construction of head-arrays simultaneously scanning multiple tracks becomes possible, areal storage density can be greatly increased by means of track narrowing. The main advantage of using multiple-heads is their capability to partly recover the loss in performance due to inter-track-interference (ITI), which is a prominent noise source in narrowtrack systems. Since track-narrowing also results in a decrease in signal-to-noise ratio (SNR), multi-dimensional modulation codes for improving noise immunity are needed to compensate for this. We show that codes designed for improving noise immunity in single- track, single-head systems provide the same coding gain when used in multitrack, multi-head systems when ITI satisfies certain conditions. These conditions are only sufficient but they do not impose significant requirements for most common ITI models where only adjacent tracks interfere. For the special case of the two-track, twohead, dicode channel, we design a class of two-dimensional constrained codes capable of recovering the performance loss incurred by both presence of ITI and decrease in SNR for large interference levels. The construct finite-state encoders with sliding block decoders and reduced-complexity Viterbi detectors for several high rate codes in this class. The codes discussed here are derived for a special model of interference that exists between tracks even if there is no servo positioning error. However, the codes are expected to be applicable to systems with known and unknown servo positioning errors as well. We show that these multi-track, multi-head, coded systems potentially provide a substantial areal density increase even in cases of high ITI. |
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| Item Description: | Vita. "Major Subject: Electrical Engineering". |
| Physical Description: | xi, 89 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |