http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Coding for improving noise immunity in multi-track, multi-head recording systems
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
"Major Subject: Electrical Engineering".
Issued also on microfiche from University Microfilms Inc.