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Extremely Efficient Dc-free RLL codes for Optical Recording

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Abstract

We report on new DC-free runlength-limited codes (DCRLL) intended for the next generation of DVD. The efficiency of the newly developed DCRLL schemes is extremely close to the theoretical maximum, and as a result, significant density gains can be obtained with respect to prior art coding schemes
910
IEEE
Transactions
on
Consumer Electronics,
Vol.
47,
No.
4,
NOVEMBER
2001
EXTREMELY
EFFICIENT DC-FREE RLL CODES FOR OPTICAL RECORDING
Kees A. Schouhamer Immink, Jin-Yong Kim, Sang-Woon Suh and Seong Keun Ahn
AESTRACT
We will report on new dc-free runlength-limited codes
(DCRLL) intended for the next generation
of
DVD. The
efficiency of the newly developed DCRLL schemes is ex-
tremely close to the theoretical maximum, and as a result,
significant density gains can be obtained with respect to
prior art coding schemes.
Keywords: optical recording, capacity, constrained code,
runlength-limited, RLL sequence,
(d,
k)
sequence, dc-free
code
I. INTRODUCTION
Optical recording, developed in the late 60s and early
70s, is the enabling technology of a series of very success-
ful products for digital consumer electronics systems such
as Compact Disc (CD), CD-ROM, CD-R, DVD, and many
other products that are still in the offing. Notably spec-
tral shaping (dc-free) and runlength-limited (RLL) codes
have found widespread usage in consumer-type mass stor-
age systems such as Compact Disc, DAT, DVD, and
so
on
[l].
The design of codes for optical recording is essen-
tially the design of combined
dc-free
and
runlength limited
(DCRLL) codes. Eight to Fourteen Modulation (EFM) de-
veloped by Immink
&
Ogawa
in
the early eighties [2] was
adopted as the recording code for the Compact Disc
(CD).
EFMPlus [3]; used in the DVD, is a code wit,h the same
basic parameters as
EFM
and a useful six percent higher
efficiency. Table
I
gives a survey of recording codes, which
are part of consumer-type optical recording products.
TABLE
I
Survey
of
recording codes and their application area
Device Code Type d,k Ref.
CD EFM DCRLL
1,lO
[2]
MiniDisc EFM DCRLL
1,lO
DVD EFMPlus DCRLL
1,10
[3]
DVR (1,7)PP DCRLL 1,7 [4]
Kees
A.
Schouhamer Immink is with Turing Machines Inc,
15
W. Alexanderlaan, 5664
AN
Geldrop, The Netherlands. E-mail:
immink@turing-machines.com.
Jin-Yong
Kim,
Sa,ig-Woon Suh,
Seong Keun Ahn are with DCT Team, Multi-Media Labs, LG Elec-
tronics Inc., 16 Woomyeon-Dong, Seocho-Gu, Seoul 137-724, Korea
11. RUNLENGTH-LIMITED CODES
Binary sequences generated by
a
(d,
k)
RLL encoder have
at least
d
and
at
most
k
’zero’s between successive ’one’s.
Let the integers
m
and
n,
denote the information word
length and codeword length, respectively. The
code rate,
R
=
m/n,
is
a measure
of
the code’s efficiency. The maxi-
mum rate
of
an RLL code, given values of
d
and
k,
is called
the
Shannon capacity,
and
it
is denoted by
C(d,
k).
As
an
TABLE I1
Capacity
C(1,
k)
and
C(2,
k)
as
a
function of
k.
k
C(1,k) C(2,k)
7
0.6793 0.5174
8 0.6853 0.5293
9 0.6888 0.5369
10
0.6909 0.5418
11
0.6922 0.5450
cc
0.6942 0.5515
example, Table
I1
tabulates
C(d
=
1,k) and
C(d
=
2,k)
for relevant values of
k.
We may observe, for example, that
for
d
=
1
and
k
=
7 the Shannon capacity, C(117), has a
value of 0.6793. Thus, an encoder that translates arbitrary
sequences
into
sequences
that have
at
least
d
=
1
and at
most
IC
=
7
0’s
between successive
l’s,
cannot have
a
rate
larger than 0.6793.
Information recording has a constant need for enhancing
the information density on the record carrier, and a possible
solution to this end is an increase of the rate of the code.
111.
VERY
EFFICIENT
CODING
SCHEMES
For
ease of presentation we will first focus on the design
of RLL codes with
d
=
1. Later we will extend the ideas
to the design of codes with
d
=
2.
Rate 213, (1,7) codes are known in the art for more than
a quarter of a century, see for example [5, 61. The code
rate, 213, of the (1,7) code is slightly less than the Shannon
capacity,
0.6793,
and the code is therefore
a
highly efficient
one. The efficiency of an RLL code
is
usually measured by
a quantity called
code eficiency,
77,
defined by
There are only two approaches for constructing
a
(1,k)
RLL code, whose rate is larger than two-thirds. Firstly, we
may relax the maximum runlength
k
to
a
value larger than
7.
Note that a (1,7) code was first put to practical use in
Original manuscript received June
25,
2001
Revised manuscript received September 26, 2001
0098
3063/00
$10.00
@
2001 IEEE
Immink: Extremely
Efficient Dc-free RLL codes
for
Optical
Recording
91
1
the early seventies, and that since the advent of hard-disk
drives
(HDDs),
significant improvements in signd process-
ing for timing recovery circuits have made it possible to
employ codes with a much larger maximum runlength
IC.
Secondly, on top of that we may endeavor to design a more
efficient code.
The efficiency of the rate
2/3, (1,7)
code
is
0.6667/0.6793
=
0.981,
which reveals that we can
at
most gain
1.9%
in
rate by an alternative, more efficient, code redesign.
If
we
fully relax the
k
constraint, i.e. set
k
=
00,
we can at most
gain
3.97%
in code rate. In other words, a viable improve-
ment in code rate of
a
(d
=
1)
encoder ranges from
1.9
to
3.97%.
To the best of the author's knowledge, extremely
efficient
(d
=
1)
codes having
a
rate exceeding two-thirds
have not been reported in the literature. In the sequel of
the paper, we will systematically design such extremely effi-
cient codes. We start, in the next subsection, with
a
simple
problem, namely finding integers
m
and
n
that improve the
rate,
213,
of
the industry standard code.
A.
Suitable integers
m
and
n
for
d
=
1
We will start with
a
simple, but very illuminating exer-
cise, namely
a
search for pairs of integers
m
and
n
that
are suitable candidates for a coding rate exceeding
213.
All pairs of integers
2/3
<
m/n
<
C(l,co),
n
<
50,
are
shown in Table
111.
Surprisingly there are just six
m
and
n
pairs whose quotient is larger than
213.
We omitted trivial
pairs, such as
18
and
26
etc., that are multiples
of
given
smaller pairs. Perusal of the table reveals that the code
rate
m/n
=
9/13
is
highly attractive as it is just
0.28%
below the Shannon capacity
C(1,co).
The fact that the
quotient
9/13
is
less
than
capacity
does
not
mean that
a
code with that, rate can be
practically
constructed.
TABLE
111
Integers
m
and
n
such that 2/3
<
R
=
m/n
<
C(1,oa).
The
quantity
11
=
R/C(l,
a)
expresses the code efficiency.
m
n
1-q%
34 49 0.0525
9
13
0.2786
11 16 0.9711
13 19 1.4449
15 22 1.7895
17 25 2.0514
B.
Encoder description
We start with
a
few ubiquitous definitions. The encoder
has
r
states, which are divided into two state subsets of a
first and second type. The state subsets are
of
size
1-1
and
TZ(=
r
-
rl),
respectively.
A
codeword is
a
binary string of
length
n
that satisfies the
d
=
1
constraint. The encoder
state-transition rules are easily described. Codewords that
end with a
'O',
i.e., codewords in subsets
Eo0
and
El0
may
enter any of the
r
encoder states. Codewords that end with
a
'1'
may be followed by codewords in the
r1
states of the
first type only. With the above model we were able to con-
struct many new codes including
a
rate
9/13, (1,14)
code.
Clearly this new code improves the rate of the traditional
rate
2/3, (1,7)
code by
a
factor
of
27/26
(=
1.038)
without
seriously compromising the timing regeneration.
IV.
EFFICIENT
d
=
2
CODES
Up till now we have concentrated on the design of effi-
cient
d
=
1
codes, and as both code parameters,
d
=
1
and
d
=
2,
are of great practical interest for optical recording,
we will now repeat the exercise for the case
d
=
2.
A.
Suitable integers
m
and
n
ford
=
2
RLL
codes with minimum runlength parameter
d
=
2
have been widely published. The highest reported rate of
such a
(d
=
2)
code is
8/15l.
Table I1 tabulates
C(2,
IC)
as
a function of
k,
and from this table the reader can easily
discern the head room available for the design of a code of
rate
R
=
m/n
>
8/15.
The rate
8/15
is, see Table
11,
3.3%
below channel capacity
C(2,
00).
Table IV shows values of
m
and
n,
where
8/15
5
m/n
<
C(2,co)
and
n
<
50.
The
pairs of integers are ordered according to their efficiency
R/C(2,co).
Clearly, the quotients
11/20, 6/11,
and
7/13
TABLE
IV
Integers
m
and
n
such that 8/15
<
R
=
m/n
<
C(2,
w).
The
quantity
r)
=
R/C(2,
oa)
expresses the code efficiency.
m
n
1-~%
11 20 0.2720
17
6
19
13
20
7
15
8
31
11
35
24
37
13
28
15
-
0.5644
1.0962
1.5672
1.7830
1.9872
2.3642
2.8623
3.2940
are suitable candidate rates for the creation
of
small
(d
=
2)
codes.
B.
Encoder descraption
In this section we will describe
a
finite-state encoder that
generates sequences that satisfy the
d
=
2
constraint (note
that the
k
constraint will be ignored for
a
while). The
encoder is assumed to have
T
states, which are divided into
three state subsets
of
states
of
a
first, second, and third
type. The state subsets are
of
size
TI,
TZ,
and
r3(=
'r
-
r1
-
TZ),
respectively. Codewords that end with the string
'00'
may enter any of the
r
encoder states. Codewords
that end with a
'10'
may not be followed by codewords in
a state of the third type. Similarly, codewords that end
with a
'1'
may only be followed by codewords belonging
to states of the first type. Table V summarizes the new
'At press time, the author became aware that Kim
(71
has been
granted a
US.
Patent
on
an example
of
a rate 7/13, (2,25) code.
912
IEEE Transactions on Consumer Electronics,
Vol.
47,
No.
4,
NOVEMBER
2001
-15
-20
RLL codes,
d
=
1
and
d
=
2, we have found.
As
we can
see, the efficiency of the majority of the new codes is just
a few tenths of a percent below capacity.
At
this junction,
TABLE
V
Survey
of
newly developed codes.
-
~
m
n
d
k
states
11
=
R/C(d,k)
11
20
2
23 9 0.9975
7
13
2
11
9 0.9880
6
11
2
15 9 0.9915
9 13
1
14 13 0.9979
9
13
1
18
5
0.9973
11
16
1
10 13 0.9951
we have completed the description of the new RLL codes,
and we are in the position to describe how we can turn the
newly developed RLL codes into DCRLL codes.
V.
GUIDED
SCRAMBLING
There are various methods to transform an RLL code
into a DCRLL code [l] by adding redundant dc-control bits,
which are chosen by the encoder to optimize the spectral
performance of the generated sequence. Obviously, we can
multiplex, either at data
or
channel level, the data stream
with the dc-control bits. Alternatively,
a
promising method
for adapting an RLL code is
Guided Scrambling (GS)
[l].
In
GS,
each information word can be represented by a member
of
a
selection set consisting of
L
=
2P,
p
2
1,
codewords.
The encoder generates the selection set, and the "best"
(according to
a
predefined penalty function) codeword in
the selection set is selected
for
transmission. The RLL
codes, listed in Table
V,
will be employed in conjunction
with
GS
for achieving four goals:
spectral shaping;
rejection of long runs of
'0's:
k
constraint;
rejection of long transition runs of '01's
(d=l)
or
'001's
(d=2):
MTR
constraint;
rejection of predefined sync(hronization) patterns, sync
constraint.
The maximum runlength constraint,
IC,
imposed by the
GS
penalty function can be made smaller than that of the in-
ner RLL code.
It
has been found that constraining a long
repetition of minimum transition runs (MTR constraint),
'1010101
...'
(d=l)
or
'1001001001
...'
(d=2),
in conjunction
with Partial-Response (PR) detection is beneficial to the
system margins. Naturally, the
GS
method cannot fully
guarantee the
k
and MTR constraints, but, the probability
of
occurrence of such vexatious subsequences can be made
extremely small.
A.
Format
In the
GS
format, ml user bits are multiplexed with
p
redundant bits, which are
a
part of the input of the chan-
nel encoder. The
p
redundant bits are used to generate a
selection set of size
L
=
2p. Each member of the selection
set is generated and tested by the encoder with respect to
the penalty function. In the proposed coding format, the
channel encoder input comprises
p
redundant bits plus ml
user bits that from a
super
block. The integers
p
and
ml
are integers chosen such that
Km
=
p
+
ml,
(2)
where
K
is an integer that denotes the number of m-bit
information words in a super block. In a practical environ-
ment of a byte-oriented system, ml
is
preferably
a
multiple
of eight, i.e. ml mod 8
=
0.
Under the rules of the RLL
code, the
p
+
ml
=
Km-bit super block is translated into
Kn
channel bits. Thus, the overall rate,
R,,
of
the code is
B.
Results and comparison with prior art methods
The Power Spectral Density (PSD),
H(f),
and other rel-
evant characteristics can easily be measured using com-
puter simulation. As
a
typical example, we will show re-
sults obtained with the rate 9/13, (1,14) RLL code. Fig-
ure
1
shows the spectrum,
H(f),
versus (channel) fre-
quency,
f,
for
p
=
5,
k
=
10,
and
K
=
45. The overall
coderateis
R,
=
(Km-p)/Kn=
(45x9-5)/(45~13)=
0.68376. Note that the overall code is byte oriented as
Km
-
p
=
400 is
a
multiple of eight. In the runlength
51,
I
0.001
0.01
0.1
-25[
' ' '
0.0001
channel
frequency
1
Fig.
1.
Simulation results
of
a
PSD
function
of
a
(d
=
l,k
=
10)
code
of
overall rate
R,
=
0.68376.
The
straight
line
is
a 'best fit'
estimate
of
the low-frequency part
of
the spectrum.
We
simply
discern that
H(f
=
=
-24.3
dB
penalty function, we set the maximum 'zero' runlength to
k
=
10, which means that the code essentially behaves as
a
(d
=
1,
k
=
10) code. The spectrum,
H(f),
versus fre-
quency
f
has a parabolic shape in the low-frequency range,
which shows as a straight line as
a
result of the logarithmic
frequency axis used. We can employ the spectral density
at a, given, low frequency
as
the low-frequency (If) spec-
tral performance yard stick of a DCRLL code. Results are
shown in Figure
2
for
p
=
5 and
p
=
8.
In order to compare
our
results with the maximum theoret,ical performance of
DCRLL codes, we invoked the algorithms found in
[l,
pages
282-2861 which compute the
maxentropic
performance of
Immink: Extremely Efficient Dc-free
RLL
codes
for
Optical
Recording
913
.451
"
"
"
"
'
I
0
64
0
645
0.65
0.655
0.66
0
665
0.67
0.675
0
68
0.685
0.69
Fig. 2. The two upper curves show the If suppression, H(10-4), as
a
function
of
the overall code rate
R,.
The upper curve shows
results
for
p
=
5,
and the lower curve
for
p
=
8. The maximum
imposed runlength
for
both cases is
IC
=
10.
The curve denoted
by (1,7)PP gives results
of
a prior art code [SI.
(d,
k)
codes. The maxentropic performance sets
a
theoret-
ical limit to the performance of any implemented DCRLL
code. Figure 2 shows that the implemented codes operate
very close to the best theoretical performance.
For
p
=
5
the implemented codes are 2-3 dB, (for
p
=
8,
1-2 dB)
below the theoretical ceiling.
As
a further comparison we
plotted the performance of
a
prior art rate 2/3, (1,7) code
[4],
which is extended with dc-control bits on data sequence
level.
Figure
3
shows the
If
spectral performance
of
the rate
6/11, (2,15) code
in
conjunction with Guided Scrambling.
Results are given for
p
=
5
and
p
=
8.
As
reported in the
above
d
=
1
case, the combination of an efficient RLL code
and
GS
works quite satisfactorily as only 2-3 dB can be
gained with respect to the theoretical ceiling.
-10
1
l
0
525
0
53
0
535
0
54
o
545
-40
I
0
52
Overall
code
iale
Fig.
3. The two upper curves show the
If
suppression,
H(10-4),
as
a
function
of
the overall rate
R,.
The upper curve
is
for
p
=
5,
and
the lower curve is for
p
=
8.
The maximum imposed runlength for
both cases is
k
=
12.
As a comparison we plotted the theoretical
ceiling,
io-^),
of
maxentropic
(d
=
2,k
=
12) sequences.
VI.
CONCLUSIONS
We have studied the construction of extremely efficient
Iunlength-limited (RLL) codes. We have shown that there
is
a
very limited number of pairs of integers
m
and
n,
whose
quotient
m/n8
form
a
suitable coding rate for
(d
=
1)
and
(d
=
2) RLL codes that are more efficient than prior art
codes. Suitable values for the rate of
a
(d
=
1) code
are
9/13 and 11/16, while for
(d
=
2) codes we have 11/20,
7/13, and 6/11.
We have disclosed a novel technique for designing very
efficient RLL codes. Using the novel technique we con-
structed a series of new RLL codes, whose rate
i~
only a few
tenths below capacity.
For
example, we have found
a
13-
state rate 9/13,
(1,14)
RLL code, whose rate
is
only 0.2%
below channel capacity C(1,14).
In
addition, we have con-
structed a new rate 6/11, (2,15) code,
a
rate 11/20, (2,23)
code, and a rate 7/13, (2,ll) code.
The above, and other, RLL codes can be employed in
conjunction with Guided Scrambling
(GS)
,
or
other tech-
niques, to turn them into DC-free
RLL
codes, which sup-
press the low frequency (If) components. Under the rules
of the
GS
algorithm, a selection set of alternative candi-
date codewords
is
generated, and the candidate with the
least
If
spectral content
(or
other desirable attributes) is
transmitted. Results of computer simulations have shown
that the arrangement of the newly developed RLL codes
in conjunction with GS is extremely efficient in terms of
overall rate and spectral performance. With the newly de-
veloped rate 9/13,
d
=
l
code
as
an inner code, we have
achieved
a
4.5% better overall rate than possible with the
prior art (1,7)PP code, and with the newly developed rate
6/11,
d
=
2 code we have achieved
a
9.3% higher overall
rate than that of EFMPlus.
The new DCRLL codes perform quite well in absolute
terms as we have shown that only a few dB in spectral
performance can be gained with respect to the theoretical
ceiling.
REFERENCES
K.A.S. Immink,
Codes
for
Mass Data Storage
Systems,
ISBN
90-
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H.
Ogawa, 'Method
for
Encoding Binary
Data',
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Patent 4,501,000,
Feb.
1985.
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the MultiMe-
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J.A.H.
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G.
van den Enden, T. Naka-
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Y.
Shinpuku,
T.
Narahara, and
K.
Nakamura, 'Apparatus
and method
for
modulation/demodulation with consecutive min-
imum runlength limitation', Patent Application WO 9963671A1,
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Dec.
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P.A. Franaszek, 'On Future-dependent Block Coding
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restricted Channels',
IBM
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vol. 23, pp. 75-81,
1979.
G.V.
Jacoby and R.
Kost,
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M.J. Kim, '7/13 Channel Coding and Decoding Method Using
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914
IEEE
Transactions
on
Consumer Electronics, Vol.
47,
No.
4,
NOVEMBER
2001
BIOGRAPHY
Kees A. Schouhamer Immink,
obtained
M.S.
and Ph.D degrees
at
the Eindhoven Univer-
sity
of
Technology. He is founder and president of
Turing Machines Inc. Since 1995, he is an adjunct
professor at the Institute for Experimental Math-
ematics, Essen University, Germany In addition,
he
is
affiliated with the National University of
Sin-
gapore.
He has contributed to the design and development
of
a wide variety
of
consumer-type audio and video recorders such
as the Laservision video disc, Compact Disc, Compact Disc Video,
DAT, DV, DCC, and DVD. He holds 52 issued and pending
US
patents in various fields.
Dr
Immink is an elected member
of
the Royal Netherlands Academy
of
Arts and Sciences (KNAW) and holds fellowships of the IEEE,
AES, SMPTE, and
IEE.
For his contributions to the digital audio
and video revolution, he received wide recognition such
as
a Knight-
hood from
Beatrix,
Queen
of
the Netherlands, the 1999 IEEE Edison
Medal, AES Gold Medal, IEEE Masaru Ibuka Consumer Electronics
Award, and the Golden Jubilee Award
for
Technological Innovation
awarded by the IEEE Information Theory Society in 1998.
He is vice president
of
the Audio Engineering Society
(AES)
and a
governor
of
the IEEE Consumer Electronics Society, and a member
of
the
IEEE
Fellows Committee.
Jin-Yong Kim
received his
B.S.
degree in elec-
nic engineering from Seoul National University
his
M.S.
degree in electrical engineering
IST
in 1985, and Ph.D degree in electri-
eering from Iowa State University in 1992
ely. Dr. Kim is currently employed
as
a
Fellow
at Digital Media Research Labo-
G Electronics, Seoul Korea.
Sang-Woon
Suh
was born in
Seoul,
Korea,
on May
20,
1964. He received the
B.S.
degree
in electronics engineering fIom Seogang Univeristy,
Seoul, Korea, in 1987, and the
M.S.
degree in In-
formation and Communication engineering form
Korea Advances Institute
of
Science and Technol-
ogy(KAIST), Korea, in
1997.
From 1987
-
1990,
he was with Samsung Electronics Korea
as
a En-
gineer. From
1990
-
present, he was with
LG
Electronic Inc
,
Korea
as
a
senior
Research
Engi-
neer.
His current research interests included Op-
tical Data Storage, modulation code
for
optical discs and physical
format
for
optical discs.
Seong-Keun Ahn
rereived the
B.S.
and M.S.
ree
in school
of
electrical engineering from
ul National University,Seoirl,Korea
in
1996 and
8,respectively. Mr. Ahn is currently a research
ineer
at.
Digital Media Laboratory,I,G Electron-
... Finite-state RLL encoders have become very popular in recording practice as the rate of such well-designed transducers approaches capacity. Immink et al. [1] have introduced a new family of simple and efficient finite-state RLL codes. It is of engineering interest to have a knowledge of the relationship between the encoder's hardware complexity measured in the number of encoder states and the code's efficiency. ...
Conference Paper
Full-text available
We will report on a relationship between the size of certain runlength-limited (RLL) codes and encoder complexity expressed as the number of encoder states, where the number of encoder states equals a (generalized) Fibonacci number.
... The code rate is (n ; p)=n. Guided scrambling using efficient RLL encoders has been proposed in optical recording systems [6]. ...
Article
Full-text available
Suppression of the low-frequency (lf) components of the modulated data stream is a system requirement in optical recording which facilitates the usage of servo systems for reading the optical disc. Insufficient suppression of the lf components of the coded spectrum will lead to improper functioning of the servo systems, and/or acoustical noise generated by the servo systems, and/or additional power dissipation in the servo amplifiers. Low-frequency components are avoided in state of the art systems such as CD and DVD by using codes, called dc-free codes, which suppress the energy in the lf range. Clearly, the more lf suppression, the more overhead in coding rate must be spent, and a sound trade-off has to be sought between proper lf suppression and coding efficiency. It has been found that lf suppression can also be improved by coding methods, which use a look-ahead (LA) algorithm that looks ahead p codewords, and evaluates, based on a suitable metric, the full search tree of 2 p possible choices of codewords in the tree. Recently, coding schemes, which use Guided Scrambling (GS) have been proposed for suppressing the lf content. It has been shown that GS schemes can achieve a lf suppression which is very close to the theoretical maximum. In this paper, we will report on a performance comparison of coding schemes based on Look-Ahead and Guided Scrambling techniques.
Article
A novel Knuth-like balancing method for runlength-limited words is presented, which forms the basis of new variable- and fixed-length balanced runlength-limited codes that improve on the code rate as compared to balanced runlength-limited codes based on Knuth’s original balancing procedure developed by Immink et al. While Knuth’s original balancing procedure, as incorporated by Immink et al. , requires the inversion of each bit one at a time, our balancing procedure only inverts the runs as a whole one at a time. The advantage of this approach is that the number of possible inversion points, which needs to be encoded by a redundancy-contributing prefix/suffix, is reduced, thereby allowing a better code rate to be achieved. Furthermore, this balancing method also allows for runlength violating markers which improve, in a number of respects, on the optimal such markers based on Knuth’s original balancing method.
Article
A symposium on “Information Theory in the Benelux” was organized in Zoetermeer, in 1980. This symposium effectively signifies the informal naissance of the “Werkgemeenschap voor Information en Communicatietheorie” (WIC) – literally translated as ”Working Community for Information and Communication Theory”. Since 1980, the WIC Information Theory Symposium has become an annual event. The official start of the community originates from February 1984, and the subsequent formal community declaration was established in May 1986. Prof. Boxma (TU Delft), Prof. Groneveld (Univ. Twente), Prof. Schalkwijk (TU Eindhoven) and Prof. Van der Meulen (K.U. Leuven) are considered the founding fathers of the WIC community, secretarially supported by Dr. Best (Univ. Twente) in the board.
Conference Paper
High track-density recording and multi-layer recording have been investigated for large capacity optical recording discs. In this case, the recorded data will be reproduced under the low signal-to-noise ratio (SNR) condition due to crosstalk from the adjacent tracks or the other layers, and robust data detection will be required. In this paper, a novel matched spectral-null (MSN) code providing the property of run-length limitation (RLL) was described considering the optical recording channels. Trellis Coded partial response maximum likelihood (TCPRML) employing the MSN code with RLL was also proposed for the data detection method enhancing the minimum Euclidian distance. The detection performance was estimated through the simulation model, which emulates the optical recording channels based on the blu-ray disc (BD) specification.
Conference Paper
Recently, for HD video recorders, a high density rewritable disc system using a blue laser diode has been strongly recommended. At the last ODS and ISOM, we proposed extremely efficient DC-free RLL codes for a high density rewritable optical system (K.A.S. Immink et al, ODS '01, WC1, 2001, and ISOM '01, TH-J-29, pp. 152-153, 2001). Additionally, we have shown that the newly developed GS913 (guided scrambling 9 to 13), d=1 code can achieve a 4.5% higher overall rate compared with the (1,7)PP code. In this paper, we report the performance of this GS913 code for a high density rewritable disc system using a blue laser diode (405 nm), NA 0.85 and 0.1 mm thickness cover layer.
Article
A guided scrambling (GS) coding technique is practically used to suppress the DC component within a channel bit stream. It is a candidate for a DC-free code in the next generation of the DVD standard. Typically the GS technique uses a convolutional operation or an addition operation in the Galois field (GF). This paper evaluates the performance of the convolutional GS and GF-addition GS on DC-component suppression, symbol error probability, and hardware complexity, and concludes that the GF-addition GS is more suitable for the next generation of the DVD standard than the convolutional GS with respect to the symbol error probability.
Article
We derive expressions for the symbol error probabilities for a recording code concatenated with a Reed-Solomon (RS) code. The recording code is structured by a guided scrambling (GS) code for the direct current (DC) suppression in conjunction with a runlength-limited (RLL) code. As for the GS codes, convolutional GS and Galois field (GF) addition GS schemes are examined. As for the RLL codes, two types of RLL codes are investigated. One is a traditional RLL code where a bit length m of an RS symbol is an integer multiple of a bit length p of an RLL source symbol. The other is a new type of high-rate RLL code where p>m. We compute the RS symbol error rates when these RLL codes are combined with the two GS schemes.
Book
Full-text available
Preface - The advantages of digital audio and video recording have been appreciated for a long time and, of course, computers have long been operated in the digital domain. The advent of ever-cheaper and faster digital circuitry has made feasible the creation of high-end digital video and audio recorders, an impracticable possibility using previous generations of conventional analog hardware. The principal advantage that digital implementation confers over analog systems is that in a well-engineered digital recording system the sole significant degradation takes place at the initial digitization, and the quality lasts until the point of ultimate failure. In an analog system, quality is diminished at each stage of signal processing and the number of recording generations is limited. The quality of analog recordings, like the proverbial 'old soldier', just fades away.
Patent
Full-text available
A system for block encoding words of a digital signal achieves a maximum of error compaction and ensures reliability of a self-clocking decoder, while minimizing any DC in the encoded signal. Data words of m bits are translated into information blocks ofn1 bits (n1 >m) that satisfy a (d,k)-constraint in which at least d "0" bits, but no more than k "0" bits occur between consecutive "I" bits. The information blocks are concatenated by inserting separation blocks of n2 bits there between, selected so that the (d,k)-constraint is satisfied over the boundary between any two information words. For each information word, the separation block that will yield the lowest net digital sum value is selected. Then, the encoded signal is modulated as an NRZ-M signal in which a "1" becomes a transition and a "0" becomes an absence of a transition. A unique synchronizing block is inserted periodically. A decoder circuit, using the synchronizing blocks to control its timing, disregards the separation blocks, but detects the information blocks and translates them back into reconstituted data words of m bits. The foregoing technique can be used to advantage in recording digitized music on an optical disc.
Book
Full-text available
Preface to the Second Edition About five years after the publication of the first edition, it was felt that an update of this text would be inescapable as so many relevant publications, including patents and survey papers, have been published. The author's principal aim in writing the second edition is to add the newly published coding methods, and discuss them in the context of the prior art. As a result about 150 new references, including many patents and patent applications, most of them younger than five years old, have been added to the former list of references. Fortunately, the US Patent Office now follows the European Patent Office in publishing a patent application after eighteen months of its first application, and this policy clearly adds to the rapid access to this important part of the technical literature. I am grateful to many readers who have helped me to correct (clerical) errors in the first edition and also to those who brought new and exciting material to my attention. I have tried to correct every error that I found or was brought to my attention by attentive readers, and seriously tried to avoid introducing new errors in the Second Edition. China is becoming a major player in the art of constructing, designing, and basic research of electronic storage systems. A Chinese translation of the first edition has been published early 2004. The author is indebted to prof. Xu, Tsinghua University, Beijing, for taking the initiative for this Chinese version, and also to Mr. Zhijun Lei, Tsinghua University, for undertaking the arduous task of translating this book from English to Chinese. Clearly, this translation makes it possible that a billion more people will now have access to it. Kees A. Schouhamer Immink Rotterdam, November 2004
Article
Full-text available
We report on an alternative to Eight-to-Fourteen Modulation (EFM), called EFMPlus, which has been adopted as coding format of the MultiMedia Compact Disc proposal. The rate of the new code is 8/16, which means that a 6-7% higher information density can be obtained. EFMPlus is the spitting image of EFM (same minimum and maximum runlength, clock content etc). Computer simulations have shown that the low-frequency content of the new code is only slightly larger than its conventional EFM counterpart.
Article
Consider a restricted channel whose constraints may be characterized by a finite state machine model. Conventional coding techniques for such channels result in codes where the choice of a word to be transmitted is only a function of the current state and the information to be represented by this word. This paper develops techniques for constructing codes where the code word choice may also depend on future information to be transmitted. It is shown that such future-dependent codes exist for channels and coding rates where no conventional code may be constructed.
Article
Runlength-limited (RLL) codes have found widespread usage in optical and magnetic recording products. Specifically, the RLL codes EFM and its successor, EFMPlus, are used in the compact discs (CD) and the digital versatile discs (DVD), respectively. EFMPlus offers a 6% increase in storage capacity with respect to EFM. The work reports on the feasibility and limits of EFM like codes that offer an even larger capacity. To this end, we provide an overview of the various limiting factors, such as runlength constraint, dc-content, and code complexity, and outline their relative effect on the code rate. In the second part of the article we show how the performance predicted by the tenets of information theory can be realized in practice. A worked example of a code whose rate is 7.5% larger than EFMPlus, namely a rate 256/476, (d=2, k=15) code, showing a 13 dB attenuation at f<sub>b</sub>=10<sup>-3 </sup>, is given to illustrate the theory
Article
A new 2/3-rate run-length limited code with d = 1 and k = 7 is described in this paper. It is a state dependent, look-ahead code that has advantages over the MFM and 3PM (2, 7) codes. Compared to MFM the advantages are an increase of 33% in the data rate and a 33% “increase in the detection window and the minimum time between transitions (Tmin). Compared to the 3PM (2, 7) code, the window is increased by 33%, while Tmin has been reduced by 11 %. Additionally, the wavelength ratio [Tmax/Tmin) has been increased by 50% with respect to the 3PM (2, 7) code. The main parameters of the new code are shown in Fig. 12. The 33% increase in the detection window of the ISS-2/3 code allows for higher noise levels, while the slightly smaller value of Tmin somewhat increases the, effect of intersymbol interference. The net result is to allow for about a 10% increase in the data rate, compared to the 3PM code. The system has been implemented in the ISS-8470 high density disk file, featuring 4418 bits/cm data density, 2.097 MBytes/sec data rate and 683 MBytes capacity.
Apparatus and method for modulation/demodulation with consecutive min-imum runlength limitation', Patent Application WO 9963671A1, Issued Dec. 1999. P.A. Franaszek, 'On Future-dependent Block Coding forBinary Two-thirds Rate Code with Full Word Look-Ahead
  • K A S Immink
  • J A H Kahlman
  • G Van Den Enden
  • T Naka-Gawa
  • Y Shinpuku
  • T Narahara
  • K G V Nakamura
  • R Jacoby
  • Kost
K.A.S. Immink, J.A.H. Kahlman, G. van den Enden, T. Naka-gawa, Y. Shinpuku, T. Narahara, and K. Nakamura, 'Apparatus and method for modulation/demodulation with consecutive min-imum runlength limitation', Patent Application WO 9963671A1, Issued Dec. 1999. P.A. Franaszek, 'On Future-dependent Block Coding for Input-restricted Channels', IBM J. Res. Develop., vol. 23, pp. 75-81, 1979. G.V. Jacoby and R. Kost, 'Binary Two-thirds Rate Code with Full Word Look-Ahead', IEEE Trans. Magn., vol. MAG-20, no. 5, pp. 709-714, Sept. 1984. M.J. Kim, '7/13 Channel Coding and Decoding Method Using RLL(2,25) code', US Patent 6,188,336, Feb. 2001.
Apparatus and method for modulation/demodulation with consecutive minimum runlength limitation', Patent Application WO 9963671A1
  • K A S Immink
  • J A H Kahlman
  • G Van Den Enden
  • T Nakagawa
  • Y Shinpuku
  • T Narahara
  • K Nakamura
K.A.S. Immink, J.A.H. Kahlman, G. van den Enden, T. Nakagawa, Y. Shinpuku, T. Narahara, and K. Nakamura, 'Apparatus and method for modulation/demodulation with consecutive minimum runlength limitation', Patent Application WO 9963671A1, Issued Dec. 1999.
7/13 Channel Coding and Decoding Method Using RLL(2,25) code', US Patent 6
  • M J Kim
M.J. Kim, '7/13 Channel Coding and Decoding Method Using RLL(2,25) code', US Patent 6,188,336, Feb. 2001.