Coding and Signal Processing for Two-Dimensional Optical Storage (TwoDOS)

1
Coding and Signal Processing for
Two-Dimensional Optical Storage(TwoDOS)
Wim Coene

• DIMACS March 23 2004

2
Outline

• Introduction
• TwoDOS Concept
• Write-Channel
• Signal-Patterns
• Read-Out and Test-Player
• Modulation Encoding
• Signal Processing and Bit-Detection
• Experimental Results
• Conclusion

3
Principle of Traditional Optical Storage
010010110111011000 001101110001001110 101111001011
011000
pit
land
track
user data
eye-pattern
disc
track
lens
spiral
PDIC
Laser
Signal Processing
4
3 Generations of Optical Recording
CD
DVD
BD
l 650 nm NA 0.6 4.7 GBytes
l 405 nm NA 0.85 22.5 GBytes
0.65 GByte
4.7 GByte
25 GByte
1.2 mm substrate
0.6 mm substrate
0.1 mm substrate
5
Outline

• Introduction
• TwoDOS Concept
• Write-Channel
• Signal-Patterns
• Read-Out and Test-Player
• Modulation Encoding
• Signal Processing and Bit-Detection
• Experimental Results
• Conclusion

6
OneDOS Concept
Disc
Readout
Single Spiral
(spiral contains 11 bit-rows)
7
TwoDOS Concept
Disc
Readout
(spiral contains 11 bit-rows)
8
Signal processing 1DConventional Situation
TwoDOS Concept (2)
upper track noise
central track
Signal
lower track noise
radial cross talk is noise
9
Signal Processing 2D use information adjacent
bits
TwoDOS Concept (3)
upper track information
central track
Signal
lower track information
radial cross talk is information
10
TwoDOS Concept (4)
squeeze track-pitch
2D Joint Detection

• exploit FULL 2D energy-per-bit
• use a continuous 2D bit-lattice
• 2D hexagonal lattice is optimum (15 higher
  packing fraction than square lattice)

11
Effect of Joint 2D Bit-Detection
Abstracted 2D Impulse-Response (IRF) (for 2D
Linear Channel)
tangential energy 60
radial energy 40
taps 2D IRF
12
TwoDOS Targets

• Data-Rate BD x 10 gt 300 Mb/sec
• Capacity BD x 2 gt 50 GB (single-layer
  12cm disc)

at SAME physics of BD ? blue laser
(?405nm) ? lens with high numerical aperture
(NA0.85)
13
Outline

• Introduction
• TwoDOS Concept
• Write-Channel
• Signal-Patterns
• Read-Out and Test-Player
• Modulation Encoding
• Signal Processing and Bit-Detection
• Experimental Results
• Conclusion

14
Pit-Hole Mastering
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Outline

• Introduction
• TwoDOS Concept
• Write-Channel
• Signal-Patterns
• Read-Out and Test-Player
• Modulation Encoding
• Signal Processing and Bit-Detection
• Experimental Results
• Conclusion

16
Clusters on Hexagonal Lattice
17
Signal-Patterns Phase-1 / Phase-2
a 165nm
a 138nm
Phase-1 1.4x BD
Phase-2 2.0x BD
Signal Amplitude
overlap area

• closed eye gt 2D PRML

18
Outline

• Introduction
• TwoDOS Concept
• Write-Channel
• Signal-Patterns
• Read-Out and Test-Player
• Modulation Encoding
• Signal Processing and Bit-Detection
• Experimental Results
• Conclusion

19
Test-Player Set-Up

• binary grating 11 read-out spots
• 11 spots photo-detector

20
Outline

• Introduction
• TwoDOS Concept
• Write-Channel
• Signal-Patterns
• Read-Out and Test-Player
• Modulation Encoding
• Signal Processing and Bit-Detection
• Experimental Results
• Conclusion

21
Worst-Case Patterns
similar to Nyquist-patterns in 1D
(MTR-constraint)
----
diagonal lattice-planes
22
2D Nyquist Cell in 2D Frequency Space
2D-MTF

• 2D Frequency
• Space

MTF
23
Super-Structures
3 orientation-variants
2 clusters
or (opposite polarity)
24
gt constant signal-amplitude over large area
25
Partitioning of META-Spiral Strips and Rows
META-spiral
prohibit formation of critical pattern
3-row strip
merging bit-row
3-row strip
merging bit-row
3-row strip
META-spiral
26
Need for Merging Bit-Rows (1)
strip 1
strip 2
3-row areas at boundary
gt code violations at the boundaries
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Need for Merging Bit-Rows (2)
strip 1
merging row
strip 2
gt satisfy 2D constraint at strip-boundaries
28
Building Blocks for 2D Code and Format
DC-control
11-row META-spiral
DC-control
DC-control
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Coding for the 3-row Strips (1)
...
fish-bone 8-ary symbol
NRZ symbol
x
u
a b c
a
u
x
v
y
1T-precoder
w
z
xu if a0 x1-u if a1
NRZI symbol
NRZI symbol
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Coding for the 3-row Strips (2)
Example
NRZ symbol
0
1
1 1 0
1
0
0
0
NRZI symbol
NRZI symbol
(3)
?2
?3
31
Coding for the 3-row Strips (3)
States for STD

• based on NRZI-symbols
• one state for two polarities

8-ary NRZ symbols

• 0, 1, ..., 7

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Coding for the 3-row Strips (4)
Trivial STD no constraints.
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Coding for the 3-row Strips (5)
Mechanism for Generation of Critical Pattern
...
...
(5)
(2)
(7)
NRZ
NRZ
NRZ
1T-precoder for each bit-row
NRZI symbol
NRZI symbol
NRZI symbol
NRZI symbol
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Worst-Case Pattern build up (1)
allow maximum TWO fish-bones of worst-case
pattern
35
Worst-Case Pattern build up (2)
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Worst-Case Pattern build up (3)
gt allow maximum TWO fish-bones of
worst-case pattern
37
State-Transition Table
38
Connection Matrix
?5
?6
?7

• Channel Capacity

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k - constraint
NRZ
NRZ
NRZ
0
0
0
gt maximum k successive 0-symbols
emission of 0-symbol
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k - constraint k 1
D
41
k - constraint k 2
D
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Code for 3-row Strips with k2
153 3 51 gt one Code-Word comprises
51 fish-bones
...
51
43
Code for 3-row Strips DC-control (1)
DC-control (radial-servo)
Merging Fish-Bone
PURPOSE
DC-control (focus-servo)

• DC-control
• return to state ?1 before start of next word

DC-control (radial servo)
?1
?1
...
...
51
51
44
Code for 3-row Strips DC-control (2)
?1
Choice-1
Choose according to Running-Digital-Sum of
selected Bit-Row
Choice-2
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Code for 3-Row Strip
Fish-Bone 2D Code for 3-row Strip

• DC-control with one additional fish-bone Code
  Rate (152 gt 1533) gt R 0.974
• high-rate code 152 -to- 153 Mapping ? Enume
  rative Coding for M-ary symbols
  (M8) ? issue of Error-Propagation ? reve
  rse order ECC and Modulation
  Code ? Bliss-like scheme (see later)

46
Code for Merging Bit-Rows (1)
strip 1
0
1
0
0
merging row
1
0
0
1
0
0
1
0
0
strip 2
gt satisfy 2D constraint at strip-boundaries
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Code for Merging Bit-Rows (2)

• forbidden patterns (NRZI, bipolar) ...
  00100100100100 ... and
• ... 11011011011011 ...
• prohibit 11011 -sequences in NRZ bitstream
• 1D code rate 12-gt13

0110110110110
NRZ
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Channel Data-Block
1533 channel bits gt 152 user bits gt 19
Bytes
19B
6B
19B
52 channel bits gt 4 channel words (13 bit)gt
6 Bytes
6B
19B
52 bits / fish-bones
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Bliss-scheme 1D-case (encoder)
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Bliss-Scheme for 2D Fish-Bone Code (1)
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Bliss-Scheme for 2D Fish-Bone Code (2)
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Outline

• Introduction
• TwoDOS Concept
• Write-Channel
• Signal-Patterns
• Read-Out and Test-Player
• Modulation Encoding
• Signal Processing and Bit-Detection
• Experimental Results
• Conclusion

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2D Signal Processing
Overall TwoDOS Receiver Structure
Separation between Spots
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Closed eye
gt need for 2D PRML bit-detection
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2D Bit-Detection

• number-of-states increases exponentially with
  number of bit-rows within broad spiral
• sub-optimal PRML / Viterbi bit-detector

2D Stripe-Wise Viterbi Detector
(cascade-with-delay of n-row Viterbi detectors
V00, V01, ..., V10)
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Two V-shaped Iterations
processing direction
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2D Trellis Structure Stripe-Wise Viterbi
outside bit-rows
High-Reliability Border-Row
output bit-row
U02
direction of Viterbi-detection
Low-Reliability Border-Row
trellis bit-rows
sliding direction
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Complexity Stripe-Wise Viterbi
of states 26
of branches-per-state 23
Total Complexity-per-Stage-of-the-Trellis 29
branches
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Sequence-Feedback to reduce Complexity
no Sequence-Feedback 29 512 Branches
one-bit Sequence-Feedback 28 256 Branches
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Sequence-Feedback (2)
two-bit Sequence-Feedback 27 128 Branches
output bit-row
X
downward sliding direction
X
X
state ?n
state ?m
three-bit Sequence-Feedback 26 64 Branches
61
bit-Error-Rate 50GB Scalar Diffraction Model
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Outline

• Introduction
• TwoDOS Concept
• Write-Channel
• Signal-Patterns
• Read-Out and Test-Player
• Modulation Encoding
• Signal Processing and Bit-Detection
• Experimental Results
• Conclusion

63
LBR discs results
Initial feasibility test on a scaled system (LBR)

• 2.3 x BD density demonstrated (58 GB)? concept
  TwoDOS works

64
EBR discs (mastered by SONY) results (1)
7-row META-spiral
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EBR discs (mastered by SONY) results (2)
Performance under Disc-Tilt (aberration)
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Outline

• Introduction
• TwoDOS Concept
• Write-Channel
• Signal-Patterns
• Read-Out and Test-Player
• Modulation Encoding
• Signal Processing and Bit-Detection
• Experimental Results
• Conclusion

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Conclusion

• TwoDOS Concept
• Increased data rate 10x ( 350 Mb/s )
• orthogonal density increase 2x
• TwoDOS Coding
• Modulation Code prohibiting Worst-Case-Patterns
• High-Rate Code (Enumerative Coding
  Bliss-scheme)
• TwoDOS Signal Processing
• 2D-PRML with Stripe-Wise Bit-Detection Scheme
• Experiment
• Concept demonstrated up to 2.3x BD

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TwoDOS the European Project
Acknowledgement
Participants
Philips Electronics Nederland B.v. NL
Technical University Eindhoven NL
HW Communications Ltd. UK
University of Limerick IRL
University of Lancaster UK

• thanks to SONY for EBR-discs

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