WO1997050181A1 - Codage limite par longueur de ligne dans lequel m=9(2,10), d=3,75 pour donnees multiniveaux - Google Patents

Codage limite par longueur de ligne dans lequel m=9(2,10), d=3,75 pour donnees multiniveaux Download PDF

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Publication number
WO1997050181A1
WO1997050181A1 PCT/US1997/011532 US9711532W WO9750181A1 WO 1997050181 A1 WO1997050181 A1 WO 1997050181A1 US 9711532 W US9711532 W US 9711532W WO 9750181 A1 WO9750181 A1 WO 9750181A1
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WO
WIPO (PCT)
Prior art keywords
xxxx
code
code symbols
output
waveform signal
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Application number
PCT/US1997/011532
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English (en)
Inventor
Steven W. Mclaughlin
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Etom Technologies Corporation
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Publication of WO1997050181A1 publication Critical patent/WO1997050181A1/fr

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M5/00—Conversion of the form of the representation of individual digits
    • H03M5/02—Conversion to or from representation by pulses
    • H03M5/20—Conversion to or from representation by pulses the pulses having more than three levels
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/10—Digital recording or reproducing
    • G11B20/14—Digital recording or reproducing using self-clocking codes
    • G11B20/1403—Digital recording or reproducing using self-clocking codes characterised by the use of two levels
    • G11B20/1423—Code representation depending on subsequent bits, e.g. delay modulation, double density code, Miller code
    • G11B20/1426—Code representation depending on subsequent bits, e.g. delay modulation, double density code, Miller code conversion to or from block codes or representations thereof

Definitions

  • One such material providing a linear response characteristic is an electron trapping material such as is disclosed in U.S. Patents No. 4,864,536, 5,007,037, and 5,142,493, all to Lindmayer.
  • linear- response storage materials provide the ability to encode information in two dimensions - amplitude and phase.
  • the storage medium is no longer confined to storing binary or even tri-level data.
  • the concept of M-ary, or non-binary, data coding and storage is provided.
  • the increased symbol set allowed by such encoding provides the opportunity to dramatically increase the data recording density and transfer rate of the storage device.
  • the potential storage capacity of a single 5VA inch disk can be extended to several gigabytes if that disk is implemented using electron trapping materials with M-ary (multi-level) data coding.
  • input data bits are coded using an M-ary (d,k) encoder to generate code symbols.
  • input data bits x are encoded using the M-ary (d,k) encoder to generate code symbols y, where:
  • the code symbols y are multi-level symbols, each being at one of M levels.
  • the code symbol stream provided meets the code specifications of no fewer than d and no greater than k zeros between each non-zero symbol.
  • code symbols are each at one of nine levels and there is a minimum of two and a maximum of ten zeros between each non-zero symbol.
  • the code symbols y are encoded to generate a series of waveform amplitudes z.
  • the waveform amplitudes are generated by modulo M addition of the current code symbol y, with the previous waveform amplitude z ,.,
  • the waveform amplitudes are used to modulate a write laser to store information onto an optical disk or to otherwise store or communicate the input data bits x in the form of multi-level information.
  • the information stored on the medium is read and the resultant signal amplitudes are decoded.
  • Two stages of decoding are provided.
  • the waveform amplitudes are decoded to generate code symbols.
  • the code symbols are decoded to recover the original data bits.
  • coding techniques described herein are not limited to optical recording. Other recording systems capable of supporting multi-level data would benefit from the coding techniques described herein.
  • these coding techniques are also applicable to communications systems where the communications channel is capable of supporting multi-level data.
  • the waveform amplitudes could be used to modulate a signal carrier for transmission across the multi-level channel.
  • FIG. 1 is a diagram illustrating a portion of an optical storage medium and features thereon.
  • FIG. 2 is a diagram illustrating a data storage system for storing a multi ⁇ level coded data.
  • FIG. 3 is a diagram illustrating an encoder for encoding multi-level data using a multi-level (d,k) code.
  • FIG.4 is a flow diagram illustrating the operation of a multi-state encoder.
  • FIG. 5 is a diagram illustrating an example input data stream being coded using the encoder illustrated in FIG. 4.
  • FIG. 6 is a diagram illustrating a decoder for decoding multi-level (d,k) coded data.
  • FIG. 7 is a diagram illustrating a sliding block decoder.
  • FIG. 8 is a diagram illustrating encoder shut-down.
  • the present invention is directed toward an M-ary (d,k) code for use in storage and/or transmission of multi-level data, and a system and method for generating the same. This discussion is provided in several sections. In Section
  • the present invention is generally described in terms of an embodiment where multi-level data are stored on and retrieved from an optical disk.
  • the encoder and decoder described herein may be implemented for multi-level data storage in an optical disk system such as that disclosed in U.S. Patent No. 5,007,037, which is incorporated herein by reference.
  • the systems and methods of the invention can be implemented for alternative applications such as multi-level data communications and storage of multi-level data on media other than optical disks.
  • the invention can be implemented to transmit and receive data across an M-ary communications channel.
  • channel is sometimes used to refer to the optical disk. It should be understood that in the alternative embodiments the term channel can be used to describe alternative storage media and/or communications channels.
  • the input data are first encoded to create symbols.
  • the encoder is designed such that the output symbols conform to the code specifications: each 1 is followed by a minimum of d and a maximum of k 0's. These symbols are then written to the storage medium as a series of features. For example, for optical disks, a feature is the presence or absence of a burn mark. In a magnetic tape, the feature is a grouping of magnetic particles oriented in a particular manner.
  • FIG. 1 illustrates a portion of an optical storage medium 108 that stores binary data as features 102. Illustrated are shaded and unshaded features 102, indicating the absence or presence of a burn mark. Also illustrated in FIG. 1 is an example symbol stream 112 that is used to write the features 102 to medium 108. As discussed above, symbol stream 112 is the result of encoding input data using a (d,k) RLL code. Symbol stream 112 is written to medium 108 using an additional coding step as follows: the occurrence of a 1 indicates a change in the type of mark (i.e., absence or presence of a burn mark); the occurrence of a 0 indicates no change in mark type. This additional coding step is sometimes referred to as non-return-to-zero interleaved (NRZI) precoding.
  • NRZI non-return-to-zero interleaved
  • the minimum number of symbols represented by a single feature 102 is three.
  • a minimum feature size e.g., for the smallest spot size on medium 108
  • three symbols can be represented.
  • the minimum density of data written to medium 108 is 1.5 bits per fearure.
  • the density of the recording system can be increased by 50%.
  • FIG. 2 is a high-level block diagram generally illustrating a multi-level data recording system 200.
  • the recording system is comprised of an encoder 204, multi-level storage medium 208 and a decoder 212.
  • multi-level storage medium 208 can be replaced with a communications channel allowing the multi-level (d,k) code and coding scheme to be used with multi-level data communications.
  • encoder 204 and decoder 212 can be provided on both ends of the communications channel to allow bi-directional coded communications.
  • input data bits x (x 0 , x 1 , ..., x p-1 ) are the actual data that a user wishes to be stored on and retrieved from medium 208.
  • encoder 204 is implemented as a two-stage encoder.
  • FIG. 3 is a block diagram illustrating encoder 204 in this embodiment. Referring to FIG. 3, encoder 204 is comprised of a symbol encoder 304 and a waveform encoder 308, referred to herein as encoder 304 and encoder 308, respectively.
  • a second feature of encoder 304 is that the stream of code symbols y meets the code specification that there are no fewer than d and no greater than k zeros between each non-zero code symbol.
  • each waveform amplitude z generated represents, at a minimum, d+1 code symbols y. Also, because there are 1/R code symbols y generated for each input data bit x, each waveform amplitude z generated represents, at a minimum,
  • the coding system and method described above can be used to code input data using any of number of M-ary (d,k) codes. However, the design of a specific
  • M-ary (d,k) code is not a trivial matter.
  • M-ary (d,k) codes There are several factors that must be taken into consideration when designing M-ary (d,k) codes.
  • the specific coding scheme used to implement a given code impacts the performance of the encoding and decoding systems.
  • the code should be designed such that encoders and decoders can be implemented in a straight-forward and cost-effective manner.
  • the desirable code can be implemented using encoders that have a relatively small number of states while still meeting the code parameters (i.e., M, d and k).
  • the decoder required to decode the coded data should be implementable using a small sliding block window size and the decoder should have a relatively a small table size.
  • code design is not a trivial matter as there are several coding factors that affect the performance of the system.
  • the specific code implemented for a given set of parameters can impact the overall performance of the system.
  • This section of the patent document describes a specific M-ary (d,k) code and the specific encoder used to implement this code.
  • FIG. 4 is an operational flow diagram illustrating the operation of state machine 400.
  • the operation of state machine 400 is now described with reference to Table 1 and FIG. 4.
  • a step 408 an input data bit set x 0 - x 4 is received.
  • Table 1 is used to determine the output code symbol set y 0 - y 3 and next state from the current state and the input data bit set x 0 - x 4 received in step 408.
  • encoder 304 outputs code symbol set y 0 - y 3 determined in step 412.
  • state machine 400 transitions to the next state determined in step 412. At this time, the operation continues at step 408 as indicated by flow line 426.
  • an output code symbol set y 0 - y 3 of encoder 304 is a function of the input data bit set x 0 - x 4 , and the current state 404 of encoder 304.
  • Table 1 describes the output code symbol set y 0 - y 3 and next state of encoder 304 for each current state and input data bit set x 0 - x 4 .
  • FIG. 5 is a diagram further illustrating the example.
  • FIG. 5 illustrates a current state 508 and a new state 512 for the example input data stream provided in Table 2.
  • encoder 304 transitions from a current state 508 to a new state 512 and produces an output symbol set y 0 - y 3 .
  • FIG. 5 illustrates the example for 15 data bits x of the input data stream while Table 2 is an example for 20 data bits x.
  • code symbols y are further coded by waveform encoder 308 to generate a sequence of amplitudes z used to modulate the write laser.
  • each new code symbol y is modulo nine added to the previous waveform amplitude z,_, to result in the current waveform amplitude z,.
  • the code symbols y are encoded by waveform encoder 308 to waveform amplitudes z, as illustrated in Table 2.
  • the decoder uses a state independent lookup table to decode amplitude levels z read from the disk.
  • the decoder is a sliding block decoder, where a sliding window is used to decode amplitudes read from the disk.
  • FIG. 6 is a block diagram illustrating the decoder.
  • decoder 212 is comprised of a waveform decoder 604 and a sliding block decoder 608.
  • Waveform decoder 604 receives the signal amplitudes z' (multi- level) from the media and converts them to a sequence of digital code symbols y'.
  • Sliding block decoder 608 performs a table lookup to convert output code symbols y' into output data bits x'. Note that in an error free environment, output code symbols y' correspond identically to input code symbols y and output data bits x' correspond identically to input data bits x.
  • each output symbol y' is determined as being the modulo M difference between the current amplitude waveform z', and the previous amplitude waveform z',.,.
  • sliding block decoder 608 The purpose of sliding block decoder 608 is to convert the sequence of code symbols y' into a sequence of data bits x' that coincide with input data bits x.
  • the decoder is a state independent lookup table.
  • the size of the lookup table is dependent on the specific code implemented. Therefore, the design of encoder 304 affects the size of the lookup table implemented.
  • Sliding block decoder 608 is illustrated in FIG. 7.
  • Sliding block decoder comprises a sliding window 704 to decode the code symbols y' to arrive at output data bits x'.
  • sliding block decoder 608 must look at multiple code symbols y' to decode one data bit set. Specifically, for the encoder described above with reference to Table 1 , sliding block decoder 608 requires a block of twelve code symbols y- to uniquely decode one data bit set x 0 ' - x 4 '
  • sliding window 704 The actual size of sliding window 704 is determined during code design. An optimally sized sliding window 704 is large enough such that the symbols y' within sliding window 704 unambiguously define the correct output bit set x 0 ' - x 4 ' without being so large that unneeded code symbols y' are included therein. In other words, the window size is chosen as the smallest window which guarantees unique decodability.
  • sliding window 704 With the use of a sliding window 704 to decode the data, knowledge of state information is not required. In fact, the contents of sliding window 704 at any given time contain sufficient information such that state information can be determined therefrom.
  • sliding block decoder 608 is computationally less complex than conventional decoders; more importantly, the sliding block decoder limits the propagation of errors.
  • Sliding window 704 actually represents the past, present and future.
  • the one code symbol y' actually being decoded to generate a data bit x' represents the present.
  • Past symbols y' are those occurring earlier in time than the present symbol.
  • future symbols y' are those that occur after the present symbol.
  • the past is represented by '0400', the present by '0000', and the future by *1000'.
  • sliding block decoders are well known for decoding binary data.
  • One well known technique for implementing sliding block decoders with binary data is the Adler-Coppersmith-Hassner technique disclosed in U.S. Patent No. 4,413,251. Another, related technique is disclosed in U.S. Patent No.
  • the lookup table contains a plurality of entries.
  • each entry contains a possible sequence of N code symbols y', where N is the size of sliding window 704.
  • each entry of the lookup table is addressed by (directly, indirectly or via a decoding scheme) one of the possible sequences of code symbols.
  • the lookup table comprises a sufficient number of entries such that there is one entry for each of the possible occurrences of N code symbols.
  • N is chosen such that for each sequence of N code symbols y 1 an output bit set x' is unambiguously defined.
  • the preferred lookup table has 3747 entries and is illustrated in Table 3. For each entry of twelve code symbols y 1 , there is an output bit set x'. Thus, to decode code symbols y', twelve consecutive code symbols y' are loaded into sliding window 704. The entry corresponding to those twelve code symbols y' is located in the lookup table and the corresponding data bit set x' is output. To determine the next output data bit set x', sliding window 704 is 'slid' one code symbol set y' into the future (i.e., in one embodiment, a next code symbol set y' is shifted into window 704 and the oldest shifted out) and the lookup process is repeated. This sliding process continues as long as code symbols y' are provided to sliding block decoder 608.
  • t j i is the i'th component of the j'th table entry.
  • the window w is then decoded to the table entry with the minimum distance d j
  • window 704 are used as an address or used to generate an address of an entry in a memory, where the contents of that entry contain the appropriate output data bit set x'.
  • the complexity of the decoding process can be reduced significantly by making hard decisions regarding read signal amplitudes.
  • the read signal amplitudes z' are rounded-off or quantized to be one of the nine permissible amplitude levels. Even though this results in a decrease in the performance of the decoder it can significantly reduce its complexity: that is, the table can be a true lookup table requiring no distance calculations.
  • XXXX 0400 6006 10001 xxxx 0400 0004 10101 xxxx 0400 6007 10001 xxxx 0300 0040 10110 xxxx 0400 6008 10001 xxxx 0300 0050 10110 xxxx 0300 7001 10010 xxxx 0300 0060 10110 xxxx 0300 7002 10010 xxxx 0300 0070 10110 xxxx 0300 7003 10010 xxxx 0300 0080 10110 xxxx 0300 7004 10010 xxxx 0300 0005 10110 xxxx 0300 7005 10010 xxxx 0300 0006 10110 xxxx 0300 7006 10010 xxxx 0300 0007 10110 xxxx 0300 7007 10010 xxxx 0300 0008 10110 xxxx 0300 7008 10010 xxxx 0400 0040 10111 xxxx 0300 8001 10010 xxxx 0400 0050 10111 xxxx 0300 8002 10010 xxxx 0400 0060 10111 xxxx 0300 8003 10010
  • XXXX 4000 8006 10011 xxxx 3006 0002 11001 xxxx 4000 8007 10011 xxxx 3006 0003 11001 xxxx 4000 8008 10011 xxxx 3006 0004 11001 xxxx 3000 0010 10100 xxxx 3007 0010 11010 xxxx 3000 0020 10100 xxxx 3007 0020 11010 xxxx 3000 0030 10100 xxxx 3007 0030 11010 xxxx 3000 0000 10100 xxxx 3007 0000 11010 xxxx 3000 0001 10100 xxxx 3007 0001 11010 xxxx 3000 0002 10100 xxxx 3007 0002 11010 xxxx 3000 0003 10100 xxxx 3007 0003 11010 xxxx 3000 0004 10100 xxxx 3007 0004 11010 xxxx 4000 0010 10101 xxxx 3008 0010 11011 xxxx 4000 0020 10101 xxxx 3008 0020 11011 xxxx 4000 0030
  • XXXX 8004 0005 10111 xxxx 8006 0005 11101 xxxx 8004 0006 10111 xxxx 8006 0006 11101 xxxx 8004 0007 10111 xxxx 8006 0007 11101 xxxx 8004 0008 10111 xxxx 8006 0008 11101 xxxx 8005 0010 11000 xxxx 8007 0040 11110 xxxx 8005 0020 11000 xxxx 8007 0050 11110 xxxx 8005 0030 11000 xxxx 8007 0060 11110 xxxx 8005 0000 11000 xxxx 8007 0070 11110 xxxx 8005 0001 11000 xxxx 8007 0080 11110 xxxx 8005 0002 11000 xxxx 8007 0005 11110 xxxx 8005 0003 11000 xxxx 8007 0006 11110 xxxx 8005 0004 11000 xxxx 8007 0007 11110 xxxx 8006 0010 11001 xxxx 8007 0008 11110 xxxx 8006 0020 11
  • window 704 is not full. For example, referring to FIG. 7, suppose that the code symbols '0000' are the last in the data stream. Thus when decoder 212 attempts to decode code symbols '0000', there are no future code symbols available. What is needed is a way to "shut-down" encoder 204.
  • FIG. 8 is a diagram illustrating encoder shut-down.
  • window 704 is not full. For example, referring to FIG. 7, suppose that the code symbols '0001 ' are the first in the data stream. Thus when decoder 212 attempts to decode code symbols '0001', there are no past code symbols available. What is needed is a way to "start-up" encoder 204.
  • the present invention provides two ways to start-up encoder 204.
  • encoder 204 is started in a state that eliminates the need for past code symbols; in a preferred embodiment, encoder 204 is started in state 2.

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  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Signal Processing (AREA)
  • Signal Processing For Digital Recording And Reproducing (AREA)

Abstract

La présente invention concerne un système pour le codage de données numériques utilisant une numération de code à base M (d,k) pour générer des données de codage multiniveau et dans lequel M⊃2 comporte un codeur à numération à base M (d,k) pour l'acceptation des données numériques d'entrée. Le codeur à numération à base M (d,k) code les données numériques d'entrée pour produire un ensemble de symboles de code dans lequel chaque symbole de code se trouve à l'un des niveaux M et chaque paire de symboles de code différent de zéro est séparé par un nombre de zéros compris entre d et k. Un codeur de forme d'onde (204) convertit les symboles de code en amplifications de signaux de forme d'onde compatible avec un canal multiniveau. Chaque amplification de signal de forme d'onde est générée par addition d'un modulo M d'un symbole de code courant à l'amplification du signal de forme d'onde antérieure. Un code spécifique M=9(2,10) permet un enregistrement à haute densité sur un support de stockage multiniveau. Le codeur M=9(2,10) est mis en oeuvre au moyen d'un codeur à dix-huit états et d'un codeur de forme d'onde modulo neuf.
PCT/US1997/011532 1996-06-24 1997-06-24 Codage limite par longueur de ligne dans lequel m=9(2,10), d=3,75 pour donnees multiniveaux WO1997050181A1 (fr)

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US08/668,847 1996-06-24

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Citations (7)

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US4506252A (en) * 1981-05-05 1985-03-19 Sperry Corporation Ternary data encoding system
US4566044A (en) * 1984-10-29 1986-01-21 International Business Machines Corporation Direction-constrained ternary codes using peak and polarity detection
US4914438A (en) * 1987-09-01 1990-04-03 Hitachi, Ltd. Digital information coding system
US5142493A (en) * 1988-07-29 1992-08-25 Quantex Corporation Optical disk employing electron trapping material as a storage medium
US5260703A (en) * 1992-08-27 1993-11-09 Quantum Corporation Data encoding and decoding within PRML class IV sampling data detection channel of disk drive
US5390198A (en) * 1993-05-26 1995-02-14 The Boeing Company Soft decision viterbi decoder for M-ary convolutional codes
US5398260A (en) * 1993-04-15 1995-03-14 Samsung Electronics Co., Ltd. Method and apparatus for restoring multi level/phase modulation data

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4506252A (en) * 1981-05-05 1985-03-19 Sperry Corporation Ternary data encoding system
US4566044A (en) * 1984-10-29 1986-01-21 International Business Machines Corporation Direction-constrained ternary codes using peak and polarity detection
US4914438A (en) * 1987-09-01 1990-04-03 Hitachi, Ltd. Digital information coding system
US5142493A (en) * 1988-07-29 1992-08-25 Quantex Corporation Optical disk employing electron trapping material as a storage medium
US5260703A (en) * 1992-08-27 1993-11-09 Quantum Corporation Data encoding and decoding within PRML class IV sampling data detection channel of disk drive
US5398260A (en) * 1993-04-15 1995-03-14 Samsung Electronics Co., Ltd. Method and apparatus for restoring multi level/phase modulation data
US5390198A (en) * 1993-05-26 1995-02-14 The Boeing Company Soft decision viterbi decoder for M-ary convolutional codes

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