Literature Kees A. Schouhamer Immink

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K.A. Schouhamer Immink, 'Innovation in constrained codes' (invited paper), Submitted to IEEE Communications Magazine, June 2022.
Abstract - Constrained coding is a somewhat nebulous term which we may define by either inclusion or exclusion. A constrained system is defined by a constrained set of `good' or `allowable' sequences to be recorded or transmitted. Constrained coding focuses on the analysis of constrained systems and the design of efficient encoders and decoders that transform arbitrary user sequences into constrained sequences. Constrained coding has extensively been used since the advent in the 1950s of digital storage and communication devices . They have found application in all hard disk, non-volatile memories, optical discs, such as CD, DVD and Blu-Ray Disc, and they are now projected for usage in DNA-based storage. We survey theory and practice of constrained coding, tracing the evolution of the subject from its origins in Shannon's classic 1948 paper to present-day applications in DNA-based data storage systems.
K.A. Schouhamer Immink and J. H. Weber, 'Minimally modified balanced codes', Submitted to IEEE Trans. on Inform. Theory, May 2022.
Abstract - We present and analyze a new systematic construction of bipolar balanced codes where each codeword contains equally many -1's and +1's. The new code is minimally modified as the number of symbol changes made to the source word for translating it into a balanced codeword is as small as possible. The balanced codes feature low redundancy and time complexity. Large look-up tables are avoided.
G. Song, K. Cai, Y. Li, and K.A. Schouhamer Immink, 'Maximum Achievable Rate of Resistive Random-Access Memory Channels by Mutual Information Spectrum Analysis', Submitted to IEEE Trans. on Inform. Theory, Oct. 2021.
Abstract - The maximum achievable rate is derived for resistive random-access memory (ReRAM) channel with sneak-path interference. Based on the mutual information spectrum analysis, the maximum achievable rate of ReRAM channel with independent and identically distributed (i.i.d.) binary inputs is derived as an explicit function of channel parameters such as the distribution of cell selector failures and channel noise level. Due to the randomness of cell selector failures, the ReRAM channel demonstrates multi-status characteristic. For each status, as the array size is large, the fraction of cells affected by sneak paths approaches a constant value. Therefore, the mutual information spectrum of the ReRAM channel is formulated as a mixture of multiple stationary channels. Maximum achievable rates of the ReRAM channel with different settings, such as single- and across-array codings, with and without data shaping, and optimal and treating-interference-as-noise (TIN) decodings, are compared. These results provide us valuable insights on the code design for ReRAM.
Articles, books, and book chapters (most recent first).

==2022==
T.T. Nguyen, K. Cai, H. M. Kiah, K.A. Schouhamer Immink, and Y. M. Chee, 'Using One Redundant Bit to Construct Two-Dimensional Almost-Balanced Codes', 2022 IEEE International Symposium on Information Theory (ISIT), Helsink, July 2022.
Abstract - In this work, given (n, \epsilon > 0), two efficient encoding (decoding) methods are presented for mapping arbitrary data to (from) (n \times n ) binary arrays in which the weight of every row and every column is within ([(1/2-\epsilon)n,(1/2+\epsilon)n]), which is referred to as the (\epsilon)-balanced constraint. The first method combines the divide and conquer algorithm and a modification of the Knuth's balancing technique, resulting a redundancy of (\Theta(n) ) bits. On the other hand, for sufficiently large values of (n), the second method uses the sequence replacement technique, which costs only 1 redundant bit. The latter method reduces significantly the redundancy of the best known encoder for two-dimensional (p)-bounded weight constrained codes from ((n+3)) bits to a single bit.
T.T. Nguyen, K. Cai, W. Song, and K.A. Schouhamer Immink, 'Optimal Chromosome-Inversion Correcting Codes for Data Storage in Live DNA', 2022 IEEE International Symposium on Information Theory (ISIT), Helsink, July 2022.
Abstract - Advances in synthesis and sequencing technologies have made DNA macromolecules an attractive medium for digital information storage. Compared with the ex vivo method that stores data in a non-biological environment, there have been considerations and attempts to store data in living organisms, also known as the in vivo method or live DNA due to several magnificent advantages. Data stored in this medium is prone to errors arising from various mutations such as point mutations (when there is a change in a single nucleotide in DNA, i.e. deletion, insertion, or substitution) or chromosomal alterations (that change the structure of a segment of DNA, i.e. tandem duplication, inversion). In this paper, we provide error-correcting codes for errors caused by inversions, that reverse the order of a segment of DNA. In particular, we construct families of codes for correcting single inversion of a fixed length or variable length up to a given constant k with at most ( \log n + \Theta(1)) redundant bits, where the redundancy matches the optimal value up to only a constant additive term. Moreover, our codes remain order-optimal, i.e. the redundancy is at most (\log n + o(\log n)), when (k = o(\log n)). The redundancy can be further reduced when (k\le 3).
K.A. Schouhamer Immink and J. H. Weber, 'A new detection method for noisy channels with time-varying offset', IEEE Trans. on Inform. Theory, vol. 68, no. 5, pp. 3108-3114, 2022, doi: 10.1109/TIT.2022.3140613.
Abstract - We consider noisy communications and storage systems that are hampered by varying offset of unknown magnitude such as low-frequency signals of unknown amplitude added to the sent signal. We study and analyze a new detection method whose error performance is independent of both unknown base offset and offset's slew rate. The new method requires, for a codeword length n > 11, less than 1.5 dB more noise margin than Euclidean distance detection. The relationship with constrained codes based on mass-centered codewords and the new detection method is discussed.
==2021==
T.T. Nguyen, K. Cai, and K.A. Schouhamer Immink, 'Efficient Design of Subblock Energy-Constrained Codes and Sliding Window-Constrained Codes', IEEE Trans. on Inform. Theory, vol. IT-67. no. 12, pp. 7914-7924, Aug. 2021, doi: 10.1109/TIT.2021.3119568.
Abstract - The subblock energy-constrained codes (SECCs) and sliding window-constrained codes (SWCCs) have recently attracted attention due to various applications in communication systems such as simultaneous energy and information transfer. In a SECC, each codeword is divided into smaller non-overlapping windows, called subblocks, and every subblock is constrained to carry sufficient energy. In an SWCC, however, the energy constraint is enforced over every window. In this work, we focus on the binary channel, where sufficient energy is achieved theoretically by using relatively high weight codes, and study SECCs and SWCCs under more general constraints, namely bounded SECCs and bounded SWCCs. We propose two methods to construct such codes with low redundancy and linear-time complexity, based on Knuth’s balancing technique and sequence replacement technique. These methods can be further extended to construct SECCs and SWCCs. For certain codes parameters, our methods incur only one redundant bit. We also impose the minimum distance constraint for error correction capability of the designed codes, which helps to reduce the error propagation during decoding as well.
T.T. Nguyen, K. Cai, K.A. Schouhamer Immink, Y. M. Chee, 'Efficient Design of Capacity-Approaching Two-Dimensional Weight-Constrained Codes', IEEE International Symposium on Information Theory, (ISIT) 2021, Melbourne, pp. 2930-2935, June 2021, doi: 10.1109/ISIT45174.2021.9517970.
Abstract - In this work, given n, p>0, efficient encoding/decoding algorithms are presented for mapping arbitrary data to and from n x n binary arrays in which the weight of every row and every column is at most pn. Such constraint, referred as p-bounded-weight- constraint, is crucial for reducing the parasitic currents in the crossbar resistive memory arrays, and has also been proposed for certain applications in the area of holographic memory in optical storage. While low-complexity designs have been proposed in the literature for only the case p = 1/2, this work provides an efficient coding scheme that works for arbitrary values of p. The coding rate of our proposed encoder approaches the channel capacity for all p.
K.A. Schouhamer Immink and K. Cai, 'Efficient encoding of constrained block codes', IEEE Communications Letters, vol. 25, no. 11, pp. 3468-3472, Nov. 2021, doi: 10.1109/LCOMM.2021.3105327.
Abstract - We present coding methods for generating ell-symbol constrained codewords taken from a set, S, of allowed codewords. In standard practice, the size of the set S, denoted by M=|S|, is truncated to an integer power of two, which often leads to a serious waste of capacity. We present an efficient and low-complexity coding method for avoiding the truncation loss. The presented construction of Pearson codes and fixed-weight codes offers a rate close to capacity. For example, the presented 255B320B balanced code, where 255 source bits are translated into 32 10-bit balanced codewords, has a rate 0.1 % below capacity.
K.A. Schouhamer Immink and K. Cai, 'Spectral Shaping Codes', IEEE Transactions on Consumer Electronics, vol. CE-67, no. 2, pp. 158-165, May 2021, doi: 10.1109/TCE.2021.3073199.
Abstract - We investigate a new approach for designing spectral shaping block codes with a target spectrum, H_t(f), that has been specified at a plurality of frequencies. We analyze the probability density function of the spectral power density function of uncoded n-symbol bipolar code words. We present estimates of the redundancy and the spectrum of spectral shaping codes with specified target spectral densities H_t(f_i) at frequencies f_i. Constructions of low-redundancy codes with suppressed low-frequency content are presented that compare favorably with conventional dc-balanced codes currently used in data transmission and data storage devices with applications in consumer electronics.
T.T. Nguyen, K. Cai, K.A. Schouhamer Immink, and H.M. Kiah, 'Capacity-Approaching Constrained Codes with Error Correction for DNA-Based Data Storage', IEEE Trans. on Inform. Theory, vol. 67, no. 8, pp. 5602-5613, Aug. 2021, doi: 10.1109/TIT.2021.3066430.
Abstract - The subblock energy-constrained codes (SECCs) and sliding window-constrained codes (SWCCs) have recently attracted attention due to various applications in communication systems such as simultaneous energy and information transfer. In a SECC, each codeword is divided into smaller non-overlapping windows, called subblocks, and every subblock is constrained to carry sufficient energy. In a SWCC, however, the energy constraint is enforced over every window. In this work, we focus on the binary channel, where sufficient energy is achieved theoretically by using relatively high weight codes, and study the bounded SECCs and bounded SWCCs, where the weight in every window is bounded between a minimum and maximum number. Particularly, we focus on the cases of parameters that there is no rate loss, i.e. the channel capacity is one, and propose two methods to construct capacity-approaching codes with low redundancy and linear-time complexity, based on Knuth’s balancing technique and sequence replacement technique. These methods can be further extended to construct SECCs and SWCCs. For certain codes parameters, our methods incur only one redundant bit. We also impose the minimum distance constraint for error correction capability of the designed codes, which helps to reduce the error propagation during decoding as well.
R. Bu, J.H. Weber, and K.A. Schouhamer Immink, 'Maximum Likelihood Decoding for Channels with Gaussian Noise and Signal Dependent Offset, IEEE Trans. on Commun., vol. COM-69, no. 1, pp. 85-93, Jan. 2021, doi: 10.1109/TCOMM.2020.3026383.
Abstract - In many channels, the transmitted signals do not only face noise, but offset mismatch as well. In the prior art, maximum likelihood (ML) decision criteria have already been developed for noisy channels suffering from signal independent offset . In this paper, such ML criterion is considered for the case of binary signals suffering from Gaussian noise and signal dependent offset . The signal dependency of the offset signifies that it may differ for distinct signal levels, i.e., the offset experienced by the zeroes in a transmitted codeword is not necessarily the same as the offset for the ones. Besides the ML criterion itself, also an option to reduce the complexity is considered. Further, a brief performance analysis is provided, confirming the superiority of the newly developed ML decoder over classical decoders based on the Euclidean or Pearson distances.

==2020==
K.A. Schouhamer Immink and K. Cai, 'Block Codes for Energy-Harvesting Sliding-Window Constrained Channels', IEEE Communications Letters, vol. 24, no. 11, pp. 2383-2386, Nov. 2020, doi: 10.1109/LCOMM.2020.3012301.
Abstract - Energy-harvesting sliding-window constrained block codes guarantee that within any prescribed window of l consecutive bits the constrained sequence has at least t, t=1, 1’s. Prior art code design methods build upon the finite-state machine description of the (l,t) constraint, but as the number of states equals l choose t, a code design becomes prohibitively complex for mounting l and t. We present a new block code construction that circumvents the enumeration of codewords using a finite-state description of the (l,t)-constraint. The codewords of the block code are encoded and decoded using a single look-up table. For (l=4,t=2), the new block codes are maximal, that is, they have the largest possible number of codewords for its parameters.
W. Song, K. Cai, and K.A. Schouhamer Immink, 'Sequence-Subset Distance and Coding for Error Control in DNA-based Data Storage', IEEE Trans. on Inform. Theory, vol. IT-66, no. 10, pp. 6048-6065, Oct. 2020, doi: 10.1109/TIT.2020.3002611.
Abstract - The process of DNA-based data storage (DNA storage for short) can be mathematically modelled as a communication channel, termed DNA storage channel, whose inputs and outputs are sets of unordered sequences. To design error correcting codes for DNA storage channel, a new metric, termed the sequence-subset distance, is introduced, which generalizes the Hamming distance to a distance function defined between any two sets of unordered vectors and helps to establish a uniform framework to design error correcting codes for DNA storage channel. We further introduce a family of error correcting codes, referred to as sequence-subset codes, for DNA storage and show that the error-correcting ability of such codes is completely determined by their minimum distance. We derive some upper bounds on the size of the sequence-subset codes including a tight bound for a special case, a Singleton-like bound and a Plotkin-like bound. We also propose some constructions, including an optimal construction for that special case, which imply lower bounds on the size of such codes.
R. Bu, J.H. Weber, and K.A. Schouhamer Immink, 'Maximum Likelihood Decoding for Channels with Uniform Noise and Signal Dependent Offset', pp. 706-710, IEEE International Symposium on Information Theory, (ISIT) 2020, San Francisco, June 2020, doi: 10.1109/ISIT44484.2020.9174270.
Abstract - Maximum likelihood (ML) decision criteria have been developed for channels suffering from signal independent offset mismatch. Here, such criteria are considered for signal dependent offset, which means that the value of the offset may differ for distinct signal levels rather than being the same for all levels. An ML decision criterion is derived, assuming uniform distributions for both the noise and the offset. In particular, for the proposed ML decoder, bounds are determined on the standard deviations of the noise and the offset which lead to a word error rate equal to zero. Simulation results are presented confirming the findings.
T.T. Nguyen, K. Cai, K.A. Schouhamer Immink, and H.M. Kiah, 'Constrained Codes with Error Correction for DNA-Based Data Storage', pp. 694-699, IEEE International Symposium on Information Theory, (ISIT) 2020, San Francisco, June 2020d, doi: 10.1109/ISIT44484.2020.9174438. In this paper, we first propose coding techniques for DNA-based data storage which account the maximum homopolymer runlength and the GC-content.
Abstract - In particular, for arbitrary l,e>0, we propose simple and efficient (l,e)-constrained encoders that transform binary sequences into DNA base sequences (codewords), that satisfy the following properties: · Runlength constraint: the maximum homopolymer run in each codeword is at most l, · GC-content constraint: the GC-content of each codeword is within [0.5-e, 0.5+e]. For practical values of l and e, our codes achieve higher rates than the existing results in the literature. We further design efficient (l, e)-constrained codes with error-correction capability. Specifically, the designed codes satisfy the runlength constraint, the GC-content constraint, and can correct a single edit (i.e. a single deletion, insertion, or substitution) and its variants. To the best of our knowledge, no such codes are constructed prior to this work.
T.T. Nguyen, K. Cai, K.A. Schouhamer Immink, 'Binary Subblock Energy-Constrained Codes: Knuth’s Balancing and Sequence Replacement Techniques', pp. 37-41, IEEE International Symposium on Information Theory, (ISIT) 2020, San Francisco, June 2020, doi: 10.1109/ISIT44484.2020.9174430.
Abstract - The subblock energy-constrained codes (SECCs) have recently attracted attention due to various applications in communication systems such as simultaneous energy and information transfer. In a SECC, each codeword is divided into smaller subblocks, and every subblock is constrained to carry sufficient energy. In this work, we study SECCs under more general constraints, namely bounded SECCs and sliding-window constrained codes (SWCCs), and propose two methods to construct such codes with low redundancy and linear-time complexity, based on Knuth’s balancing technique and sequence replacement technique. For certain codes parameters, our methods incur only one redundant bit.
K.A. Schouhamer Immink and K. Cai, 'Properties and constructions of energy-harvesting sliding-window constrained codes', IEEE Communications Letters, vol. 24, nr. 9, 1890-1893, Sept. 2020, doi: 10.1109/LCOMM.2020.2993467.
Abstract - We study properties and constructions of constrained binary codes that enable simultaneous energy and information transfer. We specifically study sliding-window constrained codes that guarantee that within any prescribed window of l consecutive bits the constrained sequence has at least t, t > 1, 1's. We present a K-state source, K = l choose t, that models the (l, t) sliding-window constraint. We compute the information capacity of sliding-window (l, t)-constrained sequences. We design efficient coding techniques for translating source data into sliding-window (l, t)-constrained sequences.
J.H. Weber, R. Bu, K. Cai, and K.A. Schouhamer Immink, 'Binary Block Codes for Noisy Channels with Unknown Offset', IEEE Trans. on Commun., IEEE Trans. on Commun., vol. 68, Issue 7, pp. 3975-3983, July 2020, doi: 10.1109/TCOMM.2020.2986200.
Abstract - Decoders minimizing the Euclidean distance between the received word and the candidate codewords are known to be optimal for channels suffering from Gaussian noise. However, when the stored or transmitted signals are also corrupted by an unknown offset, other decoders may perform better. In particular, applying the Euclidean distance on normalized words makes the decoding result independent of the offset. The use of this distance measure calls for alternative code design criteria in order to get good performance in the presence of both noise and offset. In this context, various adapted versions of classical binary block codes are proposed, such as (i) cosets of linear codes, (ii) (unions of) constant weight codes, and (iii) unordered codes. It is shown that considerable performance improvements can be achieved, particularly when the offset is large compared to the noise.
K.A. Schouhamer Immink and K. Cai, 'Properties and constructions of constrained codes for DNA-based data storage', IEEE Access, vol. 8, pp. 49523-49531, 2020, doi: 10.1109/ACCESS.2020.2980036.
Abstract - We describe properties and constructions of constraint-based codes for DNA-based data storage which account for the maximum repetition length and AT/GC balance. Generating functions and approximations are presented for computing the number of sequences with maximum repetition length and AT/GC balance constraint. We describe routines for translating binary runlength limited and/or balanced strings into DNA strands, and compute the efficiency of such routines. Expressions for the redundancy of codes that account for both the maximum repetition length and AT/GC balance are derived.
K.A. Schouhamer Immink, 'Jan M. Romijn (1932-2020) Obituary', Journal of the Audio Engineering Society, vol. 68, nr. 9, pp. 687-687, 2020.
K.A. Schouhamer Immink and K. Cai, 'Dynamic Threshold Detection Using Clustering in the Presence of Channel Mismatch and Additive Noise', IEEE Access, vol. 8, pp. 19319-19326, 2020, doi: 10.1109/ACCESS.2020.2980036.
Abstract - We report on the feasibility of k-means clustering techniques for the dynamic threshold detection of encoded q-ary symbols transmitted over a noisy channel with partially unknown channel parameters. We first assess the performance of k-means clustering technique without dedicated constrained coding. We apply constrained codes which allows a wider range of channel uncertainties so improving the detection reliability.
T.T. Nguyen, K. Cai, K.A. Schouhamer Immink, and H.M. Kiah, 'Capacity-Approaching Constrained Codes with Error Correction for DNA-Based Data Storage', ArXiv:2001.02839, Jan. 2020.
Abstract - We propose coding techniques that limit the length of homopolymers runs, ensure the GC-content constraint, and are capable of correcting a single edit error in strands of nucleotides in DNA-based data storage systems. In particular, for given ell, epsilon>0, we propose simple and efficient encoders/decoders that transform binary sequences into DNA base sequences (codewords), namely sequences of the symbols A, T, C and G, that satisfy the following properties: (i) Runlength constraint: the maximum homopolymer run in each codeword is at most ell, (ii) GC-content constraint: the GC-content of each codeword is within [0.5-epsilon, 0.5+epsilon], (iii) Error-correction: each codeword is capable of correcting a single deletion, or single insertion, or single substitution error. For practical values of ell and epsilon, we show that our encoders achieve much higher rates than existing results in the literature and approach the capacity. Our methods have low encoding/decoding complexity and limited error propagation.

==2019==
K.A. Schouhamer Immink, 'A New DC-free Runlength Limited Coding Method for Data Transmission and Recording', IEEE Trans. on Consumer Electronics, vol. 65, Issue 4, pp. 502-505, Nov. 2019, doi: 10.1109/TCE.2019.2932795.
Abstract - This paper describes a new coding method based on binary (d, k) runlength constraints used for recording or transmitting an audio or video signal, computer data, etc. Data words of m bits are translated into codewords of n bits using a conversion table. The codewords satisfy a (d, k) runlength constraint in which at least d and not more than k '0's occur between consecutive '1's. The n-bit codewords alternate with p-bit merging words which in the prior art are selected such that the d and k are satisfied at the borders of consecutive codewords. We present a new coding method, where the codewords obey the (d, k)-constraint, but the merging words are not required to obey the (d)-constraint. The merging word that satisfies said conditions, yielding the lowest low-frequency spectral content of the encoded signal obtained after modulo-2 integration, is selected. The spectral performance of the new coding method has been appraised by computer simulations for the EFM (Eight-to-Fourteen Modulation) parameters, d = 2, k = 10, and p = 3. The low-frequency content of the signal generated by the newly presented coding method is around 4 dB lower in the relevant low-frequency range than that generated by the conventional EFM method.
K.A. Schouhamer Immink and K. Cai, 'Efficient balanced and maximum homopolymer-run restricted block codes for DNA-based data storage', IEEE Communications Letters, vol. 23, Issue 10, pp. 1676-1679, Oct. 2019, doi: 10.1109/LCOMM.2019.2930970.
Abstract - We analyze codes for DNA-based data storage which accounts for the maximum homopolymer repetition length and GC-AT balance. We present a new precoding method for translating words with a maximum run of k zeros into words with a maximum homopolymer run m = k + 1, which is atractive for securing GC-AT balance. Generating functions are presented for enumerating the number of n-symbol k-constrained codewords of given GC-AT balance Various efficient constructions are presented of block codes that satisfy a combined balance and maximum homopolymer run.
K.A. Schouhamer Immink and K. Cai, 'Properties and constructions of constrained codes for DNA-based data storage', arXiv:1812.06798, 2019.
Abstract - We describe properties and constructions of constraint-based codes for DNA-based data storage which accounts for the maximum repetition length and AT balance. We present algorithms for computing the number of sequences with maximum repetition length and AT balance constraint. We present efficient routines for translating binary runlength limited and/or balanced strings into DNA strands. We show that the implementation of AT-balanced codes is straightforwardly accomplished with binary balanced codes. We present codes that accounts for both the maximum repetition length and AT balance.
K.A. Schouhamer Immink and K. Cai, 'Computation of the spectrum of dc^2-balanced codes', IEEE Trans. on Commun., vol. 67, no. 7, pp. 4634-4640, July 2019, doi: 10.1109/TCOMM.2019.2911583.
Abstract - We apply the central limit theorem for deriving approximations to the auto-correlation function and power density function (spectrum) of second-order spectral null (dc^2-balanced) codes. We show that the auto-correlation function of dc^2-balanced codes can be accurately approximated by a cubic function. We compare the approximate auto-correlation function and spectrum with the exact auto-correlation function and spectrum of full set dc^2-balanced codes. We show that the difference between the approximate and exact spectrum is less than 0.04 dB for codeword length n = 256. We compare the spectral performance of dc-balanced versus dc^2-balanced codes in the low-frequency range.
W. Song, K. Cai, and K.A. Schouhamer Immink, 'Sequence-Subset Distance and Coding for Error Control in DNA-based Data Storage', IEEE International Symposium on Information Theory (ISIT), Paris, France, July 2019.
Abstract - The process of DNA data storage can be mathematically modelled as a communication channel, termed DNA storage channel, whose inputs and outputs are sets of unordered sequences. To design error correcting codes for DNA storage channel, a new metric, termed the sequence-subset distance, is introduced, which generalizes the Hamming distance to a distance function defined between any two sets of unordered vectors and helps to establish a uniform framework to design error correcting codes for DNA storage channel. We further introduce a family of error correcting codes, termed sequence subset codes, for DNA storage and show that the error-correcting ability of such codes is completely determined by their minimum distance. We derived some upper bounds on the size of the sequence subset codes including a Singleton-like bound and a Plotkin-like bound. We also propose some constructions, which imply lower bounds on the size of such codes.
K.A. Schouhamer Immink and K. Cai, 'Estimated Spectra of Higher-Order Spectral Null Codes', IEEE Communications Letters, vol. 23, pp. 20-23, Jan. 2019, doi: 10.1109/LCOMM.2018.2877324.
Abstract - We present an estimate of the power density function (spectrum) of binary K-th order spectral null codes. We work out the auto-correlation model in detail for second-and third-order spectral null codes. We compare the auto-correlation functions and spectra predicted by the model with those generated by full-set K-th order spectral null block codes.

==2018==
K.A. Schouhamer Immink and K. Cai, 'An Unsupervised Learning Approach for Data Detection in the Presence of Channel Mismatch and Additive Noise', arXiv:1812.09024, Oct. 2018.
Abstract - We investigate machine learning based on clustering techniques that are suitable for the detection of encoded strings of q-ary symbols transmitted over a noisy channel with partially unknown characteristics. We consider the detection of the q-ary data as a classification problem, where objects are recognized from a corrupted vector, which is obtained by an unknown corruption process. We first evaluate the error performance of k-means clustering technique without constrained coding. Secondly, we apply constrained codes that create an environment that improves the detection reliability and it allows a wider range of channel uncertainties.
K. Cai and K.A. Schouhamer Immink, 'Detection of Noisy and Corrupted Data Using Clustering Techniques', International Symposium on Information Theory and it Applications (ISITA), Singapore, October 28-31, 2018, doi: 10.23919/ISITA.2018.8664325.
Abstract - We investigate machine learning based on clustering techniques that are suitable for the detection of n-symbol words of q-ary symbols transmitted over a noisy channel with partially unknown characteristics. We consider the detection of the n-symbol q-ary data as a classification problem, where objects are recognized from a corrupted vector, which is obtained by an unknown corruption process.
J.H. Weber and K.A. Schouhamer Immink, 'Properties of Binary Pearson Codes', International Symposium on Information Theory and it Applications (ISITA), Singapore, October 28-31, 2018, doi: 10.23919/ISITA.2018.8664287.
Abstract - We consider the transmission and storage of data that use coded symbols over a channel, where a Pearson-distance based detector is used for achieving resilience against unknown channel gain and offset, and corruption with additive noise. We discuss properties of binary Pearson codes, such as the Pearson noise distance that plays a key role in the error performance of Pearson-distance-based detection. We also compare the Pearson noise distance to the well-known Hamming distance, since the latter plays a similar role in the error performance of Euclidean distance- based detection.
M. Zhang, K. Cai and K.A. Schouhamer Immink, 'Soft-Decision Decoding for DNA-Based Data Storage', International Symposium on Information Theory and it Applications (ISITA), pp. 16-20, Singapore, October 28-31, 2018, doi: 10.23919/ISITA.2018.8664305.
Abstract - This paper presents novel soft-decision decoding (SDD) of error correction codes (ECCs) that substantially improve the reliability of DNA-based data storage system compared with conventional hard-decision decoding (HDD). We propose a simplified system model for DNA-based data storage according to the major characteristics and different types of errors associated with the prevailing DNA synthesis and sequencing technologies. We compute analytically the error-free probability of each sequenced DNA oligo nucleotide (oligo), based on which the soft-decision log-likelihood ratio (LLR) of each oligo can be derived. We apply the proposed SDD algorithms to the DNA Fountain scheme which achieves the highest information density so far in the literature. Simulation results show that SDD achieves an error rate improvement of two to three orders of magnitude over HDD, thus demonstrating its potential to improve the information density of DNA-based data storage systems.
K.A. Schouhamer Immink, 'How we made the compact disc', Nature Electronics, vol. 1, Issue 4, pp. 260, April 2018. doi: 10.1038/s41928-018-0063-7.
Abstract - An international collaboration between Philips and the Sony Corporation lead to the creation of the compact disc. Kees A. Schouhamer Immink explains how it came about.
J.H. Weber and K.A. Schouhamer Immink, 'Maximum Likelihood Decoding for Gaussian Noise Channels with Gain or Offset Mismatch', IEEE Communications Letters, vol. 22, Issue 6, pp. 1128-1131, June 2018, doi: 10.1109/LCOMM.2018.2809749.
Abstract - Besides the omnipresent noise, other important inconveniences in communication and storage systems are formed by gain and/or offset mismatches. In the prior art, a maximum likelihood (ML) decision criterion has already been developed for Gaussian noise channels suffering from unknown gain and offset mismatches. Here, such criteria are considered for Gaussian noise channels suffering from either an unknown offset or an unknown gain. Furthermore, ML decision criteria are derived when assuming a Gaussian or uniform distribution for the offset in the absence of gain mismatch.
K.A. Schouhamer Immink, K. Cai, and J.H. Weber, 'Dynamic Threshold Detection Based on Pearson Distance Detection', IEEE Trans. on Communications, vol. 66, Issue 7, pp. 2958-2965, 2018, doi: 10.1109/TCOMM.2018.2814618.
Abstract - We consider the transmission and storage of encoded strings of symbols over a noisy channel, where dynamic threshold detection is proposed for achieving resilience against unknown scaling and offset of the received signal. We derive simple rules for dynamically estimating the unknown scale (gain) and offset. The estimates of the actual gain and offset so obtained are used to adjust the threshold levels or to re-scale the received signal within its regular range. Then, the re-scaled signal, brought into its standard range, can be forwarded to the final detection/decoding system, where optimum use can be made of the distance properties of the code by applying, for example, the Chase algorithm. A worked example of a spin-torque transfer magnetic random access memory (STT-MRAM) with an application to an extended (72, 64) Hamming code is described, where the retrieved signal is perturbed by additive Gaussian noise and unknown gain or offset.
T.G.Swart, J.H. Weber, and K.A. Schouhamer Immink, 'Prefixless q-ary Balanced Codes with Fast Syndrome-based Error Correction', IEEE Trans. on Information Theory, vol. 64, Issue 4, pp. 2431-2443, April 2018, doi: 10.1109/TIT.2017.2767034.
Abstract - We investigate a Knuth-like scheme for balancing q-ary codewords, which has the virtue that look-up tables for coding and decoding the prefix are avoided by using precoding and error correction techniques. We show how the scheme can be extended to allow for error correction of single channel errors using a fast decoding algorithm that depends on syndromes only, making it considerably faster compared to the prior art exhaustive decoding strategy. A comparison between the new and prior art schemes, both in terms of redundancy and error performance, completes the study.
K.A. Schouhamer Immink and K. Cai, 'Design of Capacity-Approaching Constrained Codes for DNA-based Storage Systems', IEEE Communications Letters, vol. 22, pp. 224-227, Feb. 2018, doi: 10.1109/LCOMM.2017.2775608.
Abstract - We consider coding techniques that limit the lengths of homopolymer runs in strands of nucleotides used in DNA-based mass data storage systems. We compute the maximum number of user bits that can be stored per nucleotide when a maximum homopolymer runlength constraint is imposed. We describe simple and efficient implementations of coding techniques that avoid the occurrence of long homopolymers, and the rates of the constructed codes are close to the theoretical maximum. The proposed sequence replacement method for k-constrained q-ary data yields a significant improvement in coding redundancy than the prior art sequence replacement method for the k-constrained binary data. Using a simple transformation, standard binary maximum runlength limited sequences can be transformed into maximum runlength limited q-ary sequences which opens the door to applying the vast prior art binary code constructions to DNA-based storage.
K. Cai, K.A. Schouhamer Immink, M. Zhang, and R. Zhao, 'Design of Spectrum Shaping Codes for High-Density Data Storage', ICCE, Las Vegas, pp. 1-2, Jan. 2018, doi: 10.1109/ICCE.2018.8326206.
Abstract - This paper proposes systematic code design methods for constructing efficient spectrum shaping codes with the maximum runlength limited constraint k, which are widely used in data storage systems for digital consumer electronics products. Through shaping the spectrum of the input user data sequence, the codes can effectively circumvent the interaction between the data signal and servo signal in high-density data storage systems. In particular, we first propose novel methods to design high-rate k constrained codes in the non-return-to-zero (NRZ) format, which can not only facilitate timing recovery of the storage system, but also avoid error propagation during decoding and reduce the system complexity. We further propose to combine the Guided Scrambling (GS) technique with the k constrained code design methods to construct highly efficient spectrum shaping k constrained codes. Simulation results demonstrate that the designed codes can achieve significant spectrum shaping effect with only around 1% code rate loss and reasonable computational complexity.
K.A. Schouhamer Immink and K. Cai, 'Composition Check Codes', IEEE Trans. on Inform. Theory, vol. 64, Issue 1, pp. 249-256, Jan. 2018, doi: 10.1109/TIT.2017.2721423.
Abstract - We present composition check codes for noisy storage and transmission channels with unknown gain and/or offset. In the proposed composition check code, like in systematic error correcting codes, the encoding of the main data into a constant composition code is completely avoided. To the main data, a coded label is appended that carries information regarding the composition vector of the main data. Slepian's optimal detection technique of codewords that are taken from a constant composition code is applied for detection. A first Slepian detector detects the label and subsequently restores the composition vector of the main data. The composition vector, in turn, is used by a second Slepian detector to optimally detect the main data. We compute the redundancy and error performance of the new method, and results of computer simulations are presented.

==2017==
K. Cai, K.A. Schouhamer Immink, M. Zhang, and R. Zhao, 'On the design of Spectrum Shaping Codes for High-Density Data Storage', Trans. on Consumer Electronics, vol. CE-63, pp. 477-482, Nov. 2017, doi: 10.1109/TCE.2017.015067.
Abstract - This paper proposes systematic code design methods for constructing efficient spectrum shaping codes with the maximum runlength limited constraint k, which are widely used in data storage systems for digital consumer electronics products. Through shaping the spectrum of the input user data sequence, the codes can effectively circumvent the interaction between the data signal and servo signal in high-density data storage systems. In particular, we first propose novel methods to design high-rate k constrained codes in the non-return-to-zero (NRZ) format, which can not only facilitate timing recovery of the storage system, but also avoid error propagation during decoding and reduce the system complexity. We further propose to combine the Guided Scrambling (GS) technique with the k constrained code design methods to construct highly efficient spectrum shaping k constrained codes. Simulation results demonstrate that the designed codes can achieve significant spectrum shaping effect with only around 1% code rate loss and reasonable computational complexity.
K. Cai and K.A. Schouhamer Immink, 'Cascaded Channel Model, Analysis, and Hybrid Decoding for Spin-Torque Transfer Magnetic Random Access Memory (STT-MRAM)', IEEE Trans. on Magnetics, vol. 53, Issue 11, pp. 1-11, Nov. 2017, doi: 10.1109/TMAG.2017.2711245.
Abstract - Spin-torque transfer magnetic random access memory (STT-MRAM) is a promising non-volatile memory technology widely considered to replace dynamic random access memory (DRAM). However, there still exist critical technical challenges to be tackled. For example, process variation and thermal fluctuation may lead to both write errors and read errors, severely affecting the reliability of the memory array. In this paper, we first propose a novel cascaded channel model for STT-MRAM that facilitates fast error rate simulations and more importantly the theoretical design and analysis of memory sensing and channel coding schemes. We analyze the raw bit error rate and probabilities of dominant error events, and derive the maximum likelihood decision criterion and the log-likelihood ratio of the cascaded channel. Based on these works, we further propose a two-stage hybrid decoding algorithm for extended Hamming codes for STT-MRAM. Simulation results demonstrate the effectiveness of the proposed hybrid decoding algorithm for improving the reliability of STT-MRAM in the presence of both write errors and read errors and supporting its potential applications, such as replacing DRAM.
K. Cai and K.A. Schouhamer Immink, 'A Cascaded Channel Model and Hybrid Decoding for Spin-Torque Transfer Magnetic Random Access Memory (STT-MRAM)', Proceedings IEEE Intermag, Dublin, April 2017, doi: 10.1109/INTMAG.2017.8008051.
K.A. Schouhamer Immink, 'Progress in Constrained Codes', Proceedings of Workshop AEW10: Concepts in Information Theory and Communications, Boppard, June 2017.

==2016==
K.A. Schouhamer Immink and V. Skachek, 'Minimum Pearson Distance Detection Using Mass-Centered Codewords in the Presence of Unknown Varying Offset', IEEE Journal on Selected Areas of Communications, Special Issue on Signal Processing and Coding for Digital Storage, vol. 34, pp. 2510-2517, Sept. 2016, doi: 10.1109/JSAC.2016.2603618.
Abstract - We consider the transmission and storage of data that use coded binary symbols over a channel, where a Pearson distance-based detector is used for achieving resilience against additive noise, unknown channel gain, and varying offset. We study minimum Pearson distance (MPD) detection in conjunction with a set, S, of codewords satisfying a center-of-mass constraint. We investigate the properties of the codewords in S, compute the size of S, and derive its redundancy for asymptotically large values of the codeword length n. The redundancy of S is approximately (3/2) log 2 n + a, where a = log 2 (p/24) 1/2 = -1.467.. for n odd and a = -0.467.. for n even. We describe a simple encoding algorithm whose redundancy equals 2 log 2 n+ o(logn). We also compute the word error rate of the MPD detector when the channel is corrupted with additive Gaussian noise.
J. H. Weber, T. G. Swart, and K.A. Schouhamer Immink, 'Simple Systematic Pearson Coding', IEEE International Symposium on Information Theory, Barcelona, Spain, pp. 385-389, July 2016.
V. Skachek and K.A. Schouhamer Immink, 'Minimum Pearson Distance Detection in the Presence of Unknown Slowly Varying Offset', IEEE International Symposium on Information Theory, Barcelona, Spain, pp. 195-199, July 2016. doi: 10.1109/ISIT.2016.7541288.
K.A. Schouhamer Immink, 'Low-complexity Near-optimal Detection of Dc^2-Balanced Codes', IET Electronics Letters, vol. 52, no. 9, pp. 719-720, April 2016. doi: 10.1049/el.2015.3933.
Abstract - Two constructions of a low-complexity near-optimal detection method of dc^2-balanced codes are presented. The methods presented are improvements on Slepian's algorithm for optimal detection of permutation codes.
J.H. Weber, K.A. Schouhamer Immink, and S. Blackburn, 'Pearson Codes', IEEE Trans. on Information Theory, vol. 62, no. 1, pp. 131-135, Jan. 2016. doi: 10.1109/TIT.2015.2490219.
Abstract - The Pearson distance has been advocated for improving the error performance of noisy channels with unknown gain and offset. The Pearson distance can only fruitfully be used for sets of q-ary codewords, called Pearson codes, that satisfy specific properties. We will analyze constructions and properties of optimal Pearson codes. We will compare the redundancy of optimal Pearson codes with the redundancy of prior art T-constrained codes, which consist of q-ary sequences in which T pre-determined reference symbols appear at least once. In particular, it will be shown that for q = 3, the two-constrained codes are optimal Pearson codes, while for q = 4 these codes are not optimal.

==2015==
K.A. Schouhamer Immink and J.H. Weber, 'Hybrid Minimum Pearson and Euclidean Distance Detection', IEEE Trans. on Communications, vol. 63, pp. 3290-3298, 2015, doi: 10.1109/TCOMM.2015.2458319.
Abstract - The reliability of mass storage systems, such as optical data recording and non-volatile memory (Flash), is seriously hampered by uncertainty of the actual value of the offset (drift) or gain (amplitude) of the retrieved signal. The recently introduced minimum Pearson distance detection is immune to unknown offset or gain, but this virtue comes at the cost of a lessened noise margin at nominal channel conditions. We will present a novel hybrid detection method, where we combine the outputs of the minimum Euclidean distance and Pearson distance detectors so that we may trade detection robustness versus noise margin. We will compute the error performance of hybrid detection in the presence of unknown channel mismatch and additive noise.
K.A. Schouhamer Immink and J.H. Weber, 'How to deal with channels with gain and offset mismatch?', Ninth Asian-European Workshop on Information Theory (AEW9), Matsuyama, Japan, 27-29 May 2015.
K.A. Schouhamer Immink and J.H. Weber, 'Detection in the Presence of Additive Noise and Unknown Offset', pp. 2028-2032, IEEE ICC2015, London, UK, 2015.
F. Sala, K.A. Schouhamer Immink, and L. Dolecek, 'Error Control Schemes for Modern Flash Memories: Solutions for Flash deficiencies', IEEE Consumer Electronics Magazine, pp. 66-73, Jan. 2015. doi: 10.1109/MCE.2014.2360965.
Abstract - Flash, already one of the dominant forms of data storage for mobile consumer devices, such as smartphones and media players, is experiencing explosive growth in cloud and enterprise applications. Flash devices offer very high access speeds, low power consumption, and physical resiliency. Our goal in this article is to provide a high-level overview of error correction for Flash. We will begin by discussing Flash functionality and design. We will introduce the nature of Flash deficiencies. Afterwards, we describe the basics of ECCs. We discuss BCH and LDPC codes in particular and wrap up the article with more directions for Flash coding.

==2014==
K.A. Schouhamer Immink, 'The Story of the Compact Disc... and Beethoven’s role in the specifications!', IEEE Consumer Electronics Magazine, vol. 3, no. 4, pp. 24-30, Oct. 2014, doi: 10.1109/MCE.2014.2338571.
K.A. Schouhamer Immink and J.H. Weber, 'Minimum Pearson Distance Detection for Multi-Level Channels with Gain and/or Offset Mismatch', IEEE Trans. on Information Theory, vol. 60, pp. 5966-5974, Oct. 2014. doi: 10.1109/TIT.2014.2342744.
Abstract - The performance of certain transmission and storage channels, such as optical data storage and nonvolatile memory (flash), is seriously hampered by the phenomena of unknown offset (drift) or gain. We will show that minimum Pearson distance (MPD) detection, unlike conventional minimum Euclidean distance detection, is immune to offset and/or gain mismatch. MPD detection is used in conjunction with T-constrained codes that consist of q-ary codewords, where in each codeword T reference symbols appear at least once. We will analyze the redundancy of the new q-ary coding technique and compute the error performance of MPD detection in the presence of additive noise. Implementation issues of MPD detection will be discussed, and results of simulations will be given.
K.A. Schouhamer Immink and J.H. Weber, 'The Application of Constrained Coding to Minimum Pearson Distance Detection in the Presence of Channel Mismatch', Third International Workshop on Advances in Communications. Boppard am Rhein, Germany, May 2014.
V. Skachek and K.A. Schouhamer Immink, 'Constant Weight Codes: An Approach Based on Knuth’s Balancing Method', IEEE Journal on Selected Areas in Communications, Special Issue on Mass Storage Systems, Vol. 32, No. 5, pp. 908-918, May 2014. doi: 10.1109/JSAC.2014.140511.
Abstract - In this article, we study properties and algorithms for constructing sets of constant weight codewords with bipolar symbols, where the sum of the symbols is a constant q, q\neq 0. We show various code constructions that extend Knuth's balancing vector scheme, q=0, to the case where q>0. We compute the redundancy of the new coding methods. Finally, we generalize the proposed methods to encoding of imbalanced arrays in two or more dimensions.
K.A. Schouhamer Immink, 'Coding Schemes for Multi-Level Flash Memories that are Intrinsically Resistant Against Unknown Gain and/or Offset Using Reference Symbols', IET Electronics Letters, vol. 50, no. 1, pp. 20-22, 2 Jan. 2014. doi: 10.1049/el.2013.3558.

==2013==
T.G. Swart and K.A. SchouhamerImmink, 'Prefixless q-ary Balanced Codes with ECC', IEEE Information Theory Workshop, Sevilla, Sept. 2013.
K.A. Schouhamer Immink, 'Coding Schemes for Multi-Level Channels with Unknown Gain and/or Offset', pp. 709-713, Proceedings IEEE International Symposium on Information Theory (ISIT), Istanbul, Turkey, July 2013, doi: 10.1109/ISIT.2013.6620318.
K.A. Schouhamer Immink, 'Prefixless q-ary Balanced Codes', Proceedings Eigtht Asian-European Workshop on Information Theory, Fundamental Concepts in Information Theory, Kamakura, Kanagawa, Japan, May 17-19, 2013.
J.H. Weber, K.A. Schouhamer Immink, P.H. Siegel, and T.G. Swart, 'Polarity-Balanced Codes', 2013 Information Theory and Applications Workshop, San Siego, Feb. 10-15, 2013.

==2012==
H.C. Ferreira, J.H. Weber, C.H. Heyman, and K.A. Schouhamer Immink, 'Markers to construct dc free (d, k) constrained balanced block codes using Knuth’s inversion', IET Electronics Letters, vol. 48, no. 19, pp. 1209-1211, Sept. 2012, doi: 10.1049/el.2012.1220.
Abstract - We report on Knuth's balancing scheme, which was originally developed for unconstrained binary codewords is adapted. Presented is a simple method to balance the NRZ runlength constrained block codes corresponding to (d, k) constrained NRZI sequences. A short marker violating the maximum runlength or k constraint is used to indicate the balancing point for Knuth's inversion. The marker requires fewer overhead bits and less implementation complexity than indexing the balancing point's address by mapping it onto a (d, k) or runlength constrained prefix, such as when applying Knuth's original scheme more directly. The new code construction may be attractive for future magnetic and especially optical recording schemes. In fact the current optical storage media, such as the CD, DVD and Blue Ray Disc, all attempt to achieve some suppression of low frequency components of the constrained codes, by exploiting a limited degree of freedom within the set of candidate (d, k) words.
K.A. Schouhamer Immink, 'High-Rate Maximum Runlength Constrained Coding Schemes Using Nibble Replacement', Trans. on Information Theory, pp. 6572-6580, vol. 58, No. 10, Oct. 2012, doi: 10.1109/ISIT.2011.6034135.
Abstract - In this paper, we will present coding techniques for the character-constrained channel, where information is conveyed using q-bit characters (nibbles), and where w prescribed characters are disallowed. Using codes for the character-constrained channel, we present simple and systematic constructions of high-rate binary maximum runlength constrained codes. The new constructions have the virtue that large lookup tables for encoding and decoding are not required. We will compare the error propagation performance of codes based on the new construction with that of prior art codes.
J.H. Weber, K.A. Schouhamer Immink, and H.C. Ferreira, 'Error-Correcting Balanced Knuth Codes', IEEE Trans. on Information Theory, vol. 58, pp. 82-89, Jan. 2012, doi:10.1109/TIT.2011.2167954.
Abstract - Knuth's celebrated balancing method consists of inverting the first bits in a binary information sequence, such that the resulting sequence has as many ones as zeroes, and communicating the index to the receiver through a short balanced prefix. In the proposed method, Knuth's scheme is extended with error-correcting capabilities, where it is allowed to give unequal protection levels to the prefix and the payload. The proposed scheme is very general in the sense that any error-correcting block code may be used for the protection of the payload. Analyses with respect to redundancy and block and bit error probabilities are performed, showing good results while maintaining the simplicity features of the original scheme. It is shown that the Hamming distance of the code is of minor importance with respect to the error probability.

==2011==
J. Lee and K.A. Schouhamer Immink, 'Advanced Soft-Reliability Information-Based Post-Viterbi Processor', IEEE Trans. on Consumer Electronics, vol. 57, pp. 1586-1591, Nov. 2011, doi: 10.1109/TCE.2011.6131129.
Abstract - This paper proposes a new soft-reliability information-based post-Viterbi processor with advanced noise-robustness for reducing probability of miss-correction and no correction of a conventional soft-reliability-based post-Viterbi processor. Among all likely error starting positions for prescribed error events, the two schemes are equal to attempt to correct error-type corresponding to a position with minimum one only if there exist positions where a soft-reliability estimate is negative. The main difference between the two schemes is how they acquire the softreliability estimate. The soft-reliability estimate of the new scheme is obtained through the elimination of the noisesensitive component from the log-likelihood ratio of the posteriori probabilities, which is the soft-reliability estimate of conventional scheme. As a result, the new scheme is based on more reliable soft-reliability information so reducing the probability of miss-correction and no correction.
V. Skachek and K.A. Schouhamer Immink, 'Constant Weight Codes: An Approach Based on Knuth’s Balancing Method', Proceedings IEEE International Symposium on Information Theory (ISIT), pp. 286-290, St. Petersburg, Russia, Aug. 2011.
K.A. Schouhamer Immink, J.H. Weber, and H.C. Ferreira, 'Balanced Runlength Limited Codes Using Knuth's Algorithm', Proceedings IEEE International Symposium on Information Theory (ISIT), pp. 282-285, St. Petersburg, Russia, Aug. 2011, doi: 10.1109/ISIT.2011.6034136.
K.A. Schouhamer Immink, 'High-Rate Maximum Runlength Constrained Coding Schemes Using Nibble Replacement', Proceedings IEEE International Symposium on Information Theory (ISIT), pp. 278-281, St. Petersburg, Russia, Aug. 2011.
J. Lee and K.A. Schouhamer Immink, 'A New Post-Viterbi Processor Based on Soft-Reliability Information', Trans. on Consumer Electronics, vol. 57, no. 2, pp. 842-847, May 2011, 10.1109/TCE.2011.5955231.
Abstract - This paper proposes a soft-reliability information- based post-Viterbi processor for reducing miss-correction of an error correlation filter-based post-Viterbi processor. The essential difference between the soft-reliability information- based and the error correlation filter-based post-Viterbi processors, is how to locate the most probable error starting position. The new scheme determines an error starting position based on a soft-reliability estimate, while the conventional scheme chooses an error starting position based on likelihood value. Among all likely error starting positions for prescribed error events, the new scheme attempts to correct error- type corresponding to the position only if there exists a position where the soft-reliability estimate is negative, while the conventional scheme performs error correction based on error- type and its error starting position of an error event associated with the maximum likelihood value. A correction made by the conventional scheme may result in miss-correction because the scheme does not have any criterion for judgment whether an estimated error starting position is correct. In case error correction is only performed when a position with negative soft-reliability estimate exists, the probability of miss-correction of the new scheme is less than the one of the conventional scheme.
J.H. Weber, K.A. Schouhamer Immink, and H.C. Ferreira, 'Extension of Knuth's Balancing Algorithm with Error Correction', Proceedings of the 32nd WIC Symposium on Information Theory in the Benelux, First joint WIC/IEEE SP Symposium on Information Theory and Signal Processing in the Benelux, ISBN 9789081721905, Brussels, Belgium, pp. 43-50, May 10-11, 2011.

==2010==
F. Song, S. Tao, F.T. Yu, S. Jutamulia, K.A. Schouhamer Immink, and K. Shono, Editors, Information Optics and Optical Data Storage, SPIE Society of Photo-Optical Instrumentation, Beijing, Nov. 2010, ISBN 9-78081948381-2.
J. Lee and K.A. Schouhamer Immink, 'Advanced Signal Processing Technique for Storage Systems', IEEE Trans. on Consumer Electronics, vol. 56. pp. 2373-2379, Nov. 2010, doi: 10.1109/TCE.2011.6131129.
Abstract - A post-Viterbi processor has found wide acceptance in recording systems since it can correct dominant error events at the channel detector output using only a few parity bits, and thereby significantly reduce the correction capacity loss of the error correction code. This paper presents two novel techniques for minimizing the mis-correction of a post-Viterbi processor based on an error detection code. One is a method for achieving a low probability of mis-selection in actual error-type. The other is a method for achieving a low probability of mis-positioning in error-location of an occurred error event. Simulation results show that an application of these techniques to conventional post-Viterbi processor considerably reduces the probability of mis-correction and the performance approaches the corresponding bit error rate and symbol error rate bound.
K.A. Schouhamer Immink, 'High-Rate Maximum Runlength Constrained Coding Schemes Using Base Conversion', Proceedings ISITA 2010, Taichung, Taiwan, pp. 469-472, Oct. 2010.
J.H. Weber and K.A. Schouhamer Immink, 'Knuth's Balanced Codes Revisited', IEEE Trans. Inform Theory, vol. 56, no. 4, pp.1673-1679, March 2010, doi: 10.1109/TIT.2010.2040868.
Abstract - In 1986, Don Knuth published a very simple algorithm for constructing sets of bipolar codewords with equal numbers of 1s and -1s, called balanced codes. Knuth's algorithm is well suited for use with large codewords. The redundancy of Knuth's balanced codes is a factor of two larger than that of a code comprising the full set of balanced codewords. In this paper, we will present results of our attempts to improve the performance of Knuth's balanced codes.
K.A. Schouhamer Immink, 'Any Song, Anytime, Anywhere', AES Journal, vol. 59, pp. 73-79, Jan/Feb. 2010.
K.A. Schouhamer Immink and J. Weber, 'Very Efficient Balanced Codewords', IEEE Journal on Selected Areas of Communications, Special Issue on Signal processing and coding for digital storage, vol. 28, no. 2, pp. 188-192, 2010, doi: 10.1109/JSAC.2010.100207.
Abstract - The prior art construction of sets of balanced codewords by Knuth is attractive for its simplicity and absence of look-up tables, but the redundancy of the balanced codes generated by Knuth's algorithm falls a factor of two short with respect to the minimum required. We present a new construction, which is simple, does not use look-up tables, and is less redundant than Knuth's construction. In the new construction, the user word is modified in the same way as in Knuth's construction, that is by inverting a segment of user symbols. The prefix that indicates which segment has been inverted, however, is encoded in a different, more efficient, way.
A. van Wijngaarden and K.A. Schouhamer Immink, 'Construction of Maximum Run-Length Limited Codes using Sequence Replacement Techniques', IEEE Journal on Selected Areas of Communications, Special Issue on Signal processing and coding for digital storage, vol. 28, no. 2, pp. 200-207, 2010, doi: 10.1109/JSAC.2010.100209.
Abstract - The sequence replacement technique converts an input sequence into a constrained sequence in which a prescribed subsequence is forbidden to occur. Several coding algorithms are presented that use this technique for the construction of maximum run-length limited sequences. The proposed algorithms show how all forbidden subsequences can be successively or iteratively removed to obtain a constrained sequence and how special subsequences can be inserted at predefined positions in the constrained sequence to represent the indices of the positions where the forbidden subsequences were removed. Several modifications are presented to reduce the impact of transmission errors on the decoding operation, and schemes to provide error control are discussed as well. The proposed algorithms can be implemented efficiently, and the rates of the constructed codes are close to their theoretical maximum. As such, the proposed algorithms are of interest for storage systems and data networks.
K. Cai, K.A. Schouhamer Immink, Y.X. Lee, and Z. Qin, 'The Art of Combining Distance-Enhancing Constrained Codes with Parity-Check Codes for Data Storage Channels', IEEE Journal on Selected Areas of Communications, Special Issue on Signal processing and coding for digital storage, vol. 28, pp. 208-217, 2010.
Abstract - A general and systematic code design methodology is proposed to efficiently combine constrained codes with PC codes for data storage channels. The proposed constrained PC code includes two component codes: the normal constrained (NC) code and the parity-related constrained (PRC) code. The NC code can be any distance-enhancing constrained code, such as the maximum transition run (MTR) code or repeated minimum transition runlength (RMTR) code. The PRC code can be any linear binary PC code. The constrained PC codes can be designed either in non-return-to-zero-inverse (NRZI) format or non-return-to-zero (NRZ) format. The rates of the designed codes are only a few tenths of a percent below the theoretical maximum. The proposed code design method enables soft information to be available to the PC decoder and facilitates soft decoding of PC codes. Furthermore, since errors are corrected equally well over the entire constrained PC codeword, error propagation due to parity bits is avoided. Efficient finite-state encoding methods are proposed to design capacity-approaching constrained codes and constrained PC codes with RMTR or MTR constraint. The generality and efficiency of the proposed code design methodology are shown by various code design examples for both magnetic and optical recording channels.

==2009==
J. Lee and K.A. Schouhamer Immink, 'DC-free Multimode Code Design Using Novel Selection Criteria for Optical Recording Systems', IEEE Trans. on Consumer Electronics, vol. 55. pp. 553-559, June 2009.
Abstract - DC-free run-length limited codes have been the cornerstone of all three generations of optical recording, CD, DVD and BD. Research into very efficient coding methods is paramount for the upcoming fourth generation. Guided Scrambling (GS) is an efficient coding method that has been reported in the literature. Under GS rules, a user word is translated into a plurality of possible candidate words, and among the candidate words the encoder selects the codeword with the least low-frequency spectral content. In our paper, we will present results of our attempts to improve the performance of GS-based codes. We will present new selection criteria and evaluate their performance and complexity. Specifically, we will evaluate the new selection criteria to the 2/3 (1,7) parity preserving code used in Blu-Ray Disc.
K.A. Schouhamer Immink and J. Weber, 'Simple Balanced Codes that Approach Capacity', Proc. IEEE ISIT2009 Conference, Seoul, Korea, pp. 1554-1858, June-July 2009, doi: 10.1109/ISIT.2009.5205828.
Abstract - The prior art construction of sets of balanced codewords by Knuth is attractive for its simplicity and absence of look-up tables, but the redundancy of the balanced codes generated by Knuth's algorithm falls a factor of two short with respect to capacity. We present a new construction, which is simple, does not use look-up tables, and is less redundant than Knuth's construction. In the new construction, the user word is modified in the same way as in Knuth's construction, that is by inverting a segment of user symbols. The prefix that indicates which segment has been inverted, however, is encoded and decoded in a different, more efficient, way.
A. Kumar and K.A. Schouhamer Immink, 'Design of Close-to-Capacity Constrained Codes for Multi-Level Optical Recording', IEEE Trans. on Communications, vol. 57, no. 4, pp. 954-959, April 2009, doi: 10.1109/TCOMM.2009.04.041138..
Abstract - We report a new method for designing (M,d, k) constrained codes for use in multi-level optical recording channels. The method allow us to design practical codes, which have simple encoder tables and decoders having fixed window length. The codes presented here for the d = 1 and d = 2 cases, achieve higher storage densities than previously reported codes, and come within 0.3 - 0.7% of capacity.
J. Lee and K.A. Schouhamer Immink, 'An Efficient Decoding Strategy of 2D-ECC for Optical Recording Systems', IEEE Trans. on Consumer Electronics, vol. 55, no. 3, pp. 1360-1363, Aug. 2009, doi: 10.1109/TCE.2009.5278000.
Abstract - Two-dimensional error correction codes (2DECCs) have been the cornerstone of all three generations of optical recording - CD, DVD and BD. Research into powerful error correction methods is paramount for the development of high-capacity optical recording systems. A Reed-Solomon product-code (RS-PC) for DVD systems performs error and erasure decoding by giving and taking erasure information between two ECCs. In this paper, we will present a new error correction method that performs erasure decoding using the only erasure information supplied from a modulation code decoder - more specifically, the EFMPlus code for DVD systems. We will evaluate the decoding efficiency of the new error correction method under a channel environment with various error types.
K.A. Schouhamer Immink and K. Cai, 'Simple classes of constrained systems with unconstrained positions that outperform the maxentropic bound', IEEE Trans. on Information Theory, vol. 55, no. 5, pp. 2000-2003, May 2009, doi: 10.1109/TIT.2009.2016053.
Abstract - The Wijngaarden-Immink (WI) scheme is a combined modulation/ECC coding scheme, where arbitrary user data are translated into a constrained sequence in which predefined positions are reserved for error-correcting codes (ECC) parity. Besides offering the benefit of combined modulation/ECC coding, the WI scheme has two extra benefits. They are (a) error propagation is limited to the constrained symbols, since symbols on the unconstrained positions are not related, and (b) code hardware is limited to a lookup table of the coded part. We will describe classes of simple bit-stuffing schemes that require less redundancy than predicted by the bound based on the performance of maxentropic constrained systems presented by Campello and Poo.

==2008==
K. Cai, K.A. Schouhamer Immink, and Z. Qin, 'Distance-Enhancing Constrained Codes for Optical Recording Channels', IEEE Globecom Conference, New Orleans, Dec. 2008.
A. Kumar and K.A. Schouhamer Immink, 'Construction of Capacity Achieving (M,d,infty) Constrained Codes with Least Decoder Window Length', IEEE Trans. on Information Theory, vol. 54, nr. 10, pp. 4724-4726, Oct. 2008, doi: 10.1109/TIT.2008.928971.
Abstract - We present capacity achieving multilevel run-length-limited (ML-RLL) codes that can be decoded by a sliding window of size 2.
K. Cai and K.A. Schouhamer Immink, 'A General Construction of Constrained Parity-Check Codes for Optical Recording,' IEEE Trans. on Communications, vol. 56, no. 7, pp. 1070-1079, July 2008, doi: 10.1109/TCOMM.2008.060502.
Abstract - This paper proposes a general and systematic code design method to efficiently combine constrained codes with parity-check (PC) codes for optical recording. The proposed constrained PC code includes two component codes: the normal constrained (NC) code and the parity-related constrained (PRC) code. They are designed based on the same finite state machine (FSM). The rates of the designed codes are only a few tenths below the theoretical maximum. The PC constraint is defined by the generator matrix (or generator polynomial) of a linear binary PC code, which can detect any type of dominant error events or error event combinations of the system. Error propagation due to parity bits is avoided, since both component codes are protected by PCs. Two approaches are proposed to design the code in the non-return-to-zero-inverse (NRZI) format and the non-return-to-zero (NRZ) format, respectively. Designing the codes in NRZ format may reduce the number of parity bits required for error detection and simplify post-processing for error correction. Examples of several newly designed codes are illustrated. Simulation results with the Blu-Ray disc (BD) systems show that the new d = 1 constrained 4-bit PC code significantly outperforms the rate 2/3 code without parity, at both nominal density and high density.
K.A. Schouhamer Immink and K. Cai, 'Simple classes of constrained systems with unconstrained positions that outperform the maxentropic bound', IEEE ISIT2008 Conference, Toronto, pp. 1553-1556, July 2008, doi: 10.1109/ISIT.2008.4595248.
Abstract - The Wijngaarden-Immink (WI) scheme is a combined modulation/ECC coding scheme, where arbitrary user data are translated into a constrained sequence in which predefined positions are reserved for ECC parity. Besides offering the benefit of combined modulation/ECC coding, the WI scheme has two extra benefits. They are a) error propagation is limited to the constrained symbols, since symbols on the unconstrained positions are not related, and b) code hardware is limited to a look-up table of the coded part. We will describe classes of simple bit-stuffing schemes that require less redundancy than predicted by the bound based on the performance of maxentropic constrained systems presented by Campello et al. [1] and Poo et al. [21].
J.H. Weber and K.A. Schouhamer Immink, 'Knuth's Balancing of Codewords Revisited', Proceedings IEEE International Symposium on Information Theory (ISIT), Toronto, Canada, pp. 1567-1571, July 2008, doi: 10.1109/ISIT.2008.4595251.
Abstract - In 1986, Don Knuth published a very simple algorithm for constructing sets of bipolar codewords with equal numbers of 1s and 0s, called balanced codes. Knuth's algorithm is, since look-up tables are absent, well suited for use with large codewords. The redundancy of Knuths balanced codes is a factor of two larger than that of a code comprising the full set of balanced codewords. In our paper we present results of our attempts to improve the performance of Knuths balanced codes.

==2007==
K.A. Schouhamer Immink, Shannon, Beethoven, and the Compact Disc, IEEE Information Theory Society Newsletter, Vol. 57, No. 4, Dec. 2007.
Abstract - An audio compact disc (CD) holds up to 74 minutes, 33 seconds of sound, just enough for a complete mono recording of Ludwig von Beethoven's Ninth Symphony ('Alle Menschen werden Brüder') at probably the slowest pace it has ever been played, during the Bayreuther Festspiele in 1951 and conducted by Wilhelm Furtwängler. Each second of music requires about 1.5 million bits, which are represented as tiny pits and lands ranging from 0.9 to 3.3 micrometers in length. More than 19 billion channel bits are recorded as a spiral track of alternating pits and lands over a distance of 5.38 kilometers (3.34 miles), which are scanned at walking speed, 4.27 km per hour. This year it is 25 years ago that Philips and Sony introduced the CD. In this jubilee article I will discuss the various crucial technical decisions made that would determine the technical success or failure of the new medium.
K.A. Schouhamer Immink, 'The Birth of the Compact Disc', IEEE Consumer Electronics Society Newsletter, Dec. 2007.
K. Cai, K.A. Schouhamer Immink, Z. Qin, X.S. Miao, L.P. Shi, and T.C. Chong, 'Error Correction Code Failure Rate Analysis for Parity-Check-Coded Optical Recording Systems', Proceedings ISOM Conference, Singapore, pp. 196-197, Oct. 21-25, 2007.

==2006==
K. Cai and K.A. Schouhamer Immink, 'On the Number of Encoder States for Certain Capacity Approaching d=1 Codes'. IEEE Trans. on Inform. Theory, vol. 52, no. 7, pp. 3313-3319, July 2006, doi: 10.1109/TIT.2006.876231.
Abstract - The relationship between the number of encoder states and the probable size of certain runlength-limited (RLL) codes is derived analytically. By associating the number of encoder states with (generalized) Fibonacci numbers, the minimum number of encoder states is obtained, which maximizes the rate of the designed code, irrespective of the codeword length.
K. Cai, K.A. Schouhamer Immink, J. Bergmans, and L.P. Shi, 'Constrained Parity-Check Code and Post-Processor for Advanced Blue Laser Disc', JJAP, vol. 45, No. 2B, pp. 1071-1078, 2006.

==2005==
K. Cai and K.A. Schouhamer Immink, 'On the Number of Encoder States for Certain Capacity Approaching d=1 Codes', IEEE ISIT2005 Conference, Adelaide, Sept. 2005, doi: 10.1109/ISIT.2005.1523590.
Abstract - The number of encoder states is a key measure of complexity of a finite-state constrained code. In this paper, we derive analytically the relationship between the number of encoder states and the size of capacity approaching d = 1 codes. By defining the number of encoder states as (generalized) Fibonacci numbers, we obtain the optimum encoder states, which maximize the size of the designed code with minimum number of states, for any desired codeword length
D. Xu, K.A. Schouhamer Immink, and K. Shono, Advances in Optical Data Storage Technology, SPIE Society of Photo-Optical Instrumentation, Beijing, Jan. 2005, ISBN 0-8194-5598-9.
K. Cai and K.A. Schouhamer Immink, 'On the Design of Efficient Constrained Parity-Check Codes for Optical Recording', Proceedings IEEE International Symposium on Information Theory (ISIT), Adelaide, Sept. 2005, doi: 10.1109/ISIT.2005.1523588.
Abstract - This paper proposes a general and systematic way to efficiently combine constrained codes with parity-check (PC) codes for optical recording.
K. Cai, K.A. Schouhamer Immink, J. Bergmans, and L.P. Shi, 'Novel Constrained Parity-Check Code and Post-Processor for Advanced Blue Laser Disk', International Symposium on Optical Memory and Optical Data Storage, ISOM/ODS05, Honolulu, Hawaii, July 10-14, 2005, doi: 10.1364/ISOM_ODS.2005.TuB5.

==2004==
K.A. Schouhamer Immink, Codes for Mass Data Storage Systems, Second fully revised edition, Shannon Foundation Publishers, Eindhoven, The Netherlands, Nov. 2004. ISBN 90-74249-27-2. Download here
K.A. Schouhamer Immink, Coding and Signal Processing for Magnetic Recording Systems, B. Vasic and E.M. Kurtas (Editors), CRC Press, Series: Computer Engineering Volume: 2, Nov. 2004, ISBN 08-49315-24-7.
K.A. Schouhamer Immink, Codes for Mass Data Storage Systems (in Chinese), Science Press, Beijing, China, 2004. ISBN 7-03-013379-X.
A.J. van Wijngaarden and K.A. Schouhamer Immink, 'On Guided Scrambling with Guaranteed Maximum Run-length Constraints', IEEE Int. Symposium on Information Theory (ISIT), Chicago, June 2004, doi: 10.1109/ISIT.2004.1365126.
A.J. van Wijngaarden and K.A. Schouhamer Immink, 'On the Selection of Guided Scrambling Sequences that Provide Guaranteed Maximum Run-length Constraints', WIC Symposium on Information Theory, Rolduc, pp. 25-29, May 2004.
J.H. Weber, L.M.G.M. Tolhuizen, and K.A. Schouhamer Immink, 'Channel Coding', Chapter 4 (pp. 89-116) in "Information Theory in the Benelux: An overview of WIC symposia 1980-2003", R.L. Lagendijk, L.M.G.M. Tolhuizen, and P.H.N. de With (Editors), Werkgemeenschap voor Informatie- en Communicatietheorie (WIC), Enschede, May 2004, ISBN 90-71048-19-5.
K.A. Schouhamer Immink and K. Cai, 'On the Size of a Type of RLL codes', WIC Symposium on Information Theory, Rolduc, pp. 39-46, May 2004.
K.A. Schouhamer Immink, 'From Analog to Digital', Heyser Memorial Lecture, AES 116th Convention, Messe Berlin - Berlin, Germany, May 9, 2004.

==2003==
A.J. van Wijngaarden and K.A. Schouhamer Immink, 'On Error Propagation Assessment of High-rate Runlength-Limited Codes', IEEE Int. Symposium on Information Theory (ISIT), Yokohama, June 2003.
Ming Jin, K.A. Schouhamer Immink, and B. Farhang-Boroujeny, 'Design Techniques for Weakly Constrained Codes', Trans. on Communications, vol. 51, no. 5, pp. 709-714, May 2003, doi: 10.1109/TCOMM.2003.811377.
Abstract - A general method of constructing run-length limited (d, k) constrained codes from arbitrary sequences is introduced. This method is then combined with the method of guided scrambling for constructing a class of weakly constrained codes. The proposed codes are analyzed for the case of d=0 and are shown to give results which are better or comparable to those of the best available codes, however, at the cost of failure with some very low probability. For d>0, the code efficiency of the codes constructed according to the proposed method reduces significantly.
K.A. Schouhamer Immink, J.Y. Kim, S.W. Suh, and S.K. Ahn, 'Efficient Dc-free RLL codes for Optical Recording', IEEE Trans. on Communications, vol. 51, no. 3, pp. 326-331, March 2003, doi: 10.1109/TCOMM.2003.809752.
Abstract - Runlength-limited (RLL) codes, generically designated as (d, k) RLL codes, have been widely and successfully applied in modern magnetic and optical recording systems. The design of codes for optical recording is essentially the design of combined dc-free and runlength limited (DCRLL) codes. We discuss the development of very efficient DCRLL codes, which can be used in upcoming generations of high-density optical recording products.

==2002==
K.A. Schouhamer Immink, 'President's Message', AES Journal, vol. 51, pp. 1011, Dec. 2002.
K.A. Schouhamer Immink, 'A Comparison of the Low-Frequency Properties of DC-free Codes Generated by Look-Ahead and Guided Scrambling Techniques', Proc. ISITA 2002, Xi'an, China, pp. 271-273, Oct. 2002
K.A. Schouhamer Immink, J.Y. Kim, S.W. Suh, and S.K. Ahn, 'Construction of Efficient Dc-free RLL codes for Optical Recording', Japanese Journal on Applied Physics , Part 1, vol. 41, No. 3B, pp. 1777-1780, March 2002.
S.W. Suh, S.K. Ahn, J.Y. Kim, and K.A. Schouhamer Immink, 'Performance of GS913 (guided scrambling nine to thirteen) modulation code for high density rewritable optical disc', Optical Memory and Optical Data Storage Topical Meeting, Honolulu, pp. 153-155, 2002, doi: 10.1109/OMODS.2002.1028598.
==2001==
K.A. Schouhamer Immink, 'Levensbericht (obituary) Claude E. Shannon', Koninklijke Nederlandse Akademie van Wetenschappen, pp. 101-105, 2001.
K.A. Schouhamer Immink, J.Y. Kim, S.W. Suh, and S.K. Ahn, 'Extremely Efficient Dc-free RLL codes for Optical Recording', IEEE Trans. on Consumer Electronics, pp. 910-914, Nov. 2001.
Ming Jin, K.A. Schouhamer Immink, and B. Farhang-Boroujeny, 'A Novel Design Technique for Weakly Constrained Codes', Proceedings IEEE Glocecom, San Antonio, Nov. 2001, doi: 10.1109/GLOCOM.2001.965975.
K.A. Schouhamer Immink, 'Codes for Optical Recording', Proc. of the 6th International Symposium on Communications Theory and Applications, Ambleside, UK, 15-20 July 2001.
K.A. Schouhamer Immink, J.Y. Kim, S.W. Suh, and S.K. Ahn, 'Extremely Efficient Dc-free RLL codes for Optical Recording', Proc. ICCE, Los Angeles, pp. 260-261, June 2001.
K.A. Schouhamer Immink, 'Efficient Dc-free RLL codes for optical recording', Proc. IEEE ISIT2001, pp. 270, Washington, USA, June 23, 2001, doi: 10.1109/ISIT.2001.936133.
K.A. Schouhamer Immink, J.Y. Kim, S.W. Suh, and S.K. Ahn, 'Extremely Efficient Dc-free RLL codes for Optical Recording', Proceedings SPIE ODS, Santa Fe, USA, April 2001.
J. Moon, H. Thapar, B.V.K.V. Kumar, and K.A. Schouhamer Immink, 'Editorial Signal Processing for High Density Storage Channels', IEEE Journal on Selected Areas of Communications, Special Issue on Signal processing and coding for digital storage, vol. 19, pp. 577-581, April 2001, doi: 10.1109/JSAC.2001.920166.
A. van Wijngaarden and K.A. Schouhamer Immink, 'Maximum Runlength Limited Codes with Error Control Capabilities', IEEE Journal on Selected Areas of Communications, Special Issue on Signal processing and coding for digital storage, vol. 19, no. 4, pp. 602-611, April 2001.
Abstract - New methods are presented to protect maximum runlength-limited sequences against random and burst errors and to avoid error propagation. The methods employ parallel conversion techniques and enumerative coding algorithms that transform binary user information into constrained codewords. The new schemes have a low complexity and are very efficient. The approach can be used for modulation coding in recording systems and for synchronization and line coding in communication systems. The schemes enable the usage of high-rate constrained codes, as error control can be provided with similar capabilities as for unconstrained sequences.
K.A. Schouhamer Immink, 'A Survey of Codes for Optical Disc Recording', IEEE Journal on Selected Areas of Communications, Special Issue on Signal processing and coding for digital storage, vol. 19, no. 4, pp. 756-764, April 2001, 10.1109/49.920183.
Abstract - Codes were designed for optical disk recording system and future options were explored. The designed code was a combination of dc-free and runlength limited (DCRLL) codes. The design increased minimum feature size for replication and sufficient rejection of low-frequency components enabling a simple noise free tracking. Error-burst correcting Reed-Solomon codes were suggested for the resolution of read error. The features of DCRLL and runlength limited (RLL) sequences was presented and practical codes were devised to satisfy the given channel constraints. The mechanism of RLL codes supressed the components of the genarated sequences. The construction and performance of alternative Eight to fourteen modulation (EFM)-like codes was studied.

==2000==
V. Braun and K.A. Schouhamer Immink, 'An Enumerative Coding Technique for Dc-free Runlength-Limited Sequences', IEEE Trans. on Communication, vol. 48, no. 12, pp. 2024-2031, Dec. 2000, 10.1109/26.891213.
Abstract - We present an enumerative technique for encoding and decoding DC-free runlength-limited sequences. This technique enables the encoding and decoding of sequences approaching the maxentropic performance bounds very closely in terms of the code rate and low-frequency suppression capability. Use of finite-precision floating-point notation to express the weight coefficients results in channel encoders and decoders of moderate complexity. For channel constraints of practical interest, the hardware required for implementing such a quasi-maxentropic coding scheme consists mainly of a ROM of at most 5 kB
W.Y.H. Wang, K.A. Schouhamer Immink, X.B. Xu, and C.T. Chong, 'Guided Scrambling: A New Coding Technique for Holographic Storage', Proc. IEEE GlobeCom 2000, San Francisco, Dec. 2000.
K.A. Schouhamer Immink, 'Coding for optical disc recording', IEEE ICC2000 Workshop, New Orleans, USA, June 2000.
K.A. Schouhamer Immink and A.J.E.M. Janssen, 'Capacity of weakly (d,k) constrained sequences', Proc. IEEE ISIT2000, Sorrento, Italy, pp. 144, June 16-21, 2000.
K.A. Schouhamer Immink and W.Y.H. Wang, 'A comparison of two dc-free rll coding schemes', Proc. IEEE ISIT2000, Sorrento, Italy, pp. 352, June 16-21, 2000.
A.J.E.M. Janssen and K.A. Schouhamer Immink, An Entropy Theorem for Computing the Capacity of Weakly (d,k) Constrained Sequences', IEEE Trans. Inform. Theory, vol. 46, no. 3, pp. 1034-1038, May 2000, doi: 10.1109/18.841180.
Abstract - We find an analytic expression for the maximum of the normalized entropy -S_ieTp_iln p_i/S_ieTip_i where the set T is the disjoint union of sets S_n of positive integers that are assigned probabilities P_n, S_nP_n=1. This result is applied to the computation of the capacity of weakly (d,k)-constrained sequences that are allowed to violate the (d,k)-constraint with small probability
W.Y.H. Wang, K.A. Schouhamer Immink, X.B. Xu, and C.T. Chong, 'An Efficient Coding Technique for Holographic Storage with the Method of Guided Scrambling,Proc. SPIE ODS 2000, pp. 191-196, Whistler, Canada, 14-17, May 2000.
K.A. Schouhamer Immink, 'Dc-free codes of rate n/(n-1), n odd', IEEE Trans. Inform. Theory, pp. 633-634, March 2000.

==1999==
K.A. Schouhamer Immink, Codes for Mass Data Storage Systems, Shannon Foundation Publishers, Eindhoven, The Netherlands, 1999. ISBN 90-74249-23-X. Download here
K.A. Schouhamer Immink and A.J.E.M. Janssen, 'Error Propagation Assessment of Enumerative Coding Schemes', IEEE Trans. Inform. Theory, pp. 2591-2594, no. 7, Nov. 1999.
Y.H.W. Wang, K.A. Schouhamer Immink, X.B. Xu, and C.T. Chong, 'Comparison of two coding schemes for generating dc-free RLL sequences', Int. Symp. on Optical Data Storage, Hawaii, July 1999.
K.A. Schouhamer Immink, 'The Future of Digital Audio Recording', J. Audio Eng. Soc., vol. 47, pp. 171-172, 1999.
G. Khachatrian and K.A. Schouhamer Immink, 'Construction of simple runlength-limited codes', IEE Electronics Letters, vol. 35, no 2, pp. 140, 1999.
K.A. Schouhamer Immink, 'A Survey of High-rate Codes', Proc. Asian Symposium on Information Storage Technology', pp. 133-139, Singapore, Jan. 25-26, 1999.
K.A. Schouhamer Immink, P.H. Siegel, and J.K. Wolf, 'Codes for recording channels', Information Theory: 50 Years of Discovery, S.W. McLaughlin and S. Verdu (Editors), IEEE Press, 1999, pp. 216-255, ISBN 7-80353-63-3.

==1998==
K.A. Schouhamer Immink, P.H. Siegel, and J.K. Wolf, 'Codes for recording channels', Invited for the special issue of IEEE Trans. Inform. Theory, pp. 2260-2299, Oct. 98, vol. 44, 1998 which commemorates the 50th anniversary of Shannon's landmark paper, doi: 10.1109/18.720539.
Abstract - Constrained codes are a key component in digital recording devices that have become ubiquitous in computer data storage and electronic entertainment applications. This paper surveys the theory and practice of constrained coding, tracing the evolution of the subject from its origins in Shannon's classic 1948 paper to present-day applications in high-density digital recorders. Open problems and future research directions are also addressed
K.A. Schouhamer Immink, 'Dc-free codes of rate n/(n-1), n odd', Proc. IEEE ISIT98, Boston, USA, Aug 16-21, 1998.
A. van Wijngaarden and K.A. Schouhamer Immink, 'Efficient Error Control Schemes for Modulation and Synchronization Codes', Proceedings IEEE ISIT98, Boston, USA, Aug. 16-21, 1998.
K.A. Schouhamer Immink and A.J.E.M. Janssen, 'Error Propagation Assessment of Enumerative Coding Schemes', Proc. IEEE ICC98, Atlanta, June 1998.
K.A. Schouhamer Immink, 'The Compact Disc Story', AES Journal, pp. 458-465, May 1998.

==1997==
K.A. Schouhamer Immink, 'High-rate constrained codes', Journal of IEICE, IT97-56, (1997-12), Dec. 1997 (Invited paper).
K.A. Schouhamer Immink and A.J.E.M. Janssen, 'Effects of Floating-Point Arithmetic in Enumerative Coding', Proc. 18th Symposium on Information Theory Symposium in the Benelux, Veldhoven, The Netherlands, pp. 70-75, May 1997.
A.J. van Wijngaarden and K.A. Schouhamer Immink, 'On the Construction of Constrained Codes employing Sequence Replacement Techniques', Proceedings IEEE International Symposium on Information Theory (ISIT), Ulm, Germany. pp. 144, June 1997.
K.A. Schouhamer Immink, 'Weakly constrained codes', IEE Electronics Letters, vol. 33, no. 23, pp. 1943-1944, Nov. 1997.
K.A. Schouhamer Immink, 'Channel Codes for Digital Magnetic and Optical Recorders', Chapter 8, Digital Consumer Electronics Handbook, McGraw-Hill, 1997.
K.A. Schouhamer Immink, 'EFM coding: Squeezing the last bits', IEEE Trans. Consumer Electr., vol. CE-43, pp. 491-495, Aug. 1997, doi: 10.1109/30.628663.
Abstract - 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
K.A. Schouhamer Immink, 'A Practical Method for Approaching the Channel Capacity of Constrained Channels', IEEE Trans. Inform. Theory, vol. IT-43, no. 5, pp. 1389-1399, Sept. 1997, doi: 10.1109/18.623139.
Abstract - A new coding technique is proposed that translates user information into a constrained sequence using very long codewords. Huge error propagation resulting from the use of long codewords is avoided by reversing the conventional hierarchy of the error control code and the constrained code. The new technique is exemplified by focusing on (d, k)-constrained codes. A storage-effective enumerative encoding scheme is proposed for translating user data into long dk sequences and vice versa. For dk runlength-limited codes, estimates are given of the relationship between coding efficiency versus encoder and decoder complexity. We show that for most common d, k values, a code rate of less than 0.5% below channel capacity can be obtained by using hardware mainly consisting of a ROM lookup table of size 1 kbyte. For selected values of d and k, the size of the lookup table is much smaller. The paper is concluded by an illustrative numerical example of a rate 256/466, (d=2, k=15) code, which provides a serviceable 10% increase in rate with respect to its traditional rate 1/2, (2, 7) counterpart
K.A. Schouhamer Immink, 'A Survey of Channel Codes for Digital Recorders', Tijdschrift van het NERG, vol. 62, nr. 1, pp. 20-29, 1997.
K.A. Schouhamer Immink and L. Patrovics, 'Performance Assessment of DC-free Multi-Mode Codes', IEEE Trans. Commun., vol. COM-45, no. 3, pp. 293-299, March 1997, doi: 10.1109/26.558690.
Abstract - We report on a class of high-rate de-free codes, called multimode codes, where each source word can be represented by a codeword taken from a selection set of codeword alternatives. Conventional multimode codes will be analyzed using a simple mathematical model. The criterion used to select the "best" codeword from the selection set available has a significant bearing on the performance. Various selection criteria are introduced and their effect on the performance of multimode codes will be examined.
K.A. Schouhamer Immink, 'Digital Versatile Disc (DVD)', IEE Half-Day Colloquium on New High Capacity Digital Media and Their Application, 1997.

==1996==
K.A. Schouhamer Immink and G. van den Enden, 'A Comparison of Rotary- and Stationary-Head Video Tape Recorders', IEEE Trans. Consumer Electr., vol. CE-42, pp. 998-1002, no. 4, Nov. 1996, doi: 0.1109/30.555805.
Abstract - In magnetic tape recording, two approaches have emerged in which essentially the same medium is tracked in two different ways: rotary- and stationary-head recorders. Both approaches are commonly employed in digital audio and data recording, but since the introduction of the first analog video recorders in the early 50s, rotary-head recorders (either helical or transverse scan) have held undivided sway in the video domain. The advent of various new enabling techniques such as (MPEG) source coding and multi-trade heads may affect the hegemony of the rotary-head machine. The article appraises both types of transport in an attempt to establish which approach might be considered for a given application
K.A. Schouhamer Immink, 'Code configuration for avoiding error propagation', IEE Electronics Letters, vol. 32, No. 24, pp. 2191-2192, Nov. 1996.
K.A. Schouhamer Immink, 'EFMPlus: The coding technique of the DVD', Nikkei Electronics, no. 675, pp. 161-165, Nov. 1996 (in Japanese).
K.A. Schouhamer Immink and A. van Wijngaarden, 'Simple High-Rate Constrained Codes', IEE Electronics Letters, vol 32, pp. 1877, no. 20, Sept. 1996.
L. Patrovics and K.A. Schouhamer Immink, 'Encoding of dklr-sequences using one weight set', IEEE Trans. Inform. Theory, vol. IT-42, pp. 1553-1555, no. 5, Sept. 1996, doi: 0.1109/18.532899.
Abstract - Traditional schemes for encoding and decoding runlength-constrained sequences using the enumeration principle require two sets of weighting coefficients. A new enumeration is presented requiring only one set of coefficients
K.A. Schouhamer Immink, 'A rate 4/6, (d=1, k=11) Block Decodable RLL Code', IEEE Trans. Inform. Theory, vol. IT-42, no. 5, pp. 1551-1553, Sept. 1996, doi: 10.1109/18.532898.
Abstract - A new rate 4/6, (d=1, k=11) runlength-limited code which is well adapted to byte-oriented storage systems is presented. The new code has the virtue that it can be decoded on a block basis, i.e., without knowledge of previous or next codewords, and, therefore, it does not suffer from error propagation. This code is particularly attractive as many commercially available Reed-Solomon codes operate in GF(2^8)
K.A. Schouhamer Immink, 'The Digital Versatile Disc (DVD): System Requirements and Channel Coding', SMPTE Journal, vol. 105, pp. 483-489, no. 8, Aug. 1996.
A. van Wijngaarden and K.A. Schouhamer Immink, 'Combinatorial construction of high-rate runlength-limited codes', Proceedings IEEE Globecom, London, pp. 343-347, Nov. 1996.
K.A. Schouhamer Immink, 'Figure 1 Revisited', Proceedings ISITA'96, Victoria, Canada, Sept. 1996.

==1995==
L.M.G.M. Tolhuizen, K.A. Schouhamer Immink, and H.D.L. Hollmann, 'Constructions and Properties of Block Codes for Partial-Response Channels', IEEE Trans. Inform. Theory, vol. 41, no. 6, pp. 2019-2026, Nov. 1995, doi: 10.1109/18.476329.
Abstract - We report on block-coding techniques for partial-response channels with transfer function (1∓D^m), m=1, 2, ... . We consider various constructions of block codes with prescribed minimum Euclidean distance. Upper and lower bounds to the size of a code with minimum squared Euclidean distance greater than unity are furnished. A table is presented of cardinalities of codes of small length with prescribed minimum squared Euclidean distance.
K.A. Schouhamer Immink, 'EFMPlus: The Coding Format of the MultiMedia Compact Disc', IEEE Trans. Consumer Electr., vol. CE-41, no. 3, pp. 491-497, Aug. 1995, doi: 10.1109/30.468040.
Abstract - 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.
K.A. Schouhamer Immink, G.J. van den Enden, and J.A.H. Kahlman, 'System Requirements of a Stationary-Head Multi-Track Recorder', IEEE Trans. Magn., vol 31, no. 2, pp. 1027-1030, March 1995, doi: 10.1109/20.364779.
Abstract - We report on the design considerations of stationary-head multi-track magnetic recorders. We focus on the particular reasons for adopting the rate 8/10, DC-free recording code, the full-response detection method, and the clock recovery circuitry. Implementation issues of the channel chip, particularly related to cost and power consumption, are addressed. A new multi-track phase-lock loop (PLL) has been developed, in order to improve the recorder's robustness against time-base variations.
J.A.H. Kahlman and K.A. Schouhamer Immink, 'Channel Code with Embedded Pilot Tracking Tones for DVCR', IEEE Trans. Consumer Electr., vol. CE-41, no. 1, pp. 180-185, Feb. 1995, doi: 0.1109/30.370325.
Abstract - The proper functioning of a digital video recorder is largely governed by the selection of a suitable channel code in conjunction with both the detection method and the tracking system. The channel code for the digital video cassette recorder (DVCR) satisfies a variety of design requirements. The paper provides an overview of those requirements. A detailed description is given of the constriction of the new channel code, called 24?25 code, that complies with the given constraints and involves only a minor drawback in terms of the overhead needed. The servo position information is recorded as low-frequency components, pilot tracking tones, which are embedded in the recorded stream of binary digits.
K.A. Schouhamer Immink, 'MultiMedia Compact Disc: Channel Coding and System Requirements', Proceedings 99th AES Convention, New York, Oct. 1995.
K.A. Schouhamer Immink, Editor, Proceedings IEEE International Symposium on Synchronization, Essen, Germany, Dec 1995, Shannon Foundation Publishers, ISBN 90-74249-07-8.
L. Patrovics and K.A. Schouhamer Immink, 'Performance Assessment of Guided Scrambling', Proceedings IEEE Third Symposium on Communications and Vehicular Technology in the Benelux, Eindhoven, The Netherlands, pp. 122-127, Oct 25-26, 1995.
K.A. Schouhamer Immink, 'Constructions of Almost-Block-Decodable RLL Codes', IEEE Trans. Inform. Theory, vol. 41, no. 1, pp. 284-287, Jan. 1995, doi: 10.1109/18.370099.
Abstract - Describes a new technique for constructing fixed-length (d,k) runlength-limited block codes. The new codes are very close to block-decodable codes, as decoding of the retrieved sequence can be accomplished by observing (part of) the received codeword plus a very small part (usually only a single bit) of the previous codeword. The basic idea of the new construction is to uniquely represent each source word by a (d,k) sequence with specific predefined properties, and to construct a bridge of ß, 1⩽ß⩽d, merging bits between every pair of adjacent words. An essential element of the new coding principle is look ahead. The merging bits are governed by the state of the encoder (the history), the present source word to be translated, and by the upcoming source word. The new constructions have the virtue that only one look-up table is required for encoding and decoding.

==1994==
V. Braun, K.A. Schouhamer Immink, M. Ribeiro, and G. v.d. Enden, 'On the Application of Sequence Estimation Algorithms in the DCC', IEEE Trans. Consumer Electr., vol. CE-40, no. 4, pp. 992-998, Nov. 1994, doi: 10.1109/30.338350.
Abstract - In the current digital compact cassette (DCC) recorder, a straightforward threshold detection scheme is applied which does not exploit the distance properties of the 8-to-10 modulation (ETM) code. More advanced detection schemes are investigated to see if they improve system performance. Two soft decision sequence estimation algorithms are considered: a fully-fledged Viterbi algorithm realizing maximum likelihood sequence estimation (MISE) and a suboptimal trellis detection algorithm.
K.A. Schouhamer Immink, RS Codes and the Compact Disc, Chapter 3 in Reed-Solomon Codes and Their Applications, S.B. Wicker and V.K. Bhargava (Editors), IEEE Press, 1994. For info click here
V. Braun, K.A. Schouhamer Immink, M. Ribeiro, and G. v.d. Enden, 'Sequence estimation algorithms for the digital compact cassette', Proceedings IEEE International Symposium on Information Theory, 27 June-1 July 1994.

==1992==
K.A. Schouhamer Immink and P. de Bot (Editors), Proceedings 14th Information Theory Symposium in the Benelux, Veldhoven, The Netherlands, May 1993, ISBN 90-71048-09-8.
K.A. Schouhamer Immink, 'Block-decodable Runlength-limited Codes Via Look-ahead Technique',Philips J. Res., vol. 46, no. 6, pp. 293-310, 1992.
Abstract - The terms (d,k)- constrained sequence and runlength-limited (RLL) sequence are usually used as synonyms, and traditionally the design of encoders that generate RLL sequences is almost always conducted by designing encoders that generate (d,k)-constrained sequences followed by a precoder. It is generally believed that this design procedure does not entail a losss of performance in terms of coder complexity and error propagation. In this paper, however, we will show that it is surprisingly profitable in terms of error propagation to design RLL encoders directly, i.e. without the intermediate step of a (d,k)-constrained sequence.
K.A. Schouhamer Immink and H.D.L. Hollmann, 'Prefix-synchronized Run-Length-Limited Sequences', IEEE Journal on Selected Areas in Communications., Special Issue on Signal processing and coding for digital storage, vol. 10, no. 1, pp. 214-222, Jan. 1992, doi: 10.1109/49.124480.
Abstract - In digital recorders, the coded information is commonly grouped in large blocks, called frames. The authors concentrate on the frame synchronization problem of run-length-limited sequences, or (d, k) sequences.

==1991==
H.D.L. Hollmann and K.A. Schouhamer Immink, 'Performance of Efficient Balanced Codes', IEEE Trans. Inform. Theory, vol. IT-37, no. 3, pp. 913-918, May 1991, doi: 10.1109/18.79961.
Abstract - The problem of appraising the spectral performance of codes based on a new algorithm for generating zero-disparity codewords presented by D.E. Knuth (1986) is addressed. In order to get some insight into the efficiency of Knuth's construction technique, the authors evaluate the spectral properties of its code streams. The structure of Knuth codes allows the derivation a simple expression for (an approximation to) the sum of variance of these codes. This quantity plays a key role in the spectral performance characterization of DC-balanced codes. The authors evaluate this expression and compare the sum variance of Knuth codes with the sum variance of the polarity bit codes for fixed redundancy. Under the premise that the sum variance can serve as a quantity to judge the width of the spectral notch, the authors conclude that codes based on Knuth's algorithm offer less spectral suppression than polarity bit codes with the same redundancy.
K.A. Schouhamer Immink, Coding Techniques for Digital Recorders, Prentice-Hall, Inc., Englewood Cliffs, New Jersey, 1991. (Out of sale)
A.J.E.M. Janssen and K.A. Schouhamer Immink, 'Entropy and Power Spectral Density of Asymmetrically Dc-constrained Sequences', IEEE Trans. Inform. Theory, vol. IT-37, no. 3, pp. 923-927, May 1991, doi: 10.1109/18.79963.
Abstract - The eigenstructure of bidiagonal Hessenberg-Toeplitz matrices is determined. These matrices occur as skeleton matrices of finite-state machines generating certain asymmetrically DC-constrained binary sequences that can be used for simulating pilot tracking tones in digital magnetic recording. The eigenstructure is used to calculate the Shannon upper bound to the entropy of the finite state machine as well as the power spectrum of the maxentropic process generated by it.
H. Ogawa and K.A. Schouhamer Immink, 'Optical Recording', Proceedings ICC, Denver, USA, 23-26 June 1991.

==1990==
K.A. Schouhamer Immink, 'Runlength-Limited Sequences', Proceedings IEEE, vol. 78, no. 11, pp. 1745-1759, Nov. 1990, doi: 10.1109/5.63306.
Abstract - Coding techniques are used in communication systems to increase the efficiency of the channel. Not only is coding equipment being used in point-to-point communication channels, but coding methods are also used in digital recording devices such as sophisticated computer disk files and numerous domestic electronics such as stationary- and rotary-head digital audio tape recorders, the Compact Disc, and floppy disk drives. Since the early 1970s, coding methods based on runlength-limited sequences have played a key role for increasing the storage capacity of magnetic and optical disks or tapes. A detailed description is furnished of the limiting properties of runlength-limited sequences, and a comprehensive review is given of the practical aspects involved in the translation of arbitrary data into runlength-limited sequences.
K.A. Schouhamer Immink, Editor, Proceedings International IEEE Workshop on Information Theory Symposium, Veldhoven, The Netherlands, June 1990.
K.A. Schouhamer Immink, 'Error detecting runlength-limited sequences', IEEE/IEE Eighth International Conference on Video, Audio and Data Recording, pp. 176-182, 24-26 April 1990.
K.A. Schouhamer Immink, 'Spectral Null Codes', IEEE Trans. on Magnetics, vol. MAG-26, no. 2, pp. 1130-1135, March 1990, doi: 10.1109/20.106515.
Abstract - The servo position information of magnetic tape or disk recorders is often recorded as low-frequency components usually called pilot tracking tones. Binary codes giving rise to a spectral null at an arbitrary frequency are used to provide space for the allocation of auxiliary pilot tones. Here, encoding methods are treated in which binary data are mapped into constrained binary sequences for shaping the spectrum. The rate and power spectral density function of memoryless codes that exhibit spectral nulls are computed. The relationship between the code redundancy and spectral notch width is quantified with a parameter called the sum variance. It is found that twice the product of the spectral notch width times the sum variance is approximately unity.

==1989==
K.A. Schouhamer Immink, 'Coding Techniques for the Noisy Magnetic Recording Channel, A State-of-the-Art Report', IEEE Trans. Commun., vol. COM-37, no. 5, pp. 413-419, May 1989, doi: 0.1109/26.24592.
Abstract - Coding techniques for improving the reliability of information storage on noisy magnetic recording channels are considered. It is assumed that the Lorentzian channel model applies and that the retrieved signal is perturbed with additive white Gaussian noise. The immunity against additive noise of state-of-the-art codes such as DC-free, runlength-limited, and trellis codes are assessed.
K.A. Schouhamer Immink, 'Graceful Degradation of Magnetic Recording Channels', IEEE Trans. Magn., vol. MAG-25, pp. 2780-2786, no. 3, May 1989, doi: 10.1109/20.24522.
Abstract - Coding techniques are shown to provide an effective means of controlling the effects of bandwidth and gain variation associated with space losses. The combination of a specific channel code and a suitable partial-response detection technique is proposed and studies for the purpose of obtaining enhanced robustness.
R.J. van der Vleuten and K.A. Schouhamer Immink, 'A maximum likelihood detector for a class IV PR response magnetic recording system', Proceedings 10th Symp. Inform. Theory in the Benelux, pp. 117-123, May 1989.
==1988==
K.A. Schouhamer Immink, 'Coding Techniques for Partial-Response Channels', IEEE Trans. Commun., vol. COM-36, no. 10, pp. 1163-1165, Oct. 1988, doi:10.1109/26.7534.
Abstract - A coding technique for improving the reliability of digital transmission over noisy partial-response channels with characteristics (± D ^m), m =1, 2, where the channel input symbols are constrained to be ±1, is presented. In particular, the application of a traditional modulation code as an inner code of a concentrated coding scheme in which the outer code is designed for maximum (free) Hamming distance is considered.
K.A. Schouhamer Immink, 'Transmission of Digital Sound over Channels with Unforeseen Bandwidth Limitation', J. IERE, pp. 49-56, March/April 1988.
K.A. Schouhamer Immink, 'The performance of recording codes for digital magnetic storage', IERE Conference on video, audio, and data recording, 1988.
K.A. Schouhamer Immink, Editor, Proceedings Ninth Information Theory Symposium in the Benelux, Mierlo, The Netherlands, May 1988, ISBN 99-71048-04-7.
K.A. Schouhamer Immink, 'Signal-to-Noise Ratio of Pilot Tracking Tones Embedded in Binary Coded Signals', IEEE Trans. Magn., vol. MAG-24, no. 2, pp. 2004-2009, March 1988, doi: 10.1109/20.11672.
Abstract - The signal-to-noise ratio of pilot tracking tones embedded in binary coded formats has been assessed. It has been found that the signal-to-noise ratio can be improved when the redundancy of the code is increased. Since the signal-to-noise ratio of the pilot tracking tone limits the maximum attainable bandwidth of the servo system, a compromise has to be found between the redundancy of the code and the performance of the servo system. The signal-to-noise ratio of pilot tones based on the polarity switch technique, which is attractive as no lookup tables are required for encoding and decoding, is substantially smaller than that of codes based on the fixed disparity format.
K.A. Schouhamer Immink, 'Graceful Degradation of Digital Audio Transmission Systems', J. Audio Eng. Soc., vol. 36, pp. 27-33, Jan/Feb 1988.
Abstract - A new technique for encoding and decoding digital audio signals is presented. It offers the advantage of a graceful degradation of the audio performance when the signal is conveyed over channels with a wide range of bandwidths. The flexibility of the new techniques also provides a key to the future evolution of the quality of digital audio or video systems within the same digital format. The class of systems described may well be of particular value in applications involving the storage or broadcast of digital audio signals when the exact bandwidth of the communication system is unknown.

==1987==
K.A. Schouhamer Immink and G.F.M. Beenker, 'Binary Transmission Codes with Higher Order Spectral Zeros at Zero Frequency', IEEE Trans. Inform. Theory, vol. IT-33, no. 3, pp. 452-454, May 1987, doi: 10.1109/TIT.1987.1057296.
Abstract - A method is presented for designing binary channel codes in such a way that both the power spectral density function and its low-order derivatives vanish at zero frequency. The performance of the new codes is compared with that of channel codes designed with a constraint on the unbalance of the number of transmitted positive and negative pulses. Some remarks are made on the error-correcting capabilities of these codes.
K.A. Schouhamer Immink, 'Graceful Degradation of Digital Audio Transmission Systems', Proc. AES 82nd Convention, preprint 2434-c3, March 1987.

==1986 and earlier==
K.A. Schouhamer Immink, 'Coding Methods for High-Density Optical Recording', Philips J. Res., vol. 41, pp. 410-430, 1986.
Abstract - Maximum-likelihood sequence estimation of binary coded and uncoded information, stored on an optical disc, corrupted with additive Gaussian noise is considered. We assume the presence of inter-symbol interference and channel/receiver mismatch. The performance of the maximum-likelihood detection of runlength-limited sequences is compared against both uncoded information and information encoded by Hamming-distance-increasing convolutional codes.
K.A. Schouhamer Immink, 'On the Systematic Design of Dc-constrained Recording Codes', Proceedings 6th Int. Conference on Video, Audio and Data Recording, Brighton, pp. 147-150, March 1986.
K.A. Schouhamer Immink, Properties and cnstructions of binary channel codes, PhD Thesis, Eindhoven University of Technology, May 1985 (supervisors: Pieter Schalkwijk and Kenneth W. Cattermole).
G. Bouwhuis, J. Braat, A. Huijser, J. Pasman, G. van Rosmalen, and K.A. Schouhamer Immink, Principles of Optical Recording, Adam Hilger Ltd., Bristol and Boston, 1985. (Out of sale)
K.A. Schouhamer Immink, 'Spectrum Shaping with Binary DC²-constrained codes',Philips J. Res., vol. 40, pp. 40-53, 1985.
Abstract - A method is presented for designing binary channel codes in such a way that both the power spectral density function and its second-derivative vanish at zero frequency. Recursion relations are derived to determine the number of codewords that can be used in this coding scheme. A simple algorithm for encoding and decoding codewords is developed. The performance of the new codes is compared with that of classical channel codes designed with a constraint on the unbalance of the number of transmitted positive and negative pulses.
K.A. Schouhamer Immink, 'Construction of Binary DC-constrained Codes', Philips J. Res., vol. 40, pp. 22-39, 1985.
G.F.M. Beenker and K.A. Schouhamer Immink, 'On the number of codewords of a DC²-balanced code', Proc. of the 6th Symp. Information Theory in the Benelux, pp. 133-139, May 1985.
K.A. Schouhamer Immink, 'Performance of Simple Binary DC-constrained Codes', Philips J. Res., vol. 40, pp. 1-21, 1985.
K.A. Schouhamer Immink and J.J.M. Braat, 'Experiments Toward an Erasable Compact Disc', J. Audio Eng. Soc., vol. 32, pp. 531-538, 1984.
Abstract - Recording experiments of erasable information in magnetooptical amorphous layers on pregrooved disks are described. The recording and reading of information is done on a recorder provided with an AIGaAs laser and equipped for polarization-sensitive readout of the Kerr effect. The signal-to-noise ratio and the bit error rate of the recorded information have proved to be sufficient for half an hour of digital music according to the Compact Disc digital audio standard on a 120-mm-diameter disk (equivalent to 400 00 bit/mm2). With only slight modifications the recorder can be used to read out normal Compact Disc records.
K.A. Schouhamer Immink, A.H. Hoogendijk, and J. Kahlman, 'Digital Audio Modulation in the PAL and NTSC Video Disc Coding Formats', J. Audio Eng. Soc., vol. 32, pp. 883-888, 1984.
Abstract - An extension of the current optical video disk format that includes a digital audio signal is presented. The feasibility of a combined digital audio signal according to the Compact Disc digital audio format and the current analog audio signals in the NTSC video format is described, which permits the realization of a compatible system. For the PAL and SECAM video formats the feasibility of digital audio is shown, but it cannot be combined with the analog audio carriers.
K.A. Schouhamer Immink, 'Performance of dc-constrained codes', Proceedings of the Fifth Symposium on Information Theory in the Benelux, pp. 133-139, Aalten, May 1984.
K.A. Schouhamer Immink, 'Coding for Digital Optical Disc Systems', Proceedings 5th Int. Conf. Video and Data Recording, Southampton, pp. 107, 1984.
K.A. Schouhamer Immink, A.H. Hoogendijk, and J. Kahlman, 'Digital Audio Modulation in the PAL and NTSC Video Disc Coding Formats', 'Digital Audio Modulation in the PAL and NTSC LaserVision Video Disc Coding Formats', IEEE Trans. Consumer Electr., vol. CE-29, pp. 543-551, Nov. 1983.
Abstract - An extension of the current optical video disk format that includes a digital audio signal is presented. The feasibility of a combined digital audio signal according to the Compact Disc digital audio format and the current analog audio signals in the NTSC video format is described, which permits the realization of a compatible system. For the PAL and SECAM video formats the feasibility of digital audio is shown, but it cannot be combined with the analog audio carriers.
K.A. Schouhamer Immink and R.M. Aarts, 'Maximization of Information Density in Te-alloys', SPIE Conference on Optical Recording, Geneva, vol. 396, pp. 181-188, April 1983.
G.F.M. Beenker and K.A. Schouhamer Immink, 'A Generalized Method for Encoding and Decoding Runlength-limited Binary Sequences', IEEE Trans. Inform. Theory, vol. IT-29, pp. 751-754, 1983
J.P.J. Heemskerk and K.A. Schouhamer Immink, 'Compact Disc: Systeem aspecten and modulatie', Nederlands Tijdschrift voor Fotonica, pp. 11-21, Aug. 1983 (in Dutch).
J.P.M. Braat, K.A. Schouhamer Immink, and M. Urner-Willer, 'High-Density Magneto-Optical Recording', Proceedings SPIE Int. Conf., Arlington, vol. 420, pp. 206-214, June 1983.
K.A. Schouhamer Immink and U. Gross, 'Optimization of Low-frequency Properties of Eight-to-Fourteen Modulation (EFM)', Radio and Electronic Engineer, vol. 53, no. 2, pp. 63-66, Feb. 1983, doi: 10.1049/ree.1983.0017.
K.A. Schouhamer Immink, 'Runlength-limited Code with Small Error Propagation', IEE Electronics Letters, vol. 19, pp. 323-324, 1983.
K.A. Schouhamer Immink, 'Comments on "Channel codings for digital audio recording', J. Audio Eng. Soc., vol. 31, pp. 939-940, Dec. 1983.
H. Ogawa and K.A. Schouhamer Immink, 'EFM - The Modulation for the Compact Disc Digital Audio System', Collected Papers from the AES Premiere Conference, Rye, New York, pp. 178-188, 1982.
J.P.J. Heemskerk and K.A. Schouhamer Immink, 'Compact Disc: System aspects and modulation', Philips Tech. Review, vol. 40, pp. 157-164, 1982.
K.A. Schouhamer Immink, 'Modulation systems for digital audio discs with optical read-out', Proceedings IEEE Int. Conf. on Acoustics, speech and signal processing, Atlanta, pp. 587-589, June 1981.
L.B. Vries, K.A. Schouhamer Immink, J.B. Nyboer, H. Hoeve, T.T. Doi, K. Odaka and H. Ogawa, 'The Compact Disc Digital Audio System: Modulation and Error correction', 67th AES Convention, no 1674, New York, Oct. 1980.
K.A. Schouhamer Immink, 'Controller design based on a limit criterion', Automatica, vol. 12, pp. 623-627, 1976.
Last updated: June 2022