Optical disk storage systems use both error control (EC) codes and dc-free constrained sequence (CS) codes in order to increase the reliability of the data read from the disk. We present a method of integrating these ...
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Optical disk storage systems use both error control (EC) codes and dc-free constrained sequence (CS) codes in order to increase the reliability of the data read from the disk. We present a method of integrating these coding techniques in order to overcome drawbacks with the conventional manner in which these coding procedures are concatenated. Our technique is based on the principle of multimode coding. Each source word (SW) is represented by a set of complementary EC codewords (CWs), and from this set the encoder selects the EC CW that best meets the CS goals of the system. The decoding structure avoids the problem of error propagation during CS decoding by performing error correction before removing the effects of the CS code. Power spectra of encoded sequences generated by a hardware implementation have a null at 0 Hz, confirming that these coded sequences are dc-free. BER simulations demonstrate the superior performance of this combined EC and CS code on a dc-constrained noisy channel(1).
multimode coding is a promising coding method owing to the simplicity of its code design and the attainment of high code rate. The authors present a multimode coding scheme for generating two-dimensional balanced t-co...
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multimode coding is a promising coding method owing to the simplicity of its code design and the attainment of high code rate. The authors present a multimode coding scheme for generating two-dimensional balanced t-conservative arrays for holographic storage. The multimode encoding process involves adding each unconstrained input array to a set of control arrays to form the selection set and selecting a pseudo-balanced t-conservative array from the selection set. By appropriately encoding the indices of the control arrays and using the remaining bits in the extra column or row appended to the selected pseudo-balanced t-conservative array to jointly balance the entire encoded array and to ensure that the extra column or row contains a sufficient number of transitions, the final output of the multimode encoder satisfies both the balanced and the t-conservative constraints. The decoding process is straightforward given the knowledge of the control array that was applied to the input array during the encoding process.
DC-free codes and error-control (EC) codes are widely used in digital transmission and storage systems. To improve system performance in terms of code rate, bit-error rate (BER), and low-frequency suppression, and to ...
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DC-free codes and error-control (EC) codes are widely used in digital transmission and storage systems. To improve system performance in terms of code rate, bit-error rate (BER), and low-frequency suppression, and to provide a flexible tradeoff between these parameters, this paper introduces a new class of codes with both dc-control and EC capability. The new codes integrate dc-free encoding and EC encoding, and are decoded by first applying standard EC decoding techniques prior to de-free decoding, thereby avoiding the drawbacks that arise when dc-free decoding precedes EC decoding. The dc-free code property is introduced into standard EC codes through multimode coding techniques, at the cost of minor loss in BER performance on the additive white Gaussian noise channel, and some increase in implementation complexity, particularly at the encoder. This paper demonstrates that a wide variety of EC block codes can be integrated into this dc-free coding structure, including binary cyclic codes, binary primitive BCH codes, Reed-Solomon codes, Reed-Muller codes, and some capacity-approaching EC block codes, such as low-density parity-check codes and product codes with iterative decoding. Performance of the new dc-free EC block codes is presented.
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