The Grassmannian space G(q) (n, k) is the set of all k-dimensional subspaces of the vector space F-q(n). Recently, codes in the Grassmannian have found an application in network coding. The main goal of this paper is ...
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The Grassmannian space G(q) (n, k) is the set of all k-dimensional subspaces of the vector space F-q(n). Recently, codes in the Grassmannian have found an application in network coding. The main goal of this paper is to present efficient enumerative encoding and decoding techniques for the Grassmannian. These coding techniques are based on two different orders for the Grassmannian induced by different representations of k-dimensional subspaces of F-q(n). One enumerative coding method is based on a Ferrers diagram representation and on an order for G(q) (n, k) based on this representation. The complexity of this enumerative coding is O(k(5/2)(n - k)(5/2) digit operations. Another order of the Grassmannian is based on a combination of an identifying vector and a reduced row echelon form representation of subspaces. The complexity of the enumerative coding, based on this order, is O(nk(n - k) log n log log n) digit operations. A combination of the two methods reduces the complexity on average by a constant factor.
A k-polar Grassmannian is a geometry having as pointset the set of all k-dimensional subspaces of a vector space V which are totally isotropic for a given non-degenerate bilinear form mu defined on V. Hence it can be ...
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A k-polar Grassmannian is a geometry having as pointset the set of all k-dimensional subspaces of a vector space V which are totally isotropic for a given non-degenerate bilinear form mu defined on V. Hence it can be regarded as a subgeometry of the ordinary k-Grassmannian. In this paper we deal with orthogonal line Grassmannians and with symplectic line Grassmannians, i.e. we assume k = 2 and kt to be a non-degenerate symmetric or alternating form. We will provide a method to efficiently enumerate the pointsets of both orthogonal and symplectic line Grassmannians. This has several nice applications;among them, we shall discuss an efficient encoding/decoding/error correction strategy for line polar Grassmann codes of either type. (C) 2017 Elsevier Inc. All rights reserved.
Efficient enumerative coding for tree sources is, in general, surprisingly intricate-a simple uniform encoding of type classes, which is asymptotically optimal in expectation for many classical models, such as FSMs, t...
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Efficient enumerative coding for tree sources is, in general, surprisingly intricate-a simple uniform encoding of type classes, which is asymptotically optimal in expectation for many classical models, such as FSMs, turns out not to be so in this case. We describe an efficiently computable enumerative code that is universal in the family of tree models in the sense that, for a string emitted by an unknown source whose model is supported on a known tree, the expected normalized code length of the encoding approaches the entropy rate of the source with a convergence rate (K/2)(log n)/n, where K is the number of free parameters of the model family. Based on recent results characterizing type classes of context trees, the code consists of the index of the sequence in the tree type class, and an efficient description of the class itself using a nonuniform encoding of selected string counts. The results are extended to a twice-universal setting, where the tree underlying the source model is unknown.
Various methods have been proposed for the construction of balanced run-length limited codes. Amongst these methods is the enumerative coding approach by Kurmaev. The advantage of this approach is that the code has ma...
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Various methods have been proposed for the construction of balanced run-length limited codes. Amongst these methods is the enumerative coding approach by Kurmaev. The advantage of this approach is that the code has maximum cardinality and thus approaches capacity with increasing codeword length. However, enumerative coding has the disadvantage of becoming prohibitively complex for large codeword lengths. We propose an alternative enumerative coding method that reduces the encoding and decoding complexity. We call it quasi-enumerative coding as it does not follow a strict lexicographic order, but retains a one-to-one mapping between rank and the corresponding balanced run-length limited codeword.
Gray codes for vector spaces are considered in two graphs: the Grassmann graph, and the projective-space graph, both of which have recently found applications in network coding. For the Grassmann graph, constructions ...
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Gray codes for vector spaces are considered in two graphs: the Grassmann graph, and the projective-space graph, both of which have recently found applications in network coding. For the Grassmann graph, constructions of cyclic optimal codes are given for all parameters. As for the projective-space graph, two constructions for specific parameters are provided, as well some nonexistence results. Furthermore, encoding and decoding algorithms are given for the Grassmannian Gray code, which induce an enumerative-coding scheme. The computational complexity of the algorithms is at least as low as known schemes, and for certain parameter ranges, the new scheme outperforms previously known ones.
This brief presents a technique that can fully exploit the data dependency of flash memory cell damage to improve the program/erase (P/E) cycling endurance of NAND flash memory. The key is to opportunistically leverag...
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This brief presents a technique that can fully exploit the data dependency of flash memory cell damage to improve the program/erase (P/E) cycling endurance of NAND flash memory. The key is to opportunistically leverage data lossless compressibility and utilize the compression gain to realize memory-damage-aware data manipulation to reduce the cycling-induced physical damage. Based upon experiments using commercial sub-22-nm MLC NAND flash memory chips, we show that the proposed design technique can improve the P/E cycling endurance by 50%. We further carried out application-specific integrated circuit design to demonstrate the practical feasibility for implementing the proposed design technique.
In this correspondence, we introduce a new enumerative encoding method for (d, k) codes. The encoding algorithm, which is based on enumeration of multiset permutations, is conceptually simpler and computationally less...
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In this correspondence, we introduce a new enumerative encoding method for (d, k) codes. The encoding algorithm, which is based on enumeration of multiset permutations, is conceptually simpler and computationally less expensive than other algorithms proposed thus far. We also describe a new application of enumerative encoding methods for phrase length distribution shaping of run-length-limited (RLL) sequences. We demonstrate that by reducing the probability of occurrence of long phrases in maxentropic RLL sequences, the frequency of patterns that account for most of the errors in magnetic recording systems can be decreased.
enumerative coding is an attractive algorithmic procedure for translating long source words into codewords and vice versa. The usage of long codewords makes it possible to approach a code rate which is as close as des...
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enumerative coding is an attractive algorithmic procedure for translating long source words into codewords and vice versa. The usage of long codewords makes it possible to approach a code rate which is as close as desired to Shannon's noiseless capacity of the constrained channel. enumerative encoding is prone to massive error propagation as a single hit error could ruin entire decoded words. This contribution will evaluate the effects of error propagation of the enumerative coding of runlength-limited sequences.
The energy efficiency of enumerative coding algorithms is investigated for amplitude shaping in the context of binary transmission. First, a simple method for the calculation of the amplitude distribution is derived f...
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The energy efficiency of enumerative coding algorithms is investigated for amplitude shaping in the context of binary transmission. First, a simple method for the calculation of the amplitude distribution is derived for enumerative sphere shaping (ESS). For ultra-short blocklengths, ESS-which orders sequences lexicographically-is shown to be less energy-efficient than algorithms that use energy-based ordering such as shell mapping. Second, ESS is optimized heuristically such that its energy efficiency is improved. Simulations show that optimized ESS achieves the same error probabilities as energy-based ordering methods for the additive white Gaussian noise (AWGN) channel, even at ultra-short blocklengths.
Practical implementation of enumerative sphere shaping (ESS) is considered. First, an on-the-fly computation method is proposed such that the required storage is significantly decreased, e.g., by a factor of 7 for 8-a...
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Practical implementation of enumerative sphere shaping (ESS) is considered. First, an on-the-fly computation method is proposed such that the required storage is significantly decreased, e.g., by a factor of 7 for 8-ary amplitude-shift keying (ASK) at blocklength N = 64 and shaping rate of 1.75 bit/amplitude. Then a sliding window shaping (SWS) architecture is introduced to eliminate the necessity to realize high precision arithmetic operations, and to decrease the computational complexity of ESS. The SWS procedure only requires three 16-bit arithmetic operations per output symbol for 8-ASK.
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