Showing papers by "Jack K. Wolf published in 2004"
27 Jun 2004
TL;DR: This paper describes the analysis of convolutional codes on the erasure channel and compares the maximum likelihood (ML) sequence decision and the maximum a posteriori (MAP) symbol decision for codes, which are transmitted over the erasures channel.
Abstract: This paper describes the analysis of convolutional codes on the erasure channel. We compare the maximum likelihood (ML) sequence decision and the maximum a posteriori (MAP) symbol decision for codes, which are transmitted over the erasure channel. When a codeword from a linear error correcting code with elements from the field GF is transmitted over a q-ary erasure channel, the symbol error rate of the maximum likelihood (ML) sequence decision is the same as that of the symbol maximum a posteriori (MAP) probability decision. When decoding convolutional codes transmitted over an AWGN channel, it is widely known that the probability of symbol error for the Viterbi algorithm (which is a sequence ML decoder) is generally higher than that for the more complex BCJR algorithm (which is a symbol MAP decoder).
10 citations
TL;DR: In this article, the effects of packing fraction, grain size distribution, and anisotropy orientation on uniform magnetization noise were examined using numerically generated arrays of grains, and the results showed that the dc noise increases with increasing grain size and decreases with increasing packing fraction.
Abstract: Uniform magnetization (dc) noise is studied using numerically generated arrays of grains. The effects of packing fraction, grain size distribution, and anisotropy orientation are examined. From electron microscopy results, in this initial study, the intergranular grain boundary separation is held fixed. In general, the dc noise increases with increasing grain size distribution and decreases with increasing packing fraction. For a planar random anisotropy distribution, the noise is about an order of magnitude larger than that for well-oriented media. For typical parameters, the dc noise can be less than the transition noise for oriented media and is always significantly larger for planar random media.
7 citations
TL;DR: A postprocessing approach is proposed which uses a single-parity, interleaved block code for correcting the errors made by a Viterbi detector.
Abstract: A postprocessing approach is proposed which uses a single-parity, interleaved block code for correcting the errors made by a Viterbi detector. The code proposed here was simulated for an EPR4 channel with two sets of interleave depth D and code word length N with rates 39/40 and 19/20. Simulation showed a realized coding gain of 1.33 dB at a BER=10/sup -5/ and 1.59 dB at a BER=10/sup -6/ for the code with 39/40 rate. The corresponding numbers for the code with 19/20 rate are 1.54 dB and 1.76 dB.
5 citations
27 Jun 2004
TL;DR: This work proposes 2D block codes with rectangular codewords which achieve coding rates larger than 0.5 and describes the hard-square model, a two-dimensional constrained system consisting of all binary 2D rectangles.
Abstract: The hard-square model is a two-dimensional (2D) constrained system consisting of all binary 2D rectangles in which 1's are isolated both horizontally and vertically. We propose 2D block codes with rectangular codewords which achieve coding rates larger than 0.5.
4 citations
20 Oct 2004
TL;DR: This work proposes a modification to the bit stuffing algorithm and shows analytically that the proposed algorithm achieves improved average rates over bit stuffing for most (d, k) constraints.
Abstract: The bit stuffing algorithm is a technique for coding constrained sequences by the insertion of bits into an arbitrary data sequence. This approach was previously introduced and applied to (d, k) constrained codes. Results show that the maximum average rate of the bit stuffing code achieves capacity when k=d+1 or k=/spl infin/, while it is suboptimal for all other (d, k) pairs. We propose a modification to the bit stuffing algorithm. We show analytically that the proposed algorithm achieves improved average rates over bit stuffing for most (d, k) constraints.
3 citations
TL;DR: A fast waveform simulator based on the microtrack model for high-density perpendicular recording is presented and it is indicated that a throughput of 1 Mbps can be achieved with negligible distortion on a contemporary desktop computer.
Abstract: We present a fast waveform simulator based on the microtrack model for high-density perpendicular recording The simulator characterizes dominant noise sources to create realistic recording outputs that allow useful evaluation of modern software channels A novel model architecture was developed to overcome the computational burden due to the long perpendicular response Speed and distortion tradeoffs are quantified and indicate that a throughput of 1 Mbps can be achieved with negligible distortion on a contemporary desktop computer
2 citations
Patent•
12 May 2004
TL;DR: In this article, the inner convolutional encoder is used to group the data bits into symbols, each symbol having "m" bits, and then the symbols are mapped to a complex plane using quadrature amplitude modulation (QAM).
Abstract: In an orthogonal frequency division multiplexing (OFDM) system which uses an outer Reed-Solomon encoder and interleaver an inner convolutional encoder, after the inner convolutional encoding the data bits are interleaved, and then grouped into symbols, each symbol having "m" bits. After grouping, the symbols are mapped to a complex plane using quadrature amplitude modulation (QAM). Thus, bits, not symbols, are interleaved by the inner interleaver. A receiver performs a soft decision regarding the value of each bit in each complex QAM symbol received.
1 citations