Presented is an area-efficient architecture of a VLSI circuit that can perform various DCT-based transforms for a video decoder supporting multiple standards such as JPEG, MPEG-4, VC-1 and H.264. The proposed architec...
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Presented is an area-efficient architecture of a VLSI circuit that can perform various DCT-based transforms for a video decoder supporting multiple standards such as JPEG, MPEG-4, VC-1 and H.264. The proposed architecture uses a novel concept of a delta coefficient matrix and shares resources such as adders and shifters as much as possible. Multipliers are not included.
Upper bounds are derived for codes in Stiefel and Grassmann manifolds with given minimum chordal distance. They stem from upper bounds for codes in the product of unit spheres and projective spaces. The new bounds are...
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Upper bounds are derived for codes in Stiefel and Grassmann manifolds with given minimum chordal distance. They stem from upper bounds for codes in the product of unit spheres and projective spaces. The new bounds are asymptotically better than the previously known ones.
The authors investigate the design of linear dispersion (LD) codes, aiming at flexible encoding schemes that allow various rate-performance tradeoffs under a common coding structure. First, the capacity of LD codes is...
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The authors investigate the design of linear dispersion (LD) codes, aiming at flexible encoding schemes that allow various rate-performance tradeoffs under a common coding structure. First, the capacity of LD codes is studied. It is shown that the maximum attainable multiplexing gain of a linear dispersion code is the number of symbols per channel use of the code (i. e. coding rate in symbols). In addition, conditions on the construction of linear dispersion matrices for various multiplexing gains are established. A general multilayered linear dispersion coding scheme that allows various multiplexing gains is then proposed. In the proposed scheme, coding rate can be adapted by employing different numbers of dispersion matrices. Furthermore, phase shifting among input symbols is applied to optimise the error performance without loss of multiplexing gain. The construction of dispersion matrices and the optimisation of the phase shifts together constitute a structured approach for the design of linear dispersion codes. Simulation results demonstrate that the new codes outperform conventional LD codes at various data rates.
Hermitian codes are a class of very long algebraic-geometric (AG) codes constructed from Hermitian curves, which outperform Reed-Solomon codes defined over the same finite fields and with the same code rates, as recen...
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Hermitian codes are a class of very long algebraic-geometric (AG) codes constructed from Hermitian curves, which outperform Reed-Solomon codes defined over the same finite fields and with the same code rates, as recently demonstrated by the authors. However, since there are no soft-decision decoding algorithms for AG codes in the literature, the performance of Hermitian codes is limited and their potential is yet to be realized. An alternative method for achieving more significant coding gains is presented in this paper by serially concatenating long Hermitian codes with ring-trellis-coded modulation codes over the ring of integers Z(4) and evaluating their performance through simulation results on the AWGN and Rayleigh fading channels. The scheme achieves large coding gains over single Hermitian and Reed-Solomon codes with no increase in bandwidth use and a performance comparable with the well-known capacity-approaching codes. Copyright (C) 2007 John Wiley & Sons, Ltd.
In May 2005 the ITU-T approved ITU-T G.722.1 Annex C. This Annex extends the G.722.1 codec from 7 kHz audio bandwidth to 14 kHz, 1 octave better than the current ITU-T wideband algorithms. It is a low-complexity audio...
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In May 2005 the ITU-T approved ITU-T G.722.1 Annex C. This Annex extends the G.722.1 codec from 7 kHz audio bandwidth to 14 kHz, 1 octave better than the current ITU-T wideband algorithms. It is a low-complexity audio codec operating at 24, 32, and 48 kb/s. Like the main ITU-T G.722.1 Recommendation, its main application is videoconferencing. This article presents the standardization stages from the definition of the foreseen applications and specification of the requirements to the performance evaluation. The adaptation and design of new software tools (included in the ITU-T Software Tool Library, STL), and the utilization of ITU-T P-series Recommendations (dealing with transmission characteristics and performance characterization of telephone transmission quality) are also presented.
A simple yet efficient technique is proposed to improve the performance of distributed sorting based K-best detection. The proposed technique is to interleave partially sorted elements so as to reduce the distribution...
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A simple yet efficient technique is proposed to improve the performance of distributed sorting based K-best detection. The proposed technique is to interleave partially sorted elements so as to reduce the distribution skew that is the major cause of performance degradation of distributed sorting. Experimental results show that the proposed interleaving almost fully recovers the degradation and makes the performance close to that of the original K-best detection.
In this correspondence, we describe a heuristic method for the construction of linear codes with given parameters n, k, q, and a prescribed minimum distance of at least d. Our approach is based on a function estimatin...
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In this correspondence, we describe a heuristic method for the construction of linear codes with given parameters n, k, q, and a prescribed minimum distance of at least d. Our approach is based on a function estimating the probability that a code of dimension k and blocklength n' < n over G F (q) is extendable to a code with the given properties. Combining this evaluation function with a search algorithm, we were able to improve 40 entries in the international tables for the best known minimum distance in the cases q = 2 5 71 9 and found at least two new optimal linear codes.
A low-cost encoder for the 802.11n standard is presented. Recent standards such as 802.16e or 802.11n include a special parity check matrix structure that allows efficient encoding and decoding. However, the hardware ...
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A low-cost encoder for the 802.11n standard is presented. Recent standards such as 802.16e or 802.11n include a special parity check matrix structure that allows efficient encoding and decoding. However, the hardware requirements for implementation with fully parallel architectures could be high. Described is a way of encoding low density parity check (LDPC) codes, with parity check matrices under the schemes used in the 802.11 n or 802.16e standards, in a serial way. Exploiting the special topology of these standards' parity matrix, the encoder proposed requires about 12 times less hardware than a fully parallel one, while only increasing the time between input frames by about three times.
The key to good decoding performance in distributed video coding systems lies in the efficient prediction of frames using side information. Previously, this process has been performed without considering the progressi...
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The key to good decoding performance in distributed video coding systems lies in the efficient prediction of frames using side information. Previously, this process has been performed without considering the progressive nature of the synthesis of the final frame. Observing the fact that incorrectly predicted areas of the current frame can be detected at different levels of final frame synthesis, an algorithm is proposed for refinement of side information synthesis based on an additional stage of motion estimation. The additional stage is performed on correctly decoded DC frames and is used to significantly improve the motion prediction of the final resolution frames, which leads to enhanced performance of the overall system.
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