Browsing by Author "Chao, Chi-chao"

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Canonical Convolutional Encoders for Unequal Error Protection
(2008)
Wang, Chung-Hsuan
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Chao, Chi-chao
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電信工程研究所
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Institute of Communications Engineering
In this paper, canonical convolutional encoders are studied for unequal error protection (UEP) from an algebraic theoretical viewpoint. We show that for any convolutional code there exists at least a canonical generator matrix which has the greatest separation vector, and hence the optimal UEP capability, among all canonical ones. A procedure for obtaining such desirable generator matrices is also proposed.
Decoding Scheduling for Unequal Error Protection Quasi-Cyclic Low-Density Parity-Check Codes
(2019-01-01)
Wu, Jia-Jyun
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Wang, Chung-Hsuan
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Chao, Chi-chao
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電信工程研究所
;
Institute of Communications Engineering
Algebraic constructions of quasi-cyclic (QC) low-density parity-check (LDPC) codes with unequal error protection (UEP) capabilities have recently been proposed, which can provide different error-correcting capabilities for different parts of the coded bits. However, conventional decoding algorithms are not designed for LDPC codes with UEP. In this paper, we propose three decoding schemes for UEP QC-LDPC codes extended from existing scheduling strategies, tailored to the special structures of the parity-check matrices. Simulation results show that the proposed schemes can provide improved error rate performance especially for coded bits on low protection levels. The decoding convergence can also be accelerated, thereby reducing the computational complexity.
New Constructions of Variable-Rate QC-LDPC Codes by Adding Column-Blocks or Removing Row-Blocks
(2016-01-01)
Wu, Chi-Jen
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Wang, Chung-Hsuan
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Chao, Chi-chao
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電機工程學系
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Department of Electrical and Computer Engineering
In this paper, new constructions of variable-rate quasi-cyclic low-density parity-check (QC-LDPC) codes are proposed. The criteria which guarantee that a higher-rate QC-LDPC code can be obtained by adding column-blocks to or removing row-blocks from the parity-check matrix of a given lower-rate QC-LDPC code are derived. Based on these criteria, new families of variable-rate QC-LDPC codes can he constructed. Simulation results show that the constructed codes provide a variety of error protection capabilities against different channel conditions.
On Parameter Estimation for Ultra-Wideband Channels with Clustering Phenomenon
(2008)
Wu, Wei-De
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Wang, Chung-Hsuan
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Chao, Chi-chao
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Witrisal, Klaus
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電信工程研究所
One of the unique characteristics of ultra-wideband channels is the clustering phenomenon resolved by the ultra-wide signal bandwidth. Channel structures extended from the Saleh-Valenzuela model, e. g., the IEEE 802.15.3a and IEEE 802.15.4a models, have been proposed to describe such phenomenon. It is, however, noticed that a clear and systematic procedure to estimate the model parameters is still missing. Based on the recently developed analytical results, a new estimation approach is proposed in the paper to resolve the inconvenience and ambiguity in previous methods. The key step is to match the statistical profiles of interests by formulating an optimization problem with an explicit analytical objective function that can be systematically solved. Numerical tests have also been conducted to demonstrate the effectiveness of the proposed method.
Rank Analysis of Parity-Check Matrices for Quasi-Cyclic LDPC Codes
(2018-01-01)
Yang, Po-Chun
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Wang, Chung-Hsuan
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Chao, Chi-chao
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電信工程研究所
;
Institute of Communications Engineering
Quasi-cyclic low-density parity-check (QC-LDPC) codes are an important class of LDPC codes which can be encoded and decoded with low complexity and suitable for many applications. As the code dimension, which describes the number of protected information bits, is equal to the code length minus the rank of the parity-check matrix and the parity-check matrix for QC-LDPC codes is usually not full-rank, determining the rank of the parity-check matrix is of essential importance. In this paper, we study the rank of the parity-check matrix for QC-LDPC codes based on the associated polynomials for circulant matrices. A formula for the rank of the parity-check matrix with only one row-block is first derived. We then extend the result to matrices with two, three, or more row-blocks. Some bounds are also presented for matrices with arbitrary numbers of row-blocks. Furthermore, the exact rank is determined for a class of algebraically constructed parity-check matrices.
Signal-to-Interference-Plus-Noise Ratio Analysis for Direct-Sequence Ultra-Wideband Systems in Generalized Saleh-Valenzuela Channels
(2007-10-01)
Wu, Wei-De
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Lee, Cheng-Chia
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Wang, Chung-Hsuan
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Chao, Chi-chao
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電信工程研究所
In this paper, exact signal-to-interference-plus-noise ratio (SINR) analysis of direct-sequence ultra-wideband (UWB) systems with Rake receiving in the presence of inter-symbol interference and multiple-access interference over a generalized Saleh-Valenzuela (GSV) channel with a generic pulse shaping function is provided. The SINR expression, for synchronized multiple-access, is first obtained without assuming random spreading. The GSV channel structure under consideration is a generalization of the Saleh-Valenzuela channel structure with generalized path-gain and path-arrival models, examples of which can include all the IEEE 802.15.3a UWB channel models and some of the IEEE 802.15.4a models. Then, by the novel treatment of renewal processes, the exact average SINR over the GSV channel statistics is obtained. Our analytical results well match computer simulations and can readily be applied to evaluate and improve the performance of UWB systems over realistic channel and interference models.
UEP Constructions of Quasi-Cyclic Low-Density Parity-Check Codes via Masking
(2017-10-01)
Wu, Chi-Jen
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Wang, Chung-Hsuan
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Chao, Chi-chao
;
電信工程研究所
;
Institute of Communications Engineering
In this paper, the algebraic constructions of quasi-cyclic low-density parity-check (QC-LDPC) codes with the unequal error protection (UEP) property are considered. A criterion for constructing such codes via the masking technique is proposed, based on which explicit conditions on the base parity-check matrices and masking matrices to achieve UEP are provided. We also give three specific constructions of UEP QC-LDPC codes. Furthermore, a sufficient condition to ensure strict UEP is presented. Simulation results demonstrate the superiority of our constructed codes over time-sharing schemes. The constructed codes also have competitive error performance against randomly constructed equal-error-protection LDPC codes and irregular UEP LDPC codes designed based on the degree distribution.
Unequal Error Protection QC-LDPC Codes via Masking
(2012)
Wu, Chi-Jen
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Wang, Chung-Hsuan
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Chao, Chi-chao
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電機工程學系
;
Department of Electrical and Computer Engineering
In this paper, a generalized construction of quasi-cyclic low-density parity-check (QC-LDPC) codes for unequal error protection (UEP) is proposed based on the masking technique. We can obtain UEP QC-LDPC codes as long as the Tanner graph of the masking matrix satisfies a general condition which can include our previous UEP construction as a special case. A sufficient condition to have flexible choice of protection levels is then presented. Simulation results show that the constructed codes can indeed provide codeword bits with different bit-error-rate performance.