This paper reports the characteristics and performance of a new type of luby transform codes, namely scale-free lubytransform (SF-LT) codes. In the SF-LT codes, the degree of the encoded symbol follows a modified pow...
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This paper reports the characteristics and performance of a new type of luby transform codes, namely scale-free lubytransform (SF-LT) codes. In the SF-LT codes, the degree of the encoded symbol follows a modified power-law distribution. Moreover, the complexity and decoding performance of SF-LT codes are compared with LT codes based on robust soliton degree distribution and LT codes based on suboptimal degree distribution. The results show that SF-LT codes outperform other LT codes in terms of the probability of successful decoding over an ideal channel and a binary erasure channel. Moreover, the encoding/decoding complexity for the SF-LT codes is superior.
Given the same number of encoded symbols, a lubytransform (LT) decoder is more likely to decode successfully when there is little redundancy among the symbols. With the use of a Tanner graph, we describe two kinds of...
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Given the same number of encoded symbols, a lubytransform (LT) decoder is more likely to decode successfully when there is little redundancy among the symbols. With the use of a Tanner graph, we describe two kinds of redundancy appearing in LT codes in this paper. We further propose an encoding algorithm called Low Redundancy (LR) algorithm used in the formation of the encoded symbols. The algorithm aims to reduce the redundancy of LT codes and to improve the decoder performance under the same complexity. Simulation results show various LT codes improve in terms of average overhead factor and probability of successful decoding when the codes are encoded using the proposed LR algorithm. Moreover, the encoding complexity remains unchanged.
The lubytransform (LT) code is the first practical implementation of the digital fountain code, and its utilisation over a noisy channel invokes iterative decoding with soft information. For a good decoding performan...
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The lubytransform (LT) code is the first practical implementation of the digital fountain code, and its utilisation over a noisy channel invokes iterative decoding with soft information. For a good decoding performance, the role of the encoder degree distribution is vital. Especially, when utilising the soft iterative decoder, the bit error rate (BER) performance of the LT code can be improved by increasing the number of the degree-1 encoding nodes and reducing the number of lower-degree variable nodes. This study proposes an efficient LT-code encoding algorithm that satisfies the conditions for improving the BER performance. The proposed scheme applies different priorities for selecting the neighbouring source nodes for given degrees of the encoding nodes. The simulation results demonstrate that the proposed scheme outperforms the existing schemes.
WBAN consists of several tiny sensors that are located inside and outside human body for continuous monitoring of vital parameters of patients suffering from chronic diseases. The wearable sensor unit consists of tran...
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WBAN consists of several tiny sensors that are located inside and outside human body for continuous monitoring of vital parameters of patients suffering from chronic diseases. The wearable sensor unit consists of transmitter, receiver and central process unit (gateway). The gateway is used to connect wearable sensors on human body to the internet. To increase the lifetime of such networks, the energy spent by the sensors has to be minimized. In this work we analyzed the feasibility and performance of fountain code based raptor code for error correction to overcome the energy and reliability issues. Versatility of raptor code in terms of code rate and coding gain is advantageous to increase the energy efficiency of WBAN network. Simulation results considering different fading channels show that the raptor coded packet transmission is more energy efficient than that of LT code, traditional BCH code and ARQ error control technique.
Ever since deoxyribonucleic acid (DNA) was considered as a next-generation data-storage medium, lots of research efforts have been made to correct errors occurred during the synthesis, storage, and sequencing processe...
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Ever since deoxyribonucleic acid (DNA) was considered as a next-generation data-storage medium, lots of research efforts have been made to correct errors occurred during the synthesis, storage, and sequencing processes using error correcting codes (ECCs). Previous works on recovering the data from the sequenced DNA pool with errors have utilized hard decoding algorithms based on a majority decision rule. To improve the correction capability of ECCs and robustness of the DNA storage system, we propose a new iterative soft decoding algorithm, where soft information is obtained from FASTQ files and channel statistics. In particular, we propose a new formula for log-likelihood ratio (LLR) calculation using quality scores (Q-scores) and a redecoding method which may be suitable for the error correction and detection in the DNA sequencing area. Based on the widely adopted encoding scheme of the fountain code structure proposed by Erlich et al., we use three different sets of sequenced data to show consistency for the performance evaluation. The proposed soft decoding algorithm gives 2.3% similar to 7.0% improvement of the reading number reduction compared to the state-of-the-art decoding method and it is shown that it can deal with erroneous sequenced oligo reads with insertion and deletion errors.
We present a simple model of inactivation decoding for LT codes which can be used to estimate the decoding complexity as a function of the LT code degree distribution. The model is shown to be accurate in variety of s...
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ISBN:
(纸本)9781479959990
We present a simple model of inactivation decoding for LT codes which can be used to estimate the decoding complexity as a function of the LT code degree distribution. The model is shown to be accurate in variety of settings of practical importance. The proposed method allows to perform a numerical optimization on the degree distribution of a LT code aiming at minimizing the number of inactivations required for decoding.
We consider serial concatenation of a lubytransform (LT) code with a differential quadrature phase-shift-keying (DQPSK) modulator for transmission over an additive white Gaussian noise (AWGN) Channel. Assuming a targ...
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ISBN:
(纸本)9781612842547
We consider serial concatenation of a lubytransform (LT) code with a differential quadrature phase-shift-keying (DQPSK) modulator for transmission over an additive white Gaussian noise (AWGN) Channel. Assuming a target average rate for the operation of the rateless LT DQPSK scheme, the degree distribution of the LT code is optimized in terms of convergence threshold using extrinsic information transfer (EXIT) charts. From the EXIT chart analysis, we show that the proposed LT DQPSK scheme has a similar convergence performance, but lower complexity, as compared to a Raptor code with differential modulation, and a LDPC code optimized for DQPSK. The EXIT chart analysis framework is also applied to evaluate the throughput performance for the three schemes in terms of the average code rate as a function of the signal-to-noise ratio. The comparison demonstrates that the proposed structure is well-suited for adaptive-rate transmission over a wide range of rates.
luby transform code (LT code) is the first practical digital fountain code and has been widely used as basic components in many communication applications. The coding behavior of LT code is mainly decided by a probabi...
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ISBN:
(纸本)9781424481262
luby transform code (LT code) is the first practical digital fountain code and has been widely used as basic components in many communication applications. The coding behavior of LT code is mainly decided by a probability distribution of codeword degrees. In order to customize a degree distribution for different purposes, multi-objective evolutionary algorithm is introduced to optimize degree distributions in this paper. Two critical performance indicators of LT code are considered in our experiments. Some applications hope to minimize the overhead of extra packets and some require to limit the computational cost of the coding system. To handle this problem, MOEA/D is applied to optimize two objectives simultaneously. We expect to obtain the Pareto front (PF) formed by partial optimal solutions and provide those available degree distributions to different LT code applications. Not only promising results are represented in this paper but also the behavior of LT code is thoroughly explored by optimizing the degree distribution according to multi-objectives.
luby transform code (LT code) has been a popular and practical technique in the field of channel coding since its proposal. One of the key components of LT code is a degree distribution which is used to determine the ...
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ISBN:
(纸本)9781424481262
luby transform code (LT code) has been a popular and practical technique in the field of channel coding since its proposal. One of the key components of LT code is a degree distribution which is used to determine the relationship between source data and codewords. luby in his proposal suggested two general methods to construct feasible degree distributions. Such general designs work appropriately in typical situations but not optimally in most cases. To explore the full potential of LT code, in this work, we make the first attempt to introduce evolutionary algorithms to optimize the degree distribution in LT code. Degree distributions are encoded as real-valued vectors and evaluated by numerical simulation of LT code. For applications of different natures, two objectives are implemented to search good degree distributions with different decoding behavior. Compared with the original design, the experimental results are quite promising and demonstrate that the degree distribution can be customized for different purposes. In addition to manually adjusting the degree distribution as the common practice, the work presented in this paper provides an efficient alternative approach to use and adapt LT code for both practitioners and researchers.
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