In this paper, a new variable length code transmission technique utilizing multicode DS/SS is proposed. A common problem associated with the use of variable length codes over wireless channels is loss of synchronizati...
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In this paper, a new variable length code transmission technique utilizing multicode DS/SS is proposed. A common problem associated with the use of variable length codes over wireless channels is loss of synchronization due to bit inversion caused by channel noise. The loss of synchronization produces burst errors in the received source symbols. The proposed system assigns multiple spreading codes to a single user to transmit variable length codes. The number of the spreading codes is equal to the maximum bit length of the codewords. All the bits of the codeword are spread and transmitted at one time by utilizing the assigned multiple spreading codes. Therefore no synchronization of the codeword is required. This paper evaluates the performance of the proposed technique over an AWGN channel and a Rayleigh fading channel. Our results show that the proposed technique improves the symbol error rate (SER) performance by 2-3 dB on the AWGN channel and 10-20 dB on the Rayleigh fading channel as compared with a conventional transmission technique. The source-channel coding suitable for the proposed technique improves the performance by another 15 dB on the Rayleigh fading channel. The proposed transmission technique works even in a low Es/No region.
The error recovery capability of variable length code (VLC) has been considered as an important performance and design criterion in addition to its coding efficiency. However, almost all of the existing methods for ev...
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The error recovery capability of variable length code (VLC) has been considered as an important performance and design criterion in addition to its coding efficiency. However, almost all of the existing methods for evaluating the error recovery capability of VLC assume that the transmission fault is a random single bit inversion. In this paper, we consider a more generalized problem of precisely evaluating the error recovery capability of VLC in the case that the encoded bit stream is transmitted over a BSC with arbitrary crossover probability. By making use of the Perron-Frobenius Theorem, we derive a very simple expression for the exact mean error propagation rate (MEPR), and show that the variance of error propagation rate (VEPR) is zero. We also prove that in the regime of very low crossover probability, the mean error propagation length (MEPL) derived for single inversion error case approaches a scaled value of the MEPR. Furthermore, we briefly discuss the problem of evaluating the error detection capability of non-exhaustive code over BSC.
variable length codes (VLCs), used in data compression, are very sensitive to error propagation in the presence of noisy channels. Addressing this problem with joint source-channel turbo techniques has been proposed i...
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variable length codes (VLCs), used in data compression, are very sensitive to error propagation in the presence of noisy channels. Addressing this problem with joint source-channel turbo techniques has been proposed in the literature and looks quite promising. But to date, most code-related conclusions are based on simulations. This paper states and proves several theoretical results about the robustness of prefix VLCs concatenated with linear error correcting codes (ECC), assuming a maximum likelihood decoder. Especially, an approximate and asymptotically tight distance spectrum of the concatenated code (VLC+ECC) is rigorously developed. Together with the union bound, it provides upper bounds on the symbol and frame/packet error rates.
variable length codes (VLCs), used in data compression, are very sensitive to error propagation in the presence of noisy channels. To address this problem, several joint source-channel turbo techniques have been propo...
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variable length codes (VLCs), used in data compression, are very sensitive to error propagation in the presence of noisy channels. To address this problem, several joint source-channel turbo techniques have been proposed in the literature. In this paper, we focus on pairs of source/VLC of low redundancy, i.e., when there is a good match between the source statistics and the length distribution of the VLC. It is a case not considered. extensively in the literature so far and the classical concatenation of a VLC and a convolutional code is not satisfying. Through EXIT chart and interleaving gain analysis, we show that the introduction of a repetition code between the VLC and the convolutional code considerably improves global performance. In particular, excellent symbol error rates are obtained with reversible VLCs which are used in recent source codecs.
When a telecommunication system is constrained in terms of delay and complexity, it is usually wise to allow some cross-layer cooperation between the source and channel layers. In this context, the success of joint so...
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When a telecommunication system is constrained in terms of delay and complexity, it is usually wise to allow some cross-layer cooperation between the source and channel layers. In this context, the success of joint source-channel turbo techniques has been attested several times in the literature, in particular to transmit variable length code (VLC) streams which are very sensitive to error propagation. Capitalizing on previously developed performance upper bounds, this paper investigates whether the VLC can contribute to the interleaving gain of concatenated codes just as a convolutional code with non-catastrophic encoder would. To this end, the important concept of bounded VLC spectrum is introduced and is proved to be a sufficient condition for the VLC to contribute indeed to the interleaving gain. This concept is also proved to be closely related to non-catastrophic VLCs and, under certain assumptions, to the well known concept of statistically synchronizable VLCs.
JPEG coder is still the most attractive compression scheme for still image. Using Huffman coding makes the JPEG coder very sensitive to communication error. In this paper we propose a simple modification to JPEG coder...
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JPEG coder is still the most attractive compression scheme for still image. Using Huffman coding makes the JPEG coder very sensitive to communication error. In this paper we propose a simple modification to JPEG coder by using reversible variable length code designed for the DC coefficients of each block. The results show great improvement in error resilience in a binary symmetric channel transmission with an average reduction of 5-10% in compression ratio.
Joint source and channel decoding (JSCD) of variable length codes (VLCs) has been attracting considerable attention in recent years. It is a capacity-approaching technique to decode in an iterative way, or known as it...
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ISBN:
(纸本)9781479932061
Joint source and channel decoding (JSCD) of variable length codes (VLCs) has been attracting considerable attention in recent years. It is a capacity-approaching technique to decode in an iterative way, or known as iterative source-channel decoding (ISCD) of VLCs. When the side information of both bit length and symbol length of the VLC sequence are available, VLC-block trellis can be constructed, which exploits the knowledge of both lengths. The ISCD based on VLC-block trellis generally performs better than that based on the more widely used Balakirsky trellis. However, the complexity of VLC-block trellis is much higher, and grows exponentially with the sequence size. In this paper we study a sub-optimal solution by pruning some states and branches of the trellis. Simulation results show that this method can adjustably reduce complexity with acceptable performance loss.
Recently, we proposed in [10] a joint source-channel (JSC) turbo-(de)coder combining a variable length code (VLC) with a turbo-code. The simulation results showed the better performance and the lower decoding complexi...
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ISBN:
(纸本)0780389387
Recently, we proposed in [10] a joint source-channel (JSC) turbo-(de)coder combining a variable length code (VLC) with a turbo-code. The simulation results showed the better performance and the lower decoding complexity of this new scheme,over the previous ones. In this paper, we provide tools for the analysis and the performance prediction of this scheme. The bit, symbol and frame distance spectra are developed for VLCs and for the More general case of VLCs turbo-concatenated with an error correcting code (ECC). These spectra are then used to get the union bounds on the bit, symbol and frame error probabilities, and to shed some light on previous :simulation-based results. These tools are also valid for a wide variety of other similar schemes currently explored in the literature and, hence, can be used to analyze and to compare them.
This paper presents a low-power variablelength decoder exploiting the statistics of successive codewords. The decoder employs small look-up tables working as fixed caches to reduce the number of activations of a vari...
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This paper presents a low-power variablelength decoder exploiting the statistics of successive codewords. The decoder employs small look-up tables working as fixed caches to reduce the number of activations of a variable length code detector where considerable power is consumed. The power simulation results estimated using PowerMill show that 35% energy is reduced on the average compared to the previous low-power scheme.
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