A novel indoor localization scheme based on fingerprinting technique And CDMA signals

International audience—In this paper, we propose a novel acoustic local-ization system based on fingerprinting technique. It deploys the Time Of Arrival of CDMA signals emitted by speakers to locate a microphone. The system is inspired from our earlier proposed scheme [1] which deploys the lateration method. Here, we adopt the fingerprinting technique since it is more applicable to indoor environments. The position estimation is accomplished through nonparametric kernel regression. Performance are evaluated by experiments, performed in a hall of interns in National School of Engineers of Le Mans. Results have shown that our proposed scheme provides an accuracy of 8.5 cm within 80% precision

Décodage MVP des codes arithmétiques

International audienceDans cet article, un algorithme de décodage conjoint source canal, selon le critère MVP (Maximum de Vraisemblance a Posteriori), d'un code arithmétique intégrant la détection d'erreurs est présenté. Ce décodage conjoint est appliqué à un système de transmission d'images fixes sur un canal bruité. L'algorithme sous optimal de recherche séquentielle SA (Stack Algorithm) est utilisé pour réduire l'espace de recherche et déterminer, dans cet espace, laséquence la plus vraisemblable a posteriori, qui ne présente pas d'erreur détectée par le décodeur arithmétique. Cet algorithme est appliqué à un système de transmission progressive d'images utilisant le codeur SPIHT. Dans un premier temps, les effets des paramètres internes de l'algorithme présenté sont étudiés. Ensuite, les performances du système étudié sont comparées à celles d'un système de codage classique utilisant le code CRC pour la détection d’erreurs et le code RCPC pour leur correction. En terme de TEP, et dans le cas de décodage pondéré, le système utilisant le décodage conjoint est plus performant que le système classique pour les rapports signal à bruit relativement élevés

Décodage MVP des codes arithmétiques

International audienceDans cet article, un algorithme de décodage conjoint source canal, selon le critère MVP (Maximum de Vraisemblance a Posteriori), d'un code arithmétique intégrant la détection d'erreurs est présenté. Ce décodage conjoint est appliqué à un système de transmission d'images fixes sur un canal bruité. L'algorithme sous optimal de recherche séquentielle SA (Stack Algorithm) est utilisé pour réduire l'espace de recherche et déterminer, dans cet espace, laséquence la plus vraisemblable a posteriori, qui ne présente pas d'erreur détectée par le décodeur arithmétique. Cet algorithme est appliqué à un système de transmission progressive d'images utilisant le codeur SPIHT. Dans un premier temps, les effets des paramètres internes de l'algorithme présenté sont étudiés. Ensuite, les performances du système étudié sont comparées à celles d'un système de codage classique utilisant le code CRC pour la détection d’erreurs et le code RCPC pour leur correction. En terme de TEP, et dans le cas de décodage pondéré, le système utilisant le décodage conjoint est plus performant que le système classique pour les rapports signal à bruit relativement élevés

Low-complexity chase-like decoding of variable-length codes

International audienceMost source coding standards (voice, audio, image and video) use Variable-Length Codes (VLCs) for compression. However, the VLC decoder is very sensitive to transmission errors in the compressed bit-stream. Previous contributions, using a trellis description of the VLC codewords to perform soft decoding, have been proposed. Significant improvements are achieved by this approach when compared with prefix decoding. Nevertheless, for realistic VLCs, the complexity of the trellis technique becomes intractable. In this paper, we propose a soft-input VLC decoding method using an a priori knowledge of the lengths of the source-symbol sequence and the compressed bit-stream with Maximum A Posteriori (MAP) sequence estimation. Performance in the case of transmission over an Additive White Gaussian Noise (AWGN) channel is evaluated. Simulation results show that the proposed decoding algorithm leads to significant performance gain in comparison with the prefix VLC decoding besides exhibiting very low complexity. A new VLC decoding method generating additional information regarding the reliability of the bits of the compressed bit-stream is also proposed. We consider the serial concatenation of a VLC with two types of channel code and perform iterative decoding. Results show that, when concatenated with a recursive systematic convolutional code (RSCC), iterative decoding provides remarkable error correction performance. In fact, a gain of about 2.3 dB is achieved, in the case of transmission over an AWGN channel, with respect to tandem decoding. Second, we consider a concatenation with a low-density parity-check (LDPC) code and it is shown that iterative joint source/channel decoding outperforms tandem decoding and an additional coding gain of 0.25 dB is achieved

Low-complexity joint source/channel turbo decoding of arithmetic codes with image transmission application

International audienceIn this paper a novel joint source channel (JSC) decoding technique is presented. The proposed approach enables iterative decoding for serially concatenated arithmetic codes and convolutional codes. Iterations are performed between Soft In Soft Out (SISO) component decoders. For arithmetic decoding, we proposed to employ a low complex trellis search technique to estimate the best transmitted codewords and generate soft outputs. Performance of the presented system are evaluated in terms of PER, in the case of transmission across the AWGN channel. Simulation results show that the proposed JSC iterative scheme leads to significant gain in comparison with a traditional separated decoding. Finally, the practical relevance of the proposed technique is validated under an image transmission system using the SPIHT codec

Low complexity treillis-based iterative decoding of arithmetic codes with transmission application

International audienceIn this paper, a novel joint source channel (JSC) decoding technique is presented. The proposed approach enables iterative decoding for serially concatenated arithmetic codes and convolutional codes. Iterations are performed between Soft Input Soft Output (SISO) component decoders. For arithmetic decoding, we proposed to employ a low complex trellis search technique to estimate the best transmitted codeword and generate soft outputs. Performances of the presented system are evaluated in terms of PER, in the case of transmission across the AWGN channel. Simulation results show that the proposed JSC iterative scheme leads to significant gain in comparison with a traditional separated decoding. Finally, the practical relevance of the proposed technique is validated under an image transmission system using the SPIHT codec

Low-complexity chase-like decoding of variable-length codes

International audienceMost source coding standards (voice, audio, image and video) use Variable-Length Codes (VLCs) for compression. However, the VLC decoder is very sensitive to transmission errors in the compressed bit-stream. Previous contributions, using a trellis description of the VLC codewords to perform soft decoding, have been proposed. Significant improvements are achieved by this approach when compared with prefix decoding. Nevertheless, for realistic VLCs, the complexity of the trellis technique becomes intractable. In this paper, we propose a soft-input VLC decoding method using an a priori knowledge of the lengths of the source-symbol sequence and the compressed bit-stream with Maximum A Posteriori (MAP) sequence estimation. Performance in the case of transmission over an Additive White Gaussian Noise (AWGN) channel is evaluated. Simulation results show that the proposed decoding algorithm leads to significant performance gain in comparison with the prefix VLC decoding besides exhibiting very low complexity. A new VLC decoding method generating additional information regarding the reliability of the bits of the compressed bit-stream is also proposed. We consider the serial concatenation of a VLC with two types of channel code and perform iterative decoding. Results show that, when concatenated with a recursive systematic convolutional code (RSCC), iterative decoding provides remarkable error correction performance. In fact, a gain of about 2.3 dB is achieved, in the case of transmission over an AWGN channel, with respect to tandem decoding. Second, we consider a concatenation with a low-density parity-check (LDPC) code and it is shown that iterative joint source/channel decoding outperforms tandem decoding and an additional coding gain of 0.25 dB is achieved

Chase like decoding of arithmetic codes with image transmission applications

International audience

Distributed video coding in pixel domain using spatial correlation at the decoder

International audienceThe application of distributed coding in many media applications, where low power and low-complexity encoder device is essential, is a new paradigm. In this paper, we propose a new pixel-domain Distributed Video Coding (DVC) scheme, in which both temporal and spatial correlations are exploited at the decoder. The Slepian-Wolf decoder is modified by introducing a source decoder to exploit Wyner-Ziv frame's spatial correlation. We assume the most significant bitplanes to be one-dimensional stationary markov process. The markov characteristic means that this source has a residual redundancy providing additional information for the receiver and can be exploited to correct some errors introduced by the virtual channel, through a joint source-channel decoding scheme

Joint source/channel Chase-like decoding of entropy-encoded sources

International audienceIt was demonstrated in recent contributions that Joint Source/Channel (JSC) decoding could be a good issue to make error correction in the case of transmission of entropy-encoded data. This paper addresses a new scheme for JSC decoding of Variable-Length Codes (VLC) and Arithmetic Codes (AC) based on Maximum a posteriori (MAP) sequence estimation. Previous contributions used a trellis description of the entropy encoding machine to perform soft input decoding. Referred to hard input classical decoding, significant improvements are achieved. Nevertheless, for realistic contexts, the complexity of the trellis-based technique becomes intractable. The decoding algorithm we propose performs Chase-like decoding using a priori knowledge of the source symbol sequence and the compressed bit-stream lengths. Performance in the case of transmission on an Additive White Gaussian Noise (AWGN) channel is evaluated in terms of Packet Error Rate (PER). Simulation results show that the proposed decoding algorithm leads to significant performance gain in comparison to classical VLC and AC decoding while exhibiting very low complexity. The practical relevance of the proposed technique is validated in the case of image transmission across the AWGN channel. Lossless and lossy image compression schemes are considered, and the Chase-like entropy decoder shows excellent results in terms of PER and reconstructed image quality