The Experts below are selected from a list of 144 Experts worldwide ranked by ideXlab platform

Khalid Sayood - One of the best experts on this subject based on the ideXlab platform.

  • joint source channel coding for variable length codes
    IEEE Transactions on Communications, 2000
    Co-Authors: Khalid Sayood, Hasan H. Otu, N Demir
    Abstract:

    When using entropy coding over a noisy channel, it is customary to protect the highly vulnerable bitstream with an error correcting code. In this paper, we propose a technique which utilizes the Residual Redundancy at the output of the source coder to provide error protection for entropy coded systems.

  • a joint source channel coder with block constraints
    IEEE Transactions on Communications, 1999
    Co-Authors: Hasan H. Otu, Khalid Sayood
    Abstract:

    The assumptions made about the source during source coder design result in a Residual Redundancy at the output of the source coder. This Redundancy can be utilized for error protection without any additional channel coding. Joint source/channel coders obtained using this idea via maximum a posteriori probability decoders tend to fail at low probability of error. In this paper, we propose a modification of the standard approach which provides protection at low error rates as well.

  • joint source channel coding for variable length codes
    Data Compression Conference, 1998
    Co-Authors: N Demir, Khalid Sayood
    Abstract:

    When using entropy coding over a noisy channel it is customary to protect the highly vulnerable bitstream with an error correcting code. In this paper we propose a technique which utilizes the Residual Redundancy at the output of the source coder to provide error protection for entropy coded systems. The proposed approach provides 4-10 dB improvement over the standard approaches at a reduced rate.

  • a constrained joint source channel coder design
    IEEE Journal on Selected Areas in Communications, 1994
    Co-Authors: Khalid Sayood, Fuling Liu, Jerry D. Gibson
    Abstract:

    The design of joint source/channel coders in situations where there is Residual Redundancy at the output of the source coder is examined. It has previously been shown that this Residual Redundancy can be used to provide error protection without a channel coder. In this paper, this approach is extended to conventional source coder/convolutional coder combinations. A family of nonbinary encoders is developed which more efficiently use the Residual Redundancy in the source coder output. It is shown through simulation results that the proposed systems outperform conventional source-channel coder pairs with gains of greater than 9 dB in the reconstruction SNR at high probability of error. >

  • a joint source channel coder design
    International Conference on Communications, 1993
    Co-Authors: Khalid Sayood, Fuling Liu, Jerry D. Gibson
    Abstract:

    The situation in which there is Residual Redundancy at the source coder output is examined. It has previously been shown that this Residual Redundancy can be used to provide error correction without a channel encoder. This approach is extended to conventional source coder/convolutional coder combinations. A design for nonbinary encoders for this situation is developed. It is shown through simulation results that the proposed systems consistently outperform conventional source-channel coder pairs with gains of greater than 10 dB at high probability of error. >

T. Hindelang - One of the best experts on this subject based on the ideXlab platform.

  • combined source channel de coding can a priori information be used twice
    International Symposium on Information Theory, 2000
    Co-Authors: T. Hindelang, Tim Fingscheidt, Nambirajan Seshadri, Richard Vandervoort Cox
    Abstract:

    In the digital transmission of speech, audio, images and video signals Residual Redundancy is often left after source coding due to the complexity and delay constraints. This Redundancy remains both inside one block or frame but also in a time correlation of subsequent frames. Both kinds of Redundancy are used in an iterative process of source and channel decoding to improve the quality of the transmitted parameters. For better understanding, Gaussian distributed and time correlated parameters are used.

  • combined source channel de coding can a priori information be used twice
    International Conference on Communications, 2000
    Co-Authors: T. Hindelang, Tim Fingscheidt, Nambirajan Seshadri, Richard Vandervoort Cox
    Abstract:

    In digital transmission of speech, audio, images and video signals Residual Redundancy is often left after source coding due to the complexity and delay constraints. This Redundancy remains both inside one block or frame but also in a time correlation of subsequent frames. We describe an approach to improve channel and source decoding by using both kinds of correlation. Further on we consider the bit-mapping and the multiplexing in coding and its effect on decoding. The mutual information as measurement for the gain in decoding through a priori information is explained. In this work on combined source and channel decoding, we try to answer the following question: can a priori information that models the source parameters be used twice; first at the channel decoder and then at the source decoder. The channel decoder uses the a priori information that models the bit stream generated by the source coder. This does not capture all the details of the source parameter level statistics. By exploiting the a priori knowledge of parameters (once more) at the source decoder, we show that it is possible to achieve better reconstruction than if this information was used at either of the decoders.

  • quality enhancement of coded and corrupted speeches in gsm mobile systems using Residual Redundancy
    International Conference on Acoustics Speech and Signal Processing, 1997
    Co-Authors: T. Hindelang, C Erben
    Abstract:

    There is often Residual Redundancy remaining in coded speech data, even if a powerful speech codec (e.g. the full rate coder used in GSM mobile communications) is employed. By using such Redundancy together with the information provided by the channel decoder, such as soft output (L-value), the number of channel bits inverted by the decoder, or a cyclic Redundancy check, the bit error rate can be further reduced and a more graceful degradation of speech quality can be achieved, especially under bad channel conditions. In this paper, we report on the study with regard to this aspect for GSM full rate speech transmission and error concealment. The algorithms developed can be easily implemented with a currently available DSP designed for GSM mobile phones.

Thomas E. Fuja - One of the best experts on this subject based on the ideXlab platform.

  • design of joint source channel decoding algorithms for the 2400 bps melp speech coder
    1999
    Co-Authors: Thomas E. Fuja, Tahereh Fazel
    Abstract:

    Mixed excitation linear predictive speech coding (MELP) is the new U.S. federal standard for 2400 bits/sec speech compression. Although, MELP's performance is much better that its predecessor, linear predictive coding (LPC) and code excited linear coding (CELP), it is not a perfect source coder. As a result there is Redundancy in its output bit stream. In this dissertation, we consider the problem of reliable transmission MELP-encoded speech over noisy communication channels. The goal is to use this Redundancy to improve the quality of reconstructed speech. Our objective is to design joint source-channel codes compatible with MELP bit stream. We begin by modeling some of the MELP parameters as one-step Markov chains. Then using this model, we quantify the Residual Redundancy of the MELP output bit stream. We find out that more than 20% of the bits in the multistage vector quantizer indices (MSVQ parameter) and pitch index and gain indices are redundant. We design a convolutional decoder to exploit the Residual Redundancy in the MELP bit stream using the Markov model parameters. Some simulation results are presented to compare the new source controlled decoder with an ordinary convolutional decoder. Our next contribution is the design of a source-controlled symbol (non-binary) turbo decoder compatible with the MELP bit stream. We introduce a new modified BCJR algorithm for source-controlled turbo decoding. Results indicates that in presence of source Redundancy, the new decoder outperforms the regular turbo decoder. In the last chapter, we design a new source-controlled Generalized Minimum Distance (GMD) algorithm to exploit the Redundancy of the pitch and gain and MSVQ bits. This new decoder can be used with a regular error/erasure decoder for block codes. We choose Reed-Solomon codes for our simulation and the results show that the new source-controlled GMD decoder is more successful in a very noisy channel than a regular GMD decoder.

  • joint source channel decoding of variable length encoded sources
    Information Theory Workshop, 1998
    Co-Authors: A.h. Murad, Thomas E. Fuja
    Abstract:

    In systems that employ source coding, imperfect compression may leave some Redundancy in the data at the input to the channel encoder. This paper presents a new method for exploiting that Redundancy via joint source-channel maximum a posteriori (MAP) decoding. The technique may be applied to systems that employ a variable-length source code in conjunction with a channel code; the decoder uses the Residual Redundancy that remains after compression to enhance robustness. The proposed technique (applicable to both memoryless and Markov sources) combines the source model, the source decoder and the channel decoder to construct a joint decoder with a conventional Viterbi structure. Simulation results comparing the performance of this approach with the conventional tandem decoding approach are presented.

Ragnar Thobaben - One of the best experts on this subject based on the ideXlab platform.

  • iterative joint source channel decoding of variable length codes using Residual source Redundancy
    IEEE Transactions on Wireless Communications, 2005
    Co-Authors: Jorg Kliewer, Ragnar Thobaben
    Abstract:

    We present a novel symbol-based soft-input a posteriori probability (APP) decoder for packetized variable-length encoded source indexes transmitted over wireless channels where the Residual Redundancy after source encoding is exploited for error protection. In combination with a mean-square or maximum APP estimation of the reconstructed source data, the whole decoding process is close to optimal. Furthermore, solutions for the proposed APP decoder with reduced complexity are discussed and compared to the near-optimal solution. When, in addition, channel codes are employed for protecting the variable-length encoded data, an iterative source-channel decoder can be obtained in the same way as for serially concatenated codes, where the proposed APP source decoder then represents one of the two constituent decoders. The simulation results show that this iterative decoding technique leads to substantial error protection for variable-length encoded correlated source signals, especially, when they are transmitted over highly corrupted channels.

Richard Vandervoort Cox - One of the best experts on this subject based on the ideXlab platform.

  • combined source channel de coding can a priori information be used twice
    International Symposium on Information Theory, 2000
    Co-Authors: T. Hindelang, Tim Fingscheidt, Nambirajan Seshadri, Richard Vandervoort Cox
    Abstract:

    In the digital transmission of speech, audio, images and video signals Residual Redundancy is often left after source coding due to the complexity and delay constraints. This Redundancy remains both inside one block or frame but also in a time correlation of subsequent frames. Both kinds of Redundancy are used in an iterative process of source and channel decoding to improve the quality of the transmitted parameters. For better understanding, Gaussian distributed and time correlated parameters are used.

  • combined source channel de coding can a priori information be used twice
    International Conference on Communications, 2000
    Co-Authors: T. Hindelang, Tim Fingscheidt, Nambirajan Seshadri, Richard Vandervoort Cox
    Abstract:

    In digital transmission of speech, audio, images and video signals Residual Redundancy is often left after source coding due to the complexity and delay constraints. This Redundancy remains both inside one block or frame but also in a time correlation of subsequent frames. We describe an approach to improve channel and source decoding by using both kinds of correlation. Further on we consider the bit-mapping and the multiplexing in coding and its effect on decoding. The mutual information as measurement for the gain in decoding through a priori information is explained. In this work on combined source and channel decoding, we try to answer the following question: can a priori information that models the source parameters be used twice; first at the channel decoder and then at the source decoder. The channel decoder uses the a priori information that models the bit stream generated by the source coder. This does not capture all the details of the source parameter level statistics. By exploiting the a priori knowledge of parameters (once more) at the source decoder, we show that it is possible to achieve better reconstruction than if this information was used at either of the decoders.