Channel codes that exploit the residual redundancy in CELP-encoded speech

Alajaji, Fady; Phamdo, N.; Fuja, T.E.

doi:10.1109/89.536927

Cited by 115 publications

(63 citation statements)

References 8 publications

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“…sources over BPSK-modulated AWGN and Rayleigh fading channels with known CSI. 3 In the following, all NSTCs adopt the decoder discussed in Section IV-B, while all systematic codes employ the BCJR algorithm with the modification proposed in [29].…”

Section: Numerical Results and Discussionmentioning

confidence: 99%

“…It is proved that for a discrete memoryless source and channel pair, there exist convolutional codes of rate that can be used to perform reliable joint source and channel coding (under maximum a posteriori (MAP) decoding) as long as , where is the source entropy and is the channel capacity. Recently, several studies 0090-6778/04$20.00 © 2004 IEEE (e.g., [1]- [3], [7]- [22], etc.) have also shown that appropriate use of the source redundancy can significantly improve the system performance.…”

mentioning

confidence: 99%

“…However, most existing source encoders are suboptimal, particularly fixed-length encoders that are commonly used for transmission over noisy channels; thus, the source-encoder output contains some residual redundancy. For example, the 4.8 kb/s US FS 1016 CELP speech vocoder produces line spectral parameters that contain 41.5% of residual redundancy due to nonuniformity and memory [3]. Variable-length or entropy codes (e.g., Huffman codes), which can be asymptotically optimal (for sufficiently large blocks of source symbols), could be employed instead of fixed-length codes or in conjunction with them.…”

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confidence: 99%

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Transmission of Nonuniform Memoryless Sources via Nonsystematic Turbo Codes

Zhu

Alajaji

Bajcsy

et al. 2004

IEEE Trans. Commun.

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Abstract-We investigate the joint source-channel coding problem of transmitting nonuniform memoryless sources over binary phase-shift keying-modulated additive white Gaussian noise and Rayleigh fading channels via turbo codes. In contrast to previous work, recursive nonsystematic convolutional encoders are proposed as the constituent encoders for heavily biased sources. We prove that under certain conditions, and when the length of the input source sequence tends to infinity, the encoder state distribution and the marginal output distribution of each constituent recursive convolutional encoder become asymptotically uniform, regardless of the degree of source nonuniformity. We also give a conjecture (which is empirically validated) on the condition for the higher order distribution of the encoder output to be asymptotically uniform, irrespective of the source distribution. Consequently, these conditions serve as design criteria for the choice of good encoder structures. As a result, the outputs of our selected nonsystematic turbo codes are suitably matched to the channel input, since a uniformly distributed input maximizes the channel mutual information, and hence, achieves capacity. Simulation results show substantial gains by the nonsystematic codes over previously designed systematic turbo codes; furthermore, their performance is within 0.74-1.17 dB from the Shannon limit. Finally, we compare our joint source-channel coding system with two tandem schemes which employ a fourth-order Huffman code (performing near-optimal data compression) and a turbo code that either gives excellent waterfall bit-error rate (BER) performance or good error-floor performance. At the same overall transmission rate, our system offers robust and superior performance at low BERs ( 10 4 ), while its complexity is lower.Index Terms-Additive white Gaussian noise (AWGN) and Rayleigh fading channels, joint source-channel coding, nonsystematic turbo codes, nonuniform independent and identically distributed (i.i.d.) sources, Shannon limit.Paper approved by A. K. Khandani, the Editor for Coding and Information Theory of the IEEE Communications Society.

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Section: Numerical Results and Discussionmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Transmission of Nonuniform Memoryless Sources via Nonsystematic Turbo Codes

Zhu

Alajaji

Bajcsy

et al. 2004

IEEE Trans. Commun.

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“…That means we should use as a priori information the joint probability of bits representing a source coder symbol instead of single bit probabilities. Such scheme was applied in [3] to the particular case of the FS 4.8 kbit/s CELP coder. For most general case, Heinen [5] derives an approximate method to exploit joint a priori probabilities of bits groups within the channel decoding process.…”

Section: Introductionmentioning

confidence: 99%

“…One approach ( [1], [2]) considers that the residual redundancy may be used alone to perform error correction without any explicit channel coding. Another approach ( [3], [4]) consists in combining the residual redundancy with explicit redundancy inserted by a convolutional coder in order to provide better error protection. The latter approach is particularly suited if one want to ensure a low error rate over a wide range of channel qualities.…”

Section: Introductionmentioning

confidence: 99%

Channel decoding using inter- and intra-correlation of source encoded frames

Veaux

Scalart²,

Gilloire³

Proceedings DCC 2000. Data Compression Conference

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The goal of source controlled channel decoding is to improve the performance of the channel decoder by using the residual redundancy of the source encoded data. The original approach exploits only the interframe correlation between bits and few simple scheme have been devised in order to use the intraframe correlation. In this paper, we present an efficient method to exploit the intraframe correlation during the channel decoding process. We estimate an a priori soft value of the bit being decoded from the bits already decoded along the trellis path. This estimate is then used together with the estimate obtained from interframe correlation in the Viterbi metric. We also introduce an adaptive estimator of bit correlation that takes into account the reliability of the bits at the decoder output. Our channel decoding algorithm is applied to the full-rate and enhanced full-rate speech codecs in the GSM system and results in a noticeable improvement of the bit error rate.

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Bibliography

2010

Near‐Capacity Variable‐Length Coding

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Channel codes that exploit the residual redundancy in CELP-encoded speech

Cited by 115 publications

References 8 publications

Transmission of Nonuniform Memoryless Sources via Nonsystematic Turbo Codes

Transmission of Nonuniform Memoryless Sources via Nonsystematic Turbo Codes

Channel decoding using inter- and intra-correlation of source encoded frames

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