Joint Iterative Decoding of Trellis-Based VQ and TCM
Joint Iterative Decoding of Trellis-Based VQ and TCM
A joint video and channel coded system employing an iteratively decoded serial concatenation of a Vector Quantization (VQ) based video codec and a Trellis-Coded Modulation (TCM) scheme is proposed. The video codec imposes VQ-induced code constraints, which may be completely described by a trellis structure, which is employed as the basis for optimal minimum mean-squared-error VQ-encoding and -decoding. In the latter case, the Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm is employed to facilitate the iterative exchange of soft information between the VQ and TCM decoder. An error-free video reconstruction quality is supported using 16-level Quadrature Amplitude Modulation (16QAM) based TCM for transmission over Rayleigh-fading channels at a Signal-to-Noise Ratio (SNR) per bit of 5.25 dB. This value is within 1.29 dB of the Rayleigh channel’s capacity at our system’s effective bandwidth-efficiency of 2 bits/s/Hz. Owing to its ability to exploit the VQ-induced code constraints during iterative decoding, the joint video and channel coding approach is found to consistently outperform the Shannonian source and channel separation philosophy. This is achieved at the cost of a 1.6 times higher computational complexity. Finally, the convergence of the iterative decoder is investigated with the aid of a novel so-called EXtrinsic Information Transfer (EXIT) chart.
video, vector quantization, VQ, variable length coding, VLC, iterative decoding, EXIT chart, serial concatenation, joint source and channel coding, trellis, BCJR, Viterbi, MMSE, soft
1327-1336
Maunder, R. G.
76099323-7d58-4732-a98f-22a662ccba6c
Kliewer, J.
e500e56d-f2d2-45df-8962-56274e41a1a1
Ng, S. X.
e19a63b0-0f12-4591-ab5f-554820d5f78c
Wang, J.
dc08532d-c8db-4f40-83ae-f5abf4acc068
Yang, L.-L.
ae425648-d9a3-4b7d-8abd-b3cfea375bc7
Hanzo, L.
66e7266f-3066-4fc0-8391-e000acce71a1
April 2007
Maunder, R. G.
76099323-7d58-4732-a98f-22a662ccba6c
Kliewer, J.
e500e56d-f2d2-45df-8962-56274e41a1a1
Ng, S. X.
e19a63b0-0f12-4591-ab5f-554820d5f78c
Wang, J.
dc08532d-c8db-4f40-83ae-f5abf4acc068
Yang, L.-L.
ae425648-d9a3-4b7d-8abd-b3cfea375bc7
Hanzo, L.
66e7266f-3066-4fc0-8391-e000acce71a1
Maunder, R. G., Kliewer, J., Ng, S. X., Wang, J., Yang, L.-L. and Hanzo, L.
(2007)
Joint Iterative Decoding of Trellis-Based VQ and TCM.
IEEE Transactions on Wireless Communications, 6 (4), .
Abstract
A joint video and channel coded system employing an iteratively decoded serial concatenation of a Vector Quantization (VQ) based video codec and a Trellis-Coded Modulation (TCM) scheme is proposed. The video codec imposes VQ-induced code constraints, which may be completely described by a trellis structure, which is employed as the basis for optimal minimum mean-squared-error VQ-encoding and -decoding. In the latter case, the Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm is employed to facilitate the iterative exchange of soft information between the VQ and TCM decoder. An error-free video reconstruction quality is supported using 16-level Quadrature Amplitude Modulation (16QAM) based TCM for transmission over Rayleigh-fading channels at a Signal-to-Noise Ratio (SNR) per bit of 5.25 dB. This value is within 1.29 dB of the Rayleigh channel’s capacity at our system’s effective bandwidth-efficiency of 2 bits/s/Hz. Owing to its ability to exploit the VQ-induced code constraints during iterative decoding, the joint video and channel coding approach is found to consistently outperform the Shannonian source and channel separation philosophy. This is achieved at the cost of a 1.6 times higher computational complexity. Finally, the convergence of the iterative decoder is investigated with the aid of a novel so-called EXtrinsic Information Transfer (EXIT) chart.
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Published date: April 2007
Keywords:
video, vector quantization, VQ, variable length coding, VLC, iterative decoding, EXIT chart, serial concatenation, joint source and channel coding, trellis, BCJR, Viterbi, MMSE, soft
Organisations:
Southampton Wireless Group
Identifiers
Local EPrints ID: 264077
URI: https://eprints.soton.ac.uk/id/eprint/264077
PURE UUID: d9059e57-26fc-4072-ae4e-29f07ed504a1
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Date deposited: 23 May 2007
Last modified: 06 Jun 2018 13:14
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