• Proceedings of the KOSOMBE Conference
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• v.1991 no.11
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• pp.44-47
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• 1991

There exists a transform trellis code that is optimal for stationary Gaussian sources and the squared-error distortion measure at all rates. In this paper, we train an asymptotically optimal version of such a code to obtain one which is matched better to the statistics of real world data. The training algorithm uses the M-algorithm to search the trellis codebook and the LBG-algorithm to update the trellis codebook. To adapt the codebook for the varying input data. we use two gain-adaptive methods. The gain-adaptive scheme 1, which normalizes input block data by its gain factor, is applied to images at rate 0.5 bits/pixel. When each block is encoded at the same rate, the nonstationarity among the block variances leads to a variation in the resulting distortion from one block to another. To alleviate the non-uniformity among the encoded image, we design four clusters from the block power, in which each cluster has its own trellis codebook and different rates. The rate of each cluster is assigned through requiring a constant distortion per-letter. This gain-adaptive scheme 2 produces good visual and measurable quality at low rates.

• Journal of the Institute of Convergence Signal Processing
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• v.5 no.3
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• pp.223-229
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• 2004

Recently, OFDM and STC techniques have been considered to be candidate to support multimedia services in the next generation mobile radio communications and have been developed the many communications systems in order to achieve the high data rates. In this paper, we propose the Trellis-Coded Differential Space Time Modulation-OFDM system with multiple symbol detection. The Trellis-code performs the set partition with unitary group codes. The Viterbi decoder containing new branch metrics is introduced in order to improve the bit error rate (BER) in the differential detection of the unitary differential space time modulation. Also, we describe the Viterbi algorithm in order to use this branch metrics. Our study shows that such a Viterbl decoder improves BER performance without sacrificing bandwidth and power efficiency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.12C
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• pp.1601-1605
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• 2004

When codeword sequence has two or less successive transitions, the performance of 4th-order partial response maximum-likelihood (PRML) detector can be improved. However, the code leads to an unacceptable loss of performance due to the low code rate. For a rate 718 code that MTR constraint (i) of each codeword is limited to 2, and j is allowed to be 3 when codewords are connected, we modified the trellis of PRML detector to combine j=2 with J=3. We confirmed that the rate 718 coded 4th-order PRML detection with combined trellis achieves the SNR gain more than 2dB compared to the rate 819 coded 4u_order PRML detection at 10-s BER in high-density longitudinal or perpendicular magnetic recording systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.2
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• pp.86-91
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• 2014

Holographic data storage (HDS) has a number of advantages, including a high transmission rate through the use of a charge coupled device array for reading two-dimensional (2D) pixel image data, and a high density capacity. HDS also has disadvantages, including 2d intersymbol interference by neighboring pixels and interpage interference by multiple pages stored in the same holographic volume. These problems can be eliminated by modulation codes. We propose a 7/9 error-correcting modulation code that exploits a Viterbi-trellis algorithm and has a code rate larger (about 0.778) than that of the conventional 6/8 balanced modulation code. We show improved performance of the bit error rate with the proposed scheme compared to that of the simple 7/9 code without the trellis scheme and the 6/8 balanced modulation code.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.38-38
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• 2004

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.10
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• pp.569-573
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• 2014

Holographic data storage is a strong contender to become the next-generation data storage method. Its major weaknesses are two-dimensional intersymbol interference between neighboring pixels and interpage interference caused by storing multiple pages in a single volume of hologram. In this paper, we present a trellis encoding scheme of 6/8 balanced modulation code, to address the two weaknesses. The proposed modulation coding scheme captures on characteristics of the balanced code: the scheme relaxes IPI and enables error correction by exploiting the trellis structure. The proposed method showed improved SNR over the conventional 6/8 modulation code.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.3 no.2
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• pp.30-38
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• 1992

In this paper, in order to apply the $\pi$/4 shift QPSK to TCM, we propose the $\pi$/8 shift 8PSK modulation technique and the trellis-coded $\pi$/8 shift 8PSK performing signal set expansion and set partition by phase difference. In addition, the Viterbi decoder with branch metrics of the squared Euclidean distance of the first phase difference as well as the Lth phase difference is introduced in order to improve the bit error rate(BER) performance in differential detection of the trellis-coded $\pi$/8 shift 8 PSK. The proposed Viterbi decoder is conceptually the same as the sliding multiple de- tection by using the branch metric with first and Lth order phase difference. We investigate the performance of the uncoded .pi. /4 shift QPSK and the trellis-coded $\pi$/8 shift 8PSK with or without the Lth phase difference metric in an additive white Gaussian noise (AWGN) and Rayleigh fading channel using the Monte Carlo simulation. The study shows that the $\pi$/4 shift QPSK with the Trellis-code i. e. the trellis-coded $\pi$/8 shift 8PSK is an attractive scheme for power and bandlimited systems and especially, the Viterbi decoder with first and Lth phase difference metrics improves BER performance. Also, the next proposed algorithm can be used in the TC $\pi$/8 shift 8PSK as well as TC MDPSK.

• The Journal of the Acoustical Society of Korea
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• v.11 no.1
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• pp.22-34
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• 1992

There exists a transform trellis code that is optimal for stationary Gaussian sources and the squared-error distortion measure at all rates. In this paper, we train an asymptotically optimal version of such a code to obtain one which is matched better to the statistics of real world data. The training algorithm uses the M algorithm to search the trellis codebook and the LBG algorithm to update the trellis codebook. We investigate the trained transform trellis coding scheme for the first-order AR(autoregressive) Gaussian source whose correlation coefficient is 0.9 and actual speech sentences. For the first-order AR source, the achieved SNR for the test sequence is from 0.6 to 1.4 dB less than the maximum achievable SNR as given by Shannon's rate-distortion function for this source, depending on the rate and surpasses all previous known results for this source. For actual speech data, to achieve improved performance, we use window functions and gain adaptation at rate 1.0 bits/sample.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.9
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• pp.34-43
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• 1994

The unequal symbol error probability of TCM(trellis coded modulation) is analyzed and applied to the derivation of bit error probability of /RS/Trellis concatenated coded-modulation system. An upper bound of the symbol error probability of TCM concatenated with RS code is obtained by exploiting the unequal symbol error probability of TCM, and it is applied to the derivation of the upper bound of the bit error probability of the RS/Trellis concatenated coded-modulation system. Our upper bounds of the concatenated codes are tighter than the earlier established other upper bounds.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.1C
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• pp.18-24
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• 2005

In this paper, a new trellis-coded differential unitary space-time modulation (TC-DUSTM) scheme based on amplitude/phase-shift-keying (APSK) signals is proposed. In particular, the design criterion of the trellis coding is proposed to combine the trellis coding and DUSTM scheme based on APSK constellation. From the computer simulations, we verify the superiority of the proposed TC-DUSTM based on APSK signals at the higher transmission rate. In addition, the proposed scheme can suppress the irreducible error of the differential scheme.