• Proceedings of the IEEK Conference
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.2039-2042
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• 2002

In this paper, we propose a technique used to simplify the trellis diagram, thus, reduce the complexity of Viterbi decoder in term of the number of Compare-Select (CS) operations needs in decoding process. It is shown that if the branch metrics are properly decomposed into orthogonal components. The trellis diagram can be modified that each original state with large number branches terminating to it can be broken into a number of sub-states having smaller number of branches terminating to them. Simulation results shown that the newly proposed technique can be used reduced the complexity of 8 and 16 PSK-TCMs without degrading the BER performance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• 제47권3호
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• pp.240-244
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• 2019

SOQPSK-TG which consists of differential precoder and CPM modulator was adopted as telemetry standard because of its high power and bandwidth efficiency. We proposed four-state Viterbi decoder for SOQPSK-TG. Reducing the trellis state to four was possible by simplifying frequency pulse of SOQPSK-TG to square pulse of symbol length 2 and combing this with differential precoder. Compared with conventional SOQPSK-TG receivers, computer simulation result shows about 1 dB performance improvement was achieved at BER of $10^{-5}$ in AWGN channel.

• Proceedings of the IEEK Conference
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• 대한전자공학회 2004년도 하계종합학술대회 논문집(1)
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• pp.265-268
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• 2004

In this paper. we propose an adaptive step-size algorithm for the adaptive interference canceller (AIC) in the space-time trellis coded DS-CDMA system. In the AIC, the performance of the blind LMS algorithms that updates the tap-weight vector of the AIC is heavily dependent on the choice of step-size. To improve the performance of the fixed step-size AIC (FS-AIC), the regular adaptive step-size algorithm is extended in complex domain and applied to the joint AIC and ML decoder scheme. Simulation results show that the joint adaptive step-size AIC (AS-AIC) and ML decoder scheme using the proposed algorithm has boner performance than not only the conventional ML decoder but also the joint FS-AIC and ML decoder scheme without much increase of the decoding delay and complexity.

• Journal of the Institute of Electronics Engineers of Korea SD
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• 제46권8호
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• pp.86-94
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• 2009

An idea to improve the performance of error correction with the amplification of input symbol errors is proposed to ease the mismatching problem which occurs in the hardware implementation of the differential analog PRML decoder. The differential analog PRML decoder is the decoder with two blocks of trellis diagram one of which is without branches of "0" and the other one is without the branches of "1". Decoding is performed by comparing the outputs of two blocks. The decoding error is likely to occur when the difference of two outputs is very small and the hardware implementation is not precise due to mismatching. The proposed idea is to increase the discrimination margin for the output "0" and "1" by amplifying the symbol error while the larger path metrics are saturated. To show the performance improvement of decoding with the proposed idea, simulation results are included

• The Journal of Korean Institute of Communications and Information Sciences
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• 제29권3A호
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• pp.324-330
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• 2004

In this paper, we propose the TCM(Trellis coded modulation) decoding scheme that reduces the number of operations in branch metric with STBC(space time block codes) channel information and present the implementation results. The proposed TCM decoding scheme needs only 1 signal point in each TCM subset. Using bias point scheme, It detects the minimum distance symbol. The proposed TCM decoding scheme can reduce the branch metric calculations. In case of 16QAM 8 subset, the reduction ratio is about 50％ and for 64QAM 8 subset, about 80％ reduction can be obtained. The results of logic synthesis for the TCM and STBC decoder with the proposed scheme are 57.6K gate count.

• The Transactions of the Korean Institute of Electrical Engineers D
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• 제52권11호
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• pp.650-656
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• 2003

A high speed Viterbi decoder with a circularly connected 2-dimensional analog processing ceil array Is proposed. The proposed Viterbi .decoder has a 2-dimensional parallel processing structure in which an analog processing cell is placed at each node of a trellis diagram, the output column of the analog processing cells is connected to the decoding column, and thus, the output(last) column becomes a column right before the decoding(first) column. The reference input signal given at a decoding column is propagated to the whole network while Its magnitude is reduced by the amount of a error metric on each branch. The circuit-based decoding is done by adding a trigger signals of same magnitudes to disconnect the path corresponding to logic 0 (or 1) and by observing its effect at an output column (the former column of the decoding column). The proposed Viterbi decoder has advantages in that it is operated with better performance of error correction, has a shorter latency and requires no path memories. The performance of error correction with the proposed Viterbi decoder is tested via the software simulation.

• Journal of Navigation and Port Research
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• 제36권10호
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• pp.845-849
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• 2012

The next-generation wireless communication requires fast transmission speeds with various services and high reliability. In order to satisfy these needs we study MIMO system used layered space time coded system (LST) combining space time trellis codes (STTC) with turbo codes. In LST, two codes that are inner and outer codes are concatenated in the serial fashion. The inner codes are turbo Pi codes suggested in DVB-RCS NG system, and outer codes are STTC codes proposed by Blum. The interleaver technique is used to efficiently combine two codes. And we proposed and simulated that a full iteration method between turbo decoder and BCJR decoder to improve the performance instead of only processing inner-iteration turbo decoder. The simulation results of proposed effective layered method show improving BER performance about 1.3~1.5dB than conventional one.

• The Journal of Korean Institute of Information Technology
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• 제17권3호
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• pp.31-41
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• 2019

In this paper, we design and implement the simulator for the transmitter and receiver of 4D-8PSK TCM with 2.0, 2.25, 2.5, and 2.75 bits/symbol-channel transmission efficiency recommended by the CCSDS for satellite communications, and then analyze the BER performance of 4D-8PSK TCM system in AWGN channel. The transmitter of 4D-8PSK TCM is designed in accordance with the recommendation in the CCSDS standard. Meanwhile, for the receiver design of 4D-8PSK TCM, we design the differential decoder generalizing the differential encoder/decoder scheme. The trellis decoding algorithm is designed by applying the auxiliary trellis information and the Viterbi algorithm, and an 8-dimensional constellation mapper equation given in the CCSDS standard is deconstructed to design constellation mapper. Especially, we present the optimized receiver for 4D-8PSK TCM system by investigating the BER performances for the traceback lengths in the Viterbi decoder through computer simulations..

• The Journal of The Korea Institute of Intelligent Transport Systems
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• 제8권6호
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• pp.141-148
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• 2009

Space-time block codes (STBC) have no coding gain but they provide a full diversity gain with relatively low encoder/decoder complexity. Therefore, STBC should be concatenated with an outer code which provides an additional coding gain. In this paper, we consider the concatenation of multiple trellis-coded modulation (MTCM) codes with STBC for achieving significant coding gain with full antenna diversity. Using criteria of equal transmit power, spectral efficiency and the number of trellis states, the performance of concatenated scheme is compared to that of previously known space-time trellis codes (STTC) in terms of frame error rate (FER). Simulation results show that MTCM codes concatenated with STBC offer better performance on fast Rayleigh fading channels, than previously known STTC with two transmit antennas and one receive antenna.

• Proceedings of the Acoustical Society of Korea Conference
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• 한국음향학회 1998년도 학술발표대회 논문집 제17권 2호
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• pp.211-214
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• 1998

TCM(Trellis-Coded Modulation)은 대역폭과 전력이 제한된 채널환경에서 채널부호화 기술과 변조기술을 결합시켜 대역폭의 증가없이 에러정정능력을 개선시키는 통신 기술이다. 본 논문에서는 TCM 신호의 복호시 사용되는 Viterbi decoder에서 traceback depth의 감소에 따른 BER(Bit Error Rate)의 증가를 개선하기 위해 수신부에서 설정하는 traceback depth를 주기로 blocking하여 TCM encoder의 입력시퀀스에 zero padding bits를 추가시키는 새로운 알고리듬을 제안한다. 모의실험결과, traceback depth가 50인 hard decision의 경우 약 2~2.5dB, 4-level soft decision과 8-level soft decision의 경우 약 0.3~2dB의 coding gain을 얻을 수 있었다.