• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 I
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• pp.202-205
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• 2003

The performance of space-frequency trellis coded (SFTC) OFDM system is analyzed in frequency selective fading channel. Using a pairwise error probability upper bound expression, we design the code and interleaver that can maximize the diversity and coding gain. To alleviate the performance degradation due to the inter-antenna product terms, we propose a new SFTC scheme that employs non-overlapped interleaving for each antenna A new code is optimized for the non-overlapped interleaving and a practical sub-optimal decoding algorithm is proposed. It is shown that the proposed scheme can substantially improve the performance compared to the conventional scheme that employs identical interleaving for all antennas.

• 전자공학회논문지S
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• 제35S권3호
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• pp.47-53
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• 1998

Multi-dimensional DC-free trellis codes based on two-dimensional constellation which can be omplemented more easily than conventional codes are proposed and their performances are analyzed in this paper. 2N-dimensional constellation of the proposed codes is constructed by concatenating N 2-dimensional constellation. Thus, for the proposed codes, information bits can be assigned easily to each signal point of the 2-dimensional consteellation and DC-free characteristic can be simply obtained by the symmetric structure of the constellation. In addition, since Viterbi decoder can calculate multi-dimensional Euchlidean distance between signals by simple sum of each 2-dimensional Euclidean distanc, decoding complexity can be reduced. The performance analysis shows that the proposed codes have almost same spectral characteristic and error performance as compared with conventional codes. However, the complexity is shown to be reduced further due to the construction method of contellation and the simple decoding algorithm of the proposed codes.

• 전자공학회논문지A
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• 제31A권4호
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• pp.39-46
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• 1994

In this paper, the idea of using a multiple symbol obervation interval to improve error probability performance is applied to differential detection of MTCM(multiple trellis code modulation) with ${\Pi}$/4 shift QPSK, 8DPSK and 16DPSK. We propose two types of sliding multiple symbol differential detection algorithm, type 1 and type 2. The two types of sliding detection scheme are examined and compared with conventional(symbol-by-symbol) detection and bolck detection with these modulation formats in an additive white Gaussian noise(AWGN) using the Monte Carlo simulation. We show that the amount of improvement over conventional and block detection depends on the number of phases and the number of additional symbol intervals added to the observation. Computer simulagtion results are presented for 2,4,8 states in AWGN channel.

• 한국통신학회논문지
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• 제17권12호
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• pp.1401-1412
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• 1992

TCM(Trellis Coded Modulation)은 위성통신이나 음성통신과 같이 대역폭이 제한된 채널에서 코딩과 변조가 결합되어 대역폭의 증가없이 코딩 이득을 가져올수 있는 하나의 통신 방식이다. 본 논문에서는 PAM, PSK, QAM 변조를 TCM에 적용하고, Viterbi decoding의 단점을 개선할수 있는 확장된 path back method 복호 알고리즘을 제안하여 TCM의 복호 알고리즘에 적용하였다. 또한, Monte Carlo simulation을 이용하여 각 변조기법에 따른 성능과 복호 효율성에 대하여 분석하였다.

• Journal of Communications and Networks
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• 제9권1호
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• pp.11-17
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• 2007

In this paper, system performance of turbo trellis coded modulation (turbo TCM) is presented and analyzed through computer simulations over two typical channels, namely additive white Gaussian noise (AWGN) and Rayleigh fading channels. We use and compare different mapping strategies based on Ungerboeck partitioning (UP), block partitioning (BP), mixed partitioning (MP), Gray partitioning (GP), and Ungerboeck-Gray partitioning (UGP) of the signal constellation of the turbo TCM system. Furthermore, taking 8PSK modulation of turbo TCM as an example, our simulation results show that turbo TCM with UP can obtain better performance than turbo TCM with BP, MP, GP, and UGP in both AWGN and Rayleigh fading channels.

• Journal of Communications and Networks
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• 제4권2호
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• pp.90-96
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• 2002

We present a family of constant-amplitude constellations of even dimensions 8 and above. These constellations allow trellis coded modulation to be implemented without the usual penalty paid for constellation expansion. The new constellations are generated by concatenating either n QPSK points or n QPSK points rotated by 45 degrees, for any n $\geq$ 4. Our constellations double the number of points available for transmission without decreasing the distance between points and without increasing the average or peak energies, introducing asymmetry, or increasing the modulation level. Effective gains of 2.65 dB with minimum complexity through 6.42 dB with moderate complexity are demonstrated using the 8D constellation.

• ETRI Journal
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• 제26권2호
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• pp.92-100
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• 2004

In this paper, we propose an efficient method to broadcast digital television signals using single frequency networks (SFNs) within the Advanced Television Systems Committee (ATSC) transmission systems. In implementing the SFNs of an 8-vestigial side band (8-VSB) Digital Television (DTV) system, the ambiguity problem of the trellis coder is unavoidable in a conventional ATSC transmission system. We propose a memory initialization of the trellis coder to resolve this ambiguity problem. Since the proposed scheme to synchronize multiple transmitters minimizes the changes from the conventional ATSC system, the hardware complexity for these changes is very low. Our simulation results show that the proposed scheme makes a less than 0.1 dB degradation at the threshold of visibility with a bit error rate of $3{\times}10^{-6}$ in the additive white Gaussian noise (AWGN) channel. It is possible to reduce the performance degradation by increasing the initialization period of the proposed scheme.

• 한국전자파학회논문지
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• 제12권3호
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• pp.417-424
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• 2001

본 논문은 부가 백색 가우시안 잡음 채널에서 M-ary PSK 트렐리스 부호화변조기법의 비트 오차 성능을 향상시키기 위하여 기존의 심볼사상방법에 비해 개선된 오류특성을 나타낼 수 있는 새로운 심볼사상방법을 제안하고 그 성능향상을 확인한 내용을 담고 있다. 본 논문에서 제안된 새로운 심볼사상방법은 셋분할 하는 경우 유클리드 거리뿐 아니라 해밍거리도 고려한 심볼사상방법으로 본 방법에 의한 성능향상을 기존 방식과 비교하여 수식을 이용한 분석한 컴퓨터 시뮬레이션을 통해 검증하였다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2002년도 추계종합학술대회
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• pp.766-769
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• 2002

본 논문에서는 802.l1b WLAN에서 채택된 CCK(complementary code keying)의 성능을 높이기 위해 새로운 완전직교 방법을 제안한다. CCK 변조기를 통해 생성된 codeword들이 모두 orthogonal한 성질을 유지할 수 있도록 전체 256개의 codeword를 trellis coding 방식을 이용하여 8개의 subset으로 나누었으며, 나누어진 각각의 subset내에서 생성된 codeword들은 완전한 orthogonality를 유지할 수 있다. 그 결과 최대 전송속도는 9.625Mbps로 제한되지만, 기존의 CCK변조 방식보다는 BER 10E-5에서 약 1.5dB의 성능향상을 얻을 수 있다.

• 한국통신학회논문지
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• 제17권9호
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• pp.1020-1028
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• 1992

본 논문에서는 TCM(Trellis Coded Modulation)에서 연집에러 검출 및 최대 확률론적 복호 방식으로 구성된 연집에러 정정을 위한 적응 복호방식을 제시하고 있다. 복호기는 보통 비터비 복호기로서 동작하고, 미터비 복호기에 의해 정정될 수 없는 에러가 검출될 경우 연집 에러 정정 모드로 절환된다. 이동통신에서의 채널특성인 연집에러가 빈번히 발생하는 다경로 페이딩 채널에서 적응 복호방식을 이용한 TCM은 기존의 방식에 비해 비트오율면에서 향상된 성능을 나타내고 있다.