• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.9C
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• pp.841-847
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• 2009

In this paper we propose a high-performance Hybrid ARQ scheme employing Chase combining based on LDPC (Low-Density Parity-Check) codes. The proposed scheme uses symbol mapping diversity and turbo demodulation to improve decoding performance. We analyze the performance of the proposed scheme by EXIT (EXtrinsic Information Transfer) chart and compare its performance with several symbol mappings.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.8
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• pp.21-27
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• 2013

In this paper, we propose a low-complexity Turbo coded BICM-ID (bit-interleaved coded modulation with iterative decoding) system. A Turbo code is a powerful error correcting code with a BER (bit error rate) performance very close to the Shannon limit. In order to increase spectral efficiency of the Turbo code, a coded modulation combining Turbo code with high order modulation is used. The BER performance of Turbo-BICM can be improved by Turbo-BICM-ID using iterative demodulation and decoding algorithm. However, compared with Turbo-BICM, the decoding complexity of Turbo-BICM-ID is increased by exchanging information between decoder and demodulator. To reduce the decoding complexity of Turbo-BICM-ID, we propose a low-complexity Turbo-BICM-ID system. When compared with conventional Turbo-BICM-ID, the proposed scheme not only show similar BER performance but also reduce the decoding complexity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.10C
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• pp.597-604
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• 2011

In this paper, we propose group Manchester code (GM) modulation scheme for medical in-body wireless body area network (WBAN) systems. In IEEE, the WBAN system is assigned as 802.15. Task Group 6 (TG 6), and the related standardization is being progressed, Recently, in this Group, group pulse position modulation (GPPM), which can obtain data rate increase by grouping pulse position modulation (PPM) symbols, is proposed as a new modulation scheme for low-power operation of WBAN system. However, the conventional method suffers from BER performance degradation due to the absence of gray coding and its demodulation characteristics. Therefore, in this paper, we propose a modified GM scheme which groups Manchester code instead of PPM. In the proposed GM scheme, a low-complexity maximum likelihood (ML) demodulation method is employed in order to maximize the BER performances, Also, log likelihood ratio (LLR) decision method is proposed to employ the Turbo code as forward error correction (FEC), Finally, we verified that the proposed method has a good performance and is an appropriate scheme for in-body WBAN system through extensive performance evaluation.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.1
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• pp.17-23
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• 2015

In this paper, we propose an efficient joint demodulation and decoding scheme for FTN (Faster than Nyquist) systems. Several previous works have demonstrated that ISI (Inter Symbol Interference) cancellation schemes based on BCJR (Bahl-Cocke-Jelinek-Raviv) algorithm are suitable for FTN systems. Unfortunately, required complexity of the previous ISI cancellation schemes is very high, especially when a multi-level modulation scheme is employed. In this paper, we propose a joint demodulation and decoding scheme for FTN systems with an iteratively decodable channel coding scheme and a multi-level modulation. Compared with the previously proposed schemes, the proposed scheme not only offers reliable performance but also requires relatively low complexity. Also, the proposed scheme can be easily applied to the FTN system with a multi-level modulation with a minor modification.