• Journal of Advanced Navigation Technology
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• v.12 no.6
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• pp.598-603
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• 2008

Relay system is a promising technique for the high downlink throughput or coverage extension in the next generation wireless systems. In this paper, the transmit scheme for orthogonal frequency division multiplexing (OFDM) based relay system with hierarchical modulation is designed. Without using much power from the base station, the proposed scheme can guarantee the cell edge users to get high data rates as the inner cell users. In the simulation, the performance of proposed scheme was compared with the conventional one in which there is no hierarchical modulation. Numerical results show that the proposed scheme can save much power whether the unicast case or multicast case.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.4
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• pp.375-380
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• 2009

Bit error rate(BER) performance of each bit for hierarchical M-ary phase shift keying(H-MPSK) modulation scheme is changed according to the phase parameters. Thus, a method to find the phase parameters appropriate to the requests of the system is needed. In this paper, we propose a method to obtain the phase parameters from an approximate approach of BER for H-MPSK and verify a validity of the proposed method through the previously provided expression for analyzing an exact error probability of H-MPSK.

• Information and Communications Magazine
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• v.24 no.6
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• pp.29-40
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• 2007

유비쿼터스 네트워크 시대가 도래함에 따라 표준화된 기술의 파악 및 이에 따른 응용 서비스 요구가 증대되고 있다. 본 고에서는 저속(Low Rate) 통신규격을 제공하는 표준인 IEEE 802.15.4의 표준화의 기술적 개관 및 물리계층에 대하여 서술한다. 2006년 9월 판 표준안에 제시된 물리계층(PHY)의 주파수 대역별 데이터율과 변조방식 및 심볼 사상에 관하여 기술한다. 또한, 변조 방식 및 전송 주파수에 따른 전송 특성, 채널 할당 방식 그리고 스펙트럼 방사 출력 등에 관해 기술한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.3C
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• pp.304-310
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• 2009

This paper proposes a successive MAP (maximum a posteriori probability) detection scheme with SoIC(soft interference cancellation) to reduce the receiver complexity of hierarchical M-ary QAM system. For the successive MAP detection, modulation symbols generated from the other data streams are treated as Gaussian noise or eliminated as the soft interference according to their priorities. The log-likelihood ratio of the a posteriori probability (LAPRP) of each bit is calculated by the MAP detector with an adjusted noise variance in order to take the elimination and Gaussian assumption effect into account. By separating the detection process into the successive steps, the detection complexity is reduced to increase linearly with the number of bits per hierarchical M-ary QAM symbol. Simulation results show that the proposed detection provides a small performance degradation as compared to the optimal MAP detection.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6C
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• pp.434-441
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• 2005

For LDPC decoding, received symbols are splitted bit by bit based using the received in-phase and quadrature components. The method of bit-splitting is affected on decoding performance because its method depend on distance over symbol constellation. Therefore this paper propose the bit split method using the sector information with sacrifice a little performance loss compared to Euclidean distance method. Futhermore DVB-S2 specification supports BC(Backward Compactible) mode which using the hierarchical modulation method, this paper also analyze the decoding performance according to deviation angle of 8PSK constellation for various LDPC coding rates.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.10
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• pp.2409-2416
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• 2014

In this paper, an automatic recognition algorithm for linearly modulated signals like PSK, QAM under noncoherent asynchronous condition is proposed. Frequency, phase, and amplitude characteristics of digitally modulated signals are changed periodically. By using this characteristics, cyclic moments and higher order cumulants based features are utilized for the modulation recognition. Hierarchial decision tree method is used for high speed signal processing and totally 4 feature extraction parameters are used for modulation recognition. In the condition where the symbol number is 4,096, the recognition accuracy of the proposed algorithm is more than 95% at SNR 15dB. Also the proposed algorithm is effective to classify the signal which has carrier frequency and phase offset.

• Journal of Broadcast Engineering
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• v.12 no.1 s.34
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• pp.2-10
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• 2007

We analyzed the receiving performance of the DVB-S2 transmission system in the BC(Backward Compatibility) mode. The transmitter employs the hierarchical modulation, and the receiver can be implemented by the direct demodulation or the hierarchical demodulation. The performance of each demodulation scheme is analyzed by a statistical method and a computer simulation for the AWGN and nonlinear channels. The ratio of the LP/HP streams which is proper in the domestic satellite broadcasting environments, is also suggested.

• Journal of Broadcast Engineering
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• v.14 no.4
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• pp.509-517
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• 2009

This paper introduces an Advanced Terrestrial DMB (AT-DMB) system which provides higher efficiency of transmission and better quality of service than conventional T-DMB system. In AT-DMB, a hierarchical modulation method is applied to transmit more data while maintaining backward compatibility to conventional T-DMB receivers. This method can provide not only high quality video service but also lots of broadcasting channels. In this paper, the performance of the hierarchical modulation in AT-DMB system is analyzed with computer simulation in several environments compared with the performance of T-DMB system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.1
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• pp.10-17
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• 2007

Hierarchical modulation technology which can make the advanced T-DMB(terrestrial-digital multimedia broadcasting) system backward compatible with the conventional T-DMB system and provide high-rate and high-quality services is introduced in this paper. As additional data streams are embedded within the conventional data streams by the hierarchical modulation, the advanced T-DMB system can provide high-quality video service and more broadcasting service channels. In order to guarantee the quality of both the conventional and additional services powerful error correcting scheme is required. The error performance of advanced T-DMB system with hierarchical modulation is investigated and analyzed according to the various error correcting schemes in this paper.

• The Journal of the Korea Contents Association
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• v.7 no.12
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• pp.254-261
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• 2007

In this paper, we propose a blind equalization method for advanced terrestrial digital multimedia broadcasting (AT-DMB) systems which use hierarchical modulation. The AT-DMB system adopts hierarchical 16-ary quadrature amplitude modulation (16-QAM) to ensure backward-compatibly with the differential quadrature phase shift keying (DQPSK) signal of the legacy terrestrial digital multimedia broadcasting (T-DMB) systems and to support higher transmission rate. Due to the hierarchical modulation, the conventional T-DMB signal and the additional signal have different error rate at same signal to noise ratio (SNR). By weighting the decided symbols differently according to the reliability of the symbols, i.e., high priority symbol with low error rate and low priority symbol with high error rate, we can improve the channel estimation accuracy. In this paper, we analyze SNR loss by hierarchical modulation and confirm it through simulations. Moreover, through simulations, we verify that the proposed weighting method improve BER compared to the no-weighting method.