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학술대회 Directional Diversity Reception for Hierarchically Modulated T-DMB System
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배재휘, 김영수, 김주연, 임종수, 이수인, 한동석
Vehicular Technology Conference (VTC) 2008 (Fall), pp.1-4
08MR3700, 지상파 DMB 전송 고도화 기술개발, 임종수
We propose a reception improvement method for OFDM based DQPSK-QPSK hierarchical modulation system in severe multipath channels using directional diversity. In an OFDM based transmission system with DQPSK modulation, data rate can be increased with hierarchical modulation by adding new QPSK signal to existing DQPSK signal. New added QPSK signal has much smaller amplitude compared with the existing QPSK signal to reduce the influences on the existing DQPSK signal, so the reception performance of new added QPSK signal is degraded when there are severe multipaths interferences due to small amplitude. To overcome this problem, the directional diversity is suggested. By applying directional diversity, we can eliminate undesired multipaths and change the reception channel characteristics near to frequency flat fading, so improve reception performance. We demonstrate the performance of proposed method under severe multipath channel and show it can improve the reception of new added QPSK signal. ©2008 IEEE.
KSP 제안 키워드
Channel Characteristics, Directional diversity, Flat fading, Hierarchical modulation, Improvement method, Multipath channels, OFDM based transmission, QPSK signal, Small amplitude, Transmission system, data rate