Browsing by Author "Sheu, Chorng-Ren"

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A Differential Sliding Correlation Scheme for Symbol Timing Detection in Time Domain Synchronous OFDM Systems
(2009)
Sheu, Chorng-Ren
;
Huang, Chia-Chi
;
電信工程研究所
;
Institute of Communications Engineering
In this paper, a new symbol timing detection scheme robust to carrier frequency offset is proposed for Time Domain Synchronous (TDS) OFDM systems. The proposed method computes the sliding correlation from both the differential received signal and the differential PN sequence. Rapid symbol timing detection can be obtained based on the correlation peaks. As differential operation is adopted before sliding correlation in the proposed method, the time-dependent linear phase effect caused by the carrier frequency offset will not influence the correlation peaks. Nevertheless, the incorrect correlation peaks caused by the cross terms of the multipath may be detected. An ambiguity protection module is added to validate the correlation peak detection results and further improve the system performance. Our simulation results show that the proposed scheme for symbol timing detection is accurate and simultaneously robust to carrier frequency offset for TDS-OFDM systems in both a time-varying TU6 channel and a fixed two-path channel.
A Low Complexity Interference Suppression Scheme for High Mobility STBC-OFDM Systems
(2012)
Sheu, Chorng-Ren
;
Liu, Jia-Wei
;
Huang, Chuan-Yuan
;
Huang, Chia-Chi
;
電信工程研究所
A novel low complexity scheme based on received data symbol pair reordering and optimal selection, is proposed for space time block coded (STBC) OFDM systems to suppress co-channel interference (CCI) and inter-carrier interference (ICI) caused by time-varying channels. The proposed scheme reorders the conventional received data symbol pairs to produce extra received data symbol pairs. Then, the STBC decoding is performed on all the received data symbol pairs, and the STBC decoding output signals are used to obtain multiple combined signals. Finally, the optimal combined signal with minimum interference is selected to suppress CCI and ICI, and the system performance will be improved as long as the channels are mutually uncorrelated. Our computer simulation results verify that the proposed low complexity scheme achieves good performance for high mobility 2x2 STBC-OFDM systems in the ITU Vehicular A (VA) channels.
Theory and Technology for Standard WiMAX Over Fiber in High Speed Train Systems
(2010-08-15)
Yeh, Chien-Hung
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Chow, Chi-Wai
;
Liu, Yen-Liang
;
Wen, Sz-Kai
;
Chen, Shi-Yang
In this investigation, we propose and investigate the standard WiMAX access in high speed railway (HSR) using radio over fiber (RoF) link. We also discuss the theory of mobile WiMAX at a target speed of 300 km/hr in simulation. We also analyze the effect of the Doppler frequency shift over HSR. The effective transmission fiber length in the WiMAX-RoF system was limited due to the time-division-duplex (TDD) protocol in the practical WiMAX. Thus, we also demonstrate the transmission limitation and performance of the standard WiMAX access in RoF link. The performances of throughput and packet loss at different fiber lengths are also investigated and discussed. Furthermore, a WiMAX-RoF field trial is also demonstrated based on a simple two RAUs RoF architecture. It was tested and measured in the SongShan tunnel of the Taiwan high speed railway (THSR).