| Summary: | 碩士 === 國立臺灣大學 === 電機工程學研究所 === 87 === A blind receiver that can demodulate the 16/32/64/128 QAM constellation without an initial training sequence is proposed. In the wave of digital communication, broadcasting systems will be implemented digitally. However, broadcasting system is different from traditional communication systems, it is a one-to-multiple network. The initial sequence synchronization method used in traditional point-to-point communication system is usually not applicable here. In order to adjust adaptive components in the receiver and achieve frequency synchronization, some novel algorithms and system structures are required. In this thesis, we develop a system that can do
timing recovery, carrier recovery, equalization, and constellation identification all blindly when using the 16/32/64/128 QAM constellation of V.32/V.32bis. The timing recovery uses an algorithm called band-edge timing recovery (BETR), and the equalization uses an algorithm called constant modulus algorithm (CMA). The carrier recovery algorithm and the constellation identification algorithm are newly developed based on traditional RC-PLL and a neural network algorithm. This system can be used in a digital broadcasting system and a multipoint network where the initial training sequence or pilot channel is not required. This system can also be easily modified to demodulate other kinds of QAM communication system such as V.29 and 4/8 PSK system. We implemented this system in software without complicated mathematical computation so that in the future it can be implemented on a real time DSP.
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