| Summary: | 碩士 === 國立中興大學 === 電機工程學系 === 90 === With the booming growth of multimedia and wireless communications, the demand for wireless bandwidth is urgent. So, how to transmit more information within a limited bandwidth is an important issue.
Quadrature Overlapping Modulation has been proven a bandwidth efficiency modulation technique. The main theories are the baseband pulse waveform shapping of overlapping pulse and quadrature combining before carrier modulation. This modulation technique can possess a larger roll-off factor. For example, the sidelobes of Quadrature Overlapped Raised-Cosine (QORC) modulation drop off much faster ().
Several types of receivers are investigated about the adaptation with Quadrature Overlapping Modulation. Analysis and simulations of several kinds of detection schemes are presented, including Half Symbol Period Correlation, Whole Symbol Period Correlation, Whole Symbol Period Average Waveform Matched Filter, Central Half Symbol Period Correlation, Central Half Symbol Period Average Waveform Matched Filter, Decision Feedback, Hard Maximum Likelihood Sequence Detection (Hard MLSD) and Soft Hard Maximum Likelihood Sequence Detection (Soft MLSD). Simulation was done with Matlab, the result shows that the Soft MLSD is the optimum detection and Central Half Symbol Period Average Waveform Matched Filter could be considered as the sub-optimum detection for high performance evaluation and advantages of ‘simple structure' and ‘no delay'. It also shows that the combination of sub-optimum detection with QOTC modulation performs outstandingly both in bandwidth efficient aspect and bit-error-rate performance.
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