| Summary: | 碩士 === 國立中央大學 === 電機工程學系 === 85 === Because the M-ary differential phase shift keying (MDPSK) has
constant envelo-pe and good spectrum efficiency characteristics,
it has been used as the stan-dard of the modulation in the
mobile communication systems recently. The IS-54system of the
North America and the PHS mobile phones system of Japan, for ex-
ample, use pi/4-differential quadrature phase shift keying
(pi/4-DQPSK) as themodulation. This project states the
influences of the system performance underthe circumstance of
cochannel interference. Nyquist shaped pulses are used
andnoncoherent block detection is employed at the receiver to
analyze and evalua-te the system performance. Block detection
means a decision detects multiple-symbol, that is, multiple
symbols are detected every decision as opposed to symbol-by-
symbol detection. The performance has improved dramatically in
com-parison with traditional differential detection as the
observation intervalincreases in the thesis. In this project,
cochannel interference is modeled asGaussian to be investigated.
This project also applies computer simulation tomatch and
compare the result of the analysis. In which,the simulation
includescochannel interference modeling Gaussian and exact model
(with the same modul-ation and data rate as desired signal)
and decision feedback demodulation.keyword:MDPSK, cochannel
interference, noncoherent block detection, Nyquist shaped
pulses,decision feedback
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