| Summary: | 碩士 === 國立中正大學 === 電機工程學系 === 85 === TDMA(time-division multiple access) architecture has been
proposed for portableradio application to provide efficient
digital services including voice and dataapplications. The
advantages of a TDMA channel architecture are often offset by
the requirement of a significant overhead for syn-chronization.
Two key elements in the design of a demodulator are symboltiming
synchronization and offset frequency synchronization . The
applicationof digital techniques to demodulation processing for
short TDMA bursts canimprove TDMA efficiency by removing the
need for overhead for symbol timingand frequency offset
synchronization. This paper studied the demodulatordesign to a
set of specifications code-named PACS (Personal Access Communi-
cation Service) proposed by Bellcore (Bell communication
research) in theUnited States. Bellcore has proposed a method of
implementing the PACS demo來dulator which has been patented. We
investigate an alternative methodof implementation which will
perform as well as the Bellcore method. The Bellcore metdulator
obtains (1)symbol timing synchronization, (2) an estimate of the
offset frequency, and (3)the "figure of merit",i.e., an estimate
of the channel (path) quality simultaneously after a
predetermined set of computations. The new method developed in
this paper obtains symbol syn-chronization and a frequency
offset estimate through separate calculations,with symbol
synchronization preceding frequency offset estimation.
Howeverthe total of the two calculations does not exceed the one
data burst limit. Furthermore, the channel quality estimation is
obtained as a byproduct ofthe frequency offset estimation. The
amount of computation in this new method is comparable to that
of the Bellcore method.
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