| Summary: | 碩士 === 國立清華大學 === 電機工程研究所 === 82 === Spectrum efficiency is of vital importance in designing
cellular mobile communication systems since bandwidth is a very
limited resource. Hence how to effectively use the available
bandwidth is a challenging task. The method of fixed channel
assignment (FCA) have been widely adopted in current mobile
phone systems. In this thesis, performance analysis of cellular
systems employ- ing FCA is first studied. Two priority schemes
for handoff calls are considered: one is adding queue and the
other is reserving a fixed number of channels. Results obtained
show that if priori- ty schemes exist for handoff calls, the
forced termination proba- bility will be much lower than he new
call blocking probability. Sectorization has been well-known
for reducing the number of co- channel cells. Our analysis on
spectrum efficiency based on diff- erent constraints on the new
calls blocking and forced terminati- on probability, show that,
however, if not properly designed, the sectored system might be
worse than the system without sectori- zation. Finally, the
performance of systems using the optimum DCA method, the
``maximumm packing''(MP) strategy, is analyzed by computer
simulation. Again higher priority for handoff calls is
considered. Results obtained show that tthe new call blocking
probability and forced termination probability of systems using
the MP strategy will be smaller than those of systems employing
the FCA method under most all of the interesting new call
arrival rates.
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