| Summary: | 碩士 === 國立台灣工業技術學院 === 電子工程技術研究所 === 85 === In this thesis, we consider a seven-cell microcellular mobile
communication system to study its channel assignment strategies.
In order to check if a call generated in neighboring cells will
be handed off to the target cell, we define the handoff region
as a rectangular about cell boundaries. From this definition,
the time that handoff calls stay in this region, i.e. dwell
time, can also be computed. The distribution of dwell time
obtained in this thesis shows that the exponential distribution
assumption in previous works is not reasonable. For the study of
channel assignment strategies with handoff in microcellular
mobile communication networks, both the preemptive and non-
preemptive disciplines are employed in the double queue model
and the single queue model. The basic concept of channel
assignment strategy we used is borrowed from the fixed channel
assignment with guard channels. The impacts of emergency calls
on the system performance are also considered by using guard
channels. We observe the variation of the blocking probability
of general calls, emergency calls and the forced termination
probability of handoff calls by changing the number of emergency
guard channels and handoff guard channels. As to the preemptive
service discipline, we define the dropping probability as the
probability for ongoing general calls being preempted by
emergency calls which find no available channels upon arrival.
Two cost functions are defined to compute the costs of different
schemes. We compare the performance of the above schemes with
that of the FIFO scheme and the results show that the single
queue with preemptive scheme is a better channel assignment
strategy than the other schemes.
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