| Summary: | 碩士 === 國立清華大學 === 資訊科學學系 === 82 === Cyclic-Reservation Multiple-Access (CRMA) is an access scheme
for high-speed local and metropolitan area networks based on a
dual-bus configuration. CRMA provides high throughput
efficiency and fairness independent of the network speed or
distance. In CRMA, the headend generates the reserve commands
periodically. Each station reserves a number of slots in each
reserve command if necessary. The headend will generate a
sequence of cycles each of which is used to service the
reservations on the corresponding reserve command. The length
of each cycle is equal to the total number of slots reserved by
the stations in the corresponding reserve command. Generally, a
longer cycle length will conduct a longer access delay and a
lower slots utilization. It is desirable to have a scheme to
make the cycle length as short as possible. In this
dissertation, we prove that the problem of finding a shortest
cycle for a CRMA reservation (called as cycle compression
problem) is NP-complete by showing that it is equivalent to
the interval coloring problem. We also propose an O(n^2)
approximation algorithm to solve this problem; where n is the
number of stations in the network. The effectiveness of the
algorithm is evaluated via simulation. Simulations results show
that compared to the traditional CRMA reservation scheme, the
new scheme makes a much shorter cycle length and hence the
obtained throughput is much better than the traditional scheme.
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