With the big improvement of wireless technology, people can get their desired
information at any time and any place. Due to communication asymmetry -
physical asymmetry and/or information ow asymmetry, broadcast data deliv-
ery is rapidly becoming the method of choice for disseminating information from
server to clients. The main advantage of broadcast delivery is its scalability:
it is independent of the number of users the system is serving. Acharya et al.
have proposed the use of a periodic dissemination architecture in the context of
mobile systems, called Broadcast Disks. Broadcast Disks can construct a mem-
ory hierarchy in which the highest level contains a few items and broadcasts
them with high frequency while subsequent levels contain more and more items
and broadcast them with less and less frequency. However, based on Acharya
et al.'s approach, some broadcast slots may be unused, which resulting in the
waste of bandwidth and the increase of access time. Yang has presented a com-
plementary approach to solve the empty slots problem, which also reduces the
mean access time. However, based on the complementary approach, the dis-
tances between slots containing the same page may not be a constant, resulting
in an increase of the mean access time. Therefore, in this thesis, we propose
two eÆcient broadcast programs to mitigate the above phenomenon and also
to solve the empty slots problem. The rst one is a revised version of the com-
plementary approach, and the second one is an adaptive approach. Most of the
previous approaches assume that each mobile client needs only one data page.
However, in many situations, a mobile client might need data of more than one
page. Ke has proposed the SNV strategy for query set broadcast scheduling
in multiple channels. In the SNV strategy, the data pages of the same query
set are put as together as possible and it tries to avoid scheduling two or more
pages of one query set at the same time slot of di erent channels. However,
there are two disadvantages in the SNV strategy: (1) a data page with high
access frequency may be scheduled at a time slot near the end of the broad-
cast cycle, which results in the longer access time for requiring the whole query
sets; (2) it may extend the number of slots in a certain chain, which results
in the wasteness of bandwidth of the other channels. Therefore, we propose
an eÆcient broadcast scheduling strategy, the Hybrid Version of the Set-based
strategy ( HVS ) to improve these two disadvantages. From our performance
analysis and simulation, we show that both our revised version of the com-
plementary approach and adaptive approach create smaller number of slots in
one broadcast cycle than Acharya et al.'s algorithm and require shorter mean
access time than Acharya et al.'s algorithm and the complementary approach.
Moreover,from our performance analysis and simulation, we also show that our
HVS strategy requires shorter total expected delay access time, and creates
smaller number of slots and smaller number of empty slots in one broadcast
cycle than the SNV strategy.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0718101-145752 |
| Date | 18 July 2001 |
| Creators | Chiu, Shih-Ying |
| Contributors | Ye-In Chang, Chien-I Lee, San-Yih Hwang, Gen-Huey Chen |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0718101-145752 |
| Rights | restricted, Copyright information available at source archive |
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