Efficient Broadcast Schedulers of Hierarchical Data Dissemination Systems
Date
2005-07-18
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Abstract
With the increasing popularity of portable wireless devices and the
need to access data anytime and anywhere, mechanisms to efficiently and
effectively transmit information to wireless clients are of significant
interest. Several research studies address broadcast scheduling algorithms for
centralized systems. However, broadcast scheduling in hierarchical data
dissemination systems are largely ignored. In these systems a primary server
accepts updates that are broadcasted to secondary servers and then to wireless
clients. This paper focuses on broadcast scheduling at the primary server
side. First, we show that a straightforward broadcast scheduler that ignores
clients' access patterns can provide participating clients with outdated
information more than 80% of the time. Then, we propose three broadcast
scheduling algorithms. The proposed algorithms primarily differ in how data
broadcasts are guided at the primary and secondary servers. We present
guidance mechanisms that are based on real and predicted clients' access
patterns. We experimentally evaluate the proposed scheduling algorithms using
simulation while running an extensive set of experiments. The performance
study illustrates that the third proposed algorithm, which depends on
predictive scheduling at both the primary and the secondary servers, provides
the best performance in terms of the response time of the clients' requests
and the reception of outdated information.
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Computer Science