Information Technology Reference
In-Depth Information
rate and amount of communication. Broadcasting is a potential solution to this lim-
itation. In broadcasting, information is generated and broadcast to all users on the
air channels. Mobile users are capable of searching the air channels and pulling
their required information. The main advantage of broadcasting is due to the fact
that it scales up as the number of users increases, eliminating the need to multiplex
the bandwidth among users accessing the air channel. In addition, broadcast chan-
nel can be considered as an additional storage available over the air for the mobile
clients. Finally, it is shown that pulling information from the air channel consumes
less power than pushing information to the air channel. Broadcasting is an attractive
solution, because of the limited storage, processing capability, and power sources
of the mobile unit. Within the scope of broadcasting one needs to address three is-
sues:
Broadcast contents;
Network latency; and
Power consumption of the mobile unit.
For broadcasting applications, in general, the information to be broadcast is of
multimedia or hypertext nature originated from an information source(s) governed
by multiple, possibly heterogeneous, database management systems. The object-
oriented paradigm has proven to be a suitable methodology for modeling multimedia
databases
[6,23,32,43]
. In addition, in a distributed environment, object-oriented
methodology provides a systematic mechanism to model the association and transla-
tion of the data from multiple sites
[10,11,33]
. Therefore, in this chapter, we model
the information units on the air channel(s) as objects. Within the scope of object-
oriented database systems, object clustering has proven to be an effective means
of reducing response times
[7,13,17,19,20,45]
. The employment of broadcasting in
the mobile-computing environment motivates the need to study the proper organi-
zation of objects along the air channel(s). Due to the natural differences between
the serial air channel and the random-access disk, one has to look at different and
efficient methodologies to organize and cluster objects on the air channels in order
to reduce the response time. In addition, the network latency (response time) is the
major source of power consumption at the mobile unit
[35-38,65]
. The reduction in
response time translates into the reduced amount of time a mobile unit spends ac-
cessing the channel(s) and thus, it has its impact on conserving energy at the mobile
unit. It is the goal of this chapter to address issues pertinent to broadcasting in a
mobile environment.
Section
2
briefly addresses the background material on mobile systems. Techno-
logical limitations are outlined and their effects on the global information sharing
environment are discussed. Issues such as data selection methodologies, semantic
