Page 71 - Mobile Computing

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Datacasting or Data Broadcasting

 Datacasting (data broadcasting) is the broadcasting of data over a wide area
via radio waves.
 It most often refers to supplemental information sent by television stations
along with digital television, but may also be applied to digital signals on
analog TV or radio. It generally does not apply to data which is inherent to
the medium, which defines virtual channels for DTV or direct broadcast
satellite systems; or to things like cable modem or satellite modem, which
use a completely separate channel for data.
 Datacasting often provides news, weather, traffic, stock market, and other
information which may or may not relate to the program[s] it is carried
with. It may also be interactive, such as gaming, shopping, or education.

The need for Data Broadcast:

 Due to the limited bandwidth of the mobile systems, data should be
organized and presented to the users based on its need.
 Data Broadcast can be used to manage sending (pushing) the same data
interest to the listening clients without a prior request (or lock).

Client Broadcasting Witbful

Client Station Network
(Fixed)
Client

Client

Data Broadcasting

• Server continually broadcasts data to MUs.

• Scalability: Cost does not depend on number of users listening.

• Mobile Unit may/may not have cache.

• Facilitates data access during disconnected periods.

• Allows location dependent data access.

• No need to predict with 100% accuracy the future data needs.

• Broadcast based on probability of access.

• Periodic broadcasting of all data.