Information Technology Reference
In-Depth Information
2.2.2 Mobility
Mobility is the second characteristic that distinguishes the mobile environment
and poses challenges beyond the scope of traditional environment. This is due to the
fact that processing units in the mobile environment can be used at multiple locations
and in transition between these locations. Mobility results in several issues including
disconnections due to hand-off processes, motion management, location dependent
information, heterogeneous and fragmented network, security, and privacy.
2.2.3 Portability
There are many variations of portable computer systems with different physical
characteristics and capabilities. However, all these portable units share many com-
mon features such as limited memory, processing power, user interface, and power
source. The ideal goal would be to develop a device that is compact, durable, and
light that consumes a minimum amount of power.
3.
Broadcasting Issues
In a mobile computing environment, desire to have “timely and reliable” access to
information is compromised by the power consumption and network latency. The ne-
cessity of minimizing power consumption and network latency lies in the limitation
of current technology—the expected increase of the capacity of batteries is at much
lower rate than the increase of the chip density
[35,36]
. The hardware of the mobile
units has been designed to overcome this limitation by operating in various opera-
tional modes such as active, doze, sleep, nap, etc., to conserve energy. A mobile unit
can be in active mode (maximum power consumption) while it is searching or ac-
cessing data objects; otherwise, it can be in doze mode (reduced power consumption)
when the unit is not performing any computation.
Along with the architectural and hardware enhancements, efficient power man-
agement and energy aware algorithms can be devised to (i) organize and cluster
related data entities on broadcast channel(s) and (ii) schedule data retrieval from
broadcast channel(s). It is the major theme of this chapter to articulate some of these
efforts.
The cost of communication is normally asymmetric—sending information re-
quires, in general, 2-10 times more energy than receiving the information. As a
result, for public information, popular information can be generated and dissemi-
nated over the air channel. The mobile user looking for certain information can tune
to the broadcast channel(s) and access the desired information from the air in an
orderly manner. This scenario, however, brings out three issues:
