Mobile Computing Issues

Topics: Personal digital assistant, Mobile phone, Mobile computing Pages: 7 (2189 words) Published: October 1, 2014
Introduction
• There are several characteristics of wireless networks
and mobile devices that give rise to issues that do not
pose a problem in fixed, wired infrastructure.
– Adaptive behaviour
p
– Battery power
– Limitation on local resources
– Small display size
– Disparity in the availability of remote services
– Unpredictable variation in QoS.

Issues in Mobile Computing

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Adaptive Behaviour

Effective use of smart space
space.
Invisibility.
Localised scalability.
Masking uneven conditioning.

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• Other reasons for a mismatch:
– The availability of compute servers or data-staging
server is location-dependent and affects techniques
such as cyber foraging.
– In case of mobile code, low-level resources and
interactive resources may vary widely between the
source and destination systems. As time elapses,
the resource level may change, for example, residual
power on a laptop is depleted as battery drains.

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• Adaptive behaviour arises due to a significant mismatch
between supply and demand for resources.
– Often in low level systems, e.g. bandwidth, memory.
• As a mobile user moves, services and resources may
become available or disappear.
• Mismatch may occur even when the user is static
static.
• The system has to handle the variation in a way that
minimises inconvenience to users and does not abruptly
interfere with the task the user is trying to accomplish.

• Adaptability is critical to support pervasive
computing.
• Pervasive computing extends the problem domain:





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• The mismatch cannot be ignored as it will result in
unsatisfactory user experience.
• Adaptation is important not only as users move
resource-rich to resource-poor environment but also
in the other direction.
– E a user should not b d i d of b tt quality
E.g.
h ld t be deprived f better
lit
video or speedier file transfer if more bandwidth is
now available.

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1

• Adaptation decisions require timely knowledge of
current resource level – change in available
resource and its detection should occur promptly.

• 3 adaptation strategies:

– If the change justifies a modification in the amount of
resources consumed by an application, it should be
executed promptly
promptly.

• Requires the OS to play a role in managing
resources, such as bandwidth and battery power, in
addition the traditional resources such as CPU
cycles and memory.
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• Which strategy to choose depends on the smart
space environment.

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• Defines 2 attributes to support adaptability: agility
and fidelity.
• Agility is the speed and accuracy with which an
application detects and responds to changes in
resource availability.

– The system may need to switch between different
strategies to guarantee a smooth and seamless
transition.

• Has to balance between providing a proactive
system and transparency.
• Odyssey is a platform for mobile data access that
supports application-aware adaptation that is
targeted at applications that access rich, resourcedemanding data.

– I a complex attribute because different applications
Is
l
tt ib t b
diff
t
li ti
may have different sensitivity to different resources.
– For example, a mobile conferencing system is more
sensitive to bandwidth fluctuation than in battery
power level.

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• Fidelity is the degree to which data presented to a
mobile client matches the reference copy at the
server.

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• Examples of dissimilarity between data types.

– A reference copy is the most complete, current and
detailed version of a data item.

• Factors that determine fidelity depends on the type
of data and the applications using it.
• In order to support adaptability for efficient resource
usage, some form of awareness has to be
incorporated into the...
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