• 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
– Battery power
– Limitation on local resources
– Small display size
– Disparity in the availability of remote services
– Unpredictable variation in QoS.
Issues in Mobile Computing
Effective use of smart space
Masking uneven conditioning.
• 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.
• 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
• 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
• Pervasive computing extends the problem domain:
• 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
h ld t be deprived f better
video or speedier file transfer if more bandwidth is
• 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
• 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.
• Which strategy to choose depends on the smart
• Defines 2 attributes to support adaptability: agility
• Agility is the speed and accuracy with which an
application detects and responds to changes in
– The system may need to switch between different
strategies to guarantee a smooth and seamless
• 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
tt ib t b
may have different sensitivity to different resources.
– For example, a mobile conferencing system is more
sensitive to bandwidth fluctuation than in battery
• Fidelity is the degree to which data presented to a
mobile client matches the reference copy at the
• 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...
Please join StudyMode to read the full document