Information Technology Reference
In-Depth Information
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Difficult use
Miniaturization
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Too many devices in the
environment
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Need for continuous power
supply
Power consumption
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User distraction
Lack of proper
display
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Low-quality images
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User distraction
Figure 3: Problems related to size and power consumption.
consumption and the need of providing continuous energy to a large set of
devices is then another limiting factor, contrasting with a ubiquitous vision
and moving back towards a desktop-centric vision. The following figure
summarizes the aforementioned problems and highlights the main issues
related to size and power limitations for ubiquitous systems (Figure 3).
Many techniques are employed nowadays on microprocessor to
dynamically control individual core energy consumption, mostly connected
to software control of transistor operating frequency. Another concurrent
approach aims at improving power density for batteries, but also to find
alternative ways to derive energy from the external environment, relying on
concealed solar cells or piezoelectric sensors capable to extract energy from
body movements or body vibrations. Other alternatives look at transmitting
energy to the devices, as in
active electronic tagging
[16]. Lastly, display size
must always be adequate to the type of contents to be provided and must
always provide the appropriate contrast and colour quality to maintain user's
attention focused on the contents and not on the device.
5.2
Control loss and lack of feedback
As states Weiser in [1], interaction between users and ubiquitous systems must
be dynamic and perceived as most natural as possible. This implies on one
hand making fairly autonomous systems capable of deciding by themselves on
a number of using scenarios and, on the other hand, depriving the users from
the possibility to change system behaviours beyond indicating some basic
preferences. This control loss is particularly negative when default behaviours
do not match user's intentions, to the point to either distract him or even plainly
annoying him. It is thus indispensable to implement
overriding
functionalities
