2.11 Lifetime
Depending on the application, the required lifetime of a sensor
network may range from some hours to several years.
The necessary lifetime has a high impact on the required
degree of energy efficiency and robustness of the nodes.
2.12 Other QoS Requirements
Depending on the application, a sensor network must support
certain quality-of-service aspects such as real-time constraints
(e.g., a physical event must be reported within
a certain period of time), robustness (i.e., the network
should remain operational even if certain well-defined failures
occur), tamper-resistance (i.e., the network should
remain operational even when subject to deliberate attacks),
eavesdropping-resistance (i.e., external entities cannot
eavesdrop on data traffic), unobtrusiveness or stealth
(i.e., the presence of the network must be hard to detect).
These requirements may impact on other dimensions of the
design space such as coverage and resources.
3 Applications
In this section we justify our design space model by locating
a number of applications at different points in the design
space. For this, we have selected concrete applications
that are well-documented and that have advanced beyond a
mere vision. Some of the applications listed are field experiments,
some are commercial products, and some are advanced
research projects that use sensor networks as a tool.
For classification, we have used the reported parameters that
were actually used in practical settings and we have deliberately
refrained from speculation as to what else could have
been done.
Note that there are usually different technical solutions
for a single application, which means that the concrete
projects described below are only examples drawn from a
whole set of possible solutions. However, these examples
reflect what was technically possible and desirable at the
time the projects were set up. Therefore, we have decided
to base our discussion on these concrete examples rather
than speculating about the inherent characteristics of a certain
type of application. Table 1 classifies the sample applications
according to the dimensions of the design space
described in the previous section.
3.1 Bird Observation on Great Duck Island
A wireless sensor network (WSN) is being used to observe
the breeding behavior of a small bird called Leach’s Storm
Petrel [9] on Great Duck Island, Maine, USA. These birds
are easily disturbed by the presence of humans, hence WSN
seems an appropriate way of better understanding their behavior.
The breeding season lasts for seven months from
April to October. The biologists are interested in the usage
pattern of their nesting burrows, changes in environmental
conditions outside and inside the burrows during the breeding
season, variations among breeding sites, and the parameters
of preferred breeding sites.
Sensor nodes are installed inside the burrows and on the
surface. Nodes can measure humidity, pressure, temperature,
and ambient light level. Burrow nodes are equipped