Image Processing Reference
In-Depth Information
Programming on a low-level fosters type errors and requires hardware interaction neces-
sitating close attention to timing, resource arbitration, and the interrupt strategy. Detailed
understanding of the hardware is important, including susceptibility to environmental
conditions, long sleep cycles, and the architecture of the sensor node as a composition of
interacting components. Traditional embedded test and debugging systems may be used
for a single node: Emulators such as Avrora or execution on a real node and exposing
internal state via a serial interface. Debugging help is provided by tools such as JTAG or
Marionette []. For hardware-independent problems, simulators such as TOSSIM can
be used. The details of modeling of wireless communication heavily influence the pro-
tocol stack. Asymmetry of links, anisotropy, and noise in the environment drastically
influence protocol performance. As communication is optimized for efficient energy use,
the optimization must rely on valid assumptions and models of the actual deployment
environment.
11.2.1.2 Example Instances of Test Platforms
hetestplatformsusedinWSNvalidationincludewell-knownsimulatorswiththeiroriginintra-
ditional (wireless) network design like Ns- [] or GloMoSim []. Libraries have been developed
by the community to include the domain-specific aspects of WSN, particularly the radio. hey offer
scalability, but since they were not designed for WSN, they typically provide a higher ease-of-use and
accuracy for other domains than for WSN. Simulation libraries for discrete event simulators, espe-
cially targeted for WSNs, such as Castalia [] based on OMNeT++, provide a sensor node agnostic
test platform. Such libraries are targeted for validation of sensornet algorithms. WSN-specific simu-
lators have been established, like EmSim [] and TOSSIM [], which make use of the actual target
code and link it with simulation libraries to run on a host computer for simulation.
Simulation deficiencies and realism of deployment challenges has triggered an increased interest
in testbed implementations such as Motelab [] or the DSN []. [].These typically are installations at
the department building or on the university campus to better grasp deployment characteristics and
the nondeterministic nature of the wireless communication.
Other significant parameters in the system space, such as solar energy scavenged for sustainable
operations and others effect of a outdoor environment, require either physical stimulation and con-
trol or a representative outdoor testbed such as Trio []. Nevertheless, testbed characteristics for
radio communication, topology, or harvestable energy may still differ considerably to the actual
deployment site.
Researches have proposed field trials [] in order to attain deeper insight into WSN deploy-
ments. Turau et al. discuss that such prototypical deployments are expensive, but nevertheless
provide invaluable information about the environment and actual system execution on a large-scale,
especially as systematic verification and testing methodologies and tools are still in their infancy.
Each individual test platform has its benefits concerning a specific design under test, design stage,
and a set of tests. A distinct approach is integration of tools: Hybrid solutions (EmStar []) offer
simulation, emulation, and testbed execution in a single framework. COOJA [] allows for cross-
level simulation, thereby leveraging the benefits of individual tools. A distributed testing framework
for WSNs [] supports continuous testing throughout the design cycle by exploiting the ability to
design and test on different abstraction levels with a common test specification, promoting regression
testing and test integration into a periodic build process.
11.2.2 Software Testing Methodologies
Design-by-contract [] is an established methodology in software engineering. For embedded soft-
ware, contracts on component interfaces help to determine faults in the form of contract violations.
