Image Processing Reference
In-Depth Information
applications containing their current state. Optional components, such as graphical user interfaces
can install callbacks to receive this information.
12.4.3.3 Application Server
The AS manages instances of node applications on one host (Figure .). It acts as bridge between
node applications and the NS. Usually, at least one AS exists within the SeNeTs network. Ideally, only
one node application should be installed on an AS to prevent quasiparallel effects during runtime.
The AS runs independent of the NS. It connects to the NS via a pipe to receive commands. Each
command is multiplexed to one of the connected node applications. Moreover, if the pipe to the NS
breaks, node applications will not be affected besides losing logging and controlling facilities. Later,
the NS can establish the pipe again.
Generally, an AS starts as service together with the host's OS. At startup, it requires configuration
parameters of the node's hardware. With these parameters, the AS assigns hardware to node appli-
cations. Suppose a host system that comprises two devices representing sensor nodes as principally
shown in Figure .. Then, the AS requires device number, physical position of the node, etc. to
configure the dynamically installed node applications at runtime.
12.4.3.4 SeNeTs Application
Applications for wireless sensor nodes are usually designed based on a layered software model as
depicted in Figure .a []. On top of the node's hardware, a specialized OS is set up such as
TinyOS []. A sensor driver contains software to initialize the measurement process and to obtain
sensor data. Above the OS and the sensor driver, middleware components are located containing
services to aggregate data or to determine the node's position. he aforementioned modular design
allows:
•
Abstraction of hardware, for example, sensors, communication devices, memory, etc.
•
Adaptation of the node's OS
•
Addition of optional components, e.g., logging and configuration
Sensor node application
SeNeTs
adaptation
Algorithms
Modules
Services
Logging
Sensor node
application
Middleware management
Controlling
Operating system
Sensor driver
Debugging
Target type
SeNeTs hardware
abstraction
Environment
emulation
Simulator
Node
SeNeTs
(a)
(b)
FIGURE .
(a)SotwarelayermodelofaSNAand(b)SotwarelayermodelofaSeA.
