Image Processing Reference
In-Depth Information
The EnviroTrack programming system consists of
•
EnviroTrack compiler
: In EnviroTrack programs, a list of context declarations is defined.
Each definition includes an activation statement, an aggregate state definition, and a list
of objects attached to the definitions. The EnviroTrack compiler includes C program
templates. he whole project is then built using the TinyOS development tools.
•
Group management protocol
:Allsensorsassociatedtoagrouparemaintainedbythis
protocol. A group leader is selected out of the group members when the critical mass of
nodes and freshness of the approximate aggregate state is reached. The group manage-
ment protocol ensures that only a single group leader per group exists. he leader sends
a periodical heartbeat to inform its members that the leader is alive. Additionally, the
heartbeat signal is used to synchronize the nodes and to inform nodes that are not part
of the group, but fulfils the sensing condition.
•
Object naming and directory services
: hese services maintain all active objects and their
locations. The directory service provides a way to retrieve all objects of a given context
type.Italsoassignsnamestogroupssotheycanbeaccessedeasily.Ithandlesdynamical
joining and leaving of group members.
•
Communication and transport services
: The migration transport protocol (MTP) is
responsibleforthetransportationofdatapacketsbetweennodes.Allmessagesarerouted
via group leader nodes. Group leader nodes identify the context group of the target node
and the position of its leader using the directory service. he packet is then forwarded to
the leader of the destination group. All leadership information provided by MTP packets
is stored in the leaders on a least recently used basis to keep the leader up-to-date and to
reduce directory lookups.
EnviroTrack enables the construction of an information infrastructure for the tracking of environ-
mental conditions. It manages dynamic groups of redundant sensor nodes and attaches computa-
tion to external events in the environment. Furthermore, EnviroTrack implements noninterrupted
communication between dynamically changing physical locales defined by environmental events.
12.3.7 SeNeTs
SeNeTs is a middleware architecture for wireless sensor networks. It is developed at the University
of Rostock []. The SeNeTs middleware is primarily designed to support the developer of a wire-
less sensor network during the predeployment phase (programming aspect). SeNeTs supports the
creation of small and energy-saving programs for heterogeneous networks. One of the key features
of SeNeTs is the optimization of APIs. The required configuration, optimization, and compilation
of software components are processed by a development environment. Besides the programming
aspect, the middleware supports the behavioral aspect as well, such as task change or evolution over
time (Figure .).
12.3.7.1 SeNeTs Architecture
SeNeTs is based on the software layer model introduced in Section .. To increase flexibility
and enhance scalability of sensor node software, it separates small functional blocks as shown in
Figure .. In addition, the OS layer is divided into a node-specific OS and a driver layer, which
contains at least one sensor driver and several hardware drivers, such as timer driver and RF driver.
The node-speciic OS handles device-specific tasks, for example, boot-up, initialization of hardware,
memory management, and process management as well as scheduling. Host middleware is the supe-
rior software layer. Its main task is to organize the cooperation of distributed nodes in the network.
Middleware core handles four optional components, which can be implemented and exchanged
