Developing and Testing of Software for Wireless Sensor Networks - Networked Embedded Systems - page 281

Algorithms Modules Services VM

Middleware core

Node-specific operating system

Hardware drivers Sensor driver

Hardware Sensor

FIGURE . Structure of a node application.

according to the node's task. Modules are additional components that increase the functionality of
the middleware. Typical modules are routing modules or security modules. Algorithms describe the
behavior of modules. For example, the behavior of a security module can vary in the case the encryp-
tion algorithm changes. he services component contains the required software to perform local and
cooperative services. his component usually cooperates with service components of other nodes to
fulfill its task. VMs enable an execution of platform independent programs installed at runtime.
Figure . shows the expansion of the proposed architecture to a whole sensor network from the
logical point of view. Nodes can only be contacted through services of the middleware layers. The
distributed middleware coordinates the cooperation of services within the network. It is logically
located in the network layer but physically exists in the nodes. All layers together in conjunction
with their configuration compose the sensor network application. hus, nodes do not perform any

Administration terminal

Sensor network application

Distributed middleware

Node A Node B Node C

Host middleware Host middleware Host middleware

Operating system Operating system Operating system

Hardware Hardware Hardware

FIGURE . Structure of a sensor network.