02-06-2012, 01:18 PM
Middleware Challenges for Wireless Sensor Networks
Middleware Challenges.pdf (Size: 63.5 KB / Downloads: 17)
Introduction
Wireless sensor networks (WSN) [1] are an increasingly attractive
means to monitor environmental conditions and to bridge the
gap between the physical and the virtual world. A WSN consists
of large numbers of cooperating small-scale nodes capable
of limited computation, wireless communication, and sensing. By
correlating sensor output of multiple nodes, the WSN as a whole
can provide functionality that an individual node cannot. Application
areas for WSNs include geophysical monitoring (seismic activity),
precision agriculture (soil management), habitat monitoring
(tracking of animal herds), transportation (traffic monitoring),
military systems, business processes (supply chain management),
and in the future, possibly cooperating smart everyday things.
Wireless Sensor Networks
Basic Operation Deployment of a sensor network in a target area
can be a continuous process, for example to replace nodes with
depleted batteries or nodes that have been destroyed due to environmental
influences. In general, deployment establishes an
association of sensor nodes with objects, creatures, or places in
order to augment them with information-processing capabilities.
Deployment can be as diverse as establishing one-to-one relationships
by attaching sensor nodes to specific items to be monitored
[2], covering an area with locomotive sensor nodes [7], or throwing
nodes from an aircraft into an area of interest [18]. Due to their
large number, nodes have to operate unattended after deployment.
Once a sufficient number of nodes has been deployed, the sensor
network can be used to fulfill its task. This task can be issued
by an external entity connected to the sensor network, such as a
user with a PDA, an aircraft flying by, or some device on the Internet.
Also conceivable are isolated, self-contained sensor networks
which are programmed to fulfill a certain sensing task, whose result
controls actuator nodes that are also part of the network. In
hybrid architectures, the sensing results control the sensors to trigger
more detailed monitoring of a certain phenomenon, which is
then reported to the external task issuer.
Middleware Challenges
Middleware sits between the operating system and the application.
On traditional desktop computers and portable computing
devices, operating systems are well established, both in terms
of functionality and systems. For sensor nodes, however, the
identification and implementation of appropriate operating system
primitives is still a research issue [6]. In many current projects,
applications are executing on the bare hardware without a separate
operating system component. Hence, at this early stage of
WSN technology it is not clear on which basis future middleware
for WSN can typically be built.