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Introduction
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Wireless sensor networks consists of spatially
distributed autonomous sensors to cooperatively monitor
physical or environmental conditions, such as temperature,
sound, vibration, pressure, motion or pollutants.
Applications for wireless sensor networks are varied,
typically involving some kind of monitoring, tracking, or
controlling. Specific applications include habitat
monitoring, object tracking, nuclear reactor control, fire
detection, and traffic monitoring.
AWE
Communications develops a software package for the simulation of
such wireless sensor and MESH networks.
The planning tool covers the following simulation aspects:
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Connectivity between
the sensor nodes of the wireless network
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Channel assignment in a
self-organizing sensor network
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Determination of optimum paths
between sensor and gateway nodes
taking into account different
criteria, such as best SNIR, minimum path delay, etc.
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Connectivity Simulation
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The simulator provides the possibility to model wireless
sensor networks with different types of nodes, e.g. standard
and gateway nodes. In order to simulate and analyze the
connectivity between the nodes of the network in different
environments (rural,
urban and
indoor),
the occurring path loss between the sensor nodes will be
calculated based on the underlying propagation scenario.
Depending on the wireless
air interface of the system, interference calculations
can be done as well.
Path loss prediction for one horizontal plane
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Channel Assignment
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Self-organizing sensor networks are built from sensor nodes
that can spontaneously assemble the network themselves,
dynamically adapt to device failure and degradation, manage
movement of sensor nodes, and react to changes in task and
network requirements. Reconfigurable smart sensor nodes
enable sensor devices to be self-aware, self-reconfigurable
and autonomous. Within such dynamic networks, the channel
and interference conditions vary continuously, depending on the
instantaneous locations and settings of the nodes which
currently built the network. The assignment of the radio
channel, a node is using for communication with the other
nodes, can therefore be reconfigured either in specific time
intervals or on demand, in order to maximize the
signal-to-noise-and-interference-ratio (SNIR) at all nodes
of the network.
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Path Search
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Not all nodes of a sensor network might have a direct
connection to the other nodes within the network, especially
to the gateway nodes, due to limitations in the link budgets.
Therefore, the information send from a node far apart from a
gateway has to be received and re-transmitted from other
nodes of the network and passed towards a gateway node, i.e.
the information hops over several nodes, which build up a
path between the source and the sink of the information.
These 'information flow' paths can be determined depending
on the predicted radio channels between the nodes and the
specified service requirements of the
air interface.
Possible paths between sensor node
(yellow) and gateway node (blue)
Beyond this, the optimum path between a sensor node and a
gateway node can be found taking into account different user
defined criteria, such as minimum overall path delay, link
stability, etc. By default, the optimum path is determined
using the well known Dijkstra algorithm, but the user has
also the possibility to implement and use his own algorithm via an
open application interface.
Sample for path searching with Dijkstra
algorithm
The animation above shows the implemented Dijkstra
algorithm for finding the optimum 'information flow' path
between a sensor node (yellow node on the left) and a
gateway node (blue node on the right). The weight factors,
which are written on the edges between two nodes are
determined according to single or multiple user defined
criteria. |
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Simulation Results
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The planning tool for wireless sensor networks provides the
following simulation results:
- Matrices with path loss, path delay and interference
levels between all nodes of the network
- Probability of failure along paths
due to worse radio links
- Possible paths between the nodes
- Optimum path between node and gateway depending on user
defined criteria
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