Next: Sensor Network Assumptions
Up: Service Architecture
Previous: Service Architecture
The problem addressed by our architecture is more formally described as
follows. We consider a dynamically changing set of events in the
physical environment of the sensor network. Let the physical location of
each event at time be denoted . A node is said
to be in the vicinity of event at time if it is within
sensor range of the event's location, . In this paper, we assume
that environmental events are localized. In other words, their location is
described by a single point in space, as opposed to an area. This
definition applies to tracking vehicles, finding survivors, monitoring
wild animals, or detecting localized fires. It does not apply to
applications involving distributed phenomena such as detection of
large chemical spills. We assume that events can
be detected independently by individual nodes in the sensor network
based on their local measurements. For example, detecting a magnetic
signature in a desert battle area would usually be indicative of a
passing armored vehicle. Finally, we assume that events are sparse. In
other words, the signatures of different targets are
generally not overlapping.
Let denote the set of nodes in the vicinity of event . The
objective of our architecture is to maintain a unique
addressable destination associated with each event , such that
sending data to this logical event address causes delivery of this
data to regardless of the location . In the current
implementation, we elect a leader out of set . The leader, among
other things, is
responsible for communication with remote destinations. Hence,
in the above problem statement, we define delivery of a message to
as delivery of the message to the current entity leader who by
definition belongs to the set . What the leader does with the
message is an orthogonal issue in our architecture.
Note that once the aforementioned addressing and communication
problem is solved, it becomes trivial to associate
multiple communication end-points with each entity simply by
demultiplexing the received message based on a port number in the
message header, in the same sense that UDP creates multiple ports over
IP.
Next: Sensor Network Assumptions
Up: Service Architecture
Previous: Service Architecture
root
2003-03-05