The Smartball is a free-swimming ball equipped with hydrophone
and battery recording acoustic activity to identify
leaks as it moves along the pipeline. The Smartball is applicable
to 600 [mm] or larger diameter pipes, and is capable of
travelling for several kilometers (or up to 15 h).
The data is analyzed when the ball is retrieved from the
system. Laiet al. (2010) presentedamobile sensor PipeProbe pilot
test bed for determining the spatial topology of hidden water
pipelinesbehindwalls.Thecapsulelogs the sensedpressureand
angular velocity data on an EEPROM,whichis extracted after the
sensor flows out of the system. This data is used to analyze and
map the system. Trinchelro and Stefanelli (2010) explored the
implementation of mobile wireless sensor networks within
conduits used for fluid and liquid transportation. Two solutions
were shown for possible data transmission through an internal
antenna, depending on the electromagnetic characteristics of
the pipe (i.e., plastic, concrete, metallic), its location under the
ground, and the electromagnetic characteristics of the fluid.
Current MWSN technologies are not yet widely used and
are limited in their capability and applicability. These technologies,
however, are under constant development and their
deployment in water distribution systems can provide information
and insights which are not available using external
monitoring technologies.
Fig. 1 shows the schematic architecture of a mobile sensor
deployment in a water pipeline. The sensor travels along the
pipe, is transported by the water flow, and acquires and stores
physical information. It transmits gathered data out of the
conduit to fixed receiving ground units when it reaches the
proximity of their location. Once the obtained data is available
at the fixed units, it can be retransmitted for real time analysis.
Such data can be used for a variety of purposes such as
mapping the distribution system, and calibration and validation
of hydraulic and water quality models.
The objective of this study is to explore the inclusion of an
MWSNfor enhancing water distribution systems security. The
problem considered herein is where and when to release
mobile sensors in a distribution system, in addition to existing
stationary sensors, for minimizing detection times and
maximizing detection likelihoods. This work considers stationary
sensor locations as in two previously published water
distribution systems applications (Kessler et al., 1998; Ostfeld
et al., 2008), and explores optimal release times and locations
of mobile sensors for improving the overall combined (i.e.,
fixed and mobile) sensor network performance.