A complete wireless sensor network solution for carpark
management is presented in this paper. The system architecture
and design are first detailed, followed by a description
of the current working implementation, which is based on our
DSYS25z sensing nodes. Results of a series of real experimental
tests regarding connectivity, sensing and network performance
are then discussed. The analysis of link characteristics in the
car-park scenario shows unexpected reliability patterns which
have a strong influence on MAC and routing protocol design.
Two unexpected link reliability patterns are identified and documented.
First, the presence of the objects (cars) being sensed
can cause significant interference and degradation in communication
performance. Second, link quality has a high temporal
correlation but a low spatial correlation. From these observations
we conclude that a) the construction and maintenance of a fixed
topology is not useful and b) spatial rather than temporal message
replicates can improve transport reliability