- Internet access
The sensor networks at GDI must be accessible via the
Internet. An essential aspect of habitat monitoring applications
is the ability to support remote interactions with
in-situ networks. - Hierarchical network
The field station at GDI needs sufficient resources to host
Internet connectivity and database systems. However, the
habitats of scientific interest are located up to several kilometers
further away. A second tier of wireless networking
provides connectivity to multiple patches of sensor networks
deployed at each of the areas of interest. Three to four
patches of 100 static (not mobile) nodes is sufficient to start. - Sensor network longevity
Sensor networks that run for 9 months from non-rechargeable
power sources would have significant audiences today. Although
ecological studies at GDI span multiple field seasons,
individual field seasons typically vary from 9 to 12 months.
Seasonal changes as well as the plants and animals of interest
determine their durations. - Operating offthegrid
Every level of the network must operate with bounded energy
supplies. Although renewable energy, for example solar
power, may be available at some locations, disconnected operation
remains a possibility. GDI has sufficient solar power
to run many elements of the application 24x7 with low probabilities
of service interruptions due to power loss. - Management atadistance
The remoteness of the field sites requires the ability to
monitor and manage sensor networks over the Internet. Although
personnel may be on site for a few months each summer,
the goal is zero on-site presence for maintenance and
administration during the field season, except for installation
and removal of nodes. - Inconspicuous operation
Habitat monitoring infrastructure must be inconspicuous.
It should not disrupt the natural processes or behaviors under
study. Removing human presence from the study areas
both eliminates a source of error and variation in data collection,
as well as a significant source of disturbance. - System behavior
From both a systems and end-user perspective, it is critical
that sensor networks exhibit stable, predictable, and repeatable
behavior whenever possible. An unpredictable system
is difficult to debug and maintain. More importantly,
predictability is essential in developing trust in these new
technologies for life scientists. - Insitu interactions
Although the majority of interactions with the sensor networks
are expected to be via the Internet, local interactions
are required during initial deployment, during maintenance
tasks, as well as during on-site visits. PDAs serve an important
role in assisting with these tasks. They may directly
query a sensor, adjust operational parameters, or simply assist
in locating devices. - Sensors and sampling
For our particular applications, the ability to sense light,
temperature, infrared, relative humidity, and barometric pressure
provide an essential set of useful measurements. The
ability to sense additional phenomena, such as acceleration/
vibration, weight, chemical vapors, gas concentrations,
pH, and noise levels would augment them. - Data archiving
Archiving sensor readings for off-line data mining and
analysis is essential. The reliable offloading of sensor logs to
databases in the wired, powered infrastructure is an essential
capability. The desire to interactively “drill-down” and explore
individual sensors, or a subset of sensors, in near realtime
complement log-based studies. In this mode of opera-
Figure 1: System architecture for habitat monitoring
tion, the timely delivery of fresh sensor data is key. Lastly,
nodal data summaries and periodic health-and-status monitoring
requires timely delivery.
