Page 264 - Shaping smarter and more sustainable cities - Striving for sustainable development goals

This type of sensors uses ZigBee, Bluetooth and Wi‐Fi protocols to send low bandwidth data such as
temperature, humidity and CO2 levels, and high speed W‐CDMA and HSPA mobile networks to
upload video.
For security applications that require night vision mode, the new video camera sensor nodes include
dozens of high‐power infrared (IR) LEDs, making it possible to take pictures in total darkness. The
3G module is equipped with an internal GPS that adds geolocation information to all multimedia
files.

Node tracking scenarios

This indicates tracking of a tagged object through a region of space monitored by a sensor network.
There are many situations where one would like to track the location of valuable assets or personnel.
Current inventory control systems attempt to track objects by recording the last checkpoint that an
object passed through. With wireless sensor networks, objects can be tracked by simply tagging
them with a small sensor node. The sensor node will be tracked as it moves through a field of sensor
nodes that are deployed in the environment at known locations. Instead of sensing environmental
data, these nodes will be deployed to sense the radio messages of the nodes attached to various
objects. The nodes can be used as active tags that announce the presence of a device. A database
can be used to record the location of tracked objects relative to the set of nodes at known locations.
With this system, it becomes possible to request for the exact location of the object and not just the
last location where it was last scanned.

There are two main ways of performing outdoor location tracking when sensor devices are located
in a large area such as a city. The most extensive one is to use a GPS module to get the information
sent by the satellites and extract all the information possible (latitude, longitude, speed, direction).
However, this methodology is not effective when requiring mobile scenarios where the nodes can
change from an outdoor environment to an indoor one, such as going inside buildings, garages and
tunnels.
For these cases an alternative method is used which consists of taking the information sent by the
Mobile Phones Cells and looking for their location in a previously saved Data Base. This information
can include Cell ID, RSSI and Timing Advance (TA) of any of the Base Stations which are located in
the surroundings.
Both GPS and GPRS technologies are complementary to each other as a system with both
technologies allow the tracking of position inside buildings, garages, and even inside tunnels (e.g.
subway railway system) while maintaining accurate precision of where the information from the
GPS satellites can reach the sensor device. There are many technologies to obtain location
information; some of them have been reviewed in chapter 3 (geo‐localization for public safety and
emergencies).

254 ITU‐T's Technical Reports and Specifications