Page 261 - Shaping smarter and more sustainable cities - Striving for sustainable development goals

of the roads, the air pollution, the behavior of criminals or those attending sporting, cultural events
and entertainment.

2.3.2.1 System Architecture for Wireless Sensor Networks
The emerging field of wireless sensor networks combines sensing, computation, and
communication into a single tiny device. Through advanced mesh networking protocols, these
devices form a sea of connectivity that extends the reach of cyberspace out into the physical world.
As water flows to fill every room of a submerged ship, the mesh networking connectivity will seek
out and exploit any possible communication path by hopping data from node to node in search of
its destination. While the capabilities of any single device are minimal, the composition of hundreds
of devices offers radical new technological possibilities.

The power of wireless sensor networks lies in the ability to deploy large numbers of tiny nodes that
assemble and configure themselves. Usage scenarios for these devices range from real‐time tracking
or monitoring of environmental conditions, to ubiquitous computing environments, in situ
monitoring of the health of structures or equipment, among others. While often referred to as
wireless sensor networks, they can also control actuators that extend control from cyberspace into
the physical world.

The concept of wireless sensor networks is based on a simple equation:

However, actually combining sensors, radios, and CPU's into an effective wireless sensor network
requires a detailed understanding of both capabilities and limitations of each of the underlying
hardware components, as well as a detailed understanding of modern networking technologies and
distributed systems theory. Each individual node must be designed to provide the set of primitives
necessary to synthesize the interconnected web that will emerge as they are deployed, while
meeting strict requirements of size, cost and power consumption. A core challenge is to map the
overall system requirements down to individual device capabilities, requirements and actions. To
make the wireless sensor network vision a reality, an architecture that synthesizes the envisioned
applications out of the underlying hardware capabilities must be developed.

2.3.2.2 Sensor network application classes

The three application classes, which have been selected are: environmental data collection, security
monitoring, and sensor node tracking. It is believed that the majority of wireless sensor network
deployments will fall into one of these class templates.
Environmental Data Collection

An environmental data collection application is to collect several sensor readings from a set of points
in an environment over a period of time in order to detect trends and interdependencies. The idea
is to collect data from hundreds of points spread throughout the area and then to analyze the data
offline.

At the network level, the environmental data collection application is characterized by having a large
number of nodes continually sensing and transmitting data back to a set of base stations that store
the data using traditional methods. These networks generally require very low data rates and
extremely long lifetimes. In typical usage scenario, the nodes will be evenly distributed over an
outdoor environment. This distance between adjacent nodes will be minimal yet the distance across
the entire network will be significant.

ITU‐T's Technical Reports and Specifications 251