From a world of small smart objects to the big new Internet

by Luigi Fratta
Politecnico di Milano, Advanced Network Technologies Laboratory 
http://www.elet.polimi.it/upload/antlab 

Abstract:

Sensor Networks have attracted in the last years increasing interests by the
research community and manufacturers due to the huge number of application
that allow to extend the human capabilities to receive information and monitor
the physical word. Wireless Sensor Networks (WSNs) technologies are the most
promising solution since they are easy to deploy and allow to monitor even
large areas through a large set of small and inexpensive devices. However, the
interaction of human beings with the physical world does not only include
sensing, but also taking actions. Devices, such as actors or actuators, can
be interconnected through a network and remotely controlled by human
operators. Recently, Wireless Sensor and Actor Networks (WSANs) have been
envisioned as the next step of this evolution path where sensor and actor
devices are interconnected together and decisions can be taken by intelligent
actors in a distributed way based on the information provided by sensors. The
resulting network architecture poses new challenges mainly due to the critical
performance required by the network and the distributed control and
coordination algorithms among actors.

It is our opinion that in the near future the above mentioned architecture
will be further extended considering interconnected sensor and actor networks
where a set of control agents can dynamically interact with the physical
world. The convergence of communication, computing and control will be
possible by adding the decision making and control functions into the network.
We envision that the distributed control applications running on this system
should be able to interact with the physical world on different time scales
and with different levels of responsiveness based on the different events and
situations sensed, similarly to the way in which human being react to external
stimuli.

Similarly to biological control systems, a mixed distributed and centralized
scheme is of paramount importance to design large and complex sensors and
actuators networks and make them available to a large set of control
applications. Control agents can be organized in a hierarchical way and they
can collaborate to make decisions through the implementation of a distributed
processing of data provided by sensors. Depending on the responsiveness
requirements of the application and the specific action to be taken, the
controlloop can be closed either in the peripheral part of the network or in
hi gher layer controllers when more complex decisions are needed. To enable
this scenario, the network must be used as a flexible and reconfigurable
service platform. Sensor and actuator devices can be shared by different
applications running at the same time not only on application servers but also
on network nodes. The information provided by sensors can be combined and
elaborated for different purposes and used to take actions by several
distributed applications in the network. Due to the heterogeneity of data and
communication modes, the network cannot just transport information, but it
must participate to the application implementation providing computation
resources, content based data routing, event triggered communications, etc.
With today IP technology, the complexity of communications processes between
sensors, control agents and actuators, are managed by a middleware layer based
on overlay networks. Such an approach is just a remedy to IP technology
limitations. We envision that the next generation Internet technologies will
allows to base routing decisions on more rich information than IP addresses
and to share among applications not only transmission resources, but even
computation resources as well and sensing and acting devices. Due to the
heterogeneity of application needs and communication modes, different
networking approaches must coexist in next generation IP routers. A set (not
too large) of different networking functionalities may be implemented in the
devices and activated by individual packet flows based on control and
signaling information.

Even if the overlay approach will not be completely replaced, we expect that
the set of advanced networking functionalities implemented in future
generation routers will allow applications developers to program the whole
network behavior.

When a world of small smart objects is asking access to the Internet, the
traditional dumb network needs to become a little bit smarter as well!