Sensor Networks’ Integration - Application and Multidisciplinary Aspects of Wireless Sensor Networks - page 94

senselets that execute in a secure environment of the SAs. These senselets are able
to process (e.g., filter) the incoming raw sensor stream and send the processed sensor
information to nearby OAs. In addition, SAs mediate the access of senselets to the
resources of its attached sensors.
The IrisNet architecture seems to provide several desired features, ranging from
sensor network reuse, application-specific in-network processing resource media-
tion on the SAs, fault tolerance, and geographic information lookup and seems to
scale well as it provides a distributed database view for each sensing service. While
providing the possibility of sharing computation across senselets, it does little in
optimizing the data traffic from the sensor networks to the sensing services. Data is
routed via the OA overlay, which may result in suboptimal data paths (could be
alleviated by OA placement if physical hosts are arbitrarily available) and it does
not allow concurrent applications to share the same sensor data. Creating a distrib-
uted database for each sensing service may lead to services often implementing
redundant databases that could have been shared among several applications.
IrisNet also does not provide discovery mechanisms that allow sensor networks and
their capabilities to be automatically discovered by application developers at design
time, not to mention runtime. IrisNet also does not address functions for security,
privacy and trust, and accounting.

Ubiquitous Sensor Networks

The work presented in [ 16 ] represents the first step of an ongoing research activity
Telefonica is performing toward the Ubiquitous Sensor Networks concept from the
ITU-T [ 23 ]. The presented platform is being designed following a horizontally
layered approach, so networks and services can evolve independently. The four
layers of the platform, following a bottom-up approach, are: the Sensors and actua-
tors networks, the Gateway (that provides independence from the networking tech-
nology), the NGN core (IMS), and the Service Layer (where an enabler is provided).
The key elements of the platform are:

• The USN-Gateway : is a logical entity whose main goal is to provide indepen-

dence from the sensing or networking technologies used to communicate
sensors and actuators. The independence is provided by performing two trans-
formations: from one side it provides homogeneous communication toward and
from the sensors and actuators networks, and from the other side it provides
homogeneous data representation. It is being defined as an IMS User-equipment
which already provides important functionalities like AAA and it allows to be
deployed in a wide range of devices.
The

• USN-Enabler : is defined as an OMA enabler, intended to allow services to

be created in a cost-efficient way following a horizontal approach, where multiple
services can access the same sensor and actuator networks. The basic function-
alities it provides are: resource discovery, publish-subscribe-notify mecha-
nisms, event-filtering and processing, and homogeneous remote management.