Stefano Lenzi

A Novel Approach to Indoor RSSI Localization by Automatic Calibration of the Wireless Propagation Model

We propose a novel localization algorithm of mobile sensors based on wireless sensor networks providing RSSI measurements between the mobile and the fixed sensors (anchors) in the network. The algorithm selects and weights the RSSI measurements according to their strength, and it uses a propagation model to transform RSSI measurements into distances, in order to estimate the position of the mobile. The algorithm also uses a virtual calibration method of the propagation model that does not require human intervention. By an experimental setup we show that the localization algorithm increases the performance with respect to the commonly used least mean square algorithm showing also how to achieve a wished accuracy increasing the anchor density.

Virtual Calibration for RSSI-Based Indoor Localization with IEEE 802.15.4

Localization systems based on Received Signal Strength Indicator (RSSI) exploit fingerprinting (based on extensive signal strength measurements) to calibrate the system parameters. This procedure is very expensive in terms of time as it relies on human operators. In this paper we propose a virtual calibration procedure which only exploits the measurements of the RSSI between pairs of anchors. In particular, we propose two procedures for virtual calibration and we evaluate their performance with respect to an ad-hoc calibration campaign by performing measures in an indoor environment with an IEEE 802.15.4 sensor network.

Sensor data fusion for activity monitoring in the PERSONA ambient assisted living project

User activity monitoring is a major problem in ambient assisted living, since it requires to infer new knowledge from collected and fused sensor data while dealing with highly dynamic environments, where devices continuously change their availability and (or) physical location. In the context of the European project PERSONA, we have developed an activity monitoring sub-system characterized by high modularity, little invasiveness of the environment and good responsiveness. In this paper we first illustrate the functional architecture of the proposed solution from a general point of view, discussing the motivations of the design. Then we describe in details the software components—sensor abstraction and integration layer, human posture classification, activity monitor—and the resulting activity monitoring application, presenting also a performance evaluation.

Automatic virtual calibration of range-based indoor localization systems

The localization methods based on received signal strength indicator (RSSI) link the RSSI values to the position of the mobile to be located. In the RSSI localization techniques based on propagation models, the accuracy depends on the tuning of the propagation models parameters. In indoor wireless networks, the propagation conditions are hardly predictable due to the dynamic nature of the RSSI, and consequently the parameters of the propagation model may change. In this paper, we present an automatic virtual calibration method of the propagation model that does not require human intervention; therefore, can be periodically performed, following the wireless channel conditions. We also propose a novel RSSI-based localization algorithm that selects the RSSI values according to their strength, and uses a calibrated propagation model to transform these values into distances, in order to estimate the position of the mobile. Copyright

SAIL: A Sensor Abstraction and Integration Layer for Context Awareness

Wireless Sensor Networks (WSN) are an important technological support for ambient assisted applications. Up to now most WSN applications are based on ad hoc solutions, and attempts to provide reusable applications are still in their youth. Under this trend of research we propose a layered architecture called SAIL (Sensor Abstraction and Integration Layers) to be used in context aware architectures, and aimed at integrating WSN as context information sources. In the proposed approach, the applications running on WSN can be exposed using either a node centric or a data centric paradigm, and they are interfaced with different access technologies. SAIL is currently encapsulated within the OSGi framework and has been tested on MICAz motes.

Sensor Data Fusion for Activity Monitoring in Ambient Assisted Living Environments

We illustrate the PERSONA context-awareness framework applied to a major problem in Ambient Intelligence, namely user activity monitoring, that requires to infer new knowledge from collected and fused sensor data, dealing with highly dynamic environments where devices continuously change their availability and (or) physical location. We describe the Sensor Abstraction and Integration Layer (SAIL), we introduce the Human Posture Classification component, which is one particular context information provider, and finally we describe the Activity Monitor, which is a reasoner that delivers aggregated/derived context events in terms of the context ontology.

A service-oriented ZigBee gateway for Smart Environments

In the recent past Smart Environments, and in particular Smart Homes, have attracted the attention of many researchers and industrial vendors. In such environments, according to the Ambient Intelligence paradigm, heterogeneous devices may operate collectively using context information and intelligence that is usually hidden in the home networks. The networks of ZigBee devices play an important role in this scenario. However they require an easier interaction model with IP-based networks. This work presents an open source platform that seamlessly integrates ZigBee devices with applications running on smart phones and other connected devices available at home. It can be deployed on low-cost devices, such as Plug-PC, and it exploits the OSGi execution environment to discover devices and to notify the smart home of new available services.

Social networking and context management for the future 3D Internet

Current trends in 3D visualization merged with internet applications and sensor technologies will soon break the barriers to the widespread acceptance of 3D Internet, and they will enable a full user immersion in the virtual world. However this evolution will impact dramatically on the existing infrastructures since the fruition of 3D content in real time by a huge number of people poses new issues related to the system responsiveness and to the ability of managing context information. In this paper we observe that actions related to the acquisition of context from the physical and from the virtual worlds, as well as actuation in both worlds can be considered as a special case of context management and actuation. For this reason we propose an architecture for the management of such aspects within a unique framework, and an experimental testbed that validates the architecture.

User-centric universal multimedia access in home networks

Much research is currently being conducted towards Universal Multimedia Access, aiming at removing barriers that arise when multimedia content is to be consumed with more and more heterogeneous devices and over diverse networks. We argue that users should be put at the center of the research work to enable user-centric multimedia access.In this paper we present the requirements for a user-centric multimedia access system in a networked home environment. These requirements are easy access to available content repositories, context awareness, content adaptation and session migration. After showing the limits of state-of-the-art technologies, we present the architecture of a system which allows unified access to the home network content, automatically delivered to rendering devices close to the user, adapted according to the rendering device constraints, and which is also capable of session mobility.

Multi-tenancy Aware Ambient Assisted Living Platforms in the Cloud

Over the last years, Ambient Assisted Living (AAL) technologies have seen a remarkable grow up. Although this field has been researched for many years and different projects have investigated and proposed AAL platforms with a rich set of functionality, the current market situation still favors isolated solutions. A possible reason is that those platforms are too complex to be easily setup and maintained. Also, resource sharing is possible between services, but not between platforms. A promising alternative is provided by the cloud computing approach which integrates common services in a shared way.