Estimating Clock Uncertainty for Efficient Duty-Cycling in Sensor Networks

Radio duty cycling has received significant attention in sensor networking literature, particularly in the form of protocols for medium access control and topology management. While many protocols have claimed to achieve significant duty-cycling benefits in theory and simulation, these benefits have often not translated to practice. The dominant factor that prevents the optimal usage of the radio in real deployment settings is time uncertainty between sensor nodes. This paper proposes an uncertainty-driven approach to duty-cycling where a model of long-term clock drift is used to minimize the duty-cycling overhead. First, we use long-term empirical measurements to evaluate and analyze in-depth the interplay between three key parameters that influence long-term synchronization-synchronization rate, history of past synchronization beacons and the estimation scheme. Second, we use this measurement-based study to design a rate-adaptive, energy-efficient long-term time synchronization algorithm that can adapt to changing clock drift and environmental conditions while achieving application-specific precision with very high probability. Finally, we integrate our uncertainty-driven time synchronization scheme with a MAC layer protocol, BMAC, and empirically demonstrate one to two orders of magnitude reduction in the transmit energy consumption at a node with negligible impact on the packet loss rate

The SENSEI Real World Internet Architecture

The integration of the physical world into the digital world is an important requirement for a Future Internet, as an increasing number of services and applications are relying on real world information and interaction capabilities. Sensor and actuator networks (SAN) are the current means of interacting with the real world although most of the current deployments represent closed vertically integrated solutions. In this paper we present an architecture that enables efficient integration of these heterogeneous and distributed SAN islands into a homogeneous framework for real world information and interactions, contributing to a horizontal reuse of the deployed infrastructure across a variety of application domains. We present the main concepts, their relationships and the proposed real world resource based architecture. Finally, we outline an initial implementation of the architecture based on the current Internet and web technologies

The SENSEI Real World Internet Architecture

The integration of the physical world into the digital world is an important requirement for a Future Internet, as an increasing number of services and applications are relying on real world information and interaction capabilities. Sensor and actuator networks (SAN) are the current means of interacting with the real world although most of the current deployments represent closed vertically integrated solutions. In this paper we present an architecture that enables efficient integration of these heterogeneous and distributed SAN islands into a homogeneous framework for real world information and interactions, contributing to a horizontal reuse of the deployed infrastructure across a variety of application domains. We present the main concepts, their relationships and the proposed real world resource based architecture. Finally, we outline an initial implementation of the architecture based on the current Internet and web technologies

The SENSEI Real World Internet Architecture

The integration of the physical world into the digital world is an important requirement for a Future Internet, as an increasing number of services and applications are relying on real world information and interaction capabilities. Sensor and actuator networks (SAN) are the current means of interacting with the real world although most of the current deployments represent closed vertically integrated solutions. In this paper we present an architecture that enables efficient integration of these heterogeneous and distributed SAN islands into a homogeneous framework for real world information and interactions, contributing to a horizontal reuse of the deployed infrastructure across a variety of application domains. We present the main concepts, their relationships and the proposed real world resource based architecture. Finally, we outline an initial implementation of the architecture based on the current Internet and web technologies

Titan: An Enabling Framework for Activity-Aware “Pervasive Apps” in Opportunistic Personal Area Networks

Upcoming ambient intelligence environments will boast ever larger number of sensor nodes readily available on body, in objects, and in the user's surroundings. We envision "Pervasive Apps", user-centric activity-aware pervasive computing applications. They use available sensors for activity recognition. They are downloadable from application repositories, much like current Apps for mobile phones. A key challenge is to provide Pervasive Apps in open-ended environments where resource availability cannot be predicted. We therefore introduce Titan, a service-oriented framework supporting design, development, deployment, and execution of activity-aware Pervasive Apps. With Titan, mobile devices inquire surrounding nodes about available services. Internet-based application repositories compose applications based on available services as a service graph. The mobile device maps the service graph to Titan Nodes. The execution of the service graph is distributed and can be remapped at run time upon changing resource availability. The framework is geared to streaming data processing and machine learning, which is key for activity recognition. We demonstrate Titan in a pervasive gaming application involving smart dice and a sensorized wristband. We comparatively present the implementation cost and performance and discuss how novel machine learning methodologies may enhance the flexibility of the mapping of service graphs to opportunistically available nodes.ISSN:1687-1472ISSN:1687-149