This article focuses on a new type of wireless devices in the domain between RFIDs and sensor networks—Energy-Harvesting Active Networked Tags (EnHANTs). Future EnHANTs will be small, flexible, and self-powered devices that can be attached to objects that are traditionally not networked (e.g., books, furniture, toys, produce, and clothing). Therefore, they will provide the infrastructure for various tracking applications and can serve as one of the enablers for the Internet of Things. We present the design considerations for the EnHANT prototypes, developed over the past 4 years. The prototypes harvest indoor light energy using custom organic solar cells, communicate and form multihop networks using ultra-low-power Ultra-Wideband Impulse Radio (UWB-IR) transceivers, and dynamically adapt their communications and networking patterns to the energy harvesting and battery states. We describe a small-scale testbed that uniquely allows evaluating different algorithms with trace-based light energy inputs. Then, we experimentally evaluate the performance of different energy-harvesting adaptive policies with organic solar cells and UWB-IR transceivers. Finally, we discuss the lessons learned during the prototype and testbed design process.

As larger numbers of Wireless Sensor Network (WSN) applications get deployed in our homes and offices, it is desirable to use the same network to run different applications. We present and analyze the problem of scheduling and supporting the execution of multiple heterogeneous applications on top of the same WSN. First, we establish that using the same MAC or network protocol is not sufficient to obtain acceptable performance across a set of applications that require different types of communication services from the protocol stack (e.g., low-rate reliable many-toone collection vs point-to-point low-latency bulk-data streaming). Hence, we propose a framework to dynamically reconfigure the WSN and adapt its power consumption, transmission reliability, and data throughput to the different requirements of the applications. The framework makes it possible to specify, at design time, distinct network, MAC and radio protocols for each application as well as the events and policies triggering the WSN reconfigurations. At run-time, the WSN automatically reconfigures itself in response to these events and according to these policies. Through experiments on a 119-node testbed, we show that the proposed approach can reconfigure the whole network in few hundreds of milliseconds while incurring little memory and control overhead.

This paper focuses on a new type of wireless devices in the domain between RFIDs and sensor networks - Energy Harvesting Active Networked Tags (EnHANTs). Future EnHANTs will be small, flexible, and self-powered devices that can be attached to objects that are traditionally not networked (e.g., books, toys, clothing), thereby providing the infrastructure for novel tracking applications. We present the design considerations for the EnHANT prototypes, developed over the past 3 years. The prototypes harvest indoor light energy using custom organic solar cells, communicate and form multihop networks using ultralow-power Ultra-Wideband Impulse Radio (UWB-IR) transceivers, and adapt their communications and networking patterns to the energy harvesting and battery states. We also describe a small scale EnHANTs testbed that uniquely allows evaluating different algorithms with trace-based light energy inputs.

Energy Harvesting Active Networked Tags (EnHANTs) are a new class of devices in the domain between RFIDs and sensor networks. EnHANTs will be small, flexible, and energetically self-reliant. Their development is enabled by advances in ultra-low-power ultra-wideband (UWB) communications and in organic semiconductor-based energy harvesting materials. In this demo, we present UWB-enabled EnHANT prototypes. Each prototype is based on a MICA2 mote integrated with a UWB Transceiver and an energy harvesting module (EHM) that allows demonstrating energy harvesting-adaptive communications. Additional information about EnHANTs is available at [2] and http://enhants.ee.columbia.edu.

Energy Harvesting Active Networked Tags (EnHANTs) will be a new class of devices in the domain between RFIDs and sensor networks. Small, flexible, and energetically self-reliant, EnHANTs will be attached to objects that are traditionally not networked, such as books, furniture, toys, produce, and clothing. More information about the EnHANTs project is available at http://enhants.ee.columbia.edu. In this demo we present a small network of EnHANT prototypes. The current EnHANT prototypes are integrated with novel custom in-house-developed energy harvesting and communications hardware, namely organic solar cells and ultra-wide-band impulse radio (UWB-IR) transceivers. The demo showcases prototypes communicating using the novel UWB-IR transceivers and adapting their communications and networking parameters to the available environmental energy harvested by the organic solar cells.

We present a complete framework to design and deploy adaptive low power wireless networks. The framework consists of Fennec Fox, a four-layer network protocol stack, and Swift Fox, a high-level programming language. At run-time, Fennec Fox dynamically reconfigures services running on the network protocol stack layers using a library of modules optimizing a layer's performance with respect to some metric (delay, power consumption, etc.). While network reconfiguration is triggered by sensing or timer events, policies specifying how a network should be reconfigured when given events occur are programmed in Swift Fox at design time. We discuss a network that reconfigures its communication services to support 3 scenarios and that was tested on mica2, intelMote2, and telosB architectures, the last one requiring 21KB of ROM and 2KB of RAM.