Learn More
In this paper we present X-MAC, a low power MAC protocol for wireless sensor networks (WSNs). Standard MAC protocols developed for duty-cycled WSNs such as BMAC, which is the default MAC protocol for TinyOS, employ an extended preamble and preamble sampling. While this "low power listening" approach is simple, asynchronous, and energy-efficient, the long(More)
This paper examines the performance of EPC Class-1 Generation-2 UHF RFID reader systems in a realistic setting. Specifically, we identify factors that degrade overall performance and reliability with a focus on the physical layer, and we explore the degree to which reader configuration options can mitigate these factors. We use a custom software-radio based(More)
We explore a dense sensing approach that uses RFID sensor network technology to recognize human activities. In our setting, everyday objects are instrumented with UHF RFID tags called WISPs that are equipped with accelerometers. RFID readers detect when the objects are used by examining this sensor data, and daily activities are then inferred from the(More)
Mobile devices are increasingly the dominant Internet access technology. Nevertheless, high costs, data caps, and throttling are a source of widespread frustration, and a significant barrier to adoption in emerging markets. This paper presents Flywheel, an HTTP proxy service that extends the life of mobile data plans by compressing responses in-flight(More)
A new 3D code for ElectroMagnetic Induction Tomography (EMIT) with intended applications to environmental imaging problems has been developed. The approach consists of calculating the fields within a volume using an implicit finite-difference frequency-domain (FDFD) formulation. The volume is terminated by an anisotropic perfectly matched layer (PML) region(More)
We argue that sensing and computation platforms that leverage RFID technology can realize " smart-dust " applications that have eluded the sensor network community. RFID sensor networks (RSNs), which consist of RFID readers and RFID sensor nodes (WISPs), extend RFID to include sensing and bring the advantages of small, inexpensive and long-lived RFID tags(More)
Computational RFID (CRFID) tags embed sensing and computation into the physical world. The operation of the tags is limited by the RF energy that can be harvested from a nearby power source. We present a CRFID run-time, Dewdrop, that makes effective use of the harvested energy. Dewdrop treats iterative tasks as a scheduling problem to balance task demands(More)
A programmable wireless identification and sensing device is powered through energy harvesting and a software-defined RFID reader provides the means to investigate optimization approaches for RFID systems. ABSTRACT | The next generation internet will be the internet of things (and not just of computing devices like PCs, PDAs); this is presumed to be enabled(More)
We demonstrate a simple <i>RFID sensor network</i> comprised of an Intel WISP and a commodity UHF RFID reader. WISPs are devices that gather their operating energy from RFID reader transmissions, in the manner of passive RFID tags, and further include sensors, e.g., accelerometers, and provide a very small-scale computing platform. We believe that the small(More)