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Best Paper Award Nominees

The Best Paper Award is sponsored by ThingMagic!
(listed in no particular order)

Coding for Tag Collision Recovery

Hessam Mahdavifar and Alexander Vardy
University of California San Diego, CA


It has been recently observed that some information can be extracted from the received signal by the reader when the tag collision happens. Using the radio cross section (RCS) technique one can determine how many tags are backscattering simultaneously. Motivated by this technique we introduce the new notion of singulation code. In a singulation code, any two collection of codewords, of size up to some number $s$, have distinct vector-sums. We propose a new protocol for tag singulation problem using the singulation codes. Upper and lower bounds on the size of singulation codes are provided. It is shown that there exists families of singulation codes that guarantee any positive throughput, asymptotically, using the singulation coding protocol. Two explicit constructions of singulation codes, with low complexity encoding and decoding algorithms, are proposed. It is shown that these constructions are feasible to be implemented in RFID tags. The singulation protocol with these explicit constructions is compared with the randomized ALOHA based algorithm. It is shown that the time required for the tag identification with the proposed protocol is reduced by a factor of log “s” comparing to the randomized ALOHA based algorithm, where “s” is the number of tags to be identified. Other advantages of the proposed protocol are also discussed.

NFC-WISP: A Sensing and Computationally Enhanced Near-Field RFID Platform

Yi Zhao, Joshua R. Smith and Alanson P. Sample
Disney Research Pittsburgh, PA


Near-field radio frequency identification (RFID) tags have a number of unique features such as being wirelessly powered, having ultra low power communication capabilities, small size, and low cost. These qualities paired with the increasing availability of commodity near field communication (NFC) enabled smart phones presents a significant opportunity to enable a wide range of new applications and usage scenarios. However, existing tags are fixed function devices that are only capable of reporting an ID when queried and thus most applications are limited to inventory management or access control.

This paper presents the NFC-WISP, which is a programmable, sensing and computationally enhanced platform designed to explore new RFID enabled sensing and user interface applications. The NFC-WISP is fully powered and read by commercially available RFID readers (including NFC enabled smart phones) using the ISO-14443 protocol. Excess harvested power can be stored in an optional super-capacitor or thin-film battery enabling operation away from the reader. This open-source platform includes temperature and acceleration sensors, 2MB of FRAM, LEDs and an optional 2.7” active bistable matrix E-ink display. Expansion headers allow access to the microcontroller allowing for rapid prototyping of new applications. The use of the NFC-WISP for a perishable goods temperature and motion monitoring application is demonstrated as well as the use of wireless power transfer based on magnetic coupled resonance for high power recharging of multiple NFC devices.

Every Smart Phone is a Backscatter Reader: Modulated Backscatter Compatibility with Bluetooth 4.0 Low Energy (BLE) Devices

Joshua F. Ensworth, and Matthew S. Reynolds
University of Washington, Seattle, WA


In this work, we show how modulated backscatter signals can be crafted to yield channelized band-pass signals akin to those transmitted by many conventional wireless devices. As a result, conventional wireless devices can receive these backscattered signals without any modification (neither hardware nor software) to the conventional wireless device. We present a proof of concept using the Bluetooth 4.0 Low Energy, or BLE, standard widely available on smart phones and mobile devices. Our prototype backscatter tag produces three-channel band- pass frequency shift keying (FSK) packets at 1 Mbps that are indistinguishable from conventional BLE advertising packets. An unmodified Apple iPad is shown to correctly receive and display these packets at a range of over 9.4 m using its existing iOS Bluetooth stack with no changes whatsoever. We create all three BLE channels by backscattering a single incident CW carrier using a novel combination of fundamental-mode and harmonic-mode backscatter subcarrier modulation, with two of the band-pass channels generated by the fundamental mode and one of the band-pass channels generated by the second harmonic mode. The backscatter modulator consumes only 28.4 pJ/bit, compared with over 10 nJ/bit for conventional BLE transmitters. The backscatter approach yields over 100X lower energy per bit than a conventional BLE transmitter, while retaining compatibility with billions of existing Bluetooth enabled smartphones and mobile devices.

WISPCam: A Battery-Free RFID Camera

Saman Naderiparizi, Aaron N. Parks, Zerina Kapetanovic, Benjamin Ransford, Joshua R. Smith
University of Washington, WA


Energy-scavenging devices with general-purpose microcontrollers can support arbitrarily complex sensing tasks in theory, but in practice, energy limitations impose severe constraints on the application space. Richer sensing such as image capture would enable many new applications to take advantage of energy scavenging. Richer sensing faces two key challenges: efficiently retaining the necessary amount of harvested energy, and storing and communicating large units of sensor data. This paper presents the WISPCam, a passive UHF RFID camera tag based on the Wireless Identification and Sensing Platform that overcomes these two challenges to support reliable image capture and transmission while powered by an RFID reader. The WISPCam uses a novel charge-storage scheme designed specifically to match the image sensor’s needs. This scheme optimally balances capacitance and leakage to improve the sensitivity and efficiency of the power harvester. The WISPCam also uses a novel data storage and communication scheme to reliably support the transfer of complete images to an RFID reader application. The WISPCam makes battery-free image capture practical for applications such as mechanical gauge reading and surveillance, both demonstrated in this paper, and opens the door to richer sensing applications on battery-free devices.