skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Drone Relays for Battery-Free Networks
Battery-free sensors, such as RFIDs, are annually attached to billions of items including pharmaceutical drugs, clothes, and manufacturing parts. The fundamental challenge with battery-free sensors is that they are only reliable at short distances of tens of centimeters to few meters. As a result, today’s systems for communicating with and localizing battery-free sensors are crippled by the limited range. To overcome this challenge, this paper presents RFly, a system that leverages drones as relays for battery-free networks. RFly delivers two key innovations. It introduces the first full-duplex relay for battery-free networks. The relay can seamlessly integrate with a deployed RFID infrastructure, and it preserves phase and timing characteristics of the forwarded packets. RFly also develops the first RF-localization algorithm that can operate through a mobile relay. We built a hardware prototype of RFly’s relay into a custom PCB circuit and mounted it on a Parrot Bebop drone. Our experimental evaluation demonstrates that RFly enables communication with commercial RFIDs at over 50 m. Moreover, its through-relay localization algorithm has a median accuracy of 19 centimeters. These results demonstrate that RFly provides powerful primitives for communication and localization in battery-free networks.  more » « less
Award ID(s):
1739723
PAR ID:
10059093
Author(s) / Creator(s):
; ;
Date Published:
Journal Name:
ACM SIGCOMM
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; (, ACM MobiCom)
    State-of-the-art RFID localization systems fall under two categories. The first category operates with off-the-shelf narrowband RFID tags but makes restrictive assumptions on the environment or the tag’s movement patterns. The second category does not make such restrictive assumptions; however, it requires designing new ultra-wideband hardware for RFIDs and uses the large bandwidth to directly compute a tag’s 3D location. Hence, while the first category is restrictive, the second one requires replacing the billions of RFIDs already produced and deployed annually. This paper presents RFind, a new technology that brings the benefits of ultra-wideband localization to the billions of RFIDs in today’s world. RFind does not require changing today’s passive narrowband RFID tags. Instead, it leverages their underlying physical properties to emulate a very large bandwidth and uses it for localization. Our empirical results demonstrate that RFind can emulate over 220MHz of bandwidth on tags designed with a communication bandwidth of only tens to hundreds of kHz, while remaining compliant with FCC regulations. This, combined with a new super-resolution algorithm over this bandwidth, enables RFind to perform 3D localization with sub-centimeter accuracy in each of the x/y/z dimensions, without making any restrictive assumptions on the tag’s motion or the environment. 
    more » « less
  2. ; ; ; (, ACM)
    There is much interest in fine-grained RFID localization systems. Existing systems for accurate localization typically require infrastructure, either in the form of extensive reference tags or many antennas (e.g., antenna arrays) to localize RFID tags within their radio range. Yet, there remains a need for fine-grained RFID localization solutions that are in a compact, portable, mobile form, that can be held by users as they walk around areas to map them, such as in retail stores, warehouses, or manufacturing plants. We present the design, implementation, and evaluation of POLAR, a portable handheld system for fine-grained RFID localization. Our design introduces two key innovations that enable robust, accurate, and real-time localization of RFID tags. The first is complex-controlled polarization (CCP), a mechanism for localizing RFIDs at all orientations through software-controlled polarization of two linearly polarized antennas. The second is joint tag discovery and localization (JTDL), a method for simultaneously localizing and reading tags with zero-overhead regardless of tag orientation. Building on these two techniques, we develop an end-to-end handheld system that addresses a number of practical challenges in self-interference, efficient inventorying, and self-localization. Our evaluation demonstrates that POLAR achieves a median accuracy of a few centimeters in each of the x/y/z dimensions in practical indoor environments. 
    more » « less
  3. ; (, American Control Conference)
    In this paper, we propose a distributed coverage control algorithm for mobile sensing networks that can account for bounded uncertainty in the location of each sensor. Our algorithm is capable of safely driving mobile sensors towards areas of high information distribution while having them maintain coverage of the whole area of interest. To do this, we propose two novel variants of the Voronoi diagram. The first, the convex uncertain Voronoi (CUV) diagram, guarantees full coverage of the search area. The second, collision avoidance regions (CARs), guarantee collision-free motions while avoiding deadlock, enabling sensors to safely and successfully reach their goals. We demonstrate the efficacy of these algorithms via a series of simulations with different numbers of sensors and uncertainties in the sensors’ locations. The results show that sensor networks of different scales are able to safely perform optimized distribution corresponding to the information distribution density under different localization uncertainties 
    more » « less
  4. ; ; (, Proceedings of the International Conference on Computing, Networking and Communications)
    In this paper, we consider the problem of constructing paths using decode and forward (DF) relays for millimeter wave (mmWave) backhaul communications in urban environments. Due to the large number of obstacles in urban environments, line-of-sight (LoS) wireless links, which are necessary for backhaul communication, often do not exist between small-cell base stations. To address this, some earlier works proposed creating multi-hop paths that use mmWave relay nodes with LoS communication between every pair of consecutive nodes to form logical links between base stations. We present algorithms, based on a novel widest-path formulation of the problem, for selecting decode and forward relay node locations in such paths. Our main algorithm is the first polynomial-time algorithm that constructs a relay path with a throughput that is proven to be the maximum possible. We also present variations of this algorithm for constrained problems in which: 1) each possible relay location can host only one relay node, and 2) minimizing the number of hops in the relay path is also an objective. For all of the proposed algorithms, the achievable throughput and numbers of relays are evaluated through simulation based on a 3-D model of a section of downtown Atlanta. The results show that, over a large number of random cases, our algorithm can always find paths with very high throughput using a small number of relays. We also compare and contrast the results with our earlier work that studied the use of amplify-and-forward (AF) relays for the same scenario. 
    more » « less
  5. ; ; ; (, ACM Transactions on Sensor Networks)
    Communication presents a critical challenge for emerging intermittently powered batteryless sensors. Batteryless devices that operate entirely on harvested energy often experience frequent, unpredictable power outages and have trouble keeping time accurately. Consequently, effective communication using today’s low-power wireless network standards and protocols becomes difficult, particularly because existing standards are usually designed to support reliably powered devices with predictable node availability and accurate timekeeping capabilities for connection and congestion management. In this article, we present Greentooth, a robust and energy-efficient wireless communication protocol for intermittently powered sensor networks. It enables reliable communication between a receiver and multiple batteryless sensors using Time Division Multiple Access–style scheduling and low-power wake-up radios for synchronization. Greentooth employs lightweight and energy-efficient connections that are resilient to transient power outages, while significantly improving network reliability, throughput, and energy efficiency of both the battery-free sensor nodes and the receiver—which could be untethered and energy constrained. We evaluate Greentooth using a custom-built batteryless sensor prototype on synthetic and real-world energy traces recorded from different locations in a garden across different times of the day. Results show that Greentooth achieves 73% and 283% more throughput compared to Asynchronous Wake-up on Demand MAC and Receiver-Initiated Consecutive Packet Transmission Wake-up Radios, respectively, under intermittent ambient solar energy and over 2× longer receiver lifetime. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email