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  • 1.
    Alonso, Juan M.
    et al.
    Inst. de Cienc. Basicas, ICB Univ. Nac. de Cuyo, Cuyo, Argentina.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems. SICS Swedish ICT, Kista.
    Varshney, Ambuj
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Bounds on the Lifetime of WSNs2013Conference paper (Refereed)
  • 2.
    Carlos, Perez Penichet
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Hermans, Frederik
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Varshney, Ambuj
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Augmenting IoT networks with backscatter-enabled passive sensor tags2016In: Proceedings of the 3rd Workshop on Hot Topics in Wireless, 2016, p. 23-27Conference paper (Refereed)
    Abstract [en]

    The sensing modalities available in an Internet-of-Things (IoT) network are usually fixed before deployment, when the operator selects a suitable IoT platform. Retrofitting a deployment with additional sensors can be cumbersome, because it requires either modifying the deployed hardware or adding new devices that then have to be maintained. In this paper, we present our vision and work towards passive sensor tags: battery-free devices that allow to augment existing IoT deployments with additional sensing capabilities without the need to modify the existing deployment. Our passive sensor tags use backscatter transmissions to communicate with the deployed network. Crucially, they do this in a way that is compatible with the deployed network's radio protocol, and without the need for additional infrastructure. We present an FPGA-based prototype of a passive sensor tag that can communicate with unmodified 802.15.4 IoT devices. Our initial experiments with the prototype support the feasibility of our approach. We also lay out the next steps towards fully realizing the vision of passive sensor tags.

  • 3.
    Carlos, Perez Penichet
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Noda, Claro
    Mid-Sweden University, Sweden.
    Varshney, Ambuj
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Battery-free 802.15. 4 Receiver2018In: 7th ACM/IEEE International Conference on Information Processing in Sensor Networks (IPSN), IEEE, 2018Conference paper (Refereed)
    Abstract [en]

    We present the architecture of an 802.15.4 receiver that, for the first time, operates at a few hundred microwatts, enabling new battery-free applications. To reach the required micro-power consumption, the architecture diverges from that of commodity receivers in two important ways. First, it offloads the power-hungry local oscillator to an external device, much like backscatter transmitters do. Second, we avoid the energy cost of demodulating a phase-modulated signal by treating 802.15.4 as a frequency-modulated one, which allows us to receive with a simple passive detector and an energy-efficient thresholding circuit. We describe a prototype that can receive 802.15.4 frames with a power consumption of 361 μW. Our receiver prototype achieves sufficient communication range to integrate with deployed wireless sensor networks (WSNs). We illustrate this integration by pairing the prototype with an 802.15.4 backscatter transmitter and integrating it with unmodified 802.15.4 sensor nodes running the TSCH and Glossy protocols.

  • 4.
    Carlos, Perez Penichet
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Noda, Claro
    Mid-Sweden University, Sweden.
    Varshney, Ambuj
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Demo Abstract: Battery-Free 802.15.4 Receiver2018In: 17th ACM/IEEE International Conference on Information Processing in Sensor Networks (IPSN), IEEE, 2018, p. 130-131Conference paper (Refereed)
    Abstract [en]

    We present the architecture for an 802.15.4 receiver that enables battery-free operation. To reach micro-power consumption, the architecture diverges from that of commodity receivers in the following ways: First, similar to backscatter transmitters, it offloads the power-hungry local oscillator to an external device. Second, we avoid the energy cost of demodulating a phase-modulated signal by treating 802.15.4 as a frequency-modulated one, allowing us to receive with a simple passive detector and an energy-efficient thresholding circuit. We demonstrate an off-the-shelf prototype of our receiver receives 802.15.4 from a distance of 470 cm with the carrier generator 30 cm away. This range is sufficient to integrate with deployed wireless sensor networks (WSNs). We demonstrate this integration by pairing our receiver with a 802.15.4 backscatter transmitter and integrating it with unmodified commodity sensor nodes running the TSCH protocol.

  • 5. Catalán Rivas, Victoria
    et al.
    Fröjd, Emil
    Holmberg, Tobias
    Ragnarsson, Felix
    Rick, Elsa
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Corneo, Lorenzo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Varshney, Ambuj
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Rohner, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Gunningberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Environmental Control at the Edge2018Conference paper (Other academic)
  • 6.
    Di Lascio, Elena
    et al.
    Universit`a degli Studi Roma Tre, Italy.
    Varshney, Ambuj
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Thiemo, Voigt
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication. SICS Swedish ICT, Uppsala, Sweden.
    Pérez-Penichet, Carlos
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Poster Abstract: LocaLight - A Battery-free PassiveLocalization System Using Visible Light2016Conference paper (Refereed)
    Abstract [en]

    Most existing indoor localization systems are battery-powered and use the changes in Radio Frequency (RF) signals to localize objects. In this paper, we present LocaLight: a battery-free indoor localization system that localizes objects using visible light by tracking the shadow they cast. By sensing a drop in the intensity of ambient light caused by the presence of a shadow, LocaLight localizes the object. Since the position of the shadow can be predicted, it is possible to localize the object in a sensitive area by carefully positioning the light sensors and the overhead lights. Our initial results suggest that LocaLight achieves an accuracy comparable to many of the state-of-the art solutions that use RF.

  • 7.
    Eriksson, Gustav
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Varshney, Ambuj
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Rohner, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Dancila, Dragos
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Towards Long-range Backscatter Communication with Tunnel Diode Reflection Amplifier2018Conference paper (Other academic)
  • 8.
    Giustiniano, Domenico
    et al.
    IMDEA Networks Institute, Madrid, Spain.
    Varshney, Ambuj
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication. RISE SICS, Uppsala, Sweden.
    Connecting Battery-free IoT Tags Using LED Bulbs2018In: HotNets-XVII: Proceedings of the 17th ACM Workshop on Hot Topics in Networks, Association for Computing Machinery (ACM), 2018, p. 99-105Conference paper (Refereed)
    Abstract [en]

    We introduce BackVLC, a system to connect battery-free IoT tags using LED bulbs. We make use of bulbs beyond illumination. We send data to the tags with visible light communication (VLC), and retrofit the bulbs with simple circuitry to enable the uplink channel current VLC systems lack, using Radio Frequency (RF) backscatter communication from the tags. Tags process and send data, harvesting energy from light and radio. We present our system design and implementation, evaluate it in preliminary simulation studies and experiments, and discuss the research challenges to develop a complete network architecture. BackVLC is the first work that combines VLC with RF backscatter.

  • 9.
    Hilmia, Abdalah
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Hewage, Kasun
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Varshney, Ambuj
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Rohner, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication. SICS, Stockholm, Sweden.
    Poster Abstract:BouKey: Location-Based Key Sharing Using Visible LightCommunication2016Conference paper (Refereed)
    Abstract [en]

    Visible Light Communication (VLC) is an emerging communication channel serving as a complement to traditional wireless communication. Visible light has many advantages over other communication channels like its inability to penetrate opaque objects. Securely sharing secret keys is a known problem in computer security. Sharing security keys using Radio Frequency (RF) communication is prone to sniffing attacks. In this paper, we introduce a system called BouKey which uses visible light to share keys. This makes BouKey immune to through the wall sniffing attacks. BouKey divides the key and shares it using multiple transmission bulbs allowing the key to be received in a specific area only. Our initial results show that the characteristics and height of the receiver, as well as the transmission angle play a key role in determining the shape and size of this area.

  • 10.
    Hylamia, Abdullah
    et al.
    KTH Royal Inst Technol, Stockholm, Sweden.
    Spanghero, Marco
    KTH Royal Inst Technol, Stockholm, Sweden.
    Varshney, Ambuj
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems. RISE SICS, Stockholm, Sweden.
    Papadimitratos, Panagiotis
    KTH Royal Inst Technol, Stockholm, Sweden.
    Demo: Security on Harvested Power2018In: WISEC'18: PROCEEDINGS OF THE 11TH ACM CONFERENCE ON SECURITY & PRIVACY IN WIRELESS AND MOBILE NETWORKS, ASSOC COMPUTING MACHINERY , 2018, p. 296-298Conference paper (Refereed)
    Abstract [en]

    Security mechanisms for battery-free devices have to operate under severe energy constraints relying on harvested energy. This is challenging, as the energy harvested from the ambient environment is usually scarce, intermittent and unpredictable. One of the challenges for developing security mechanisms for such settings is the lack of hardware platforms that recreate energy harvesting conditions experienced on a battery-free sensor node. In this demonstration, we present an energy harvesting security (EHS) platform that enables the development of security algorithms for battery-free sensors. Our results demonstrate that our platform is able to harvest sufficient energy from indoor lighting to support several widely used cryptography algorithms.

  • 11.
    Hylamia, Abdullah
    et al.
    KTH Royal Inst Technol, Stockholm, Sweden.
    Varshney, Ambuj
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Soleiman, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Papadimitratos, Panagiotis
    KTH Royal Inst Technol, Stockholm, Sweden.
    Rohner, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems. RISE SICS, Stockholm, Sweden.
    Demo: Towards Battery-free Radio Tomographic Imaging2018In: WISEC'18: PROCEEDINGS OF THE 11TH ACM CONFERENCE ON SECURITY & PRIVACY IN WIRELESS AND MOBILE NETWORKS, ASSOC COMPUTING MACHINERY , 2018, p. 293-295Conference paper (Refereed)
    Abstract [en]

    Radio Tomographic Imaging (RTI) enables novel radio frequency (RF) sensing applications such as intrusion detection systems by observing variations in radio links caused by human actions. RTI applications are, however, severely limited by the requirement to retrofit existing infrastructure with energy-expensive sensors. In this demonstration, we present our ongoing efforts to develop the first battery-free RTI system that operates on minuscule amounts of energy harvested from the ambient environment. Our system eliminates the energy-expensive components employed on state-of-the-art RTI systems achieving two orders of magnitude lower power consumption. Battery-free operation enables a sustainable deployment, as RTI sensors could be deployed for long periods of time with little maintenance effort. Our demonstration showcases an intrusion detection scenario enabled by our system.

  • 12.
    Perez Penichet, Carlos
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Noda, Claro
    Varshney, Ambuj
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication. RISE SICS, Kista, Sweden.
    Augmenting WSNs with Interoperable 802.15.4 Sensor Tags2017In: Proceedings of the 15th ACM Conference on Embedded Networked Sensor Systems, 2017Conference paper (Refereed)
    Abstract [en]

    The sensing capabilities of most sensor networks are fixed at the time of deployment. Adding new sensing capabilities to such networks is a costly and cumbersome process. We present Passive Sensor Tags, battery-free sensing devices that could be used to extend the sensing capabilities of an existing network. Sensor tags feature our new 802.15.4 receiver design which is suitable for micro-power operation, making battery-free tags possible. Because our tags can both transmit and receive 802.15.4 frames there is no need for any modification to the deployed hardware. We present preliminary measurements of transmission and reception range.

  • 13.
    Soleiman, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Varshney, Ambuj
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Mottola, Luca
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Demo: Battery-free Visible Light Sensing2017In: Proc. 4th ACM Workshop on Visible Light Communication Systems, New York: ACM Press, 2017, p. 35-35Conference paper (Refereed)
  • 14.
    Soleiman, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Varshney, Ambuj
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication. RISE SICS, Uppsala, Sweden.
    Battery-free Visible Light Sensing2017In: Proceedings Of The 23rd Annual International Conference On Mobile Computing And Networking (MOBICOM '17), 2017, p. 582-584Conference paper (Refereed)
    Abstract [en]

    We present our efforts to design the first Visible Light Sensing (VLS) system that consumes only tens of mu Ws of power to sense and communicate. Our system requires no modification to the existing light infrastructure and uses unmodulated ambient light as sensing medium. We achieve this by designing a sensing mechanism that uses solar cells to achieve sub-mu Ws of power consumption. Further, we devise an ultra-low power backscatter based transmission mechanism we call Scatterlight that transmits digital readings without incurring the processing and computation overhead of existing sensors. Based on these principles we build a preliminary prototype. Our initial results demonstrate its ability to sense and communicate three hand gestures at 20 mu Ws of power.

  • 15.
    Varshney, Ambuj
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Computer Systems. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Enabling Sustainable Networked Embedded Systems2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Networked Embedded Systems (NES) are small energy-constrained devices typically with sensors, radio and some form of energy storage. The past several years have seen a rapid growth of applications of NES, with several predictions stating billions of devices deployed in the near future. As NES are deployed at large scale, a growing challenge is to support NES for long periods of time without negatively impacting their physical or the radio environment, i.e., in a sustainable manner. In this dissertation, we identify intertwined challenges that affect the sustainability of NES systems: co-existence on the shared wireless spectrum; energy consumption; and the cost of the deployment and maintenance. We identify research directions to overcome these challenges and address them through the six research papers.

    Firstly, NES have to co-exist with other wireless devices that operate on the shared wireless spectrum. A growing number of devices contending for the spectrum is challenging and leads to increased interference among them. To enable NES to co-exist with other wireless devices, we investigate the use of electronically steerable directional antennas (ESD). ESD antennas allow software-based control of the direction of maximum antenna gain on a per-packet basis and can operate within the severe energy constraints of NES. In the dissertation, we demonstrate that ESD antennas allow solutions that outperform the state-of-the-art in sensing and communication in wireless sensor networks while supporting operations on a single wireless channel reducing the contention on the shared wireless spectrum.

    Secondly, we explore the emerging area of visible light sensing and communication to avoid the crowded radio frequency spectrum. Visible light can be an alternative or a complement to radio frequency for sensing and communication. We make two contributions in the dissertation to make the visible light communication a viable option for NES. We design a novel visible light sensing architecture that supports sensing and communication at tens of microwatts of power. An ultra-low power consumption can make visible light sensing systems pervasive. Our second contribution brings high-speed visible light communication to energy-constrained NES. We design a novel visible light receiver that adapts to the dynamics of changing light conditions, and the energy constraints of the host device while supporting a throughput comparable to radio frequency standards for NES. Through our contribution, we take a significant step to enable visible light-based sustainable NES.

    Finally, replacing batteries on sensor nodes significantly affects the sustainability of NES. Battery-free sensors that harvest small amounts of energy from the ambient environment have a great potential to enable pervasive deployment of NES. To support wide-area deployments of battery-free sensors, we develop an ultra-low power and long-range communication mechanism. We demonstrate the ability to communicate to distances as long as a few kilometres while consuming tens of microwatts at the sensor device. Our contributions pave the way for a wide-area deployment of battery-free sustainable NES.

    Through the contributions made in the dissertation, we take a significant step towards the broader goal of sustainable NES. The work included in the dissertation significantly improves the state-of-the-art in NES, in some case by orders of magnitude.

    List of papers
    1. Directional Transmissions and Receptions for High-throughput Bulk Forwarding in Wireless Sensor Networks
    Open this publication in new window or tab >>Directional Transmissions and Receptions for High-throughput Bulk Forwarding in Wireless Sensor Networks
    2015 (English)In: Proceedings of the 13th ACM Conference on Embedded Networked Sensor Systems, 2015, p. 351-364Conference paper, Published paper (Refereed)
    Abstract [en]

    We present DPT: a wireless sensor network protocol for bulk traffic that uniquely leverages electronically switchable directional (ESD) antennas. Bulk traffic is found in several scenarios and supporting protocols based on standard antenna technology abound. ESD antennas may improve performance in these scenarios; for example, by reducing channel contention as the antenna can steer the radiated energy only towards the intended receivers, and by extending the communication range at no additional energy cost. The corresponding protocol support, however, is largely missing. DPT addresses precisely this issue. First, while the network is quiescent, we collect link metrics across all possible antenna configurations. We use this information to formulate a constraint satisfaction problem (CSP) that allows us to find two multi-hop disjoint paths connecting source and sink, along with the corresponding antenna configurations. Domain-specific heuristics we conceive ameliorate the processing demands in solving the CSP, improving scalability. Second, the routing configuration we obtain is injected back into the network. During the actual bulk transfer, the source funnels data through the two paths by quickly alternating between them. Packet forwarding occurs deterministically at every hop. This allows the source to implicitly "clock" the entire pipeline, sparing the need of proactively synchronizing the transmissions across the two paths. Our results, obtained in a real testbed using 802.15.4-compliant radios and custom ESD antennas we built, indicate that DPT approaches the maximum throughput supported by the link layer, peaking at 214 kbit/s in the settings we test.

    Keywords
    Directional antennas; Bulk data transmissions; Wireless sensor networks; Electronically controlled antennas
    National Category
    Computer Systems
    Research subject
    Computer Science with specialization in Computer Communication
    Identifiers
    urn:nbn:se:uu:diva-266348 (URN)10.1145/2809695.2809720 (DOI)000380612400028 ()9781450336314 (ISBN)
    Conference
    The 13th ACM Conference on Embedded Networked Sensor Systems (SenSys 2015), November 1-4, 2015, Seoul, South Korea
    Available from: 2015-11-08 Created: 2015-11-08 Last updated: 2018-03-16Bibliographically approved
    2. dRTI: Directional Radio Tomographic Imaging
    Open this publication in new window or tab >>dRTI: Directional Radio Tomographic Imaging
    Show others...
    2015 (English)In: Proceedings of the 14th International Conference on Information Processing in Sensor Networks, 2015, p. 166-177Conference paper, Published paper (Refereed)
    Abstract [en]

    Radio tomographic imaging (RTI) enables device free localisation of people and objects in many challenging environments and situations. Its basic principle is to detect the changes in the statistics of radio signals due to the radio link obstruction by people or objects. However, the localisation accuracy of RTI suffers from complicated multipath propagation behaviours in radio links. We propose to use inexpensive and energy efficient electronically switched directional (ESD) antennas to improve the quality of radio link behaviour observations, and therefore, the localisation accuracy of RTI. We implement a directional RTI (dRTI) system to understand how directional antennas can be used to improve RTI localisation accuracy. We also study the impact of the choice of antenna directions on the localisation accuracy of dRTI and propose methods to effectively choose informative antenna directions to improve localisation accuracy while reducing overhead. Furthermore, we analyse radio link obstruction performance in both theory and simulation, as well as false positives and false negatives of the obstruction measurements to show the superiority of the directional communication for RTI. We evaluate the performance of dRTI in diverse indoor environments and show that dRTI significantly outperforms the existing RTI localisation methods based on omni-directional antennas.

    Series
    IPSN ’15
    National Category
    Computer Systems
    Identifiers
    urn:nbn:se:uu:diva-252426 (URN)10.1145/2737095.2737118 (DOI)
    Conference
    ACM/IEEE IPSN 2015
    Available from: 2015-05-06 Created: 2015-05-06 Last updated: 2018-03-16
    3. LoRea: A backscatter architecture that achieves a long communication range
    Open this publication in new window or tab >>LoRea: A backscatter architecture that achieves a long communication range
    Show others...
    2017 (English)In: Proc. 15th ACM Conference on Embedded Network Sensor Systems, New York: ACM Press, 2017Conference paper, Published paper (Refereed)
    Abstract [en]

    There is the long-standing assumption that radio communication in the range of hundreds of meters needs to consume mWs of power at the transmitting device. In this paper, we demonstrate that this is not necessarily the case for some devices equipped with backscatter radios. We present LoRea an architecture consisting of a tag, a reader and multiple carrier generators that overcomes the power, cost and range limitations of existing systems such as Computational Radio Frequency Identification (CRFID). LoRea achieves this by: First, generating narrow-band backscatter transmissions that improve receiver sensitivity. Second, mitigating self-interference without the complex designs employed on RFID readers by keeping carrier signal and backscattered signal apart in frequency. Finally, decoupling carrier generation from the reader and using devices such as WiFi routers and sensor nodes as a source of the carrier signal. An off-the-shelf implementation of LoRea costs 70 USD, a drastic reduction in price considering commercial RFID readers cost 2000 USD. LoRea's range scales with the carrier strength, and proximity to the carrier source and achieves a maximum range of 3.4 km when the tag is located at 1m distance from a 28 dBm carrier source while consuming 70 mu W at the tag. When the tag is equidistant from the carrier source and the receiver, we can communicate upto 75m, a significant improvement over existing RFID readers.

    Place, publisher, year, edition, pages
    New York: ACM Press, 2017
    National Category
    Computer Engineering
    Identifiers
    urn:nbn:se:uu:diva-335566 (URN)10.1145/3131672.3131691 (DOI)000462783500018 ()978-1-4503-5459-2 (ISBN)
    Conference
    SenSys 2017, November 5–8, Delft, The Netherlands
    Available from: 2017-11-05 Created: 2017-12-06 Last updated: 2019-08-28Bibliographically approved
    4. Towards wide-area backscatter networks
    Open this publication in new window or tab >>Towards wide-area backscatter networks
    2017 (English)In: Proc. 4th ACM Workshop on Hot Topics in Wireless, New York: ACM Press, 2017, p. 49-53Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    New York: ACM Press, 2017
    National Category
    Computer Engineering
    Identifiers
    urn:nbn:se:uu:diva-335565 (URN)10.1145/3127882.3127888 (DOI)978-1-4503-5140-9 (ISBN)
    Conference
    HotWireless 2017, October 16, Snowbird, UT
    Available from: 2017-10-16 Created: 2017-12-06 Last updated: 2018-03-16Bibliographically approved
    5. Battery-free Visible Light Sensing
    Open this publication in new window or tab >>Battery-free Visible Light Sensing
    2017 (English)In: Proc. 4th ACM Workshop on Visible Light Communication Systems, New York: ACM Press, 2017, p. 3-8Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    New York: ACM Press, 2017
    National Category
    Computer Engineering
    Identifiers
    urn:nbn:se:uu:diva-335564 (URN)10.1145/3129881.3129890 (DOI)978-1-4503-5142-3 (ISBN)
    Conference
    VLCS 2017, October 16, Snowbird, UT
    Available from: 2017-10-16 Created: 2017-12-06 Last updated: 2018-03-16Bibliographically approved
    6. Visible Light Communication for Wearable Computing
    Open this publication in new window or tab >>Visible Light Communication for Wearable Computing
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Visible Light Communication (VLC) is emerging as a means to network computing devices that ameliorates many hurdles of radio-frequency (RF) communications, for example, the limited available spectrum. Enabling VLC in wearable computing, however, is challenging because mobility induces unpredictable drastic changes in light conditions, for example, due to reflective surfaces and obstacles casting shadows.We experimentally demonstrate that such changes are so extreme that no single design of a VLC receiver can provide efficient performance across the board. The diversity found in current wearable devices complicates matters. Based on these observations, we present three different designs of VLC receivers that i) are individual orders of magnitude more efficient than the state-of-the-art in a subset of the possible conditions, and ii) can be combined in a single unit that dynamically switches to the best performing receiver based on the light conditions.Our evaluation indicates that dynamic switching incurs minimal overhead, that we can obtain throughput in the order of MBit/s, and at energy costs lower than many RF devices.

    National Category
    Communication Systems
    Research subject
    Computer Science with specialization in Computer Communication
    Identifiers
    urn:nbn:se:uu:diva-346820 (URN)
    Available from: 2018-03-21 Created: 2018-03-21 Last updated: 2018-03-23
  • 16.
    Varshney, Ambuj
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Harms, Oliver
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Pérez Penichet, Carlos
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Rohner, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Hermans, Frederik
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    LoRea: A backscatter architecture that achieves a long communication range2017In: Proc. 15th ACM Conference on Embedded Network Sensor Systems, New York: ACM Press, 2017Conference paper (Refereed)
    Abstract [en]

    There is the long-standing assumption that radio communication in the range of hundreds of meters needs to consume mWs of power at the transmitting device. In this paper, we demonstrate that this is not necessarily the case for some devices equipped with backscatter radios. We present LoRea an architecture consisting of a tag, a reader and multiple carrier generators that overcomes the power, cost and range limitations of existing systems such as Computational Radio Frequency Identification (CRFID). LoRea achieves this by: First, generating narrow-band backscatter transmissions that improve receiver sensitivity. Second, mitigating self-interference without the complex designs employed on RFID readers by keeping carrier signal and backscattered signal apart in frequency. Finally, decoupling carrier generation from the reader and using devices such as WiFi routers and sensor nodes as a source of the carrier signal. An off-the-shelf implementation of LoRea costs 70 USD, a drastic reduction in price considering commercial RFID readers cost 2000 USD. LoRea's range scales with the carrier strength, and proximity to the carrier source and achieves a maximum range of 3.4 km when the tag is located at 1m distance from a 28 dBm carrier source while consuming 70 mu W at the tag. When the tag is equidistant from the carrier source and the receiver, we can communicate upto 75m, a significant improvement over existing RFID readers.

  • 17.
    Varshney, Ambuj
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Mottola, Luca
    SICS Swedish ICT, Sweden and Politecnico di Milano, Italy.
    Carlsson, Mats
    SICS Swedish ICT, Sweden.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Directional Transmissions and Receptions for High-throughput Bulk Forwarding in Wireless Sensor Networks2015In: Proceedings of the 13th ACM Conference on Embedded Networked Sensor Systems, 2015, p. 351-364Conference paper (Refereed)
    Abstract [en]

    We present DPT: a wireless sensor network protocol for bulk traffic that uniquely leverages electronically switchable directional (ESD) antennas. Bulk traffic is found in several scenarios and supporting protocols based on standard antenna technology abound. ESD antennas may improve performance in these scenarios; for example, by reducing channel contention as the antenna can steer the radiated energy only towards the intended receivers, and by extending the communication range at no additional energy cost. The corresponding protocol support, however, is largely missing. DPT addresses precisely this issue. First, while the network is quiescent, we collect link metrics across all possible antenna configurations. We use this information to formulate a constraint satisfaction problem (CSP) that allows us to find two multi-hop disjoint paths connecting source and sink, along with the corresponding antenna configurations. Domain-specific heuristics we conceive ameliorate the processing demands in solving the CSP, improving scalability. Second, the routing configuration we obtain is injected back into the network. During the actual bulk transfer, the source funnels data through the two paths by quickly alternating between them. Packet forwarding occurs deterministically at every hop. This allows the source to implicitly "clock" the entire pipeline, sparing the need of proactively synchronizing the transmissions across the two paths. Our results, obtained in a real testbed using 802.15.4-compliant radios and custom ESD antennas we built, indicate that DPT approaches the maximum throughput supported by the link layer, peaking at 214 kbit/s in the settings we test.

  • 18.
    Varshney, Ambuj
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Mottola, Luca
    SICS Swedish ICT, Sweden and Politecnico di Milano, Italy.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Coordination of Wireless Sensor Networks using Visible Light2015In: SenSys '15 Proceedings of the 13th ACM Conference on Embedded Networked Sensor Systems, 2015, p. 421-422Conference paper (Refereed)
    Abstract [en]

    Wireless sensor networks are often deployed indoors where artificial lighting is present. Indoor lighting is increasingly being composed of Light Emitting Diodes (LEDs) that offer the ability to precisely control the intensity and the frequency of the light carrier. This can be used to coordinate wireless sensor networks (WSN). The periodic variations in the light intensity can synchronise the clocks on the sensor nodes, while the ability to modulate the light carrier enables the transmission of control information like channel assignment or transmission schedules.We present Guidelight, a simple mechanism that uses controlled fluctuations in the light intensity to coordinate sensor nodes. Guidelight can wake-up or time synchronise sensor nodes or even send small bits of control information to them. All of these have separate dedicated solutions in WSN. Guidelight aims to provide a single solution to all these problems. Our initial experiments demonstrate the ability of Guidelight to trigger sensor nodes. We demonstrate Guidelight is able to trigger sensor nodes selectively at a mean error of 21 μ s.

  • 19.
    Varshney, Ambuj
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Perez Penichet, Carlos
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Rohner, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Demo: LoRea: A backscatter architecture that achieves a long communication range2017In: Proc. 15th ACM Conference on Embedded Network Sensor Systems, New York: ACM Press, 2017Conference paper (Refereed)
    Abstract [en]

    We present LoRea an architecture consisting of a backscatter tag, a reader and multiple carrier generators that overcomes the power, cost and range limitations of existing backscatter systems such as Computational Radio Frequency Identification (CRFID). LoRea achieves this by: First, generating narrow-band backscatter transmissions. Second, by mitigating self-interference without the complex designs employed on RFID readers by keeping carrier signal and backscattered signal apart in frequency. Finally, by decoupling carrier generation from the reader and using devices such as WiFi routers and sensor nodes as a source of the carrier signal. LoRea's communication range scales with the carrier strength, and proximity to the carrier source and achieves a maximum range of 3.4 km when the tag is located 1 m from the carrier source while consuming 70 mu Ws at the backscatter tag. We present various ultra-low power and long-range features of the LoRea architecture.

  • 20.
    Varshney, Ambuj
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Pérez Penichet, Carlos
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Rohner, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Towards wide-area backscatter networks2017In: Proc. 4th ACM Workshop on Hot Topics in Wireless, New York: ACM Press, 2017, p. 49-53Conference paper (Refereed)
  • 21.
    Varshney, Ambuj
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Soleiman, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Mottola, Luca
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Battery-free Visible Light Sensing2017In: Proc. 4th ACM Workshop on Visible Light Communication Systems, New York: ACM Press, 2017, p. 3-8Conference paper (Refereed)
  • 22.
    Varshney, Ambuj
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Mottola, Luca
    Directional Transmissions and Receptions for Burst Forwarding using Disjoint Paths2014In: Proc. 13th International Symposium on Information Processing in Sensor Networks, Piscataway, NJ: IEEE Press, 2014, p. 307-308Conference paper (Refereed)
    Abstract [en]

    Bulk data transmission is an important traffic pattern of many sensor network applications. These applications deliver large amounts of sensed data to a sink node for further processing. Most of the existing bulk data transmission protocols use a single flow of communication. This is inefficient as the radio at the source node is transmitting and the sink node is receiving packets for only half of the duration of the burst. We show in this paper that reduced contention because of directional communication enables us to construct node disjoint paths from the source to the sink node using only one wireless channel. This allows us to forward subsequent packets in the burst on the disjoint paths which maximises the radio transmit and receive time at the source and the sink node respectively. We demonstrate that this doubles the sink throughput as compared to a single flow of communication.

  • 23.
    Varshney, Ambuj
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems. SICS Swedish ICT, Kista.
    Mottola, Luca
    SICS Swedish ICT, Kista and Politecnico di Milano,Italy.
    Directional transmissions and receptions for high throughput burst forwarding2013In: Proceedings of the 11th ACM Conference on Embedded Networked Sensor Systems, 2013, p. 50-Conference paper (Refereed)
    Abstract [en]

    Many sensor network applications generate large amounts of sensed data. These often need to be delivered reliably to the sink node for further processing. In such applications, high communication throughput allows for more data to be sensed. Intra-path interference is a problem in reliable forwarding of data and affects the end-to-end throughput. We show that using antennas that allow directional transmissions and receptions significantly reduces intra-path interference and enables high throughput forwarding of packet bursts over multiple hops using only one wireless channel.

  • 24.
    Varshney, Ambuj
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems. SICS Swedish ICT.
    Mottola, Luca
    SICS Swedish ICT.
    Using Directional Transmissions and Receptions to Reduce Contention in Wireless Sensor Networks2014In: Real-World Wireless Sensor Networks, 2014, p. 205-213Conference paper (Refereed)
    Abstract [en]

    Electronically Switched Directional (ESD) antennas allow software-based control of the direction of maximum antenna gain. ESD antennas are feasible for wireless sensor network. Existing studies with these antennas focus only on controllable directional transmissions. These studies demonstrate reduced contention and increased range of communication with no energy penalty. Unlike existing literature, in this chapter we experimentally explore controllable antenna directionality at both sender and receiver. One key outcome of our experiments is that directional transmissions and receptions together considerably reduce channel contention. As a result, we can significantly reduce intra-path interference.

  • 25.
    Wei, Bo
    et al.
    University of New South Wales, Sydney, Australia and CSIRO, Brisbane, Australia and SICS, Stockholm, Sweden.
    Varshney, Ambuj
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Patwari, Neal
    University of Utah, Salt Lake City and Xandem Technology, Salt Lake City.
    Hu, Wen
    University of New South Wales, Sydney, Australia and CSIRO, Brisbane, Australia and SICS, Stockholm, Sweden.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Chou, Chun Tung
    University of New South Wales, Sydney, Australia.
    dRTI: Directional Radio Tomographic Imaging2015In: Proceedings of the 14th International Conference on Information Processing in Sensor Networks, 2015, p. 166-177Conference paper (Refereed)
    Abstract [en]

    Radio tomographic imaging (RTI) enables device free localisation of people and objects in many challenging environments and situations. Its basic principle is to detect the changes in the statistics of radio signals due to the radio link obstruction by people or objects. However, the localisation accuracy of RTI suffers from complicated multipath propagation behaviours in radio links. We propose to use inexpensive and energy efficient electronically switched directional (ESD) antennas to improve the quality of radio link behaviour observations, and therefore, the localisation accuracy of RTI. We implement a directional RTI (dRTI) system to understand how directional antennas can be used to improve RTI localisation accuracy. We also study the impact of the choice of antenna directions on the localisation accuracy of dRTI and propose methods to effectively choose informative antenna directions to improve localisation accuracy while reducing overhead. Furthermore, we analyse radio link obstruction performance in both theory and simulation, as well as false positives and false negatives of the obstruction measurements to show the superiority of the directional communication for RTI. We evaluate the performance of dRTI in diverse indoor environments and show that dRTI significantly outperforms the existing RTI localisation methods based on omni-directional antennas.

1 - 25 of 25
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