| 1. |
- Carlos, Perez Penichet, et al.
(författare)
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Augmenting IoT networks with backscatter-enabled passive sensor tags
- 2016
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Ingår i: Proceedings of the 3rd Workshop on Hot Topics in Wireless. - New York, NY, USA : ACM. - 9781450342513 ; , s. 23-27
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 2. |
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| 3. |
- Hassanzadeh, Navid, et al.
(författare)
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Do Sensor Networks need Mobile MAC Protocols?
- 2012
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Ingår i: CONET'12: Proceedings of the 3rd Workshop on Networks of Cooperating Objects in conjunction with CPS Week.
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Konferensbidrag (refereegranskat)
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| 4. |
- Hassanzadeh, N., et al.
(författare)
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Efficient mobile data collection with mobile collect
- 2012
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Ingår i: Proceedings - IEEE International Conference on Distributed Computing in Sensor Systems, DCOSS 2012. - : IEEE. - 9780769547077 ; , s. 25-32
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Konferensbidrag (refereegranskat)abstract
- The main task of most deployed wireless sensor networks is data collection. While a number of solutions have been designed for static networks, there are currently no widely used data collection algorithms for mobile sensor networks. In this paper, we concentrate on scenarios where many nodes, both data sources and sinks, move along a certain track in one direction, a scenario that is common in sports events. Rather than designing a new protocol from scratch, we extend an existing data collection protocol with lightweight mechanisms to make it efficient for mobility. Our extensive simulations and results in a test bed that includes mobile robots demonstrate that our solution is able to achieve high packet delivery rates at low energy consumption. For our target scenario, our solution more than doubles packet delivery rates when the network is sparse. Our solution also works well in scenarios with a higher degree of mobility where nodes move according to a more demanding random waypoint model.
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| 5. |
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| 6. |
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| 7. |
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| 8. |
- Hermans, Frederik, et al.
(författare)
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A Lightweight Approach to Online Detection and Classification of Interference in 802.15.4-based Sensor Networks
- 2012
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Ingår i: ACM SIGBED Review. - : Association for Computing Machinery (ACM). - 1551-3688. ; 9:3, s. 11-20
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Tidskriftsartikel (refereegranskat)abstract
- With a rapidly increasing number of devices sharing access to the 2.4 GHz ISM band, interference becomes a serious problem for 802.15.4-based, low-power sensor networks. Consequently, interference mitigation strategies are becoming commonplace. In this paper, we consider the step that precedes interference mitigation: interference detection. We have performed extensive measurements to characterize how different types of interferers affect individual 802.15.4 packets. From these measurements, we define a set of features which we use to train a neural network to classify the source of interference of a corrupted packet. Our approach is sufficiently lightweight for online use in a resource constrained sensor network. It does not require additional hardware, nor does it use active spectrum sensing or probing packets. Instead, all information about interferers is gathered from inspecting corrupted packets that are received during the sensor network’s regular operation. Even without considering a history of earlier packets, our approach reaches a mean classification accuracy of 79.8%, with per interferer accuracies of64.9% for WiFi, 82.6% for Bluetooth, 72.1% for microwave ovens, and 99.6% for packets that are corrupted due to insufficient signal strength.
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| 9. |
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| 10. |
- Hermans, Frederik, et al.
(författare)
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FOCUS : Robust Visual Codes for Everyone
- 2016. - 28
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Ingår i: Proceedings of the 14th Annual International Conference on Mobile Systems, Applications, and Services (MobiSys 2016). - New York, NY, USA : ACM. - 9781450342698 ; , s. 319-332
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Konferensbidrag (refereegranskat)abstract
- Visual codes are used to embed digital data in physical objects, or they are shown in video sequences to transfer data over screen/camera links. Existing codes either carry limited data to make them robust against a range of channel conditions (e.g., low camera quality or long distances), or they support a high data capacity but only work over a narrow range of channel conditions. We present Focus, a new code design that does not require this explicit trade-off between code capacity and the reader’s channel quality. Instead,Focus builds on concepts from OFDM to encode data at different levels of spatial detail. This enables each reader to decode as much data from a code as its channel quality allows. We build a prototype of Focus devices and evaluate it experimentally. Our results show that Focus gracefully adapts to the reader’s channel, and that it provides a significant performance improvement over recently proposed designs, including Strata and PixNet.
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| 11. |
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| 12. |
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| 13. |
- Hermans, Frederik, et al.
(författare)
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Poster Abstract:Supporting Heterogeneous LCD/Camera Links
- 2014. - 10
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Ingår i: Proc. 13th International Symposium on Information Processing in Sensor Networks. - Piscataway, NJ : IEEE Press. - 9781479931460 ; , s. 289-290
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Konferensbidrag (refereegranskat)abstract
- Visible light communication over LCD/camera links offers a potential complement to traditional RF communication technology such as WiFi or cellular networks. However, the heterogeneity in receivers (e.g., mobile phone cameras) presents a challenge because the receivers differ widely in resolution, distance to the transmitter (LCD), and other factors, and therefore they differ in channel quality. We are researching a communication scheme in which each receiver can decode as much data from an LCD's transmission as the receiver's channel supports. The core idea is to encode the payload into an image's frequency representation rather than directly into pixels. We have successfully transmitted data using a prototype implementation and are currently investigating appropriate channel models.
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| 14. |
- Hermans, Frederik, et al.
(författare)
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Scalable Visual Codes for Embedding Digital Data in the Physical World
- 2015
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Ingår i: Proceedings of the 13th ACM Conference on Embedded Networked Sensor Systems. - ACM : ACM. - 9781450336314 ; , s. 457-458
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Konferensbidrag (refereegranskat)abstract
- Visual codes, such as QR codes, offer a low-cost alternative to RF technology when digital data needs to be embedded in objects in the physical world. However, in order to support receivers with a poor visual channel, e.g. low-resolution cameras, most visual codes are designed for low data capacity and short reading distances. We present our work on Focus, a visual code that avoids earlier work's explicit trade-off between code capacity and channel quality. Rather than encoding the payload directly into individual pixels, Focus encodes the payload over a range of spatial frequencies. As a result, even a receiver with a very poor visual channel (e.g., a low-resolution camera, or a camera experiencing motion blur) can still partly decode a Focus code, because the code's low-frequency components are robust to common channel impairments. A receiver with a good channel can decode all data from the same code. In our demo, we will present a prototype of Focus for smartphones and showcase how it deals with common impairments of the visual channel.
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| 15. |
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| 16. |
- Hermans, Frederik
(författare)
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Sensor Networks and Their Radio Environment : On Testbeds, Interference, and Broken Packets
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sensor networks consist of small sensing devices that collaboratively fulfill a sensing task, such as monitoring the soil in an agricultural field or measuring vital signs in a marathon runner. To avoid cumbersome and expensive cabling, nodes in a sensor network are powered by batteries and communicate wirelessly. As a consequence of the latter, a sensor network's communication is affected by its radio environment, i.e., the environment's propagation characteristics and the presence of other radio devices. This thesis addresses three issues related to the impact of the radio environment on sensor networks.Firstly, in order to draw conclusions from experimental results, it is necessary to assess how the environment and the experiment infrastructure affect the results. We design a sensor network testbed, dubbed Sensei-UU, to be easily relocatable. By performing an experiment in different environments, a researcher can asses the environments’ impact on results. We further augment Sensei-UU with support for mobile nodes. The implemented mobility approach adds only little variance to results, and therefore enables repeatable experiments with mobility. The repeatability of experiments increases the confidence in conclusions drawn from them.Secondly, sensor networks may experience poor communication performance due to cross-technology radio interference, especially in office and residential environments. We consider the problem of detecting and classifying the type of interference a sensor network is exposed to. We find that different sources of interference each leave a characteristic "fingerprint" on individual, corrupt 802.15.4 packets. We design and implement the SoNIC system that enables sensor nodes to classify interference using these fingerprints. SoNIC supports accurate classification in both a controlled and an uncontrolled environment.Finally, we consider transmission errors in an outdoor sensor network. In such an environment, errors occur despite the absence of interference if the signal-to-noise ratio at a receiver is too low. We study the characteristics of corrupt packets collected from an outdoor sensor network deployment. We find that content transformation in corrupt packets follows a specific pattern, and that most corrupt packets contain only few errors. We propose that the pattern may be useful for applications that can operate on inexact data, because it reduces the uncertainty associated with a corrupt packet.
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| 17. |
- Hermans, Frederik, et al.
(författare)
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SoNIC: Classifying Interference in 802.15.4 Sensor Networks
- 2013. - 11
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Ingår i: Proc. 12th International Conference on Information Processing in Sensor Networks. - New York, NY, USA : ACM. - 9781450319591 ; , s. 55-66
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Konferensbidrag (refereegranskat)abstract
- Sensor networks that operate in the unlicensed 2.4 GHz frequency band suffer cross-technology radio interference from a variety of devices, e.g., Bluetooth headsets, laptops using WiFi, or microwave ovens. Such interference has been shown to significantly degrade network performance. We present SoNIC, a system that enables resource-limited sensor nodes to detect the type of interference they are exposed to and select an appropriate mitigation strategy. The key insight underlying SoNIC is that different interferers disrupt individual 802.15.4 packets in characteristic ways that can be detected by sensor nodes. In contrast to existing approaches to interference detection, SoNIC does not rely on active spectrum sampling or additional hardware, making it lightweight and energy-efficient. In an office environment with multiple interferers, a sensor node running SoNIC correctly detects the predominant interferer 87% of the time. To show how sensor networks can benefit from SoNIC, we add it to a mobile sink application to improve the application's packet reception ratio under interference.
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| 18. |
- Iyer, Venkatraman, et al.
(författare)
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Detecting and Avoiding Multiple Sources of Interference in the 2.4 GHz Spectrum
- 2015. - 12
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Ingår i: Wireless Sensor Networks. - Cham : Springer International Publishing. - 9783319155814 - 9783319155821 ; , s. 35-51
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Konferensbidrag (refereegranskat)abstract
- Sensor networks operating in the 2.4 GHz band often face cross-technology interference from co-located WiFi and Bluetooth devices. To enable effective interference mitigation, a sensor network needs to know the type of interference it is exposed to. However, existing approaches to interference detection are not able to handle multiple concurrent sources of interference. In this paper, we address the problem of identifying multiple channel activities impairing a sensor network’s communication, such as simultaneous WiFi traffic and Bluetooth data transfers. We present SpeckSense, an interference detector that distinguishes between different types of interference using a unsupervised learning technique. Additionally, SpeckSense features a classifier that distinguishes between moderate and heavy channel traffic, and also identifies WiFi beacons. In doing so, it facilitates interference avoidance through channel blacklisting. We evaluate SpeckSense on common mote hardware and show how it classifies concurrent interference under real-world settings. We also show how SpeckSense improves the performance of an existing multichannel data collection protocol by 30%.
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| 19. |
- Iyer, Venkatraman, et al.
(författare)
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Detecting and Avoiding Multiple Sources of Interference in the 2.4 GHz Spectrum
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Sensor networks operating in the 2.4 GHz band often face cross-technology interference from co-located WiFi and Bluetooth devices. To enable effective interference mitigation, a sensor network needs to know the type of interference it is exposed to. However, existing approaches to interference detection are not able to handle multiple concurrent sources of interference. In this paper, we address the problem of identifying multiple channel activities impairing a sensor network s communication, such as simultaneous WiFi traffic and Bluetooth data transfers. We present SpeckSense, an interference detector that distinguishes between different types of interference using a unsupervised learning technique. Additionally, SpeckSense features a classifier that distinguishes between moderate and heavy channel traffic, and also identifies WiFi beacons. In doing so, it facilitates interference avoidance through channel blacklisting. We evaluate SpeckSense on common mote hardware and show how it classifies concurrent interference under real-world settings. We also show how SpeckSense improves the performance of an existing multichannel data collection protocol by 30%.
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| 20. |
- Perez Penichet, Carlos, et al.
(författare)
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Demo : Passive Sensor Tags
- 2016
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Ingår i: Mobicom'16. - New York, NY, USA : ACM. - 9781450342261 ; , s. 477-478
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Konferensbidrag (refereegranskat)abstract
- The sensing capabilities of an Internet-of-Things (IoT) network are usually fixed at deployment. Adding new sensing modalities is a cumbersome process because it requires altering the deployed hardware. We introduce passive sensor tags that allow to easily and seamlessly add new sensors to existing IoT deployments without requiring hardware modifications or additional energy sources. Passive sensor tags employ backscatter communication to generate transmissions that can be decoded by the radio transceivers present in today's IoT devices. Furthermore, unlike recent works, our approach does not require dedicated infrastructure to generate the unmodulated carrier used for backscatter communication. The demo showcases our prototype of a passive sensor tag collecting sensor data and delivering it to unmodified commodity IoT devices using passive 802.15.4 transmissions.
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| 21. |
- Pérez-Penichet, Carlos, et al.
(författare)
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Do Multiple Bits per Symbol Increase the Throughput of Ambient Backscatter Communications?
- 2016
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Ingår i: EWSN '16 Proceedings of the 2016 International Conference on Embedded Wireless Systems and Networks. - 9780994988607 ; , s. 355-360
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Konferensbidrag (refereegranskat)abstract
- Backscatter wireless communications have exceptionally stringent power constraints. This is particularly true for ambient backscatter systems, where energy and wireless carrier are both extracted from weak existing radio signals. The tight power constraints make it difficult to implement advanced coding techniques like spread spectrum, even though such techniques are effective in increasing the communication range and robustness in this type of systems. We draw inspiration from ?code, a previous backscatter coding approach, where data bits are encoded in single-data-bit chip sequences of considerable length to gain robustness. We introduce a new coding technique that encodes several bits in a single symbol in order to increase the data rate of ambient backscatter, while maintaining an acceptable compromise with robustness. We study the proposed technique by means of simulations and characterize the bit error rate and data rate dependencies. A comparison with ?code is drawn and the benefits of each approach are analyzed in search for the best strategy for increasing data rate while maintaining robustness to noise.
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| 22. |
- Pérez-Penichet, Carlos, et al.
(författare)
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On limits of constructive interference in backscatter systems
- 2017
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Ingår i: GIoTS 2017 - Global Internet of Things Summit, Proceedings. - : IEEE. - 9781509058730
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Konferensbidrag (refereegranskat)abstract
- Backscatter communication reduces the energy consumption of resource-constrained sensors and actuators by several orders of magnitude as it avoids the resource-consuming need to generate a radio wave. Many backscatter systems and applications suffer from low communication range. By exploiting the collective power of several tags that transmit the same data simultaneously, constructive interference may help to remedy this problem and increase the communication range. When several tags backscatter the same signal simultaneously it is not necessarily true that constructive interference occurs. As our theoretical results and previous work indicate the interference might also be destructive. Our experimental results on real hardware suggest that exploiting constructive interference to increase the communication range requires careful coordination which is difficult in decentralized settings.
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| 23. |
- Pérez-Penichet, Carlos
(författare)
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Seamless Integration of Battery-Free Communications in Commodity Wireless Networks
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ubiquitous sensing applications have countless potential benefits to society. However, batteries have long been an obstacle to their full development. Harvesting energy from the environment is a promising alternative to battery power, but traditional radio transceivers consume too much for most harvesters. This work is motivated by backscatter communications, a technique that reduces the energy that devices spend exchanging data by up to three orders of magnitude relative to regular radios. This reduction enables sensing devices that operate indefinitely without having to replace batteries; instead they leverage energy harvesting. My goal is to enable the seamless integration of battery-free devices with widespread low-power commodity networks such as Bluetooth or ZigBee/IEEE 802.15.4. Making this integration seamless is critical for the broad adoption of the new class of devices.At a high level, my dissertation outlines a series of challenges to the seamless integration of the new devices with regular low-power networks. We then propose ways to address these challenges, and demonstrate how we could integrate ultra-low-power battery-free devices with regular networks, while avoiding hardware modifications and minimizing any disruption that the addition may cause to existing and co-located communication devices.This work advances the state of the art by: First, demonstrating how to augment an existing sensor network with new sensors without any hardware modification to the pre-existing hardware. The existing network provides the unmodulated carrier that the battery-free nodes need to communicate. Second, we demonstrate a radio receiver that, if implemented in silicon, can directly receive low-power commodity wireless signals when assisted by an unmodulated carrier, and with a power consumption of a few hundred microwatts. The receiver makes battery-free devices directly compatible with regular networks. We introduce simulation models and a first-of-its-kind tool to simulate battery-free communications that integrate with regular networks. Finally, we demonstrate how to efficiently provide unmodulated carrier support for battery-free devices in the previous scenarios without unnecessarily spending energy and spectrum and without undue disturbance to co-located devices.
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| 24. |
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| 25. |
- Rensfelt, Olof, et al.
(författare)
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Repeatable experiments with mobile nodes in a relocatable WSN testbed
- 2010
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Ingår i: Proc. 6th IEEE International Conference on Distributed Computing in Sensor Systems Workshops. - : IEEE Computer Society. ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- We present Sensei-UU, a testbed that supports mobile sensor nodes. The design objectives are to provide wireless sensor network (WSN) experiments with repeatable mobility and to be able to use the same testbed at different locations, including the target location. The testbed is inexpensive, expandable, relocatable and it is possible to reproduce it by other researchers. Mobile sensor nodes are carried by robots that use floor markings for navigation and localization. The testbed is typically used to evaluate WSN applications when sensor nodes move in meters rather than millimeters, eg. when human carries a mobile data sink (mobile phone) collecting data while passing fixed sensor nodes. To investigate the repeatability of robot movements, we have measured the achieved precision and timing of the robots. This precision is of importance to ensure the same radio link characteristics from one protocol experiment to another. We find that our robot localization is accurate to #x00B1;1 cm and variations in link characteristics are acceptably low to capture fading phenomena in IEEE 802.15.4. In the paper we show repeatable experiment results from three environments, two university corridors and from an anechoic chamber. We conclude that the testbed is relocatable between different environments and that the precision is good enough to capture fading effects in a repeatable way.
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| 26. |
- Rensfelt, Olof, et al.
(författare)
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Repeatable experiments with mobile nodes in a relocatable WSN testbed
- 2011
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Ingår i: Computer journal. - : Oxford University Press (OUP). - 0010-4620 .- 1460-2067. ; 54:12, s. 1973-1986
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Tidskriftsartikel (refereegranskat)abstract
- Many sensor network application scenarios include mobile nodes, such as a moving sink. Evaluatingsuch applications in a testbed is challenging since the testbed has to support mobile nodes. Wepresent Sensei-UU, a sensor network testbed that supports mobile sensor nodes. The testbedis inexpensive, relocatable and possible to reproduce by other researchers. Its primary designobjectives are to support experiments with repeatable mobility and to support relocating thetestbed deployment to different locations. Mobile sensor nodes are carried by robots that usefloor markings for navigation and localization. The testbed can be used to evaluate applicationsin which sensor nodes move in the order of meters rather than millimeters, e.g., when a humancarries a mobile phone that collects data while passing stationary sensor nodes. To investigate therepeatability of robot movements, we measure the achieved precision and timing of the robots, andfind that our robot localization is accurate to ±1 cm. Furthermore, we investigate variations inradio signal strengths between mobile and stationary nodes. We study the impact of imprecisemovements, external sources of interference, and environmental influences. We conclude thatSensei-UU supports experiments in which these variations are acceptably low to capture small-scalefading phenomena in IEEE 802.15.4.
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| 27. |
- Rensfelt, Olof, et al.
(författare)
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Sensei-UU : a flexible testbed for heterogeneous wireless sensor networks
- 2009
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Ingår i: Testbeds and Research Infrastructures for the Development of Networks Communities and Workshops, 2009. TridentCom 2009. 5th International Conference on. ; , s. 1-2
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Konferensbidrag (refereegranskat)abstract
- We present Sensei - a nomadic, relocatable, wireless sensor network (WSN) testbed with support for mobile nodes. The nomadism makes it possible to evaluate a WSN application in different environments ranging from lab environments to in- situ installations to prototype deployments. Other WSN testbeds are often static and can not be easily moved between sites. We also support reproducibility mobility in the testbed, using robots or humans as actuators with movement patterns defined in mobility scripts.
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| 28. |
- Rensfelt, Olof, et al.
(författare)
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Sensei-UU : a relocatable sensor network testbed
- 2010
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Ingår i: Proc. 5th ACM International Workshop on Wireless Network Testbeds, Experimental Evaluation and Characterization. - New York, NY, USA : ACM Press. ; , s. 63-70
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Konferensbidrag (refereegranskat)
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| 29. |
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| 30. |
- Varshney, Ambuj, et al.
(författare)
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LoRea: A Backscatter Architecture that Achieves a Long Communication Range
- 2017
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Ingår i: Proc. 15th ACM Conference on Embedded Network Sensor Systems. - New York, NY, USA : ACM. - 9781450354592
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Konferensbidrag (refereegranskat)abstract
- There is the long-standing assumption that radio communication inthe range of hundreds of meters needs to consume mWs of powerat the transmitting device. In this paper, we demonstrate that this isnot necessarily the case for some devices equipped with backscatterradios. We present LoRea an architecture consisting of a tag, areader and multiple carrier generators that overcomes the power,cost and range limitations of existing systems such as ComputationalRadio Frequency Identication (CRFID). LoRea achieves thisby: First, generating narrow-band backscatter transmissions thatimprove receiver sensitivity. Second, mitigating self-interferencewithout the complex designs employed on RFID readers by keepingcarrier signal and backscattered signal apart in frequency. Finally,decoupling carrier generation from the reader and using devicessuch as WiFi routers and sensor nodes as a source of the carriersignal. An o-the-shelf implementation of LoRea costs 70 USD,a drastic reduction in price considering commercial RFID readerscost 2000 USD. LoRea’s range scales with the carrier strength, andproximity to the carrier source and achieves a maximum range of3:4 km when the tag is located at 1m distance from a 28 dBm carriersource while consuming 70 µW at the tag. When the tag is equidistantfrom the carrier source and the receiver, we can communicateupto 75m, a signicant improvement over existing RFID readers.
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| 31. |
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| 32. |
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| 33. |
- Wennerström, Hjalmar, 1984-, et al.
(författare)
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A Long-Term Study on the Effects of Meteorological Conditions on 802.15.4 Links
- 2012
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Ingår i: 8th Swedish National Computer Networking Workshop, Stockholm, June 7-8.
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Konferensbidrag (refereegranskat)abstract
- Remote monitoring of natural phenomena using wireless sensor networks requires these networks to successfully operate while being exposed to the surrounding environment. Weather conditions are an essential aspect of the environment, therefore it is important to understand the effects of weather on sensor networks. This understanding is especially important since weather varies strongly over time and affects the communication between sensor nodes. In our ongoing work we study how different meteorological conditions influence radio links in outdoor wireless sensor networks that use IEEE 802.15.4 for communication. We deploy an experimental setup next to a meteorological research station and aim to run experiments over several months in order to capture both short- and long-term changes in the link characteristics. We show some initial measurements of the deployment, highlighting influences on packet reception rate and signal strength.
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