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Repeatable experiments with mobile nodes in a relocatable WSN testbed
Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems. (Communication Research)
Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems. (Communication Research)
Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems. (Communication Research)
Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems. (Communication Research)
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2011 (English)In: Computer journal, ISSN 0010-4620, E-ISSN 1460-2067, Vol. 54, no 12, 1973-1986 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2011. Vol. 54, no 12, 1973-1986 p.
National Category
Computer Engineering Signal Processing
Research subject
Computer Science with specialization in Computer Communication; Electrical Engineering with specialization in Signal Processing
Identifiers
URN: urn:nbn:se:uu:diva-151814DOI: 10.1093/comjnl/bxr052ISI: 000298386300005OAI: oai:DiVA.org:uu-151814DiVA: diva2:411418
Projects
WISENETProFuN
Available from: 2011-04-18 Created: 2011-04-18 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Experimental Challenges in Wireless Sensor Networks — Environment, Mobility, and Interference
Open this publication in new window or tab >>Experimental Challenges in Wireless Sensor Networks — Environment, Mobility, and Interference
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Wireless sensor networks are used to collect sensor data in different applications such as environmental monitoring, smart building control, and health care applications. Wireless sensor nodes used are typically small, low-cost, and battery powered. The nodes are often hard to access after deployment, for example when they are in remote  locations. Another property of wireless sensor networks is that their operation is dependent on the environment they operate in, both due to the specific sensor readings but also due to the effects on communication by factors such as fading and radio interference. This makes it important to evaluate a wireless sensor network in its intendent target environment before final deployment.

To enable experiments with wireless sensor networks in their target environment, we have designed and implemented a testbed called Sensei-UU. It is designed to allow WSN experiments to be repeated in different locations, thus exposing effects caused by the environment. To allow this, the testbed is designed to be easily moved between experimental sites.

One type of WSN applications Sensei-UU is aimed to evaluate is protocols where nodes are mobile. Mobile testbed nodes are low-cost robots which follow a tape track on the floor. The localization accuracy of the robot approach is evaluated and is accurate enough to expose a protocol to fading phenoma in a repeatable manner.

Sensei-UU has helped us develop a lightweight interference classification approach, SoNIC, which runs on standard motes. The approach only use information from a standard cc2420 chipset available when packets are received. We believe that the classification accuracy is good enough to motivate specific transmission techniques avoiding interference.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 156 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 965
Keyword
Wireless Sensor Networks, Testbed, Mobility, Interference classification
National Category
Computer Science Communication Systems
Research subject
Computer Science with specialization in Computer Communication
Identifiers
urn:nbn:se:uu:diva-179807 (URN)978-91-554-8448-4 (ISBN)
Public defence
2012-10-12, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Projects
WISENET
Funder
Vinnova, P26628-4
Available from: 2012-09-20 Created: 2012-08-23 Last updated: 2014-07-22
2. Sensor Networks and Their Radio Environment: On Testbeds, Interference, and Broken Packets
Open this publication in new window or tab >>Sensor Networks and Their Radio Environment: On Testbeds, Interference, and Broken Packets
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. 73 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1171
Keyword
Sensor networks, Testbed, Mobility, Interference classification, Packet corruption
National Category
Communication Systems
Research subject
Computer Science with specialization in Computer Communication
Identifiers
urn:nbn:se:uu:diva-230769 (URN)978-91-554-9019-5 (ISBN)
Public defence
2014-10-17, Room 1311, Polacksbacken, Lägerhyddsvägen 2, Uppsala, 13:00 (English)
Opponent
Supervisors
Projects
WISENET
Funder
VINNOVA, P26628-4
Available from: 2014-09-24 Created: 2014-08-28 Last updated: 2015-01-23

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Rensfelt, OlofHermans, FrederikGunningberg, PerLarzon, Lars-ÅkeBjörnemo, Erik

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