69,174 research outputs found
The unanticipated challenges associated with implementing an observational study protocol in a large scale physical activity and GPS data collection
Background: Large-scale primary data collections are complex, costly, and time-consuming. Study protocols for trial-based research are now commonplace, with a growing number of similar pieces of work being published on observational research. However, useful additions to the literature base are publications that describe the issues and challenges faced while conducting observational studies. These can provide researchers with insightful knowledge that can inform funding proposals or project development work.
Objectives: In this study, we identify and reflectively discuss the unforeseen or often unpublished issues associated with organizing and implementing a large-scale objectively measured physical activity and global positioning system (GPS) data collection.
Methods: The SPACES (Studying Physical Activity in Children’s Environments across Scotland) study was designed to collect objectively measured physical activity and GPS data from 10- to 11-year-old children across Scotland, using a postal delivery method. The 3 main phases of the project (recruitment, delivery of project materials, and data collection and processing) are described within a 2-stage framework: (1) intended design and (2) implementation of the intended design.
Results: Unanticipated challenges arose, which influenced the data collection process; these encompass four main impact categories: (1) cost, budget, and funding; (2) project timeline; (3) participation and engagement; and (4) data challenges. The main unforeseen issues that impacted our timeline included the informed consent process for children under the age of 18 years; the use of, and coordination with, the postal service to deliver study information and equipment; and the variability associated with when participants began data collection and the time taken to send devices and consent forms back (1-12 months). Unanticipated budgetary issues included the identification of some study materials (AC power adapter) not fitting through letterboxes, as well as the employment of fieldworkers to increase recruitment and the return of consent forms. Finally, we encountered data issues when processing physical activity and GPS data that had been initiated across daylight saving time.
Conclusions: We present learning points and recommendations that may benefit future studies of similar methodology in their early stages of development
Key Generation in Wireless Sensor Networks Based on Frequency-selective Channels - Design, Implementation, and Analysis
Key management in wireless sensor networks faces several new challenges. The
scale, resource limitations, and new threats such as node capture necessitate
the use of an on-line key generation by the nodes themselves. However, the cost
of such schemes is high since their secrecy is based on computational
complexity. Recently, several research contributions justified that the
wireless channel itself can be used to generate information-theoretic secure
keys. By exchanging sampling messages during movement, a bit string can be
derived that is only known to the involved entities. Yet, movement is not the
only possibility to generate randomness. The channel response is also strongly
dependent on the frequency of the transmitted signal. In our work, we introduce
a protocol for key generation based on the frequency-selectivity of channel
fading. The practical advantage of this approach is that we do not require node
movement. Thus, the frequent case of a sensor network with static motes is
supported. Furthermore, the error correction property of the protocol mitigates
the effects of measurement errors and other temporal effects, giving rise to an
agreement rate of over 97%. We show the applicability of our protocol by
implementing it on MICAz motes, and evaluate its robustness and secrecy through
experiments and analysis.Comment: Submitted to IEEE Transactions on Dependable and Secure Computin
Digital interaction: where are we going?
In the framework of the AVI 2018 Conference, the interuniversity center ECONA has organized a thematic workshop on "Digital Interaction: where are we going?". Six contributions from the ECONA members investigate different perspectives around this thematic
Analyzing Delay in Wireless Multi-hop Heterogeneous Body Area Networks
With increase in ageing population, health care market keeps growing. There
is a need for monitoring of health issues. Wireless Body Area Network (WBAN)
consists of wireless sensors attached on or inside human body for monitoring
vital health related problems e.g, Electro Cardiogram (ECG), Electro
Encephalogram (EEG), ElectronyStagmography (ENG) etc. Due to life threatening
situations, timely sending of data is essential. For data to reach health care
center, there must be a proper way of sending data through reliable connection
and with minimum delay. In this paper transmission delay of different paths,
through which data is sent from sensor to health care center over heterogeneous
multi-hop wireless channel is analyzed. Data of medical related diseases is
sent through three different paths. In all three paths, data from sensors first
reaches ZigBee, which is the common link in all three paths. Wireless Local
Area Network (WLAN), Worldwide Interoperability for Microwave Access (WiMAX),
Universal Mobile Telecommunication System (UMTS) are connected with ZigBee.
Each network (WLAN, WiMAX, UMTS) is setup according to environmental
conditions, suitability of device and availability of structure for that
device. Data from these networks is sent to IP-Cloud, which is further
connected to health care center. Delay of data reaching each device is
calculated and represented graphically. Main aim of this paper is to calculate
delay of each link in each path over multi-hop wireless channel.Comment: arXiv admin note: substantial text overlap with arXiv:1208.240
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