Blekinge Institute of Technology
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Broadband Access Technologies for Rural Connectivity in Developing Countries
No full textRural areas especially those of the developing countries provide challenging
environment to implement communication infrastructure for data and Internet
based services. The main challenges are the high cost of network implementation
and lack of customer base, as rural areas are characterized by low income,
highly scattered and low population density. This situation drives network
operators to establish network infrastructures in urban/city centers leaving
rural areas as underserved community.
This paper surveys the available connectivity technologies with potentials to
offer broadband access network to rural areas. The scope of this survey is on
wireless access technologies, due to the fact that they are efficient in terms
of cost, time of deployment and network management for rural environment. We
provide comparison of the surveyed technologies in terms of their capacity
(data rates) and coverage. We also discuss the current deployment
of WiMAX and 3G technologies in Africa, which is a home to most of the
developing countries. The survey results indicate potential broadband access
technologies for rural areas of the developing countries
Decision Support Tools for Sustainability in Product Innovation in a Few Swedish Companies
No full textCompanies are finding that customers increasingly demand “sustainable products”
while also noticing economic benefits from eco-efficiency and other
sustainability-related design approaches. Employees making product-related
decisions need support tools to incorporate sustainability considerations —
both at strategic (e.g. regarding product lines to develop) and operational
levels (e.g. detailed design). This paper presents the results from a set of
interviews that explored where and how sustainability considerations are taken
into account in the product innovation processes of six Swedish companies.
Results are presented as a map of the overall company operations in relation to
a generic product innovation model, followed by a map of the places where
sustainability considerations are made in that model. Some of the tools that
are used to support those sustainability considerations are also briefly
described. The conclusion is that there are some, but not sufficient, tools and
methods to support inclusion of sustainability aspects in the product
innovation processes of these companies
Non-Linear Vibration and Dynamic Fracture Mechanics of Bridge Cables
No full textIn the present work, the non-linear vibrations and the corresponding dynamic
fracture mechanics of cables of cable-stayed bridges are studied. The cables
are among the most critical components in cable-stayed bridges and there are
different damage sources such as corrosion, vibration, fatigue and fretting
fatigue that can significantly affect them, thereby reducing the cable’s
service life and even producing their failure.
Cable-Parametric Resonance is the specific non-linear vibration studied in this
research. This type of vibration occurs due to displacements presented at the
cable supports. These displacements are induced by the wind and traffic loads
acting on the pylon and deck of the bridge. Under certain conditions, unstable
cable-vibration of significant amplitude can be registered. Therefore,
numerical and experimental analyses are carried out in order to describe this
phenomenon and to determine the corresponding instability conditions.
Two non-linear models of cable-parametric resonance are studied to predict the
cable response. In the simulation method, the non-linear components are treated
as external forces acting on the linear systems, which are represented by
Single Degree of Freedom systems and described by digital filters. A clear
non-linear relationship between the excitation and the cable response is
observed in the simulations and the experiments. The corresponding experimental
analysis is based on a scaled model (1:200) of the Öresund bridge and a good
agreement between the numerical and experimental results is found.
After obtaining the relationship between the cable response and the excitation,
the cable instability conditions are determined. This is done by finding the
minimum displacement required at the cable supports in order to induce
nonlinear cable vibration of considerable amplitude. The instability conditions
are determined within a wide range of excitation frequencies and conveniently
expressed in a simplified and practical way by a curve. The determination
process is rather fast and offers the possibility to evaluate all bridge cable
stays in a rather short time.
Finally, the dynamic fracture mechanics of the cable is considered by studying
the fracture toughness characteristics of the material under dynamic
conditions. Finite Element simulations on a pre-cracked three-point bending
specimen under impact loading are performed. The observed cable instability is
equivalently considered as the associated response to impact load conditions,
and a crack as a defect on the wires of a cable stay. The simulations are based
on an experimental work by using the Split Hopkinson pressure bar (Jiang et
al). The dynamic stress intensity factor KI(t) up to crack initiation is then
obtained by different methods. The numerical estimations based on the
specimen’s crack tip opening displacement (CTOD) and mid-span displacement were
closest to the experimental results. It is observed that a better estimation of
the dynamic stress intensity factor relies on a proper formulation of the
specimen’s stiffness
Empirical extension of a classification framework for addressing consistency in model based development
No full textContext: Consistency constitutes an important aspect in practical realization
of modeling ideas in the process of software development and in the related
research which is diverse. A classification framework has been developed, in
order to aid the model based software construction by categorizing research
problems related to consistency. However, the framework does not include
information on the importance of classification elements. Objective: The aim
was to extend the classification framework with information about the relative
importance of the elements constituting the classification. The research
question was how to express and obtain this information. Method: A survey was
conducted on a sample of 24 stakeholders from academia and industry, with
different roles, who answered a quantitative questionnaire. Specifically, the
respondents prioritized perspectives and issues using an extended hierarchical
voting scheme based on the hundred dollar test. The numerical data obtained
were first weighted and normalized and then they were analyzed by descriptive
statistics and bar charts. Results: The detailed analysis of the data revealed
the relative importance of consistency perspectives and issues under different
views, allowing for the desired extension of the classification framework with
empirical information. The most highly valued issues come from the pragmatics
perspective. These issues are the most important for tool builders and
practitioners from industry, while for the responders from academia theory
group some issues from the concepts perspective are equally important.
Conclusion: The method of using empirical data from a hierarchical cumulative
voting scheme for extending existing research classification framework is
useful for including information regarding the importance of the classification
elements
ROMA: A Middleware Framework for Seamless Handover
No full textThe chapter reports on a new middleware architecture suggested for seamless
handover. The middleware is part of an architectural solution suggested by
Blekinge Institute of Technology (BTH) for seamless handover, which is
implemented at the application layer. This architectures is subject for the
PERIMETER STREP and MOBICOME projects, granted by the EU FP7 and EUREKA,
respectively. The suggested middleware called ROMA represents a software system
with two sets of Application Programmer Interface (API), one for application
writers and another one for interfacing various overlay and underlay systems.
ROMA thus provides a transport-agnostic platform for future Internet
applications. The paper provides a short description of the ROMA middleware,
with particular focus on API design and address translation
IPSAG Cognitive Radio Routing Protocol: Models and Performance
No full textThe paper is about performance evaluation of IP Spectrum Aware Geographic
routing protocol (IPSAG). IPSAG is an opportunistic cognitive routing protocol
which determines a source-destination route in a hop by hop manner, based on
both global and local information. Simulation results are reported for a
particular case of IPSAG, where the cognitive radio (CR) nodes are uniformly
distributed inside the cognitive radio network (CRN), and a two-dimensional
random walk model is used to model the mobility of CR nodes. The results show
that the IPSAG protocol is performing well in the case of a highly mobile CRN
and that the source-destination path is successfully found in the majority of
the cases, especially when the network is highly populated
Classification of TCP Connection Termination Behaviors for Mobile Web
No full textMany emerging smart applications and services employ Web technology, and users
nowadays surf the Web from any device via any kind of access network.
Typically, high page latencies trigger users to abort ongoing transfers,
resulting in the abrupt terminations of the TCP connections. This paper
presents a systematic study of the termination process of the TCP connections
and identifies the reasons behind the observed sequences of termination flags.
Monitoring and classification of the termination behavior of the TCP
connections can provide indications about the user-perceived performance of Web
transfers. From the results, it is observed that the TCP termination behavior
is heavily-dependent on the client-side application. Therefore, a set of
criteria is required to identify the abortions made by the user
Impact of Disturbance Locations on Video Quality of Experience
No full textQuality of experience is getting the attention of the research community as
well as the industry. In case of real-time streaming, packet loss, delay and
jitter degrades the video quality. The player buffer can be emptied due to long
delay, which freezes video at playout, while resuming the streaming video
content causes jumps to current location. There is the question, how user is
going to react to such kind of artifacts with respect to location where they
arise. We collected user ratings for videos showing the artifacts due to delay
variation as well as freezes and jumps at different locations. We also verified
these results with Perceptual Evaluation of Video Quality (PEVQ) application.
For delay and delay variation case, the PEVQ results are aligning to the human
rating, but both differ in freeze-and-jump case. The users' responses in case
of freeze-and-jump shows interesting results with respect to location
A High Quality Adjustable Complexity Motion Estimation Algorithm For Video Encoders
No full textIn the video encoding process, the motion estimation
usually consumes a large part of the encoder computations. This paper presents
motion estimation techniques, targeted mainly for MPEG-4 video encoding but
also applicable for other video codecs e.g. H.264. A high quality adaptive
algorithm with adjustable complexity, based on partially blind prediction for
motion estimation, is proposed.The computational complexity of motion
estimation is reduced with minor loss in the video quality.
In the paper, the quality metrics PSNR, BD PSNR and PEVQ are used, and the
possible trade off between complexity and visual quality is studied
Evaluation of Protocol Treatment in 3G Networks
No full textIn this work, we present a systematic study of how the traffic of different
transport protocols (UDP, TCP and ICMP) is treated, in three operational
Swedish 3G networks. This is done by studying the impact that protocol and
packet size have on the one-way-delay (OWD) across the networks. We do this
using a special method that allows us to calculate the exact OWD, without
having to face the usual clock synchronization problems that are normally
associated with OWD calculations.
From our results we see that all three protocols are treated similarly by all
three operators, when we consider packet sizes that are smaller than 250~bytes
and larger than 1100~bytes. We also show that larger packet sizes are given
preferential treatment, with both smaller median OWD as well as a smaller
standard deviation. It is also clear that, ICMP is given a better performance
compared to TCP and UDP