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Waiting times in quality of experience for web based services
No full textA considerable share of applications such as web or e-mail browsing, online
picture viewing and file downloads imply waiting times for their users, which
is due to the turn-taking of information requests by the user and correspoding
response times until each request is fulfilled. Thus, end-user quality
perception in the context of interactive data services is dominated by waiting
times; the longer the latter, the less satisfied the user becomes. As opposed
to heavily researched multimedia experience, perception of waiting times is
still not strongly explored in the context of Quality of Experience (QoE). This
tutorial will contribute to closing this gap. In its first part, it addresses
perception principles and discusses their applicability towards fundamental
relationships between waiting times and resulting QoE. It then investigates to
which extent the same relationships can also be used to describe QoE for more
complex services such as web browsing. Finally, it discusses applications where
waiting times determine QoE, amongst other factors. For example, the past shift
from UDP media streaming to TCP media streaming (e.g. youtube.com) has extended
the relevance of waiting times also to the domain of online video services. In
particular, user-perceived quality suffers from initial delays when
applications are launched, as well as from freezes during the delivery of the
stream. These aspects, which have to be traded against each other to some
extent, will be discussed mainly for HTTP video streaming in the last part of
this tutorial
Mobile video sensitivity to packet loss and packet delay variation in terms of QoE
No full textWith the growth of the mobile internet, the popularity of multimedia services
and applications have increased rapidly. As a result, end-users become
quality-conscious. To fulfill the users' expectations, the study of quality of
experience (QoE) is becoming very important for both researchers and service
providers. This paper analyses the impact on perceived quality of received
videos encoded with the H.264 baseline profile, which is suitable for mobile
video, and streamed through an emulated network with packet loss and packet
delay variation. To evaluate the video QoE, tests are conducted on a mobile
device and on a laptop. The users' responses show that the baseline profile of
H.264 is very sensitive to packet loss and packet delay variation. Moreover,
there is no considerable impact on users' perception either test is conducted
on the mobile device or on the laptop by playing the same resolution video
Hur ser forskningssamarbetet ut på BTH - Samförfattarskap, nätverk och ämnen 2011 - mars 2012
No full textI BTHs forsknings- och utbildningsstrategi poängteras betydelsen av
gränsöverskridande forskning. Men går det då att få en överblick av
forskningssamarbetet på BTH och hur mycket man samarbetar över gränserna? Med
hjälp av en sk. samförfattarkarta kan man få en indikation om vilka
forskningskluster som existerar på BTH och vilka personer som är centrala i
dessa nätverk och hur nätverken interagerar. Lägger man sedan pussel med
klassificeringsämnen och nyckelord kan man få en uppfattning om vilka ämnen och
inriktningar som dominerar forskningen. Och tittar man på medförfattande
icke-BTH-forskares affiliationer i artiklarna så ger det en antydan om vilka
organisationer forskarna på BTH samarbetar med utanför sin egen organisation.
För att undersöka samförfattande har jag använt programvaran Network Workbench
och data från BTHs eget öppna arkiv (http://www.bth.se/fou/forskinfo.nsf/) från
2010 och fram till maj 2012. Jag har tittat på följande granskade
dokumenttyper: konferensartiklar, konferenspresentationer, tidskriftsartiklar
och bokkapitel. Dessa har sedan utgjort underlag för att ta fram
samförfattarskapskartor för hela BTH samt för varje sektion.
Taggmolnen med ämnesord är skapade genom att plocka termer från en ISI WoS
sökning i adressfältet på begreppet ”Blek*” åren 2011-mars 2012. Ur denna mängd
har sedan plockats samtliga poster med BTH affiliation (117). Dessa
importerades till Excel där termerna i ID, och SC-fälten separerades och kördes
var för sig i Wordle (http://www.wordle.net/).
Samma procedur genomfördes för att skapa informationen om samarbetspartners
utanför BTH med hjälp av fältet C1
On Perception-Based Error Protection for Mobile Multimedia
No full textRepresentation of multimedia requires large amounts of data. Therefore,
multimedia source signals are compressed to reduce the data rate that would
otherwise be required for its transmission. However, compression renders
multimedia data more vulnerable to transmission errors. Therefore, error
protection is needed when transmitting multimedia to mobile users over wireless
channels. As channel coding adds parity symbols to the data for error
protection, which in turn increases transmission data rate, efficient
utilization of this added parity budget becomes a key for insuring quality of
service for mobile multimedia.
Computing the optimal parity allocation among packets of a multimedia stream
may not be possible in realtime due to the huge number of ways the parity can
be assigned to these packets. Therefore, it is important to design powerful
error protection schemes while imposing low computational and memory demands on
the system. This is particularly true for systems having limited resources,
such as mobile handheld devices. Given that human beings are the final judges
on the quality of multimedia services, it will also be beneficial to use
perceptual quality metrics that correlate well with human perception when
evaluating different error protection schemes.
In this work, we have considered the above aspects when designing error
protection for mobile multimedia: Providing near optimal performance while
keeping complexity low; designing and evaluating of error protection schemes
based on perceptual quality metrics.
The thesis is divided into five parts. In the first part, region of interest
(ROI) identification, coding and advantages of ROI coding are investigated. In
addition, a framework is proposed for using ROI coding in wireless imaging. The
second part provides a number of unequal error protection (UEP) schemes for
wireless imaging ranging from very simple and less efficient equal error
protection to very complex yet optimal error protection. The proposed error
protection schemes provide an excellent trade-off between performance and
omplexity. In the third part, a framework for perception-based error protection
of images and video streams is proposed. This framework is based on the fact
that the human visual system is more sensitive to quality degradation in the
ROI compared to the background. The proposed error protection scheme provides
excellent performance. Part four deals with realtime systems and/or systems
having limited memory and processing resources.
Specifically, an UEP is proposed for wireless imaging systems which provides
near optimal performance and puts very low processing/memory demands on the
systems. Finally, in the fifth part, optimal UEP is analyzed. Based on the
analysis, optimal UEP is modeled using several mathematical models. Each of the
considered models is evaluated for its fitness in providing error protection.
The simulation results show that most of the investigated models give excellent
performance
Software Product Management
No full textSoftware organizations evolve and maintain software solutions with more than a
single development project. The delta specifications and artefacts that result
from each project make reuse difficult and challenge a company’s ability to
innovate. Software product management is a growing discipline for understanding
how to productise and align software with company strategy, how to evolve
software, and how to coordinate product stakeholders. With product focus, in
addition to project focus, planning accuracy can be improved, time-to-market
reduced, product quality enhanced, and economic success sustained. This chapter
provides an overview on software product management and discusses what today is
known about this discipline
Integrating a Strategic Sustainable Development Perspective in Product-Service System Innovation
No full textThere is an intersection of challenges where society’s social and ecological
problems coincide with the industrial firm’s challenge to maintain
profitability in a globalizing world. Products connect these challenges. The
development of these products together with services (product-service systems)
therefore provides a critical intervention point to address these challenges.
This includes e.g. defining what the products and services are, how they will
deliver value to users, and the business models that enable them to be
realized, as well as how these can contribute to sustainable development of
society.
The overarching goal of this research is to contribute to sustainable
development of society by better understanding how a strategic sustainable
development perspective based on backcasting from basic principles for a
sustainable society can be brought into and guide product-service system
innovation. Interviews with industry professionals, workshops with both
manufacturing companies and within student projects, and industrial cases
studies, together with a review of literature and theoretical considerations,
provide the methodological basis for this work.
This thesis contributes to clarifying theoretical and practical possibilities
and limitations for a strategic sustainable development perspective to guide
product-service system innovation and provides a basis for the integration of
these concepts. The findings indicate that the co-innovation of products and
services in product-service systems can contribute to sustainable development
of society both by supporting reduced material and energy use and by supporting
improved life cycle management of materials. Further, a strategic sustainable
development perspective can contribute to the refinement of existing tools and
methods in product-service system innovation by providing an operational
definition of sustainability articulated in the form of first-order principles
that describe the boundary conditions for a sustainable society, and by
providing guidelines for how to approach a vision of success inside those
boundaries in a strategic way.
In order to identify solutions that meet society’s pressing challenges, new
solution spaces may need to be identified, and this can be enabled by a shift
from product development with service as “add-ons” to their co-innovation in
product-service systems. An initial approach for how this could be enabled
through bringing together set-based approaches to design product-service
systems with a strategic sustainable development perspective is presented
Type checking cryptography implementations
No full textCryptographic software development is a challenging field: high performance
must be achieved, while ensuring correctness and compliance with low-level
security policies. CAO is a domain specific language designed to assist
development of cryptographic software. An important feature of this language is
the design of a novel type system introducing native types such as predefined
sized vectors, matrices and bit strings, residue classes modulo an integer,
finite fields and finite field extensions, allowing for extensive static
validation of source code. We present the formalisation, validation and
implementation of this type system
Systematic literature studies: Database searches vs. backward snowballing
No full textSystematic studies of the literature can be done in different ways. In
particular, different guidelines propose different first steps in their
recommendations, e.g. start with search strings in different databases or start
with the reference lists of a starting set of papers. In software engineering,
the main recommended first step is using search strings in a number of
databases, while in information systems, snowballing has been recommended as
the first step. This paper compares the two different search approaches for
conducting literature review studies. The comparison is conducted by searching
for articles addressing "Agile practices in global software engineering". The
focus of the paper is on evaluating the two different search approaches.
Despite the differences in the included papers, the conclusions and the
patterns found in both studies are quite similar. The strengths and weaknesses
of each first step are discussed separately and in comparison with each other.
It is concluded that none of the first steps is outperforming the other, and
the choice of guideline to follow, and hence the first step, may be
context-specific, i.e. depending on the area of study
From Offshore Outsourcing to Offshore Insourcing: Three Stories
No full textMost large software companies are involved in offshore development of some
sort, and now the trend is that
small and medium sized companies are also going global. While empirical
research suggests that offshoring are not always successful, evidence
explaining the reasons for terminated collaborations is scarce, especially for
small and medium sized companies. In this paper we explore the stories of three
Scandinavian medium-sized software companies that have terminated their
offshore outsourcing relationships and changed to offshore insourcing
arrangements. The main reason for termination was disappointing low quality of
the software delivered, being caused by insufficient domain knowledge, high
turnover and a lack of motivation among the remote and external developers. We
apply the theory of single-loop and double-loop learning in order to explain
why the companies failed to correct
the experienced problems, and the theory of escalating
commitment to explain why the companies did not correct the
failing course of action earlier. Finally we describe the change in
the choice of the principle sourcing strategy from outsourcing to
insourcing
Robust low-complexity transfer logic for two-path echo cancellation
No full textA well used approach for echo cancellation is the two-path method, where two
adaptive filters in parallel are utilized. Typically, one filter is
continuously updated, and when this filter is considered better adjusted to the
echo-path than the other filter, the coefficients of the better adjusted filter
is transferred to the other filter. When this transfer should occur is
controlled by the transfer logic.
This paper proposes transfer logic that is both more robust and more simple to
tune, owing to fewer parameters, than the conventional approach. Extensive
simulations show the advantages of the proposed method