Swedish Institute of Computer Science Publications Database
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Source-Node Selection to Increase the Reliability of Sensor Networks for Building Automation
No full textWe experimentally investigate the performance of IEEE 802.15.4 radio links and their failure modes in an office building, and, based on this study, propose an adaptation mechanism to conciliate application-level reliability requirements with the underlying network-level properties.
The mechanism has two aspects: the spatially-adaptive aspect, implemented through adaptively selecting one or more
source nodes for each application-level data connection, and
the frequency-adaptive aspect, implemented through IEEE
802.15.4 channel hopping and blacklisting.
Through extensive trace-based simulations and experiments in a test network, we show that the mechanism satisfies application requirements on maximal information age as long as at least one of the potential source nodes is connected to the rest of the network, at the same time showing lower energy consumption than non-adaptively using multiple source nodes
Testability and Software Performance: A Systematic Mapping Study
No full textIn most of the research on software testability, functional
correctness of the software has been the focus while the evidence regarding testability and non-functional properties
such as performance is sporadic. The objective of this study
is to present the current state-of-the-art related to issues
of importance, types and domains of software under test,
types of research, contribution types and design evaluation
methods concerning testability and software performance.
We found that observability, controllability and testing effort are the main testability issues while timeliness and response time (i.e., time constraints) are the main performance issues in focus. The primary studies in the area use diverse types of software under test within different domains, with real-time systems as being a dominant domain. The researchers have proposed many different methods in the area, however these methods lack implementation in practice as suggested by our figures for research type, contribution type and design evaluation methods
Supervising Towards Independence
No full textSupervising a student can be compared to teaching someone to drive a car. The student is in the driver's seat while the supervisor provides structure and guidance, and can intervene in risky and unsafe situations. It is a learning process in which the student gradually gains experience and sufficient skill to obtain a driving license, and to drive without an instructor. Similarly, a student attending the MSc project course at the technical faculty of Lund University is to "develop and demonstrate knowledge and ability required to autonomously work as an engineer" (from MSc course plan). But what factors affect a MSc project, and how can we as supervisors support students in their learning process towards independence? We performed a case study of two completed MSc projects where we interviewed the student, the supervisor and the examiner for each case. In this article we present the main conclusions drawn from the cross-case analysis of this study. Details on the studied cases and the results on which these conclusions are based can be found in our previous publication of this study
A Context Model for Architectural Decision Support
No full textDeveloping efficient and effective decision making support includes identifying means to reduce repeated manual work and providing possibilities to take advantage of the experience gained in previous decision situations. For this to be possible, there is a need to explicitly model the context of a decision case, for example to determine how much the evidence from one decision case can be trusted in another, similar context. In earlier work, context has been recognized as important when transferring and understanding outcomes between cases. The contribution of this paper is threefold. First, we describe different ways of utilizing context in an envisioned decision support system. Thereby, we distinguish between internal and external context usage, possibilities of context representation, and context inheritance. Second, we present a systematically developed context model comprised of five types of context information, namely organization, product, stakeholder, development method & technology, and market & business. Third, we exemplary illustrate the relation of the context information to architectural decision making using existing literature
Safety in Vehicle Platooning: A Systematic Literature Review
No full textVehicle platooning has been studied for several decades, with objectives such as improved traffic throughput on existing infrastructure or reduced energy consumption. All the time, it has been apparent that safety is an important issue. However, there are no comprehensive analyses of what is needed to achieve safety in platooning, but only scattered pieces of information. This paper investigates, through a systematic literature review, what is known about safety for platooning, including what analysis methods have been used, what hazards and failures have been identified, and solution elements that have been proposed to improve safety. Based on this, a gap analysis is performed to identify outstanding questions that need to be addressed in future research. These include dealing with a business ecosystem of actors that cooperate and compete around platooning, refining safety analysis methods to make them suitable for systems-of-systems, dealing with variability in vehicles, and finding solutions to various human factors issues
Executing Boolean Queries on an Encrypted Bitmap Index
No full textWe propose a simple and efficient searchable symmetric
encryption scheme based on a Bitmap index that evaluates
Boolean queries. Our scheme provides a practical
solution in settings where communications and computations
are very constrained as it offers a suitable tradeoff
between privacy and performance
A Reliable and Efficient Token-Based MAC Protocol for Platooning Applications
No full textPlatooning is both a challenging and rewarding application.
Challenging since strict timing and reliability requirements
are imposed by the distributed control system required to
operate the platoon. Rewarding since considerable fuel reductions
are possible. As platooning takes place in a vehicular ad hoc
network, the use of IEEE 802.11p is close to mandatory. However,
the 802.11p medium access method suffers from packet collisions
and random delays. Most ongoing research suggests using TDMA
on top of 802.11p as a potential remedy. However, TDMA requires
synchronization and is not very flexible if the beacon frequency
needs to be updated, the number of platoon members changes,
or if retransmissions for increased reliability are required. We
therefore suggest a token-passing medium access method where
the next token holder is selected based on beacon data age. This
has the advantage of allowing beacons to be re-broadcasted in
each beacon interval whenever time and bandwidth are available.
We show that our token-based method is able to reduce the
data age and considerably increase reliability compared to pure
802.11p
Domain-Agnostic Discovery of Similarities and Concepts at Scale
No full textAppropriately defining and efficiently calculating similarities from large data sets are often essential in data mining, both for gaining understanding of data and generating processes, and for building tractable representations. Given a set of objects and their correlations, we here rely on the premise that each object is characterized by its context, i.e. its correlations to the other objects. The similarity between two objects can then be expressed in terms of the similarity between their contexts. In this way, similarity pertains to the general notion that objects are similar if they are exchangeable in the data. We propose a scalable approach for calculating all relevant similarities among objects by relating them in a correlation graph that is transformed to a similarity graph. These graphs can express rich structural properties among objects. Specifically, we show that concepts - abstractions of objects - are constituted by groups of similar objects that can be discovered by clustering the objects in the similarity graph. These principles and methods are applicable in a wide range of fields, and will here be demonstrated in three domains: computational linguistics, music and molecular biology, where the numbers of objects and correlations range from small to very large
Performance Implications for IoT over Information Centric Networks
No full textInformation centric networking (ICN) is a proposal for a future internetworking architecture that is more efficient and scalable. While several ICN architectures have been evaluated for networks carrying web and video traffic, the benefits and challenges it poses for Internet of Things (IoT) networks are relatively unexplored. In our work, we
evaluate the performance implications for typical IoT network scenarios in the ICN paradigm. We study the behavior of in-network caching, introduce a way to make caching more efficient for periodic sensor data, and evaluate the impact of presence and location of lossy wireless links in IoT networks. In this paper, we present
and discuss the results of our evaluations on IoT networks performed through emulations using a specific ICN architecture, namely, content centric networking (CCN). For example, we show that the newly proposed UTS-LRU cache replacement strategy for improved caching performance of time series content streams reduces the number of messages transmitted by up to 16%. Our findings indicate that the performance of IoT networks using ICN are influenced by the
content model and the nature of its links, and motivates further studies to understand the performance implications in more varied IoT scenarios