Sasu Tarkoma

University of Helsinki, Helsinki, Uusimaa, Finland

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Publications (156)59.32 Total impact

  • Mohammad A. Hoque · Sasu Tarkoma

    No preview · Article · Jan 2016 · ACM SIGOPS Operating Systems Review

  • No preview · Article · Jan 2016 · IEEE Pervasive Computing
  • Julien Mineraud · Sasu Tarkoma
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    ABSTRACT: The Internet of Things (IoT) envisions that objects may be connected to the Internet, producing and consuming data in real-time. Today, numerous middleware platforms are available to facilitate the communication with these objects. Unfortunately, the interoperability of these platforms is very limited because it requires to "manually" connect the services proposed by each platform. One key design goal for our contribution is not to build yet another middleware, but rather to augment the functionalities of existing systems via an extension to support their integration into a network of heterogeneous IoT hubs. The extension includes a RESTful API to manipulate the basic component of our extension, the IoT feeds. The IoT feeds allow the platform's owner to dynamically marshal the IoT features connected to the platform, as well as the data that they produce. Furthermore, the feeds enable the owner to manage and control the data flows before connecting them to his applications. Subsequently, these feeds may also be published to meta-hubs in order to expose them to third parties. We evaluated an implementation our extension for Android systems to show the feasibility of managing the data flows using the RESTful API on this platform.
    No preview · Article · Nov 2015

  • No preview · Conference Paper · Nov 2015
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    Mohammad Ashraful Hoque · Sasu Tarkoma
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    ABSTRACT: Battery State of Charge (SOC) estimation is a fundamental component of today's smartphones that affects the internal processes and observable behavior of the devices. This article systematically investigates and analyzes the SOC estimation techniques in smartphones. First, we discover that the voltage curve of a given device implicitly captures the usable capacity of the battery while charging the mobile devices. Second, we observe that today's SOC estimation techniques do not model battery capacity loss sufficiently to accurately capture the usable capacity. Finally, we report findings based on battery analytics of 2077 devices that validate the relationship between battery voltage and the usable capacity of a device. The presented results enable the development of more accurate battery gauges and metering solutions thus resulting in better power-saving decisions, recommendations for the users, and most importantly more reliable systems.
    Full-text · Conference Paper · Oct 2015
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    ABSTRACT: The question "Where has my battery gone?" remains a common source of frustration for many smartphone users. With the increased complexity of smartphone applications, and the increasing number of system settings affecting them, understanding and optimizing battery use has become a difficult chore. The present paper develops a novel approach for constructing energy models from crowdsourced measurements. In contrast to previous approaches, which have focused on the effect of a specific sensor, system setting or application, our approach can simultaneously capture relationships between multiple factors, and provide a unified view of the energy state of the mobile device. We demonstrate the validity of using crowdsourced measurements for constructing battery models through a combination of large-scale analysis of a dataset containing battery discharge and system state measurements, and hardware power measurements. The results indicate that the models captured by our approach are both in line with previous studies on battery consumption and empirical measurements, providing a cost-effective way to construct energy models during normal operations of the device. The analysis also provides several new insights about battery consumption. For example, our analysis reveals the combined effect of high CPU activity and automatic screen brightness to be higher (resulting in 9 min shorter battery lifetime on average) than the effect of medium CPU load and manual screen brightness; a Wi-Fi signal strength drop of one bar can shorten battery life by over 13%; and a smartphone sitting in direct sunlight can witness over 50% shorter battery life than one indoors in cool conditions. Based on the crowdsourced energy models, we develop Constella, a novel recommender system for system settings. Constella provides actionable and human-readable recommendations on how to adjust system settings in order to reduce overall battery drain. We validate the effectiveness of Constella through a hardware power measurement experiment carried out using three application case studies. The results of the evaluation demonstrate that Constella is capable of generating recommendations that can provide up to 61% improvements in battery life.
    No preview · Article · Oct 2015
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    ABSTRACT: Information-Centric Networking (ICN) is a prominent topic in current networking research. ICN design significantly considers the increased demand of scalable and efficient content distribution for Future Internet. However, intermittently connected mobile environments or disruptive networks present a significant challenge to ICN deployment. In this context, delay tolerant networking (DTN) architecture is an initiative that effectively deals with network disruptions. Among all ICN proposals, Content Centric Networking (CCN) is gaining more and more interest for its architectural design, but still has the limitation in highly disruptive environment. In this paper, we design a protocol stack referred as CCNDTN which integrates DTN architecture in the native CCN to deal with network disruption. We also present the implementation details of the proposed CCNDTN. We extend CCN routing strategies by integrating Bundle protocol of DTN architecture. The integration of CCN and DTN enriches the connectivity options of CCN architecture in fragmented networks. Furthermore, CCNDTN can be beneficial through the simultaneous use of all available connectivities and opportunistic networking of DTN for the dissemination of larger data items. This paper also highlights the potential use cases of CCNDTN architecture and crucial questions about integrating CCN and DTN. Keywords—Content Centric Networking (CCN), Delay Tolerant Networking (DTN).
    Full-text · Conference Paper · Jul 2015
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    ABSTRACT: The question 'Where has my battery life gone?' remains a common source of frustration for many smartphone users. With the increased complexity of smartphone applications, and the increasing number of system settings affecting them, understanding and optimizing battery use has become a difficult chore. The present paper develops a novel approach for constructing energy models from crowdsourced measurements. In contrast to previous approaches, which have focused on the effect of a specific sensor, system setting or application, our approach can simultaneously capture relationships between multiple factors, and provide a unified view of the energy state of the mobile device. We demonstrate the validity of using crowdsourced measurements for constructing battery models through a combination of large-scale analysis of a dataset containing battery discharge and system state measurements and hardware power measurements. The results indicate that the models captured by our approach are both in line with previous studies on battery consumption and empirical measurements, providing a cost-effective way to construct energy models during normal operations of the device. The analysis also provides several new insights about battery consumption. For example, our analysis shows the energy use of high CPU activity with automatic screen brightness is actually higher (resulting in around 9 minutes shorter battery lifetime on average) than with a medium CPU load and manual screen brightness; a Wi-Fi signal strength drop of one bar can result in a battery life loss of over 13%; and a smartphone sitting in the sun can experience over 50% worse battery life than one indoors in cool conditions.
    No preview · Article · Jul 2015
  • Sumi Helal · Sasu Tarkoma
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    ABSTRACT: Physical spaces are packed with opportunities, complexities, and of course, people. Many business and social opportunities are missed, and complexities can highly degrade people's experiences in these spaces. Pervasive computing has yet to be widely exploited in physical spaces in the same way that the ubiquitous Web and smartphones have been exploited--effectively revolutionizing the way we interact with others, work, and conduct our daily lives. With the advent of the Internet of Things as a major force of change in industry and the rise of wearable computing for consumers, the time is right for revisiting the notion of a smart space. The articles in this special issue consider new technologies and approaches for developing pervasive smart spaces.
    No preview · Article · Jun 2015 · IEEE Pervasive Computing
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    ABSTRACT: An OpenStack based private cloud with the Cluster File System has been built and used with both CMS analysis and Monte Carlo simulation jobs in the Datacenter Indirection Infrastructure for Secure High Energy Physics (DII-HEP) project. On the cloud we run the ARC middleware that allows running CMS applications without changes on the job submission side. Our test results indicate that the adopted approach provides a scalable and resilient solution for managing resources without compromising on performance and high availability.
    No preview · Article · May 2015 · Journal of Physics Conference Series
  • Weixiong Rao · Kai Zhao · Yan Zhang · Pan Hui · Sasu Tarkoma
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    ABSTRACT: Many applications, such as product promotion advertisement and traffic congestion notification, benefit from opportunistic content exchange in Delay Tolerant Networks (DTNs). An important requirement of such applications is timely delivery. However, the intermittent connectivity of DTNs may significantly delay content exchange, and cannot guarantee timely delivery. The state-of-the-arts capture mobility patterns or social properties of mobile devices. Such solutions do not capture patterns of delivered content in order to optimize content delivery. Without such optimization, the content demanded by a large number of subscribers could follow the same forwarding path as the content by only one subscriber, leading to traffic congestion and packet drop. To address the challenge, in this paper, we develop a solution framework, namely Ameba, for timely delivery. In detail, we first leverage content properties to derive an optimal routing hop count of each content to maximize the number of needed nodes. Next, we develop node utilities to capture interests, capacity and locations of mobile devices. Finally, the distributed forwarding scheme leverages the optimal routing hop count and node utilities to deliver content towards the needed nodes in a timely manner. Illustrative results verify that Ameba achieves comparable delivery ratio as Epidemic but with much lower overhead.
    No preview · Article · Apr 2015 · IEEE Transactions on Mobile Computing
  • Weixiong Rao · Roman Vitenberg · Lei Chen · Sasu Tarkoma
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    ABSTRACT: Beyond offering the widely used keyword search function, many peer-to-peer systems nowadays support the subscription function. For example, Vuze allows users to create subscription filters based on the keyword search. Given the subscription, episodic or related content will be delivered to the users whenever new episodes are available. Unfortunately, these applications suffer from the downsides, for example, high network traffic in the nodes maintaining popular terms. In this paper, we propose the MTAF mechanism to overcome the issues. The key of MTAF is to carefully select a subset of terms without incurring false negatives and to forward the content item toward the home nodes of such selected terms for low content forwarding cost. Experimental results based on real datasets indicate that the proposed solutions are efficient compared to existing approaches. In particular, the similarity-based replication of filters is shown to mitigate the effect of hot spots that arise due to the fact that some document terms are substantially more popular than the others.
    No preview · Article · Apr 2015 · IEEE Transactions on Parallel and Distributed Systems
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    ABSTRACT: The emerging mobile cloud has expanded the horizon of application development and deployment with techniques such as code offloading. While offloading has been widely considered for saving energy and increasing responsiveness of mobile devices, the technique still faces many challenges pertaining to practical usage. In this article, we adopt a systemic approach for analyzing the components of a generic code offloading architecture. Based on theoretical and experimental analysis, we identify the key limitations for code offloading in practice and then propose solutions to mitigate these limitations. We develop a generic architecture to evaluate the proposed solutions. The results provide insights regarding the evolution and deployment of code offloading.
    No preview · Article · Mar 2015 · IEEE Communications Magazine
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    ABSTRACT: This article describes an experimental course where students developed Internet of Things device prototypes to improve the upkeep of an urban rooftop greenhouse. With the help of a problem-based learning approach, students were first familiarized with their new learning environment and encouraged to find issues that could be improved as a meaningful personal learning experience. A project-based learning approach was then used to develop innovative solutions while validating their relevance in collaboration with gardeners that were taking care of the greenhouse. As a result, a number of practical applications for monitoring the state of the greenhouse were developed along with new practices for its maintenance. As participants were given the freedom to choose both the topic and technologies to work with, the course provided a learning experience that was tailored to suit personal interests and competences. Having the common background story allowed students to practice teamwork skills and collaborative software engineering in the context of the emerging topic of Internet of Things.
    No preview · Conference Paper · Feb 2015
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    Julien Mineraud · Oleksiy Mazhelis · Xiang Su · Sasu Tarkoma
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    ABSTRACT: Nowadays, we experience an abundance of Internet-of-Things (IoT) middleware solutions that provide connectivity for sensors and actuators to the Internet. To gain a widespread adoption, these middleware solutions, referred to as platforms, have to meet the expectations of different players in the IoT ecosystem, including device providers, application developers, and end-users, among others. In this article, we evaluate a representative sample of these platforms, both proprietary and open-source, on the basis of their ability to meet the ecosystem expectations. The evaluation is completed by a gap analysis of the current IoT landscape with respect to (i) the support of heterogeneous hardware, (ii) the capabilities of the platform for data management, (iii) the support of application developers, (iv) the extensibility of the different platforms for the formation of ecosystems, as well as (v) the availability of dedicated marketplaces to the IoT. The gap analysis aims to highlight the deficiencies of today's solutions to improve their integration to tomorrow's ecosystem. Based on the result of the analysis, we conclude this article with a list of recommendations for extending these IoT platforms in order to fill in the gaps.
    Full-text · Article · Feb 2015
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    Julien Mineraud · Oleksiy Mazhelis · Xiang Su · Sasu Tarkoma
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    ABSTRACT: This document regroups a representative, but non-exhaustive, list of contemporary IoT platforms. The platforms are ordered alphabetically. The aim of this document is to provide the a quick review of current IoT platforms, as well as relevant information.
    Full-text · Article · Jan 2015
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    Full-text · Article · Jan 2015 · IEEE Transactions on Services Computing
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    ABSTRACT: A major challenge of future mobile networks is providing the needed elastic scaling to the increased traffic demand, number of users and applications with acceptable cost. Another challenge is suitability for numerous communications applications while curbing unwanted traffic on the air interface and the mobile devices. This paper proposes a vision of how these challenges can be met by applying the concept of Software Defined Networking (SDN) to mobile networks. We also discuss the needed migration path that minimizes unnecessary replacement investments. While we have verified some key parts of the vision with experiments, we realize that the effectiveness of the proposed approach depends on the adoption of SDN technology for other purposes so that mass production of SDN switches leads to significant economies of scale. The paper shows how we can model mobile networks using SDN concepts and migrate the 3GPP mobile architecture to SDN. The resulting control plane of the mobile architecture consists of a group of SDN applications starting from the base stations i.e., virtual eNodeBs, Backhaul transport, Mobility management, Access, Caching, Monitoring, and Services delivery. The data plane consists of simplified access points and SDN and Carrier Grade Ethernet switches. Our experiments are based on using OpenFlow as the interface between the planes.
    Full-text · Conference Paper · Nov 2014
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    Kai Zhao · Mirco Musolesi · Pan Hui · Weixiong Rao · Sasu Tarkoma
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    ABSTRACT: Human mobility has been empirically observed to exhibit Levy flight characteristics and behaviour with power-law distributed jump size. The fundamental mechanisms behind this behaviour has not yet been fully explained. In this paper, we analyze urban human mobility and we propose to explain the Levy walk behaviour observed in human mobility patterns by decomposing them into different classes according to the different transportation modes, such as Walk/Run, Bicycle, Train/Subway or Car/Taxi/Bus. Our analysis is based on two real-life GPS datasets containing approximately 10 and 20 million GPS samples with transportation mode information. We show that human mobility can be modelled as a mixture of different transportation modes, and that these single movement patterns can be approximated by a lognormal distribution rather than a power-law distribution. Then, we demonstrate that the mixture of the decomposed lognormal flight distributions associated with each modality is a power-law distribution, providing an explanation to the emergence of Levy Walk patterns that characterize human mobility patterns.
    Preview · Article · Aug 2014 · Scientific Reports
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    ABSTRACT: Wireless data transmission consumes a significant part of the overall energy consumption of smartphones, due to the popularity of Internet applications. In this paper, we investigate the energy consumption characteristics of data transmission over Wi-Fi, focusing on the effect of Internet flow characteristics and network environment. We present deterministic models that describe the energy consumption of Wi-Fi data transmission with traffic burstiness, network performance metrics like throughput and retransmission rate, and parameters of the power saving mechanisms in use. Our models are practical because their inputs are easily available on mobile platforms without modifying low-level software or hardware components. We demonstrate the practice of model-based energy profiling on Maemo, Symbian, and Android phones, and evaluate the accuracy with physical power measurement of applications including file transfer, web browsing, video streaming, and instant messaging. Our experimental results show that our models are of adequate accuracy for energy profiling and are easy to apply.
    Full-text · Article · Aug 2014 · IEEE Transactions on Mobile Computing

Publication Stats

994 Citations
59.32 Total Impact Points

Institutions

  • 2007-2015
    • University of Helsinki
      • • Department of Computer Science
      • • Helsinki Institute for Information Technology HIIT
      Helsinki, Uusimaa, Finland
    • Nokia
      Esbo, Southern Finland Province, Finland
    • Nokia Siemens Networks
      Esbo, Southern Finland Province, Finland
  • 2010-2013
    • Aalto University
      • • Department of Computer Science and Engineering
      • • Helsinki Institute for Information Technology HIIT
      Helsinki, Uusimaa, Finland
  • 2003-2011
    • Helsinki Institute for Information Technology HIIT
      Helsinki, Southern Finland Province, Finland
  • 2008
    • Nokia Research Center
      Palo Alto, California, United States