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1915 research outputs found
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Using Multiple Accounts for Harvesting Solutions in MOOCs
Get PDFDOI: 10.1145/2876034.2876037.The study presented in this paper deals with copying answers in MOOCs. Our findings show that a significant fraction of the certificate earners in the course that we studied have used what we call harvesting accounts to find correct answers that they later submitted in their main account, the account for which they earned a certificate. In total, around 2.5% of the users who earned a certificate in the course obtained the majority of their points by using this method, and around 10% of them used it to some extent. This paper has two main goals. The first is to define the phenomenon and demonstrate its severity. The second is characterizing key factors within the course that affect it, and suggesting possible remedies that are likely to decrease the amount of cheating. The immediate implication of this study is to MOOCs. However, we believe that the results generalize beyond MOOCs, since this strategy can be used in any learning environments that do not identify all registrants.TRUEpu
Demonstrating Practical Known-Plaintext Attacks against Physical Layer Security in Wireless MIMO Systems
No full textAfter being widely studied in theory, physical layer security schemes are getting closer to enter the consumer market. Still, a thorough practical analysis of their resilience against attacks is missing. In this work, we use software-defined radios to implement such a physical layer security scheme, namely, orthogonal blinding. To this end, we use orthogonal frequency-division multiplexing (OFDM) as a physical layer, similarly to WiFi. In orthogonal blinding, a multi-antenna transmitter overlays the data it transmits with noise in such a way that every node except the intended receiver is disturbed by the noise. Still, our known-plaintext attack can extract the data signal at an eavesdropper by means of an adaptive filter trained using a few known data symbols. Our demonstrator illustrates the iterative training process at the symbol level, thus showing the practicability of the attack.TRUEpu
A Channel Assignment and Routing Algorithm for Energy Harvesting Multi-Radio Wireless Mesh Networks
Get PDFWireless mesh networks are being deployed all around the world both to provide ubiquitous connection to the Internet and to carry data generated by several services (video surveillance, smart grids, earthquake early warning systems, etc.). In those cases where fixed power connections are not available, mesh nodes operate by harvesting ambient energy (e.g., solar or wind power) and hence they can count on a limited and time-varying amount of power to accomplish their functions. Since we consider mesh nodes equipped with multiple radios, power savings and network performance can be maximized by properly routing flows, assigning channels to radios and identifying nodes/radios that can be turned off. Thus, the problem we address is a joint channel assignment and routing problem with additional constraints on the node power consumption, which is NP-complete. In this paper we propose a heuristic, named MP-CARA (Minimum Power Channel Assignment and Routing Algorithm), which is guaranteed to return a local optimum for this problem. Based on a theoretical analysis that we present in the paper, which gives an upper bound on the outage probability as a function of the constraint on power consumption, we can guarantee that the probability that a node runs out of power with MP-CARA falls below a desired threshold. The performance of MP-CARA is assessed by means of an extensive simulation study aiming to compare the solutions returned by MP-CARA to those found by other heuristics proposed in the literature.pu
HDEER: A Distributed Routing Scheme for Energy-Efficient Networking
Get PDFThe proliferation of new online Internet services has substantially increased the energy consumption in wired
networks, which has become a critical issue for Internet Service Providers. In this paper, we target the network-wide, energy-saving problem by leveraging speed scaling as the energy-saving strategy. We propose a distributed routing scheme –HDEER– to improve network energy efficiency in a distributed manner without significantly compromising traffic delay. HDEER is a two-stage routing scheme where a simple distributed multi-path finding algorithm is firstly performed to guarantee loop-free routing, and then a distributed routing algorithm is executed for energy-efficient routing in each node among the multiple loop-free paths. We conduct extensive experiments on the NS3 simulator and simulations with real network topologies in different scales under different traffic scenarios. Experiment results show that HDEER can reduce network energy consumption with a fair tradeoff between network energy consumption and traffic delay.pu
SDN for 5G Mobile Networks: NORMA Perspective
Get PDFTo build a flexible and an adaptable architecture network supporting variety of services and their respective requirements, 5G NORMA introduced a network of functions based architecture breaking the major
design principles followed in the current network of entities based architecture. This revolution exploits the advantages of the new technologies like Software-Defined Networking (SDN) and Network Function Virtualization (NFV) in conjunction with the network slicing and multi-tenancy concepts. In this paper we focus on the concept of Software Defined for Mobile Network Control(SDM-C)network: its definition,
its role in controlling the intra network slices
resources, its specificity to be QoE aware thanks to the QoE/QoS monitoring and modeling component and its complementarity with the orchestration component called SDM-O. To operate multiple network slices on the same infrastructure efficiently through controlling
resources and network functions sharing among instantiated network slices, a common entity named SDM-X is introduced. The proposed design brings a set of new capabilities to make the network energy efficient, a feature that is discussed through some use cases.TRUEpu
Passive Communication with Ambient Light
Get PDFIn this work, we propose a new communication system for illuminated areas, indoors and outdoors. Light sources in our environments --such as light bulbs or even the sun-- are our signal emitters, but we do not modulate data at the light source. We instead propose that the environment itself modulates the ambient light signals: if mobile elements 'wear' patterns consisting of distinctive reflecting surfaces, single photodiode could decode the disturbed light signals to read passive information. Achieving this vision requires a deep understanding of a new type of communication channel. Many parameters can affect the performance of passive communication based on visible light: the size of reflective surfaces, the surrounding light intensity, the speed of mobile objects, the field-of-view of the receiver, to name a few. In this paper, we present our vision for a passive communication channel with visible light, the design challenges and the evaluation of an outdoor application where our receiver decodes information from a car moving at 18 km/h.TRUEpu
Lightweight Indoor Localization for 60-GHz Millimeter Wave Systems
Get PDFIn this paper, we target single-anchor localization schemes for millimeter wave (MMW) systems. The schemes are designed to be lightweight, so that even computationally constrained devices can support them. We identify the main propagation properties of MMW signals that have an impact on localization and design three algorithms that exploit these, namely a triangulation validation procedure, an angle difference of arrival approach, and a scheme based on location fingerprinting. We evaluate the algorithms by means of simulations, and draw conclusions on their robustness. We then validate our results via measurements involving commercial pre-standard 60- GHz MMW hardware. Our experiments confirm that, by relying only on a single anchor and without requiring complex signal processing at the receiver, the algorithms can localize a node with high probability, and in many cases with sub-meter accuracy. We conclude by discussing how these algorithms complement each other in terms of robustness and localization success probability.TRUEpu
African Route Collectors Data Analyzer: a compass to support peering growth in the region
No full textThe video of the presentation is available at https://www.internetsociety.org/afpif-2016/day1-presentations-and-livestream (Session 4: Measurements Panel).As of today, there are 37 IXPs in Africa hosted in 28 countries. However, less than 50% of them provide publicly accessible data on current traffic statistics and IXP colocation data. Further, only 2 IXPs host RouteViews collectors. Beyond this, locally useful data that can inform and support the growth of peering in the region is also unavailable. To correct this lack, we designed an open web application entitled ARDA (African Route-Collectors Data Analyzer) aiming at analyzing African Route-Collectors Data. Deployed at JINX, it indeed collected BGP routes over the period 2005 up to now from all PCH and RouteViews route-collectors located in the region. We analyzed this data from various angles, highlighting the evolution of visible prefixes and ASNs, the evolution of IPv4/IPv6 prefixes, the evolution of the percentage of long prefix length announcements, ASNs or prefixes by country/region assignment, etc. The application displays those statistics under different views, depending on the IXP, the set of IXPs in the region and later in each country. We aim to make this platform available to the community, discuss our results, and receive its feedbacks from stakeholders and IXP operators before its release.TRUEpu
Panel: Challenges of mobile content and interpersonal communications in high demand scenario
No full textThe increasing capabilities of mobile communication devices are changing the way people interconnect today. Similarly, almost ubiquitous connectivity is leading to the expectation that data and media are available everywhere and anytime. At the same time a trend towards more sophisticated audio-visual interpersonal communication can be observed (e.g. through applications such as WhatsApp, SnapChat, FaceBook, Twitter, Skype, etc.). This is resulting in an increasing load on communication networks. In dynamic mobile networks that particularly rely on wireless communication such data requirements paired with environmental conditions like mobility or node density increase the risk of capacity overload and network failure. This panel discusses the challenges and opportunities of mobile content and interpersonal communication in challenging environments characterised by for instance high demand scenarios (e.g. due to popular events such as rock concerts or football matches, or at transport & communication hubs) as well as in regions with under-provisioned infrastructures (e.g. rural areas).FALSEpu
The Value of Online Users: Empirical Evaluation of the Price of Personalized Ads
Get PDFAd networks use the behaviors of online users to associate them with preferences (features), and market these features to enable advertisers to target online users. Typical features associated with users include location, interests, gender, age, and etc. Furthemore, ad networks provide their clients with campaing creation tools to help to them to configure and run campains. In this paper, we study the pricing of ads using the ad campaing planning tools of ad networks. We develop tools to collect the suggested bid prices from two platforms: YouTube and Facebook. Analyzing these prices we find that United States is the most expensive country in both platforms. We also find that the most expensive preferences are different in YouTube and Facebook. In YouTube, the top preferences are related to Oil & Gas, while in Facebook are devices, ethnics or politics depending on the type of bidding. Finally, we do not find any price difference genders in Facebook.TRUEpu