Vilmos Bilicki

Defining and understanding smartphone churn over the internet: A measurement study

Smart portable devices form the largest personal computing platform so far in human history, yet the adoption of P2P techniques has been very slow. One reason is the lack of a detailed understanding of the dynamic patterns of network connectivity and battery usage. For example, we know that when a smartphone is on a charger connected to a WiFi network behind a friendly NAT device, it can act as an unrestricted P2P node. However, we do not know how to model these “good” intervals and so we do not know what P2P applications are possible at all if we restrict participation to only such intervals. This raises a problem similar to modeling churn in classical P2P research. We are not aware of any suitable and available measurement data sets or models. To address this problem, we developed a publicly available smart phone app that provides the user with information about the current network connection such as NAT type, public IP, and so on. The app also collects data about network connectivity and battery status in the background. The app has been downloaded by several hundred users from all over the world. Based on this data we identify and model the sessions during which a phone can participate in a P2P protocol. We also demonstrate through the simulation of gossip protocols that it is feasible to develop smartphone-friendly P2P applications. The raw data is also available for research purposes in an anonymized form upon request.

Scalable P2P Overlays of Very Small Constant Degree: An Emerging Security Threat

In recent years peer-to-peer (P2P) technology has been adopted by Internet-based malware as a fault tolerant and scalable communication medium for self-organization and survival. It has been shown that malicious P2P networks would be nearly impossible to uncover if they operated in a stealth mode , that is, using only a small constant number of fixed overlay connections per node for communication. While overlay networks of a small constant maximal degree are generally considered to be unscalable, we argue in this paper that it is possible to design them to be scalable, efficient and robust. This is an important finding from a security point of view: we show that stealth mode P2P malware that is very difficult to discover with state-of-the-art methods is a plausible threat. In this paper we discuss algorithms and theoretical results that support the scalability of stealth mode overlays, and we present realistic simulations using an event based implementation of a proof-of-concept system. Besides P2P botnets, our results are also applicable in scenarios where relying on a large number of overlay connections per node is not feasible because of cost or the limited number of communication channels available.

Modeling Network-Level Impacts of P2P Flows

It has been clear for a long time that P2P applications represent a large proportion of the load on the network infrastructure. This is why significant research efforts have been devoted to reducing this load, in the form of ISP friendly P2P solutions. These solutions focus on the volume of the traffic as opposed to the number of network flows. At the same time, we are witnessing a great demand for more and more intelligence in the network such as flow based monitoring and application recognition, which have an overhead that depends on the number of flows and not on the volume of the traffic. Besides, the implementation of this intelligence is moving from the access layer towards the distribution and core layers. We show through measurements that the typical devices serving in the different layers of the infrastructure are not sufficiently scalable in terms of the number of flows, and, most importantly, the combined effect of an increase in the access layer bandwidth together with an increase in the P2P (e.g., BitTorrent) population will practically disable the intelligent networking capabilities. Our conclusion is that a novel focus needs to be incorporated into P2P research that concentrates on reducing the number of network flows generated by P2P applications.

Monitoring of fetal heart rate via iPhone

Recording of fetal heart rate can be reassuring for the mother about the fetus’ wellbeing. Our smart phone application can detect, record and evaluate fetal heart rate at any time. This method is based on sound wave thus free from the effects of ultrasound, and can be used all day without harming the fetus. It does not require medical assistance and easy to use at home. It reduces the queue at outpatient care units, helps pregnant women to relieve stress by listening to their unborn baby’s heartbeat. It improves mother-child relationship yet sends an alarming message if further examinations are needed to prevent the consequences of hypoxia.

A methodology for measuring software development productivity using Eclipse IDE

During software development processes many methodologies and technologies are used which can be examined and compared by many points of view. One of the important aspects is the development productivity which aects development time and costs significantly. It is the composition of many factors but actually not all relevant and aecting factors and their relationships are known. Measuring the development productivity can be very useful if we would like to see that: • How much of the total development time takes the real development? • How long is the real development time of specific software components and layers? • How much time does a bug fix or the implementation of a new feature take in specific components or layers during software evolution? Beside the development time it is also worth to examine the quality of the software using various software metrics. Therefore a special tool is needed which can perform real time productivity measurements during the development but at present there are only a few tools for this task with limited measurement capabilities. The goal of this paper is to introduce a methodology for measuring productivity (even for specific software units) with defining a list of relevant factors and events to be observe (e.g. file and user interface events). Besides, this paper presents a measurement tool for monitoring development productivity in the Eclipse IDE (Integrated Development Environment). We have successfully measured a former project using this Eclipse-based tool and evaluated the measurement results to examine the development time of specific application layers.

End User Programming in Smart Home

In the field of ubiquitous computing, one of the most important challenges is the proper involvement of end users in the control of the system. They should be aware of what is happening and why in the smart environment. A well known approach for end user involvement in the controlling of IT systems is end user programming. There are numerous approaches for enabling the end users to define the business logic starting with decision trees and ending with domain specific languages.

Analysis of a Pulse Rate Variability Measurement Using a Smartphone Camera

Background Heart rate variability (HRV) provides information about the activity of the autonomic nervous system. Because of the small amount of data collected, the importance of HRV has not yet been proven in clinical practice. To collect population-level data, smartphone applications leveraging photoplethysmography (PPG) and some medical knowledge could provide the means for it. Objective To assess the capabilities of our smartphone application, we compared PPG (pulse rate variability (PRV)) with ECG (HRV). To have a baseline, we also compared the differences among ECG channels. Method We took fifty parallel measurements using iPhone 6 at a 240 Hz sampling frequency and Cardiax PC-ECG devices. The correspondence between the PRV and HRV indices was investigated using correlation, linear regression, and Bland-Altman analysis. Results High PPG accuracy: the deviation of PPG-ECG is comparable to that of ECG channels. Mean deviation between PPG-ECG and two ECG channels: RR: 0.01 ms–0.06 ms, SDNN: 0.78 ms–0.46 ms, RMSSD: 1.79 ms–1.21 ms, and pNN50: 2.43%–1.63%. Conclusions Our iPhone application yielded good results on PPG-based PRV indices compared to ECG-based HRV indices and to differences among ECG channels. We plan to extend our results on the PPG-ECG correspondence with a deeper analysis of the different ECG channels.

Development of a Novel Semantic-Based System Integration Framework

It is a frequent problem in system development when various different systems with similar functionality have to be integrated together. System integration generally means accessing, sharing and exchanging data among applications. This data sharing can be achieved by implementing interfaces for communication and data exchange, and services for all the applications to be integrated. However, this solution requires a large amount of human resources for software development and refactoring. Here, a novel framework is proposed for data integration that makes the process much simpler by generating all the source code needed for querying data of an integrated system. The proposed framework is based on two ontology mediators, namely, a local ontology generated for the data source to be integrated, and a global or central ontology for the common query interface. This way, the integration process is reduced to finding automatically or semi-automatically the mapping between the concepts of local and global ontologies. If this semantic matching is performed, then all the predefined SPARQL queries of global ontology will be rewritten automatically to queries belonging to data sources to be integrated. Hence, the differences between the systems to be integrated will appear just in the DAO (Data Access Object) layer that is generated according to the ontology alignments. The proposed integration technique does not need any program coding in practice (only visual concept matching has to be done semi-automatically), so the productivity of integration software development can be improved significantly. To demonstrate our concept, our novel framework is applied to real-world integration tasks. In this paper, the framework, methodology, experiences and some measurements relating to the productivity will be presented and discussed.

Scalable Stealth Mode P2P Overlays of Very Small Constant Degree

P2P technology has recently been adopted by Internet-based malware as a fault tolerant and scalable communication medium. Due to its decentralized and self-organizing nature, P2P malware is harder to detect and block, especially if it utilizes specialized techniques for hiding. We analyze a number of hiding strategies through extensive and realistic simulations over a model of the AS-level Internet topology. We show that the most effective strategy to avoid detection is to drastically reduce the maximal number of peers a node communicates with. While overlay networks of a small constant maximal degree are generally considered to be unscalable, we argue that it is possible to design them to be scalable, efficient, and robust. An important implication is that stealth mode P2P malware that is very difficult to discover with state-of-the-art methods is a plausible threat. We discuss algorithms and theoretical results that support the scalability of stealth mode overlays, and we present realistic event-based simulations of a proof-of-concept system. Besides the context of P2P malware, some of our results are of general interest in the area of constant degree overlays in connection with the problem of how to maintain reasonable performance and reliability with the smallest degree possible.