Krzysztof Gierłowski

Performance Analysis of Multicast Video Streaming in IEEE 802.11 b/g/n Testbed Environment

The aim of the work is to analyse capabilities and limitations of different IEEE 802.11 technologies (IEEE 802.11 b/g/n), utilized for both multicast and unicast video streaming transmissions directed to mobile devices. Our preliminary research showed that results obtained with currently popular simulation tools can be drastically different than these possible in real-world environment, so, in order to correctly evaluate performance of video streaming, a simple wireless test-bed infrastructure has been created. The results show a strong dependence of the quality of video streaming on the chosen transmission technology. At the same time there are significant differences in perception quality between multicast (1:n) and unicast (1:1) streams, and also between devices offered by different manufacturers. The overall results seem to demonstrate, that, while multicast support quality in different products is still varied and often requires additional configuration, it is possible to select a WiFi access point model and determine the best system parameters to ensure a good video transfer conditions in terms of acceptable QoP/E (Quality of Perception/Exellence).

A Novel Architecture for E-Learning Knowledge Assessment Systems

Thisarticlepresentstheresultsoftwostudiesthatfocusontherolethatthreadeddiscussionplaysin studentlearning.Overaperiodofthreeandone-halfyears,researchersconductedaseriesofsurveys ofgraduateandundergraduatestudentsataprivate,nonprofituniversityinSouthwesternPennsylvania todeterminehowstudentsviewedthevalueofthreadeddiscussionsinenhancingtheirabilitytolearn coursematerial.Studentswereaskedwhichtypesofthreadeddiscussionstheypreferred;whether theyfoundthethreadeddiscussiontobeabettertoolforlearningthanawrittenassignment;and, whichlearningenvironmenttheyfeltwasmoreconducivetolearning,classroomoronline.Results fromthecombinedstudiesrevealedsomestatisticallysignificantdifferencesbasedonenrollment statusandgender.Uponcomparingstudyresults,researchersfoundstatisticallysignificantdifferences withregardtoapreferenceforclassroomversusonlineinstructionandtheusefulnessofthreaded discussionstolearning. KEywoRDS Critical Thinking, Enhanced Learning, Expectations, Feedback, Interaction, Online Instruction, Perception, Value

Testbed analysis of video and VoIP transmission performance in IEEE 802.11 b/g/n networks

The aim of the work is to analyze capabilities and limitations of different implementations of IEEE 802.11 technologies (IEEE 802.11 b/g/n), utilized for both video streaming and VoIP calls directed to mobile devices. Our preliminary research showed that results obtained with currently popular simulation tools can be drastically different than these possible in real-world environment, so, in order to correctly evaluate performance of such transfers, a wireless test-bed infrastructure has been created. The results show a strong dependence of the quality of multimedia transmission on the chosen transmission technology and a particular implementation. The overall results demonstrate, that, while multimedia transmission quality in different products is still varied and often requires additional configuration, it is possible to select a WiFi access point model and determine the best system parameters to ensure a good audio/video transfer conditions in terms of acceptable QoP/E (Quality of Perception/Excellence) or MOS (Mean Opinion Score).

Comparative Analysis of IP-Based Mobility Protocols and Fast Handover Algorithms in IEEE 802.11 Based WLANs

A rapid growth of IP-based networks and services created the vast collection of resources and functionality available to users by means of an uniform method of access – an IP protocol. At the same time, advances in design of mobile electronic devices allowed them to reach utility level comparable to stationary, desktop computers, while still retaining their mobility advantage. Unfortunately, the base IP protocol does not perform very well in mobile environments, due to lack of handover support and higher layer mobility management mechanisms. In this paper we present an overview of the most popular and promising methods of handling mobility in IPv4 and IPv6 networks, covering both ISO-OSI layer 2 low level handover mechanisms in IEEE 802.11 WLAN systems and ISO-OSI layer 3+ mobility solutions.

A novel architecture for E-Learning knowledge assessment systems

In this paper we propose a novel E-Learning system, dedicated strictly to knowledge assessment tasks. In its functioning it utilizes web-based technologies, but its design differs radically from currently popular E-Learning solutions which rely mostly on thin-client architecture. Our research proved that such architecture, while well suited for didactic content distribution systems is ill-suited for knowledge assessment products. In our design we employed loosely-tied distributed system architecture, strict modularity, test and simulation-based knowledge and skill assessment and an our original communications package called Communication Abstraction Layer (ComAL), specifically designed to support communication functions of E-Learning systems in diverse network conditions (including offline environment). The system was tested in production environment on Faculty of Electronics, Telecommunications and Informatics, Technical University of Gdansk with great success, reducing staff workload and increasing efficiency of didactic process. Tests also showed systems versatility as the system was deployed in environments of classroom, remote and blended learning.

SDN testbed for validation of cross-layer data-centric security policies

Software-defined networks offer a promising framework for the implementation of cross-layer data-centric security policies in military systems. An important aspect of the design process for such advanced security solutions is the thorough experimental assessment and validation of proposed technical concepts prior to their deployment in operational military systems. In this paper, we describe an OpenFlow-based testbed, which was developed with a specific focus on validation of SDN security mechanisms - including both the mechanisms for protecting the software-defined network layer and the cross-layer enforcement of higher level policies, such as data-centric security policies. We also present initial experimentation results obtained using the testbed, which confirm its ability to validate simulation and analytic predictions. Our objective is to provide a sufficiently detailed description of the configuration used in our testbed so that it can be easily re-plicated and re-used by other security researchers in their experiments.

Broadband communication solutions for maritime ITSs: Wider and faster deployment of new e-navigation services

In its initial part, the paper presents an overview of popular technologies and systems currently developed or employed in maritime communication. These solutions are used to provide both ship-to-ship and ship-to-shore communication for the purpose of supporting specific services, often dedicated to maritime safety and e-navigation. Utility of such communication systems have been thoroughly verified over the years and their strengths and limitations are also widely known. The later include relatively low maximum throughput and/or high cost of both deployment and operation, caused by the requirement of long communication range and high reliability in difficult propagation conditions. Based on the above overview, the subsequent part of the paper presents preliminary results of research conducted at the Computer Communications Department, Faculty of Electronics, Telecommunications and Informatics, Gdansk University of Technology within the netBaltic project. The projects objective is to create a maritime communication system, able to transparently utilize various transmission technologies to form a multihop network structure and thus provide maritime vessels with Internet Protocol-based communication capabilities in diverse set of conditions and areas. For this purpose a combination of mobility management, mesh and delay tolerant network mechanisms is employed, allowing deployment of a wide range of user-level services, starting with general purpose Internet access, through navigation/weather charts distribution and ending with varied e-navigation functionalities.

Infrastruktura PL-LAB2020

Przedstawiono infrastrukture sieci badawczej PL-LAB2020. Zaprezentowano 7 laboratoriow badawczych PL-LAB umozliwiających prowadzenie badan w glownych ich obszarach zdefiniowanych dla programu Horyzont 2020. Przedstawiono szczegoly struktury operacyjnej PL-LAB2020 lączącej zasoby poszczegolnych laboratoriow zlokalizowane w 6 ośrodkach naukowo-badawczych w jedno rozproszone środowisko badawcze. Ostatecznie pokazano, jak infrastruktura PL-LAB2020 zostala polączona z innymi sieciami badawczymi w Europie.

An integrated e-learning services management system providing HD videoconferencing and CAA services

In this paper we present a novel e-learning services management system, designed to provide highly modifiable platform for various e-learning tools, able to fulfill its function in any network connectivity conditions (including no connectivity scenario). The system can scale from very simple setup (adequate for servicing a single exercise) to a large, distributed solution fit to support an enterprise. Strictly modular architecture allows users to employ only a selected set of its mechanisms and extremely easily integrate it with third-party solutions. The selection of employed modules depends completely on user needs - there is no mandatory control module or management platform which must be present. The functionality and communication requirements of the system can be very diverse, as new modules can be easily created or third-party solutions integrated. In the practical deployment of the system we utilized a number of knowledge assessment client modules. A separate part of the paper is devoted to a successful and efficient employment of videoconferencing services as an e-learning tool, due to the integration with an advanced videoconferencing system, designed specifically for Future Internet environment, able to provide HD quality video dedicated for e-learning tasks.

netBaltic System – Heterogeneous Wireless Network for Maritime Communications

Abstract In case of maritime communications, we observe a growing interest in deployment of multitask satellite-based solutions and development of new maritime-specific systems intended for improvements in safety of e-navigation. Analysis of different types of currently used maritime communication systems leads, however, to a conclusion that neither global and still very expensive satellite systems nor cheaper, but short-ranged transmission technologies can, on their own, fully meet the today’s expectations and quality requirements formulated for broadband maritime systems. This lack of reliable solutions, offering high throughput and ubiquitous availability of coverage to a wide audience at a relatively low price is one of the main barriers in a widespread implementation of e-navigation initiatives. This issue is addressed in the netBaltic project with the objective to design, deploy and validate in a real maritime environment a non-satellite wireless communication system enabling ship-to-ship and ship-to-shore information exchange via a multi-hop network composed of onshore base stations, maritime vessels and other transit elements such as buoys. In this paper, the idea of a heterogeneous wireless maritime system is presented. Details of the proposed netBaltic node architecture are described highlighting the solutions introduced in the project as a response to specific maritime communication requirements. Numerical results of communication area coverage are presented for four different scenarios utilizing different wireless transmission technologies. In particular, they indicate that when using appropriate wireless communication solutions, the number of vessels being able to connect to Internet is significantly increased as compared to traditional wireless systems (capable of one-hop communication) from 14% for short-range transmission technologies up to as high as 127% in case when relatively long-range transmission technologies are employed within the system.