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RTT+ – Time Validity Constraints in RT RTT Language, Journal of Telecommunications and Information Technology, 2012, nr 2
Get PDFMost of the traditional access control models, like mandatory, discretionary and role based access control make authorization decisions based on the identity, or the role of the requester, who must be known to the resource owner. Thus, they may be suitable for centralized systems but not for decentralized environments, where the requester and service provider or resource owner are often unknown to each other. To overcome the shortcomings of traditional access control models, trust management models have been presented. The topic of this paper is three different semantics (set-theoretic, operational, and logic- programming) of RTT , language from the family of role-based trust management languages (RT). RT is used for representing security policies and credentials in decentralized, distributed access control systems. A credential provides information about the privileges of users and the security policies issued by one or more trusted authorities. The set-theoretic semantics maps roles to a set of sets of entity names. Members of such a set must cooperate in order to satisfy the role. In the case of logic-programming semantics, the credentials are translated into a logic program. In the operational semantics the credentials can be established using a simple set of inference rules. It turns out to be fundamental mainly in large- scale distributed systems, where users have only partial view of their execution context. The core part of this paper is the introduction of time validity constraints to show how that can make RTT language more realistic. The new language, named RTT+ takes time validity constraints into account. The semantics for RTT+ language will also be shown. Inference system will be introduced not just for specific moment but also for time intervals. It will evaluate maximal time validity, when it is possible to derive the credential from the set of available credentials. The soundness and completeness of the inference systems with the time validity constraints with respect to the set-theoretic semantics of RTT+ will be proven
Skill-Based Bimanual Manipulation Planning, Journal of Telecommunications and Information Technology, 2012, nr 4
Get PDFThe paper focuses on specification and utilization of manipulation skills to facilitate programming of bimanual manipulation tasks. Manipulation skills are actions to reach predefined goals. They constitute an interface between low-level constraint-based task specification and high level symbolic task planning. The task of the robot can be decomposed into subtasks that can be resolved using manipulation skills. Rubik’s cube solving problem is presented as an example of a 3D manipulation task using two-arm robot system with diverse sensors such as vision, force/torque, tactile sensors
Prawdopodobieństwo przejścia i efektywna liczba próbek cyfrowego sygnału z multipleksacją OFDM. Telekomunikacja i Techniki Informacyjne, 2012, nr 1-2
Get PDFW artykule przedstawiono wyprowadzenie wyrażenia opisującego efektywną liczbę próbek sygnału cyfrowego z multipleksacją OFDM. Wyprowadzenie oparte jest na obliczeniu prawdopodobieństwa przejścia dla tego sygnału. Otrzymane wyrażenie wskazuje wprost zależności między efektywną liczbą próbek a parametrami sygnału i stanowi uzupełnienie modelu teoretycznego
Educating on Wireless Solutions for Environmental Monitoring, Journal of Telecommunications and Information Technology, 2012, nr 4
Get PDFEnvironmental monitoring is of growing interest around the globe and there is a clear need for better education in this area. However, the progress is incredibly fast here and wireless sensor networking is a relatively new area of research, so no standard curricula are available yet. In 2012, the International School “Sustainable Wireless ICT Solutions for Environmental Monitoring” was organized by the International Center for Theoretical Physics (ICTP) in collaboration with a few other entities. The school aimed at exposing young scientists from around the world to the newest wireless solutions for environmental monitoring. The school was followed by an awareness conference, which aimed at identifying issues that would benefit from a wider scientific collaboration. This paper begins with general information about the ICTP educational activities related to wireless technologies and applications. Then it focuses on the program of the school and conference. It shows what topics were included (and what were disregard) and what approaches were applied in order to achieve the best results with the (very) limited resources available. Details are omitted here as the complete materials of the both events are available at the Internet (http://wireless.ictp.it) under the Creative Commons
Low Complexity Greedy Power Allocation Algorithm for Proportional Resource Allocation in Multi-User OFDM Systems, Journal of Telecommunications and Information Technology, 2012, nr 4
Get PDFMulti-User Orthogonal Frequency Division Multiplexing (MU-OFDM) is an efficient technique for achieving high downlink capacity in high-speed communication systems. A key issue in MU-OFDM is the allocation of the OFDM subcarriers and power to users sharing the channel. In this paper a proportional rate-adaptive resource allocation algorithm for MU-OFDM is presented. Subcarrier and power allocation are carried out sequentially to reduce the complexity. The low complexity proportional subcarriers allocation is followed by Greedy Power Allocation (GPA) to solve the rate-adaptive resource allocation problem with proportional rate constraints for MU-OFDM systems. It improves the work of Wong et al. in this area by introducing an optimal GPA that achieves approximate rate proportionality, while maximizing the total sum-rate capacity of MU-OFDM. It is shown through simulation that the proposed GPA algorithm performs better than the algorithm of Wong et al., by achieving higher total capacities with the same computational complexity, especially, at larger number of users and roughly satisfying user rate proportionality
Wizualizacja danych z urządzeń TBA-IŁ (Komunikat). Telekomunikacja i Techniki Informacyjne, 2011, nr 3-4
Get PDFPrzedstawiono strukturę oraz funkcje opracowanego w Instytucie Łączności oprogramowania, przeznaczonego do wizualizacji na ekranie komputera PC wyników badań baterii akumulatorów w obiektach telekomunikacyjnych. Oprogramowanie, przeznaczone do urządzeń TBA160-IŁ, umożliwia także obrazowanie danych archiwalnych uzyskanych z urządzeń TBA2-IŁ, TBA59-IŁ i TBA150-IŁ
Konkurencyjność i konkurencja cenowa sektora telefonii komórkowej na Litwie, Łotwie i w Estonii w 2010 r. Telekomunikacja i Techniki Informacyjne, 2011, nr 1-2
Get PDFPrzeanalizowano konkurencyjność i konkurencję cenową w sektorach telefonii komórkowej państw nadbałtyckich (Litwy, Łotwy i Estonii) na koniec 2010 r. Analiza konkurencyjności została dokonana przez porównanie z usługami substytucyjnymi oferowanymi prze telefonię stacjonarną i internetową, konkurencja cenowa zaś na podstawie cenników publikowanych przez poszczególnych operatorów infrastrukturalnych działających na tych rynkach
Communication Platform for Evaluation of Transmitted Speech Quality, Journal of Telecommunications and Information Technology, 2011, nr 3
Get PDFA voice communication system designed and implemented is described. The purpose of the presented platform was to enable a series of experiments related to the quality assessment of algorithms used in the coding and transmitting of speech. The system is equipped with tools for recordingsignals at each stage of processing, making it possible to subject them to subjective assessments by listening tests or, objective evaluation employing PESQ or PSQM algorithms. The functionality for the simulation of distortions typical for voice communication over the Internet was implemented, making itpossible to obtain reproducible, quantifiable results. An application of the presented platform for evaluation of acoustic echo canceler algorithm based on watermarking techniques, which was developed earlier is presented as an example of an effective deployment of the described technology
Authentication and Authorization of Users and Services in Dynamic Military SOA Environments, Journal of Telecommunications and Information Technology, 2011, nr 1
Get PDFThe problem of user authentication and authorization is usually being solved in a single system. Federated environment assumes heterogeneity of systems, which brings the problem of mutual users and services authentication and authorization. In this article the authors presented security requirements for cross domain information exchange in federated environments and a method of secure access to information resources on the basis of web services. Special attention was paid to authentication and authorization of users and services. As opportunities, there were presented solutions verified in multinational experimentations and exercises