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Traffic Analysis in the Network of a Local Voice over Internet Protocol Operator, Journal of Telecommunications and Information Technology, 2013, nr 1
Get PDFVoice over Internet Protocol market is growing rapidly. This article is the initial step towards creating a method for modeling systems for Voice over Internet Protocol operators. The purpose of this research is to gather statistics of a live VoIP-operator system, analyze them and determine if it is possible to create a specific model of such system using traditional approach. After evaluation, the data will be used, in future research, to create an analytical model of VoIP-based telecommunications system
Flexible Spectrum Use and Laws of Physics. Telekomunikacja i Techniki Informacyjne, 2013, nr 3
Get PDFThis note refers to flexible-use spectrum rights that would allow the radio frequency spectrum to be traded, aggregated, divided and freely used for a wide range of user-selected services. So far, discussions on that approach have largely focused on economic aspects, without due consideration of physical realizability. We argue here that additional spectrum management rules are required to assure compatible coexistence of radio systems in congested environments
Two Semantics of Trust Management Language with Negation, Journal of Telecommunications and Information Technology, 2013, nr 4
Get PDFThe family of Role-based Trust management languages is used for representing security policies by defining a formalism, which uses credentials to handle trust 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 main topic of this paper is RT⊖, a language which provides a carefully controlled form of non-monotonicity. The core part of the paper defines two different semantics of RT⊖ language – a relational, set-theoretic semantics for the language, and an inference system, which is a kind of operational semantics. The set-theoretic semantics maps roles to a set of entity names. In the operational semantics credentials can be derived from an initial set of credentials using a set of inference rules. The soundness and the completeness of the inference system with respect to the set-theoretic semantics of RT⊖ will be proven
Recognition of the Numbers in the Polish Language, Journal of Telecommunications and Information Technology, 2013, nr 4
Get PDFAutomatic Speech Recognition is one of the hottest research and application problems in today’s ICT technologies. Huge progress in the development of the intelligent mobile systems needs an implementation of the new services, where users can communicate with devices by sending audio commands. Those systems must be additionally integrated with the highly distributed infrastructures such as computational and mobile clouds, Wireless Sensor Networks (WSNs), and many others. This paper presents the recent research results for the recognition of the separate words and words in short contexts (limited to the numbers) articulated in the Polish language. Compressed Sensing Theory (CST) is applied for the first time as a methodology of speech recognition. The effectiveness of the proposed methodology is justified in numerical tests for both separate words and short sentences
Interworking and Cross-layer Service Discovery Extensions for IEEE 802.11s Wireless Mesh Standard, Journal of Telecommunications and Information Technology, 2013, nr 3
Get PDFWith the rapid popularization of mobile end-user electronic devices, wireless network technologies begin to play a crucial role as networks access technologies. While classic point-to-multipoint wireless access systems, based on fixed infrastructure of base stations providing access to clients, remain the main most popular solution, an increasing attention is devoted to wireless mesh systems, where each connecting client can extend overall resources of the network by becoming a network node capable of forwarding transit traffic. This ability results in severe reduction of the necessary network infrastructure, provides through coverage (thereby offering significant step towards ubiquity of network access) and offers massive redundancy. One of the most promising wireless mesh solutions currently being developed is an IEEE 802.11s standard, based on popular Wi-Fi technology. It combines low deployment costs with comprehensive suite of mechanisms able to operate a self-forming, autoconfigurable, dynamically extending, and secure mesh solution. However, despite its advantages, the standard lacks sufficient support for a number of functionalities, which can lead to significant inefficiency and degradation of service quality in real-world IEEE 802.11s network deployments. In the paper we propose a number of extensions of IEEE 802.11s mechanisms, designed to provide better service quality in case of real-world deployment scenarios, especially in case of large systems. Both propositions introduce modifications to mesh path discovery and interworking procedures, while retaining compatibility with standard solution. Their basic functionality and efficiency have been verified by means of simulation model in large-scale, self-organizing mesh structure. Subsequently they have been implemented and tested in real-world, access network testbed deployment. The results clearly indicate their utility, particularly in case of larger deployments of this network system type
Traffic Type Influence on Performance of OSPF QoS Routing, Journal of Telecommunications and Information Technology, 2013, nr 3
Get PDFFeasibility studies with QoS routing proved that the network traffic type has influence on routing performance. In this work influence of self-similar traffic for network with DiffServ architecture and OSPF QoS routing has been verified. Analysis has been done for three traffic classes. Multiplexed On-Off model was used for self-similar traffic generation. Comparison of simulation results was presented using both relative and non-relative measures for three traffic classes. Results were commented and analyzed. The basic conclusion is that performance for streaming and best-effort class for self-similar traffic is higher than performance for the same class with exponential traffic (Poisson). The other important conclusion is relation between performance differences and offered traffic amount
Quality Management in 4G Wireless Networking Technology Allows to Attend High-Quality Users, Journal of Telecommunications and Information Technology, 2013, nr 3
Get PDFThe 4G networks are all-IP based heterogeneous networks that allow users to use any system at anytime and anywhere, and support a variety of personalized, multimedia applications such as multimedia conferencing, video phones, video/movie-on-demand, education-on-demand, streaming media, multimedia messaging, etc. Personalized services should be supported by personal mobility capability, which concentrates on the movement of users instead of users’ terminals. As the technology matures, traffic congestion increases, and competitive pressures mount, QoS and policy management will become more and more important. Also the users come with a number of new requirements on connectivity, and D2D networking technology must follow the idea of “Internet of things”. Operators must make sure they are working with vendors that have a strong framework to supply end-to-end QoS and are capable of supporting evolving needs. The paper discusses qualitative and quantitative indicators of telecommunication services. Main challenges that need to be addressed by nowadays and future systems are shown, and within them the massive growth in traffic volume and in the number of connected devices seems to play the most key role
Reliable and High QoS Wireless Communications over Harsh Environments, Journal of Telecommunications and Information Technology, 2013, nr 1
Get PDFOne of the most challenging research fields in which research community has taken a very active role is focused on trying to bring the features of wireless networks into line with the traditional wired solutions. Given the noisy and lossy nature of the wireless medium, it is more difficult to provide a comparable Quality of Service (QoS) and Reliability over wireless networks. This lack of reliability avoids the use of wireless solution in scenarios under harsh environment and mission-critical applications. In this paper we propose an inter-node collaborative schema with the aim of improving the achievable QoS level for multicast streaming, through the use of Network Coding and the algebra it is based on. We also present an implementation of the described algorithm on the OPNET discrete event simulation tool. Experimental results highlighting the performance achieved by the proposed algorithm and its improved efficiency as compared to other solutions are described
Blind Estimation of Linear and Nonlinear Sparse Channels, Journal of Telecommunications and Information Technology, 2013, nr 1
Get PDFThis paper presents a Clustering Based Blind Channel Estimator for a special case of sparse channels – the zero pad channels. The proposed algorithm uses an unsupervised clustering technique for the estimation of data clusters. Clusters labelling is performed by a Hidden Markov Model of the observation sequence appropriately modified to exploit channel sparsity. The algorithm achieves a substantial complexity reduction compared to the fully evaluated technique. The proposed algorithm is used in conjunction with a Parallel Trellis Viterbi Algorithm for data detection and simulation results show that the overall scheme exhibits the reduced complexity benefits without performance reduction