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Statistical Analysis of Message Delay in SIP Proxy Server, Journal of Telecommunications and Information Technology, 2014, nr 4
Get PDFSingle hop delay of SIP message going through SIP proxy server operating in carriers backbone network is being analyzed. Results indicate that message sojourn times inside SIP server in most cases do not exceed order of tens of milliseconds (99% of all SIP-I messages experience less than 21 ms of sojourn delay) but there were observed very large delays which can hardly be attributed to message specic processing procedures. It is observed that delays are very variable. Delay components distribution that is to identied are not exponentially distributed or nearly constant even per message type or size. The authors show that measured waiting time and minimum transit time through SIP server can be approximated by acyclic phase-type distributions but accuracy of approximation at very high values of quantiles depends on the number outliers in the data. This nding suggests that modeling of SIP server with queueing system of GjPHjc type may server as an adequate solution
Evaluation of the Delay-Aware NUM-Driven Framework in an Internetwork Environment, Journal of Telecommunications and Information Technology, 2014, nr 3
Get PDFNowadays, due to emergence of cloud services, even the basic uses of personal computers may require the access to the Internet. In this paper modifications to Delay-Aware Network Utility Maximization System (DANUMS) are presented, which enable it to be deployed in an internetwork environment. The proposed solution consists of DANUMS and WiOptiMo systems, which cooperate by exchanging measurements of transmitted traffic in order to improve the network utility. Additionally, WiOptiMo enhances mobility by providing facilities for soft handover. Experiments presented in this paper illustrate the benefits gained from the integrated system application
Adaptive Algorithms Versus Higher Order Cumulants for Identification and Equalization of MC-CDMA, Journal of Telecommunications and Information Technology, 2014, nr 3
Get PDFIn this paper, a comparative study between a blind algorithm, based on higher order cumulants, and adaptive algorithms, i.e. Recursive Least Squares (RLS) and Least Mean Squares (LMS) for MultiCarrier Code Division Multiple Access (MC-CDMA) systems equalization is presented. Two practical frequency-selective fading channels, called Broadband Radio Access Network (BRAN A, BRAN B) normalized for MC-CDMA systems are considered. In the part of MC-CDMA equalization, the Zero Forcing (ZF) and the Minimum Mean Square Error (MMSE) equalizer techniques were used. The simulation results in noisy environment and for different signal to noise ratio (SNR) demonstrate that the blind algorithm gives approximately the same results obtained by adaptive algorithms. However, the proposed algorithm presents the advantage to estimate the impulse response of these channels blindly except that the input excitation is non-Gaussian, with the low calculation cost, compared with the adaptive algorithms exploiting the information of input and output for the impulse response channel estimation
On-demand QoS and Stability Based Multicast Routing in Mobile Ad Hoc Networks, Journal of Telecommunications and Information Technology, 2014, nr 3
Get PDFFinding a connection path that remains stable for suciently longer period is critical in mobile ad hoc networks due to frequent link breaks. In this paper, an on-demand Quality of Service (QoS) and stability based multicast routing (OQSMR) scheme is proposed, which is an extension of ad hoc on-demand multicast routing protocol (ODMRP) to provide QoS support for real time applications. The scheme works as follows. Each node in the network periodically estimates the parameters, i.e., node and link stability factor, bandwidth availability, and delays. Next step is creation of neighbor stability and QoS database at every node by using estimated parameters. The last sequence is multicast path construction by using, route request and route reply packets, and QoS and stability information, i.e., link/node stability factor, bandwidth and delays in route information cache of nodes, and performing route maintenance in case of node mobility and route failures. The simulation results indicate that proposed OQSMR demonstrates reduction in packet overhead, improvement in Packet Delivery Ratio (PDR), and reduction in end-to-end delays as compared to ODMRP, and Enhanced ODMRP (E-ODMRP)
Cyberterroryzm szczególnym zagrożeniem bezpieczeństwa państwa. Telekomunikacja i Techniki Informacyjne, 2014, nr 1-2
Get PDFCyberterroryzm szczególnym zagrożeniem bezpieczeństwa państw
Obrazowanie stanu akumulatorów w smartfonie na podstawie SMS-ów z urządzeń TBA-IŁ. Telekomunikacja i Techniki Informacyjne, 2014, nr 1-2
Get PDFW artykule scharakteryzowano zasady eksploatacji baterii akumulatorów w obiektach telekomunikacyjnych, podano ogólne informacje o rodzinie urządzeń TBA-IŁ, przeznaczonych do pomiaru dysponowanej pojemności takich baterii w obiektach oraz opisano wprowadzoną w ostatnim okresie ich nową funkcjonalność – graficzną prezentację wyników badań w smartfonie na podstawie odebranych z tych urządzeń wiadomości SMS
New Tool for Examining QoS in the VToIP Service, Journal of Telecommunications and Information Technology, 2014, nr 1
Get PDFThis paper is dedicated to the subject of measuring QoS in the Video Telephony over IP (VToIP) service. QoS measurement models in general and then models designed specifically for measuring QoS in the VToIP service are presented. A new numerical tool for examining the quality of VToIP video streams VToIP is described. The tool’s functionality is then put to the test in a number of analysis scenarios. The results and insights gained from the analyses are then presented in several diagrams, and interpreted. The paper concludes with a summary and an outlook on further areas of work
Efficient Performance and Lower Complexity of Error Control Schemes for WPAN Bluetooth Networks, Journal of Telecommunications and Information Technology, 2014, nr 4
Get PDFThis paper presents a new technique of reduction retransmission time by decreasing the discarded packets and combating the complexity through error control techniques. The work is based on Bluetooth, one of the most common Wireless Personal Area Network. Its early versions employ an expurgated Hamming code for error correction. In this paper, a new packet format using different error correction coding scheme and new formats for the EDR Bluetooth packets are presented. A study for the Packet Error Probability of classic and Enhanced Data Rate (EDR) packets is also presented to indicate the performance. The simulation experiments are performed over Additive White Gaussian Noise (AWGN) and Rayleigh flat-fading channels. The experimental results reveal that the proposed coding scheme for EDR packets enhances the power efficiency of the Bluetooth system and reduce the losses of EDR packets
Bayesian Network Based Fault Tolerance in Distributed Sensor Networks, Journal of Telecommunications and Information Technology, 2014, nr 4
Get PDFA Distributed Sensor Network (DSN) consists of a set of sensors that are interconnected by a communication network. DSN is capable of acquiring and processing signals, communicating, and performing simple computational tasks. Such sensors can detect and collect data concerning any sign of node failure, earthquakes, floods and even a terrorist attack. Energy efficiency and fault-tolerance network control are the most important issues in the development of DSNs. In this work, two methods of fault tolerance are proposed: fault detection and recovery to achieve fault tolerance using Bayesian Networks (BNs). Bayesian Network is used to aid reasoning and decision making under uncertainty. The main objective of this work is to provide fault tolerance mechanism which is energy efficient and responsive to network using BNs. It is also used to detect energy depletion of node, link failure between nodes, and packet error in DSN. The proposed model is used to detect faults at node, sink and network level faults (link failure and packet error). The proposed fault recovery model is used to achieve fault tolerance by adjusting the network of the randomly deployed sensor nodes based on of its probabilities. Finally, the performance parameters for the proposed scheme are evaluated