Optical time-domain reflectometer (OTDR) enables simple identification and localization of a plethora of refractive and reflective events on a fiber link, including splices, connectors and breaks, ...and measuring insertion/return loss. Specifically, large enough OTDR dynamic range (DR) and thus high signal-to-noise-ratio (SNR) enable clear far-end visibility of longer fibers. We point out here that, under such conditions, the optical bit-error-rate (BER) floor is dominantly determined by reflective events that introduce significant return loss. This complements the OTDR legacy tests by appropriate optical BER floor estimation in the field. As high SNR implies inter-symbol interference as dominating error generating mechanism, we could apply the classical time-dispersion channel model for the optical BER floor determined by the root-mean-square (rms) delay spread of the actual fiber channel power-delay profile. However, as the high-SNR condition is not always fulfilled mostly due to insufficient DR, we propose here inserting a low-noise optical preamplifier as the OTDR front-end to reduce noise floor and amplify the backscattered signal. In order to verify the model for the exemplar test situation, we measured BER on the same fiber link to find very good matching between the measured BER floor values and the ones predicted from the OTDR trace.
Optical time-domain reflectometer (OTDR) is used to characterize fiber optic links by identifying and localizing various refractive and reflective events such as breaks, splices, and connectors, and ...measuring insertion/return loss and fiber length. Essentially, OTDR inserts a pulsed signal into the fiber, from which a small portion that is commonly referred to as Rayleigh backscatter, is continuously reflected back with appropriate delays of the reflections expressed as the power loss versus distance, by conveniently scaling the time axis. Specifically, for long-distance events visibility and measurement accuracy, the crucial OTDR attribute is dynamic range, which determines how far downstream the fiber can the strongest transmitted optical pulse reach. As many older-generation but still operable OTDR units have insufficient dynamic range to test the far-end of longer fibers, we propose a simple and cost-effective solution to reactivate such an OTDR by inserting a low-noise high-gain optical preamplifier in front of it to lower the noise figure and thereby the noise floor. Accordingly, we developed an appropriate dynamic range and distance span extension model which provided the exemplar prediction values of 30 dB and 75 km, respectively, for the fiber under test at 1550 nm. These values were found to closely match the dynamic range and distance span extensions obtained for the same values of the relevant parameters of interest by the preliminary practical OTDR measurements conducted with the front-end EDFA optical amplifier, relative to the measurements with the OTDR alone. This preliminary verifies that the proposed concept enables a significantly longer distance span than the OTDR alone. We believe that the preliminary results reported here could serve as a hint and a framework for a more comprehensive test strategy in terms of both test diversification and repeating rate, which can be implemented in a network operator environment or professional lab.
Deep regression models are widely employed to solve computer vision tasks, such as human age or pose estimation, crowd counting, object detection, etc. Another possible area of application, which to ...our knowledge has not been systematically explored so far, is proportion judgment. As a prerequisite for successful decision making, individuals often have to use proportion judgment strategies, with which they estimate the magnitude of one stimulus relative to another (larger) stimulus. This makes this estimation problem interesting for the application of machine learning techniques. In regard to this, we proposed various deep regression architectures, which we tested on three original datasets of very different origin and composition. This is a novel approach, as the assumption is that the model can learn the concept of proportion without explicitly counting individual objects. With comprehensive experiments, we have demonstrated the effectiveness of the proposed models which can predict proportions on real-life datasets more reliably than human experts, considering the coefficient of determination (>0.95) and the amount of errors (MAE < 2, RMSE < 3). If there is no significant number of errors in determining the ground truth, with an appropriate size of the learning dataset, an additional reduction of MAE to 0.14 can be achieved. The used datasets will be publicly available to serve as reference data sources in similar projects.
In this paper, a solution is proposed for testing TCP congestion window process in a real-life network situation during stationary time intervals. With this respect, the architecture of hardware and ...expert-system-based distributed protocol analysis is presented that we used for data acquisition and testing, conducted on a major network with live traffic (Electronic Financial Transactions data transfer), as well as the appropriate algorithm for estimating the actual congestion window size from the measured data that mainly included decoding with precise time-stamps (100ns resolution locally and 1ms with GPS clock distribution) and expert-system comments, resulting from the appropriate processing of the network data, accordingly filtered prior to arriving to the special-hardware-based capture buffer. In addition, the paper presents the statistical analysis model that we developed for the evaluation whether the data belonged to the specific (in this case, normal) cumulative distribution function, or whether two data sets exhibit the same statistical distribution - the conditio sine qua non for a TCP-stable interval. Having identified such stationary intervals, it was found that the measured-data-based congestion window values exhibited very good fitting (with satisfactory statistical significance) to the truncated normal distribution. Finally, an appropriate model was developed and applied, for estimating the relevant parameters of the congestion window distribution: its mean value and the variance.
KEY WORDS: protocol analysis, TCP-IP, testing, traffic congestion, statistical analysis, parameter estimation
With the occurrence of rapid urbanization and intensive growth of different modes of transport, we face issues such as resource management, energy demand and lack of capacity due to overcrowding. To ...help with these issues we leverage technology and the Internet of Things (IoT) to develop smart cities. In this paper, we propose an innovative approach to development of new smart city event-driven platform with which we want to simplify data input, data transformation, and decision making processes. The platform uses events, labels and reliability factor to make decisions and trigger actions. This paper begins with an overview of the smart city framework and we review the characteristics of event-driven models. The event-driven platform is presented and discussed. The paper closes with our findings, suggestions, open issues, and future research possibilities.
This paper studies how end-to-end application peiformance(of Electronic Financial Transaction traffic, in particular)depends on the actual protocol stacks, operating systemsand network transmission ...rates. With this respect, the respectivesimulation tests of peiformance of TCP and UDP protocolsrunning on various operating systems, ranging from Windows,Sun Solmis, to Linux have been implemented, and thedifferences in peiformance addressed focusing on throughputand response time.
Understanding and keeping track of business processes is one of the most important tasks in development of business software. However, any documentation other than source code cannot be completely ...reliable. On the other hand, source code is rather unreadable by non-developers and can be challenging to determine business processes distributed among many files and layers. This paper introduces a methodology for extracting business process model from source code by identifying topics from object model, analysing application architecture dependency and developing a graph data structure to store information regarding semantic relationships within source code.
This paper presents the traffic rules in the EFT (ElectronicFinancial Transactions) networks, based on the implementationof the solution called Gold-Net developed and implementedby Euronet Worldwide ...Inc. Following the traffic rulesin EFT networks, out of its worldwide experience, Gold-Netevolved a comprehensive and expandable EFT network solutiondesigned to meet an institution's needs today and in the future.It is an ITM (Integrated Transaction Management) solution,modular and expandable, and consists of a comprehensiveEFT software modules with ATM and POS driving capabilities.The combination of ATM management and the onlineconnection form the intercept processing control module. Asthe marketplace grows, this solution ensures that an ente1prisemay position itself for future growth and expanded service offerings.
Suvremene tvrtke ne mogu opstati na tržištu bez dobre i efikasne organizacije svojega poslovanja. U velikim tvrtkama takva organizacija nezamisliva je bez informatizacije. Što je tvrtka veća i što je ...njezino poslovanje složenije, to je i informatizacija složenija, počevši od same mreže računala pa do strukture baza podataka kojima se pokušava prikazati poslovanje. Sami, posebni sustavi za proizvodnju, više nisu dostatni, pa se sve više tvrtka okreće ERP sustavima. U ovom je radu na temelju analize stanja predložen model sustava proizvodnje i zahtjevi koje treba ispuniti modul ERP sustava za praćenje proizvodnje u pomorskoj industriji. Poseban je naglasak stavljen na dokumente koji se pojavljuju u procesu proizvodnje.
U radu su prikazani trendovi razvoja i implementacije VoIP nasuprot tradicionalnoj tehnologiji. Poseban naglasak dan je na statistike nekih europskih država, povećanje broja korisnika VoIP usluge i ...predviđanja razvoja spomenutoga u bliskoj budućnosti. Također je prikazana primjena sustava otvorenoga koda pri ostvarivanju telefonskih poziva. Na temelju analize postojećeg sustava, standardnih procedura i raspoložive tehnologije, predložena je jedna metoda ostvarivanja poziva temeljena na određenom sustavu otvorenoga koda telefonske centrale.
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