MPEG je jedna od najpopularnijih serija standarda za video/audio kompresiju, pogodnih za razlicite aplikacije, ali i dalje temeljenih na slicnim principima. Ako se MPEG komprimirani video signal treba prenijeti do udaljenog korisnika, na raspolaganju su razlicite mreže i tehnologije, primjerice ATM i IP, pri cemu je od interesa osigurati potrebnu kvalitetu usluge, i to koristenjem najekonomicnije tehnologije na raspolaganju. Da bi se to ostvarilo, potrebno je nadzirati parametre kvalitete usluge na razini relevantne prijenosne tehnologije (kakvi su npr. varijacije kasnjenja i gubitak podatkovnih jedinica protokola koji se koristi – okvira, celija ili paketa), te odabrati odgovarajuce metode za njihovo držanje na razini koju (usljed smanjenja redundancije) osjetljivi komprimirani MPEG niz može tolerirati. S tim u vezi, u ovome radu je, s jedne strane, predstavljen primjer tehnika mjerenja i testiranja prijenosnog sustava (ATM), a s druge strane, dostignuta perceptualna kvaliteta prenesenoga MPEG signala, a zatim su doneseni odgovarajuci zakljucci o razini utjecaja gubitaka podataka u mreži na kvalitetu primljenog video signala.

In this paper, we present the results of our theoretical, computer simulation and experimental investigations of correlation between the speech quality as per ITU-T proposed PSQM method, and various (standard) coding algorithms, data transmission speeds and satellite link error performance levels. We considered both waveform encoders and vo(ice)coders, and specifically, backward predictive and CELP encoders, in contrast to classic PCM encoders, showing that, for satellite transmission channels, the coding efficiency and transmission speed are not the only and ultimate code selection criteria, but also the quality of the received signal, code delay, susceptibility to interferences and transmission errors. Some elsewhere standard coding techniques (e.g. CELP) have been shown to be inadequate for the transmission via satellite channels.

In this paper, we extend the explicit analytical expression for the probability density function of a mobile channel signal composite envelope, during simultaneous fast Nakagami and slow (shadowing) fading. This enables analytically explicit assessment of the mobile channel transmission quality of service, in contrast to currently actual solving similar problems exclusively through numerical integration methods and time-consuming simulations. Analytical results are extensively graphically represented for characteristic parameter values of fast and slow fading

In this paper, we present the results of our experimental investigations of correlation between the speech quality as per ITU-T proposed PSQM method, and the algorithms used for speech coding and transmitting over fixed satellite link with different levels of error performance. We considered both CS-ACELP and ATC coding algorithms at various bit rates, showing that, for satellite transmission channels, the coding efficiency and transmission speed are not the only and ultimate code selection criteria, but also the quality of the received signal, code delay, susceptibility to interferences and transmission errors. Finally, we consider the possibility of dynamic assigning of different coding algorithms (each with particular bit rate) conforming to currently achievable satellite channel bandwidth, taking into account current channel error performance (BER)

The error performance of a non-standard extremely long (143 km) operational SDH microwave radio-relay link has been extensively measured throughout 30 days of the usually worst period of the year, in order to investigate the consistence of practically achieved residual error performance with the migration of its defining parameter from the residual-bit-error-ratio (RBER) to the background-block-error-ratio (BBER), as coming out of the evolution of the relevant ITU-T performance standard from the bit-error-rate based to the more stringent block-error-rate based one, where, in turn, the latter practically does also include into the performance evaluation periods of deep fading. The close matching between the actual BBER-based RBER estimation and the native RBER objective found even on such a long hop, most likely is to be attributed to the space diversity, as the ultimate and most worthy protection measure in this case.

In this paper, the impact of the transmitter/receiver filtering (in tandem with multipath propagation) on the phase-shift of the minimum shift keying (MSK) signal transmitted over a mobile radio channel with small time dispersion has been modeled in order to analytically investigate the validity of the closed-form general expression for the error floor—for various filter bandwidths of interest (e.g. DECT). Theoretical conclusions are supported by computer simulation results. Copyright © 2004 AEI

The dynamic range of many spectrum measurements can be improved by 10 dB or more by compensating for, or subtracting, the thermal noise and/or phase noise of the measuring device - microwave spectrum analyzer. Through a combination of careful measurements and straightforward mathematical operations, engineers working on microwave measurements can achieve the high dynamic range required by modern communications and radar systems.

The residual error performance of a nonstandard, extremely long (143 km) operational microwave radio-relay link (SDH STM-1) has been measured throughout 60 days of the usually worst period of the year (summertime), in order to find out how practically achieved values compare to the predictions calculated according to 1TU-R recommendations that have been proposed for much shorter links but only supposed to be valid for the longer ones as well. The error floor has been considered as block-error-rate, with the reference to the evolution of standards from the bit-error-rate based (G.821) to the block-error-rate based ones (G.826). The results of the extensive measurements campaign encourage the conclusion that, for the well designed radio-relay system, it is realistic to expect the error floor to be well within the predicted limits even for extremely long hops.

The error performance of the extremely long (143 km) live SDH STM-1 microwave radio-delay link has been measured throughout 60 days of the usually worst period of the year (summertime), in order to find out how the practically achieved transmission performance compare to the ITU-R recommendations, which have evolved from the bit-error-rate based (G.821) to block-error-rate based ones (G.826) and have been proposed for much shorter links but only supposed to be valid for the longer ones as well. The extensive measurements campaign has been made and the results encourage the conclusion that, for the well designed radio-relay system, the transmission performance can be realistically expected to be well within the predicted limits even for very long hops.

As classical test methods using an ordinary phone do not enable one to distinguish primary from secondary signals. The concepts and basic signal analysis of measuring co-channel interfering signals by means of a drive test system, are reviewed. A set of recommended typical measurements is recommended, and practical measurements results are presented and discussed.

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.