Rapid development and evolution of IP based networks had major impact on all services and their migration to Next Generation Networks (NGN) infrastructure. Frequency synchronization in this environment was one of the biggest and the most significant challenges, which has to be solved. In traditional circuit-switched networks synchronization problems have been solved using standard plesiochronous digital hierarchy (PDH) and synchronous digital hierarchy (SDH) systems. This paper describes different protocols and techniques used by real-time applications in order to achieve better synchronization degree. For testing and comparing these techniques, we developed our own application in Java programming language, for generating and sending frames through our topology created in virtual environment (MikroTik router OS). This application was also used to process the emulation results, which gave us an insight on the influence of frequency synchronization on Quality of Service (QoS). This paper also discusses an algorithm for frequency synchronization. The aim of this paper is also to compare measured results between the classical synchronization algorithm and the optimized one.

10G EPON and XG-PON1 are both recently standardized but emerging technologies, ready to replace their less capacitive predecessors, 1G EPON and GPON respectively. Both technologies offer row bit rate of 10 Gbps on downlink, but are based on significantly different signal processing principles and protocol stack's characteristics. According to these principles, different technologies introduce different amount and types of transmission overhead, which must be transmitted along with the useful information (in order to provide network functionality). While these overheads drastically reduce real available bit rates to the end users, it is of the great interest to estimate these overheads with high accuracy. Accordingly, in this paper, entire overhead (including PHY and MAC layers' overheads) introduced by 10G EPON and XG-PON1 technologies is estimated through their corresponding protocol stack analysis. Based on these estimations, final conclusions about 10G EPON and XG-PON1 efficiency and thus maximum real achievable data rates are derived. This enables network operators to make appropriate decision when choosing between the two concurrent technologies.

Wireless data services, boosted by the massive use of popular Internet-based services such as email, WWW, etc., wireless wideband networks capable of supporting mobile multimedia services have attracted increasing intention in last few years. An important requirement has been postulated for these wideband services — they cannot be substantially more expensive than the voice services offered today. This paper presents analysis of mobile wireless networks: HSPA and WiMAX made in order to compare multidimensional acceptance of investments in these technologies. Based in model in OPNET Modeler, the simulation and testing of different typical signals in these networks are made, where the Core network is taken as the same for both networks in order to neglect its influence on QoS results. The simulation results are than used as one dimension, QoS in multidimensional function of investment process. Also, business analysis of investments into these networks is also done, and 5-year investment value is taken as another dimension. The third dimension is taken as market acceptance of these technologies, which makes them cheaper or faster to implement. The result is multidimensional function which enables the operator to direct its investment process based on the same multidimensional space. It is shown that operator can decide to deploy one or another technologies based on its preferences.

— This paper gives a proposal on algorithm for adaptive adjustment of VoIP sources transmission rate based on voice quality estimated at the receiver. This adjustment is achieved through the appropriate use of differing voice codecs, as changes in network conditions occur, in order to maintain an efficient utilization of the available resources. We propose a simple algorithm for dynamic selection of voice codec, depending on network conditions during the on-going voice session. Algorithm is embedded in the source code of the programming environment OPNET Modeler 14.5. Simulation results show that the proposed algorithm makes better use of the available bandwidth, achieving superior performance in comparison to the situation without implementation of algorithm for adaptive codec selection.

When using simulation in analysis networks with number of sources, one of problems is creating traffic sources matching real network data. Credibility of conclusions acquired by simulation tools are in great deal dependent of fidelity of simulation traffic source generators. This paper presents one simple approach for real traffic source reconstruction on the basis on limited real traffic data. Source model achieved here is almost in every aspect same as measured real traffic on large IP network; necessary steps and practical applications are shown here as well.