The need for on-demand provisioning of wavelength-routed channels with service-differentiated offerings within the transport layer has become more essential because of the recent emergence of high bit rate Internet protocol (IP) network applications. Diverse optical transport network architectures have been proposed to achieve the above requirements. This approach is determined by fundamental advances in wavelength division multiplexing (WDM) technologies. Because of the availability of ultra long-reach transport and all-optical switching, the deployment of all-optical networks has been made possible. The concurrent transmission of multiple streams of data with the assistance of special properties of fiber optics is called WDM. The WDM network provides the capability of transferring huge amounts of data at high speeds by the users over large distances. There are several network applications that require the support of QoS multicast, such as multimedia conferencing systems, video-on-demand systems, real-time control systems, etc. In a WDM network, the route decision and wavelength assignment of lightpath connections are based mainly on the routing and wavelength assignment (RWA). The multicast RWA's task is to maximize the number of multicast groups admitted or minimize the call-blocking probability. The dynamic traffic-grooming problem in wavelength-routed networks is generally a two-layered routing problem in which traffic connections are routed over lightpaths in the virtual topology layer and lightpaths are routed over physical links in the physical topology layer. In this paper, a multicast RWA protocol for capacity improvement in WDM networks is designed. In the wavelength assignment technique, paths from the source node to each of the destination nodes and the potential paths are divided into fragments by the junction nodes and these junction nodes have the wavelength conversion capability. By using the concept of fragmentation and grouping, the proposed scheme can be generally applied for the wavelength assignment of multicast in WDM networks. An optimized dynamic traffic grooming algorithm is also developed to address the traffic grooming problem in mesh networks in the multicast scenario for maximizing the resource utilization and minimizing the blocking probability.
The Shunt Active Power Filter has proved to be a useful device to eliminate harmonic currents and to compensate reactive power for nonlinear loads. The basic principle of operation of a Shunt Active Power Filter is to inject a suitable non-sinusoidal current (compensating current) into the system at the point of common coupling. An current control algorithm based on the time-domain approach for three-phase Shunt Active Power Filters is analyzed in this paper. A basic overview and evaluation of the performance of existing algorithms for active power filters are presented. According to different complicated power quality issues and various compensation purposes, a current control scheme based on time domain approach is proposed. Comparing with existing algorithms; this algorithm has shorter response time delay. Different compensating current references can thus, be accurately and easily obtained by adopting the proposed algorithm. Simulation results using MATLAB / Simulink have proven excellent performance of the proposed system and it is more effective than the available approaches.
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