Current Issue : April - June Volume : 2011 Issue Number : 2 Articles : 5 Articles
Protection engineers dealing with protective relay and communication product manufacturers, strive to achieve fast tripping for all transmission line faults through communication assisted protective relaying. Directional distance and over current schemes, interfaced with communication equipment transceive logic-based information between relay terminals to determine if the external-internal faults to protected line section. Same information can be shared between relay and Personal Computer. For communication purpose microprocessor based digital relays are used. These relays contribute to improved reliability and reduced costs on electric power systems. Microprocessor based relaying scheme can report the events taking place in the system, verify the faults, analyze the voltage dip and identify the fault location. They impose little burden on CTs & PTs enabling relays to be set up for higher sensitivity. So capability of programming and faster response of digital relay helps achieving faster communication between relay and PC. Now a day many software tools are available for communication between master-PC and slaves-Relays. I.E. CAP 501, CAP 505, LIB 510/ Micro SCADA. CAP 501, Relay Setting Tools software, is a Computer Aided Programming system for medium voltage relays in the RED 500 and SPACOM series. CAP 501 is mainly used as local system near the relay. Microprocessor based digital logic communication development for relay operation using six bus sample power system was done. Balanced and unbalanced faults were created at each bus and then fault current values and bus voltages were found out. Using these values of fault currents the fault level is decided and based on this using Time-Current Characteristics for relay the operation time is decided. This paper highlights capability, functions of CAP 501 like online and offline parameterization uploading, downloading, project management, framework for relay tools. We present CAP 501 process to establish communication between microprocessor based relay and personal computer. It also investigates the fault events and event logs together with disturbance recorder tool. An attempt to decide the fault level and operation time of relay is made to establish communication between personal computer and relay....
We propose an explicit construction of full-diversity space-time block codes, under the constraint of an error correction capability. Furthermore, these codes are constructed in order to be suitable for a serial concatenation with an outer linear forward error correcting (FEC) code. We apply the binary rank criterion, and we use the threaded layering technique and an inner linear FEC code to define a space-time error-correcting code. When serially concatenated with an outer linear FEC code, a product code can be built at the receiver, and adapted iterative receiver structures can be applied. An optimized hybrid structure mixing MMSE turbo equalization and turbo product code decoding is proposed. It yields reduced complexity and enhanced performance compared to previous existing structures....
This paper presents an audiovisual quality model for IPTV services. The model estimates the audiovisual quality of standard and high definition video as perceived by the user. The model is developed for applications such as network planning and packet-layer quality monitoring. It mainly covers audio and video compression artifacts and impairments due to packet loss. The quality tests conducted for model development demonstrate a mutual influence of the perceived audio and video quality, and the predominance of the video quality for the overall audiovisual quality. The balance between audio quality and video quality, however, depends on the content, the video format, and the audio degradation type. The proposed model is based on impairment factors which quantify the quality-impact of the different degradations. The impairment factors are computed from parameters extracted from the bitstream or packet headers. For high definition video, the model predictions show a correlation with unknown subjective ratings of 95%. For comparison, we have developed a more classical audiovisual quality model which is based on the audio and video qualities and their interaction. Both quality- and impairment-factor-based models are further refined by taking the content-type into account. At last, the different model variants are compared with modeling approaches described in the literature....
We provide an analytical model for efficient dynamic capacity allocation in IEEE 802.16 wireless metropolitan area network, where the nonreal-time traffic can utilize the bandwidth unused by the real-time traffic. We investigate the uplink delay of the nrtPS service flow as a function of the capacity allocations for the rtPS (ertPS) and UGS service flows. Unicast polling is applied for the bandwidth reservation of the nrtPS and rtPS (ertPS) packets. Our analysis accounts for both reservation and scheduling delay components. The nrtPS packets arrive according to Poisson process. The model enables asymmetric capacity allocation, as well as asymmetric nrtPS traffic arrival flows. The analytical model is applied for investigating the influence of the real-time traffic on the delay of the nrtPS service flow. We discuss also the determination of several traffic parameters under different constraints, which have potential applications in network control....
The Open Profiling of Quality (OPQ) is a mixed methods approach combining a conventional quantitative psychoperceptual evaluation and qualitative descriptive quality evaluation based on na�¯ve participantsâ�� individual vocabulary. The method targets evaluation of heterogeneous and multimodal stimulus material. The current OPQ data collection procedure provides a rich pool of data, but full benefit of it has neither been taken in the analysis to build up completeness in understanding the phenomenon under the study nor has the procedure in the analysis been probed with alternative methods. The goal of this paper is to extend the original OPQ method with advanced research methods that have become popular in related research and the component model to be able to generalize individual attributes into a terminology of Quality of Experience. We conduct an extensive subjective quality evaluation study for 3D video on mobile device with heterogeneous stimuli. We vary factors on content, media (coding, concealments, and slice modes), and transmission levels (channel loss rate). The results showed that advanced procedures in the analysis cannot only complement each other but also draw deeper understanding on Quality of Experience....
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