Current Issue : April - June Volume : 2016 Issue Number : 2 Articles : 6 Articles
This paper presents the test results performed in\ninternal and external environments employing tuner\ndemodulator hardware with spatial diversity. Two types of\nantennae were used: monopole and hemispherical helical. The\nresults demonstrated the superior performance of the system\nwith spatial diversity....
This article describes experimental propagation\nmeasurements of DTV signals in the urban region of Curitiba. A\ndigital TV analyzer manufactured by Rohde & Schwarz, model\nETL was used [1], which is able to differentiate open TV channel\nsignals received via different paths. At each measuring location,\nthe geographical coordinates, the relative intensity, the relative\ndelay of each of the ten most intense echoes received, the\nrecording time, and the channel power were recorded. A vertical\nmonopole antenna tuned to the channel frequency and mounted\ntwo meters above ground level on the top of a special purpose\nvehicle was used as the receiving antenna. Signal frequency\nspectrum and the subjective quality of the received signal were\nsimultaneously observed. Both the path loss and the echo pattern\nwere measured. 1580 samples were recorded, taken\napproximately five meters apart in various regions of the city and\nwere compared with current propagation models. The power and\ndelay of every multipath version was checked to evaluate the\nefficiency of the guard interval. The effects of distance and\nelevation of the reception site were investigated, as well as the\npresence of channel-modifying obstacles. Analysis of the results\nincluded the comparison of received power measurements with\nthe Okumura-Hata model calculations. The multipath delay data\nwas analyzed as per recommendation ITU-R P.1407 [2].\nPreliminary results show the robustness of the ISDB-TB system\nagainst UHF propagation in Curitiba. Some aspects of the\nmeasurements elicit further investigations that can be carried out\nwith the same resources....
This article presents the factors that may degrade\nthe reception of a digital TV signal, through the analysis of a\ncommunication channel. Methodologies and factorial\nexperimental results with the communication channel are\npresented, and the analysis of meteorological factors that\ninfluence the reception quality of the ISDB-TB system based on\ndata regarding the quality of the digital signals collected from\nsome TV stations in S�£o Paulo. From the data obtained,\nstatistical techniques were applied, such as planning and analysis\nof factorial experiments, simple and multiple linear regressions\ntests for measurement equality in order to determine which\nfactors had greater influence on the degradation of digital TV\nsignal....
This article aims to compare video quality between\nH.264 and MPEG-2 compression methods through an objective\nanalysis. The method used to assess the video in the test is\nthrough comparison with the reference video. The tests were\nconducted using Picture Quality Analysis (PQA) equipment. The\nPQA has the following methods for an objective evaluation:\nPicture Quality Rating (PQR) and Differential Mean Opinion\nScore (DMOS). The PQR and DMOS methods are objective\nevaluations approaching subjective evaluations.\nBy only analyzing the video compression imperfections, i.e., no\npacket loss, it can be seen that H.264 presents video quality\nequivalent to MPEG-2 with a transmission rate about two times\nsmaller. However, the study completed for this article relates to\nvideo quality with packet loss in the transport layer of the ISDBTB\ntransmission system, this shows that H.264 suffers a bigger\nloss in video quality than MPEG-2 with the same value in\nrelation to signal-to-noise ratio (SNR) in the transmission\nchannel, into the ISDB-TB receiver. To generate error packets in\nthe transmission, white noise was added between the transmitted\nand received signal. The test results show that H.264 provides\nsuperior video quality when compared to MPEG-2, with no\npacket loss, but with packet loss, MPEG-2 provides better video\nquality than H.264....
This article aims to present a passive repeater for\ntransmitting digital TV signals. In this article, some projects that\nindicate the limitations in this type of repeater are presented and\nin what situations it becomes suitable for use....
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