“A path towards digital video communications at home” “A PATH TOWARDS DIGITAL VIDEO COMMUNICATIONS AT HOME” Master Thesis by Amin Ben Hossain García Amin Ben Hossain García 2009 1 “A path towards digital video communications at home” Abstract A century earlier the fact of viewing something on a screen that sometimes it's happening right in the moment was totally unbelievable. The big discovery of the TV was just the first step of a huge amount of researches that developed the image/audio transmission systems. Nowadays we are immersed in a digital age and this is why in this project is explained the main available digital video transmission systems. As the title try to show, has had a long path until the possibility of using digital video at home, but this “path” has two meanings: the historical path and the physical path. The first one begins with the analog standards and ends with the actual most advanced wireless digital transmission systems. The second one, begins in the television station and ends with the use of digital transmission devices in our own houses. The standards and technologies chosen with the purpose to explain this “path” are the following: three analog standards (NTSC, PAL and SECAM), five broadcast digital standards (DVB-S, DVB- C, DVB-T, DVBT2 and ATSC although the most important for this project are DVB-T and ATSC) and finally two indoor digital technologies (UWB and WirelessHD). Every standard is going to be described in several facets: how it works, the physical medium used, a few about source coding, channel coding, modulation, channel capacity (data rates), power features, SNR ratio, bandwidth, carrier frequency, noise and other types of interferences, etc. However not every standard will be described very deeply in every aspect, it depends on the importance of the standard for the Master Thesis and the importance of the own aspect for each standard. Apart from describing the standards and technologies is very useful the comparison between them in order to make clear the advantages and disadvantages and allow the user to choose the most suitable technology to be applied. Amin Ben Hossain García 2009 2 “A path towards digital video communications at home” Acknowledgements I would like to thank Professor Kent Palmkvist for giving me the opportunity of doing this Master Thesis and having supervised my work with flexibility and wisdom. I would like to thank my friends in Linköping for having given me support and advices in the development of this Master Thesis Finally I would like to thank all my family but specially, my father Riad, my mother Josefina, my brother Yussef and my sister Leila for having been always there for me and because without them this work would not have any sense. Thank you very much! Amin Ben Hossain García 2009 3 “A path towards digital video communications at home” Contents 1. Introduction...............................................................................................................................5 1.1 Digital Video Background.................................................................................................. 5 1.1.1 NTSC........................................................................................................................... 5 1.1.2 PAL............................................................................................................................. 8 1.1.3 SECAM....................................................................................................................... 9 1.1.4 Some features.............................................................................................................. 10 1.1.5 Analog video transmission systems conclusions........................................................ 10 1.2 Why digital video?............................................................................................................. 10 2. Broadcast digital video transmission standards....................................................................... 12 2.1 The DVB Standard............................................................................................................. 12 2.1.1 DVB-S......................................................................................................................... 12 2.1.2 DVB-C........................................................................................................................ 14 2.1.3 DVB-T........................................................................................................................ 15 2.1.4 DVBT2: The DVB-T evolution................................................................................... 25 2.2 The ATSC Standard............................................................................................................ 28 2.3 Comparison between DVB-T and ATSC........................................................................... 33 3. Indoor digital video transmission standards..............................................................................36 3.1 UWB................................................................................................................................... 36 3.2 WirelessHD.........................................................................................................................44 3.3 Comparison between WirelessHD AND UWB..................................................................... 51 4. Comparison between DVB-T and WirelessHD....................................................................... 54 5. Conclusions.............................................................................................................................. 56 6. References................................................................................................................................ 57 Amin Ben Hossain García 2009 4 “A path towards digital video communications at home” 1. Introduction Since this project is mainly about digital video transmission systems, it was thought to put the analog standards in this chapter. However without these analog standards the digital ones would not exist, so it's important to explain properly how they work although this introduction could seem a bit long. 1.1 Digital video background There are three analog standards for television. The reason for a country to have chosen to use one of the possible standards could be technical, geographical, political or even historical. Whatever is the reason, is going to be explained how these standards work, specially talking about the transmission aspects and without going very deep into other issues. The aim of this chapter is to give a background to the digital video transmission which is our goal in this master thesis, so the main analog video transmission issues are going to be described so we can see the evolution once we have studied the digital one. 1.1.1 NTSC NTSC (National Television System Committee) was the first widely adopted broadcast color system. Some matters about the modulation used in this standard, like for example kind of modulation, bandwidth, carrier frequency, etc, are going to be explained. In the next picture we can see the spectrum of a NTSC signal channel. Figure 1.1: NTSC spectrum [30] Amin Ben Hossain García 2009 5 “A path towards digital video communications at home” In the figure above the luminance luminance the monochrome signal or “black and white” signal that is represented by Y and the chrominance is the signal that carries the color and can be blue ( B ), red ( R ) or green ( G). The modulation used is amplitude modulation (both for luminance and chrominance) for the video signal and frequency modulation for the audio signal. The color modulation is quadrature amplitude modulation with suppressed carrier (that means that has been removed the carrier to waste power as less as possible in the transmission).[7] The reason for being quadrature amplitude modulation is because we have to separate the red and the blue signal by making them orthogonals. This is because the color space is three dimensional by the nature of the human vision, so we have to carry the luminance, that is the monochrome signal and we still have to carry other two dimensions. Typically the two color signals that are carried are R and B because their signal difference with luminance is stronger than the signal difference between the green and luminance. We can see better the quadrature amplitude modulation in the following picture: Figure 1.2: Chrominance quadrature amplitude [7] The video signal carrier is on the left side of the figure (fc) and it is 1.25 MHz above the lower limit of the channel . The next carrier (from left to right) is the color subcarrier (faub) and is 3.579545 MHz far from the video carrier. The audio carrier (fsound) is 4.5 MHz far from the video carrier. [1] The total bandwidth of a channel in this standard is 6 MHz. The spectrum structure is as it follows: we have a guard band of 250 KHz in the lowest part of the spectrum of each channel that separate each channel from the next one. The video signal is transmitted between 500 kHz and 5.45 MHz above the lower bound of the channel. The highest 25 kHz of each channel contains the audio Amin Ben Hossain García 2009 6 “A path towards digital video communications at home” signal.[1] NTSC uses VSB-AM. What does that mean? The video carrier generates two sidebands as we can see in the figure 1.3. Each sideband has 4.2 MHz . The whole upper sideband is transmitted, but only 750 kHz of the