02-02-2013, 01:03 PM
DVB Digital Video Broadcasting
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INTRODUCTION
DVB systems distribute data using a variety approaches, including by satellite (DVB-S, DVB-S2), cable (DVB-C), terrestrial television (DVB-T) and terrestrial television for handhelds (DVB-H).
These standards define the physical layer and data link layer of the distribution system.
Devices interact with the physical layer via a synchronous parallel interface (SPI), synchronous serial interface (SSI), or asynchronous serial interface (ASI).
DVB-T stands for Digital Video Broadcasting – Terrestrial and it is the DVB European consortium standard for the broadcast transmission of digital terrestrial television.
This system transmits a compressed digital audio/video stream, using OFDM modulation with concatenated channel coding (i.e. COFDM).
The adopted source coding methods are MPEG-2 and, more recently, H.264.
Figure 1 gives a functional block diagram of the system.
Internal encoder
A second level of protection is given by a punctured convolutional code, which is often denoted in STBs menus as FEC (Forward Error Correction).
There are five valid coding rates: 1/2 (unpunctured), 2/3, 3/4, 5/6, and 7/8.
Puncturing is a technique used to make a m/n rate code from a basic rate 1/2 code.
It is reached by deletion of some bits in the encoder output.
Bits are deleted according to puncturing matrix, Figure 3.
Mapper
The digital bit sequence is mapped into a base band modulated sequence of complex symbols.
The system uses Orthogonal Frequency Division Multiplex (OFDM) transmission.
All data carriers in one OFDM frame are modulated using either QPSK, 16-QAM, 64-QAM, non-uniform 16-QAM or non-uniform 64-QAM constellations.
The exact proportions of the constellations depend on a parameter α, which can take the three values 1, 2 or 4.
QAM Mapper
The bit sequence is mapped into a base-band digital sequence of complex symbols.
The modulation of the system is quadrature amplitude modulation with 16, 32, 64, 128, or 256 points in the constellation diagram.
Notice! The mapping is not identical with the correspondent mapping of DVB-T.
[attachment=49381]
INTRODUCTION
DVB systems distribute data using a variety approaches, including by satellite (DVB-S, DVB-S2), cable (DVB-C), terrestrial television (DVB-T) and terrestrial television for handhelds (DVB-H).
These standards define the physical layer and data link layer of the distribution system.
Devices interact with the physical layer via a synchronous parallel interface (SPI), synchronous serial interface (SSI), or asynchronous serial interface (ASI).
DVB-T stands for Digital Video Broadcasting – Terrestrial and it is the DVB European consortium standard for the broadcast transmission of digital terrestrial television.
This system transmits a compressed digital audio/video stream, using OFDM modulation with concatenated channel coding (i.e. COFDM).
The adopted source coding methods are MPEG-2 and, more recently, H.264.
Figure 1 gives a functional block diagram of the system.
Internal encoder
A second level of protection is given by a punctured convolutional code, which is often denoted in STBs menus as FEC (Forward Error Correction).
There are five valid coding rates: 1/2 (unpunctured), 2/3, 3/4, 5/6, and 7/8.
Puncturing is a technique used to make a m/n rate code from a basic rate 1/2 code.
It is reached by deletion of some bits in the encoder output.
Bits are deleted according to puncturing matrix, Figure 3.
Mapper
The digital bit sequence is mapped into a base band modulated sequence of complex symbols.
The system uses Orthogonal Frequency Division Multiplex (OFDM) transmission.
All data carriers in one OFDM frame are modulated using either QPSK, 16-QAM, 64-QAM, non-uniform 16-QAM or non-uniform 64-QAM constellations.
The exact proportions of the constellations depend on a parameter α, which can take the three values 1, 2 or 4.
QAM Mapper
The bit sequence is mapped into a base-band digital sequence of complex symbols.
The modulation of the system is quadrature amplitude modulation with 16, 32, 64, 128, or 256 points in the constellation diagram.
Notice! The mapping is not identical with the correspondent mapping of DVB-T.