What is DVB-C Technique and its Front-end Network?
In the CATV network, TV signals are transmitted in copper cables with less external interference. The QAM modulation scheme is specified in the DVB specification. Depending on the state of the transmission environment, different modulation rates of 16-QAM, 32-QAM, 64-QAM, 128-QAM or 256-QAM can be used. For systems with long transmission and high noise, a low modulation rate can be used, for example, 16-QAM, 32-QAM, otherwise a high modulation rate should be used. Currently, the CATV network uses a 64-QAM modulation rate with a data rate of up to 38.5 Mb/s in an 8 MHz bandwidth.
For signals from different media, such as TV signals received by digital satellite receivers, or audio/video AV signals from local sources, the packet structure conforms to MPEG-2 including sync byte (B). The requirements of the transport stream packet structure are as follows, with the following possible frame structures: (1) 188B packet (4B header and 184B "net payload"); (2) 204B packet (adding 16 blank bytes to the 188B packet); 3) 204B packet (channel coding has been performed).
In the CATV front-end, after multiplexing by multiplexer, the processing of DVB transport stream is summarized as: synchronous inversion and energy diffusion, Reed-Solomon coding, convolutional interleaving, byte-to-symbol transformation, differential coding, Baseband shaping, entering the QAM modulatormodulate and output the RF TV signal of a plurality of compressed digital TV programs, and then up-convert the RF to the frequency band required by the CATV network and send it to the CATV network.
Cable TV transmission DVB-C is also called cable TV CATV (Community Antenna TV or Cable Television) transmission system. It is a combination of radio, television, radio technology and computer technology.
The result of a transmission system that uses optical cables and cables to transmit multiple signals. Currently, it mainly transmits multi-channel TV signals, so this is called the cable TV system.