The DVB-T standard uses special modulation techniques and guard intervals, combined with fast Fourier transform, to provide the highest noise immunity. It allows you to vary the degree of security, transmission rate and error correction. These possibilities allow creating terrestrial digital television systems that are optimal for each locality or city.
As a result of the fast Fourier transform, there are 6817 narrowband carriers in the 8k mode and 1705 carriers in the 2k mode at the output of the transmitter. A certain number of carriers are suppressed at the receiving point as a result of interference, the remaining ones undergo an inverse Fourier transform at the receiver, and an undistorted signal is obtained at the output.
The advantage of DVB-T is the possibility of receiving TV programs in case of overlapping zones of reliable reception of several television centers operating on the same frequency. Synchronization of telecenters occurs according to the frequency standard of any available satellite. Of course, all telecentres transmitting 6-7 national programs on one carrier must transmit the program package simultaneously and identically.
It is possible, by changing the parameters of the launched signal, correcting errors and modulation types, to obtain a wide range of transmission rates from 4.98 to 31.67 Mbps in the 8 MHz frequency band.
If we ask ourselves very modest requirements for transmission quality (2 Mbps), then this corresponds to 2-16 television programs on one carrier frequency. Or half as much (up to 8 programs) at 4 Mbps with better quality. Unlike ATSC, the transmitted TV programs are not connected in any way with the structure of the signals, and both standard and high definition television formats with 525 and 625 line decomposition can be present in one transport stream.
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October 15, 2024 05:29:48 +0300 GMT
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