Nowadays many countries are replacing broadcast analog television with digital television. Digital standards use narrower bandwidth signal transmission which allows to fit more channels in a certain range of frequencies and higher resolutions. Several regions of the world are in different stages of adaptation and are implementing different broadcasting standards. DVB is the suite of open standards used in Europe and has some variations used in Japan (ISDB) or USA (ATSC). Other countries, like China (DTMB) developed their own standard.
DVB defines a a suite of standards using different coding and modulation techniques and standards to allow the transmission of the signal in different environments and conditions. This standard was developed in Europe and it is internationally accepted for most of the countries. The suite of standards for digital television includes:
- DVB-S: DVB for satellite television. It provides error protection to the MPEG-2 TS and adapts it to the channel characteristics. DVB-S use TDMA with a single carrier and QPSK modulation.
- DVB-T: DVB for the digital terrestrial television. It uses MPEG-2 TS using COFDM modulation to reduce the ISI and the fading effect that appears in terrestrial communications. Several parameters can be chosen for a DVB-T transmission channel such as the bandwidth (6, 7 or 8MHz) and the operation modes (2K or 8K).
- DVB-C: DVB over cable. It is similar to DVB-S with 64QAM modulation and without adding error protection to the MPEG-2 TS due to the channel characteristics.
- DVB-H: DVB for handhelds. It use 4K COFDM because of the handhelds low energy consumption and mobility robustness.
- DVB-SH: DVB Satellite services to Handhelds. The satellite downlink guarantees rural coverage and the terrestrial downlink is used in urban environments.
- DVB-S2: DVB-Satellite 2nd generation. It is the successor for the DVB-S system. It includes enhanced modulation (QPSK, 8PSK, 16APSK and 32APSK) schemes and higher bitrates.
- DVB-T2: DVB-Terrestrial 2nd generation. It is the extension of the DVB-T standard with higher bitrate and better usage of spectrum. It use OFDM with a large number of sub-carriers and several modes.
- DVB-T2 Lite: New profile of DVB-T2 for very low capacity applications such as mobile broadcasting. It is based on a limited subset of the modes of the T2 profile and by avoiding modes which require the most complexity and memory.
ISDB-T is the Japanese standard for digital TV. It is an extension of the DVB-T standard. It uses MPEG-2 and the same DVB-T coding and COFDM modulation.This standards enables hierarchical transmission which allows partial reception for mobile TV.
ATSC standards are a set of standards for digital television used in USA, Canada and Mexico. It also uses MPEG-2 codification like DVB but it uses new modulation techniques. The stream can be modulated on 8VSB (terrestrial) or 16VSB (cable TV) modulation which consist on modulate a sinusoidal carrier to one of eight or sixteen levels allowing high spectral efficiency and impulse noise immunity. ATSC signals use 6MHz bandwidth and achieve a throughput of 19.4Mbps.
DTMB is the TV standard used in China, Hong Kong and Middle East. The system use advanced technologies like a pseudo-random noise code, low-density parity check
encoding to protect again mistakes, modulation TDS-OFDM. The system gives flexibility to the services offered where different modes and parameters can be chosen depending on the type of service and network.