DVB-T2 is the next development of the Digital Video Broadcasting - Terrestrial standards. It builds on the technology and on the success of DVB-T to provide additional facilities and features in line with the developing DTT or Digital Terrestrial television market.
Although some may see DVB-T2 as a competitor to the existing DVB-T standard, this is not the case,. It is planned that the two standards will co-exist for many years, with DVB-T2 allowing additional features and services.
The DVB-T2 standard uses Orthogonal Frequency Division Multiplex as the basic radio transmission medium. This form of transmission is particularly robust and allows for the reception of data signals (in this case television data) in the presence of some interference or missing channels as a result of effects like multipath.
Note on OFDM:
Orthogonal Frequency Division Multiplex, OFDM is a form of signal format that uses a large number of close spaced carriers that are each modulated with low rate data stream. The close spaced signals would normally be expected to interfere with each other, but by making the signals orthogonal to each other there is no mutual interference. The data to be transmitted is shared across all the carriers and this provides resilience against selective fading from multi-path effects.
Read more about OFDM, Orthogonal Frequency Division Multiplexing.
The new DVB-T2 specification provides the facility to select a variety of different options to match the requirements of the network operator.
For error correction technology, that used for DVB-S2 has been incorporated. This comprises LDPC (Low Density Parity Check) coding combined with BCH (Bose-Chaudhuri-Hocquengham) coding. The combination of these two techniques has been proved to provide excellent performance in the presence of high noise levels and interference.
As before, several options are available in areas such as the number of carriers, guard interval sizes and pilot signals, so that the overheads can be minimised for any given transmission channel.
DVB-T2 specification highlights
|Number of carriers in signal||2k, 8k||1k, 2k, 4k, 8k, 16k, 32k|
|Modulation formats||QPSK, 16QAM, 64 QAM||QPSK, 16QAM, 64 QAM, 256QAM|
|Scattered pilots||8% of total||1%, 2%, 4%, 8% of total|
|Continual pilots||2.6% of total||0.35% of total|
|Error correction||Convolutional Coding + Reed Solomon
1/2, 2/3, 3/4, 5/6, 7/8
|LPDC + BCH
1/2, 3/5, 2/3, 3/4, 4/5, 5/6
|Guard interval||1/4, 1/8, 1/16, 1/32||1/4, 19/128, 1/8, 19/256, 1/16, 1/32, 1/128|
While DVB-T2 represents the next evolution for digital terrestrial television, it is planned to operate it alongside the current DVB-T standard for many years and evolve the changeover to DVB-T2. This evolution should occur in much the same way that has occurred between DVB-S and DVB-S2.
As DVB-T2 offers additional facilities, it will enable the broadcasters the possibility of offering new and captivating services to ensure that they are able to keep their viewers. Building on the success of the existing digital television services, DVB-T2 is bound to see a significant level of take-up over the coming years.