DVB-T2 is the world’s most advanced digital terrestrial transmission (DTT) system, offering more robustness, flexibility and at least 50% more efficiency than any other DTT system. It supports SD, HD, mobile TV, or any combination thereof.
Like its predecessor, DVB-T2 uses OFDM (orthogonal frequency division multiplex) modulation with a large number of sub-carriers delivering a robust signal, and offers a range of different modes, making it a very flexible standard. DVB-T2 uses the same error correction coding as used in DVB-S2 and DVB-C2: LDPC (Low Density Parity Check) coding combined with BCH (Bose-Chaudhuri-Hocquengham) coding, offering a very robust signal. The number of carriers, guard interval sizes and pilot signals can be adjusted, so that the overheads can be optimised for any target transmission channel.
To enable Single Frequency Network (SFN) operation, decisions on allocation and scheduling are taken once in a T2-Gateway, the results of which are distributed in such a format that each modulator in the network can unambiguously create an identical on-air signal. The DVB-T2 Modulator Interface (T2-MI) defines this format and allows reliable networks of transmitters (in both MFN and SFN configurations) to be constructed. In addition it supports the use of regenerative, off-air repeaters to feed further MFNs and SFNs.
Additional new technologies used in DVB-T2 are:
- Multiple Physical Layer Pipes allow separate adjustment of the robustness of each delivered service within a channel to meet the required reception conditions (for example in-door or roof-top antenna). It also allows receivers to save power by decoding only a single service rather than the whole multiplex of services.
- Alamouti coding is a transmitter diversity method that improves coverage in small-scale single-frequency networks.
- Constellation Rotation provides additional robustness for low order constellations.
- Extended interleaving, including bit, cell, time and frequency interleaving.
- Future Extension Frames (FEF) allow the standard to be compatibly enhanced in the future
Adoption of DVB-T2 around the world:
dualStream and DVB-T2
dualStream offers a wide portfolio of products that are located in the head-end of the operator as well as in the transmitting sites. In the following diagram the related products are presented.
DVB-T2 Base and Lite
dualStream DVB-T2 Gateways are able to transmit the DVB-T2 Base and Lite profile with the same T2-MI output with the use of FEFs. The new functionality, already considered in the standard and implemented by some transmitter manufacturers, provides a very cost effective solution for combining Base and Lite profiles in a single DVB-T2 transmission. Some vendors offer this possibility of combining T2 base and lite broadcast by using separate DVB-T2 gateways and segregated T2-MI interfaces at the modulator. However, with the dualStream multiprofile implementation, only a DVB-T2 Gateway is needed and a single T2-MI signal is required, providing a much cost effective solution in terms of number of devices and use of network. The following diagram compares both options and illustrates the efficiency proposed by the dualStream solution.