5 DVB standards
5.1 Digital video broadcasting - terrestrial

The DVB-T service was firstly implemented in United Kingdom in 1998. So far, DVB-T was deployed in more than 70 countries and the same number of countries decided for DVB-T2 which is able to broadcast standard, high, ultra-high definition and mobile TV and radio.

DVB-T/T2 services are aired terrestrially within the ultra-high frequency (UHF) band covering frequencies in a range from 300 MHz to 3 GHz [1]. They share the same band with analog TV therefore its deployment is dependent on releasing of frequencies occupied by analog television channels. An 8 MHz channel carrying single analog TV channel can carry within DVB-T several digital TV and radio channels with other information.

DVB-T technology can reuse the same infrastructure used by analog terrestrial television (the existing broadcasters and transmitters).

At the receiving side users have to buy a new end receiver that can be in the form of a standalone device (set-to-box) or as an integrated receiver decoder (IRD) in TV set.

Table 1 compares DVB-T with DVB-T2 [7].

New error correction codes: LDPC (Low Density Parity Check) combined with BCH (Bose-Chaudhuri-Hocquengham) enable DVB-T2 to transmit a very resistive signal. Both are based on OFDM (orthogonal frequency division multiplex) modulation with a large number of subcarriers (frequencies) which is very robust in a multipath propagation environment and both use bit, time and frequency interleaving. In general, DVB-T2 is very flexible because it offers a lot of modes.

OFDM places guard intervals between OFDM symbols what with a low symbol rate enable it to eliminate intersymbol interference. This principle also offers operators a possibility to create so called a single frequency network where transmitters broadcast a signal on the same frequency. DVB-T standards can incorporate a hierarchical modulation which is able to combine two separate transport streams for two different types of receivers into one DVB stream.

Table 1 Comparison of DVB-T and DVB-T2 standards

Parameters

DVB-T

DVB-T2

FEC

Convolutional & Reed Solomon Coding - 1/2, 2/3, 3/4, 5/6, 7/8

LDPC + BCH

1/2, 3/5, 2/3, 3/4, 4/5, 5/6

Modulations

QPSK, 16QAM, 64QAM

QPSK, 16QAM, 64QAM, 256QAM

Guard Interval

1/4, 1/8, 1/16, 1/32

1/4, 19/128, 1/8, 19/256, 1/16, 1/32, 1/128

Number of subcarriers

2k, 8k

1k, 2k, 4k, 8k, 16k, 32k

Bandwidth

6, 7, 8 MHz

1.7, 5, 6, 7, 8, 10 MHz

Typical data rate

24 Mbit/s

40 Mbit/s

Max. data rate (20 dB C/N)

31.7 Mbit/s (using 8 MHz)

45.5 Mbit/s (using 8 MHz)

Required C/N ratio (24 Mbit/s)

16.7 dB

10.8 dB