Module dvbt 

The OFDM frame of DVB-T (ETSI EN 300 744 V1.6.2, Secs. 4.4 to 4.6): the 2K and 8K modes, the guard intervals, the scattered and continual pilots, the carriers of the transmission parameter signalling (TPS) and the cells left to the data.

Frame

A frame is SYMBOLS_PER_FRAME = 68 OFDM symbols $l = 0, \dots, 67$, a super-frame four frames. A symbol has $K$ carriers $k = 0, \dots, K_{\max}$ (Table 4): $K = 1705$ in the 2K mode, $K = 6817$ in the 8K mode, spaced by $1/T_{U}$, $T_{U} = 2048,T$ or $8192,T$, the elementary period $T = 7/(8B)$ of a channel of bandwidth $B$ (7/64 µs at 8 MHz, Sec. 4.4); the guard interval $\Delta = T_{U}/4$, $T_{U}/8$, $T_{U}/16$ or $T_{U}/32$ is the cyclic continuation of the useful part, in front of it (Table 5). The carrier $k$ is emitted at $k’ / T_{U}$, $k’ = k - (K_{\max} + K_{\min})/2$, the centring of Ofdm (DvbtFrame::ofdm).

Reference signals and cells

• The pilots carry $\pm 4/3$ (PILOT_BOOST, $E|c|^{2} = 16/9$, Sec. 4.5.5), the sign $2(1/2 - w_{k})$ of the PRBS $X^{11} + X^{2} + 1$ started at all ones on carrier $K_{\min}$, one value per carrier (pilot_prbs, Sec. 4.5.2, Figure 10);
• the scattered pilots of symbol $l$ are the carriers $k = 3 (l \bmod 4) + 12 p$ (Sec. 4.5.3), the continual pilots those of Table 7, in every symbol (45 in the 2K mode, 177 in the 8K mode, Sec. 4.5.4);
• the TPS carriers of Table 8 (17 and 68, Sec. 4.6) carry, all alike, the differential BPSK of one bit per symbol: $\pm 2(1/2 - w_{k})$, the sign $d_{0} = 1$ in the first symbol of a frame and $d_{l} = d_{l-1} (1 - 2 s_{l})$ after (tps_signs, Sec. 4.6.3);
• the other carriers are the data cells, 1512 (2K) or 6048 (8K) in every symbol (Sec. 4.5.1), filled in the order of increasing $k$ (the order that reproduces the interleaving example of Annex C, Table C.1; the text does not state it).

Examples

use comnum_waveform::ofdm::dvbt::{DvbtFrame, Mode};
let frame = DvbtFrame::new(Mode::K2);
for l in 0..4 {
    assert_eq!(frame.data_carriers(l).len(), 1512);      // Sec. 4.5.1
}
// "PRBS sequence starts: 1111111111100", Figure 10
assert_eq!(&comnum_waveform::ofdm::dvbt::pilot_prbs(13), &[1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0]);

References

1. ETSI EN 300 744 V1.6.2, Digital Video Broadcasting (DVB); Framing structure, channel coding and modulation for digital terrestrial television, 2015, Secs. 4.4 to 4.6, Tables 4, 5, 7 and 8.

Structs

DvbtFrame

The cells of the frame of a mode: what every carrier of every symbol carries, the pilot PRBS and the data carriers (see the module).

Enums

Cell

What a carrier of a symbol carries.

Guard

The guard interval $\Delta / T_{U}$ (Table 5).

Mode

The transmission mode (Table 4).

Constants

FRAMES_PER_SUPERFRAME

Frames of a super-frame.

PILOT_BOOST

The amplitude of a pilot, $4/3$ ($E|c|^{2} = 16/9$, Sec. 4.5.5).

SYMBOLS_PER_FRAME

OFDM symbols of a frame.

Functions

elementary_period

The elementary period $T = 7 / (8 B)$ (s) of a channel of bandwidth $B$ (Hz): 7/64 µs at 8 MHz, 1/8 µs at 7 MHz, 7/48 µs at 6 MHz, 7/40 µs at 5 MHz (Sec. 4.4, Annexes E and G).

pilot_prbs

The first n values $w_{k}$ of the PRBS of the pilots, $X^{11} + X^{2} + 1$, its 11 registers started at one (Sec. 4.5.2, Figure 10): $w_{k+11} = w_{k} \oplus w_{k+2}$.

tps_signs

The signs $d_{l}$ of the TPS carriers over a frame for the 68 TPS bits $s_{0}, \dots, s_{67}$ of the frame: $d_{0} = 1$ (the first symbol is the reference, $s_{0}$ initialises the differential BPSK), $d_{l} = d_{l-1} (1 - 2 s_{l})$ (Sec. 4.6.3).