L1-Pre Signalling data

Figure 25 illustrates the signalling fields of the L1-pre signalling, followed by the detailed definition of each field.

Figure 25: The signalling fields of L1-pre signalling

TYPE: This 8-bit field indicates the types of the Tx input streams carried within the current T2 super-frame. The mapping of different types is given in table 20.

Table 20: The mapping of Tx input stream types

Value type

0x00 Transport Stream (TS) [i.1] only

0x01 Generic Stream (GSE [i.2] and/or GFPS and/or GCS) but not TS

0x02 Both TS and Generic Stream (i.e. TS and at least one of GSE, GFPS, GCS) 0x03 to 0xFF Reserved for future use

BWT_EXT: This 1-bit field indicates whether the extended carrier mode is used in the case of 8K, 16K and 32K FFT sizes. When this field is set to '1', the extended carrier mode is used. If this field is set to '0', the normal carrier mode is used. See clause 9.5.

S1: This 3-bit field has the same value as in the P1 signalling.

L1_REPETITION_FLAG: This 1-bit flag indicates whether the dynamic L1-post signalling is provided also for the next frame. If this field is set to value '1', the dynamic signalling shall be also provided for the next frame within this frame. When this field is set to value '0', dynamic signalling shall not be provided for the next frame within this frame. If dynamic signalling is provided for the next frame within this frame, it shall follow immediately after the dynamic signalling of the current frame, see clause 7.2.3.3.

GUARD_INTERVAL: This 3-bit field indicates the guard interval of the current super-frame, according to table 21.

Table 21: Signalling format for the guard interval

Value Guard interval fraction

000 1/32 001 1/16 010 1/8 011 1/4 100 1/128 101 19/128 110 19/256

111 Reserved for future use

PAPR: This 4-bit field describes what kind of PAPR reduction is used, if any. The values shall be signalled according to table 22.

Table 22: Signalling format for PAPR reduction

Value constellation

0000 No PAPR reduction is used

0001 ACE-PAPR only is used

0010 TR-PAPR only is used

0011 Both ACE and TR are used

0100 to 1111 Reserved for future use

L1_MOD: This 4-bit field indicates the constellation of the L1-post signalling data block. The constellation values shall be signalled according to table 23.

Table 23: Signalling format for the L1-post constellations

Value constellation

0000 BPSK 0001 QPSK 0010 16-QAM 0011 64-QAM

0100 to 1111 Reserved for future use

L1_COD: This 2-bit field describes the coding of the L1-post signalling data block. The coding values shall be signalled according to table 24.

Table 24: Signalling format for the L1-post code rates

Value Code rate

00 1/2

01 to 11 Reserved for future use

L1_FEC_TYPE: This 2-bit field indicates the type of the L1 FEC used for the L1-post signalling data block. The L1_FEC_TYPE shall be signalled according to table 25.

Table 25: Signalling format for the L1-post FEC type

Value L1 FEC type

00 LDPC 16K

01 to 11 Reserved for future use

L1_POST_SIZE: This 18-bit field indicates the size of the coded and modulated L1-post signalling data block, in OFDM cells.

L1_POST_INFO_SIZE: This 18-bit field indicates the size of the information part of the L1-post signalling data block, in bits, including the extension field, if present, but excluding the CRC. The value of K_{post_ex_pad} (see

clause 5.8.2.2.3.2) may be calculated by adding 32 (the length of the CRC) to L1_POST_INFO_SIZE. This is shown in figure 26.

Configurable

Dynamic

L1

padding

CRC

Extension

Figure 26: The size indicated by the L1_POST_INFO_SIZE field

PILOT_PATTERN: This 4-bit field indicates the scattered pilot pattern used for the data OFDM symbols. Each pilot pattern is defined by the D_x and D_y spacing parameters (see clause 9.2.3). The used pilot pattern is signalled according to table 26.

Table 26: Signalling format for the pilot pattern

Value Pilot pattern type

0000 PP1 0001 PP2 0010 PP3 0011 PP4 0100 PP5 0101 PP6 0110 PP7 0111 PP8 1000 to 1111 Reserved for future use

TX_ID_AVAILABILITY: This 8-bit field is used to signal the availability of transmitter identification signals within the current geographic cell. When no transmitter identification signals are used this field is set to 0x000. All other bit combinations are reserved for future use.

CELL_ID: This is a 16-bit field which uniquely identifies a geographic cell in a DVB-T2 network. A DVB-T2 cell coverage area may consist of one or more frequencies, depending on the number of frequencies used per T2 system. If the provision of the CELL_ID is not foreseen, this field shall be set to '0'.

NETWORK_ID: This is a 16-bit field which uniquely identifies the current DVB-T2 network. T2_SYSTEM_ID: This 16-bit field uniquely identifies a T2 system within the DVB-T2 network.

NUM_T2_FRAMES: This 8-bit field indicates N_T2, the number of T2-frames per super-frame. The minimum value of NUM_T2_FRAMES shall be 2.

NUM_DATA_SYMBOLS: This 12-bit field indicates L_data= L_F - N_P2, the number of data OFDM symbols per T2-frame, excluding P1 and P2. The minimum value of NUM_DATA_SYMBOLS is defined in clause 8.3.1.

REGEN_FLAG: This 3-bit field indicates how many times the DVB-T2 signal has been re-generated. Value '000' indicates that no regeneration has been done. Each time the DVB-T2 signal is regenerated this field is increased by one. L1_POST_EXTENSION: This 1-bit field indicates the presence of the L1-post extension field (see clause 7.2.3.4). When the extension field is present in the L1-post, this bit shall be set to a 1, otherwise it shall be set to a 0.

NUM_RF: This 3-bit field indicates N_RF, the number of frequencies in the current T2 system. The frequencies are listed within the configurable parameters of the L1-post signalling.

CURRENT_RF_IDX: If the TFS mode is supported, this 3-bit field indicates the index of the current RF channel within its TFS structure, between 0 and NUM_RF-1. In case the TFS mode is not supported, this field is set to '0'. RESERVED: This 10-bit field is reserved for future use.

CRC-32: This 32-bit error detection code is applied to the entire L1-pre signalling. The CRC-32 code is defined in annex F.