T2 delivery system descriptor

The T2_delivery_system_descriptor (see table 128) shall be used in the TS loop of the Network Information Table to describe DVB-T2 transmissions according to EN 302 755 [47]. This descriptor maps Transport Streams to data Physical Layer Pipes (data PLPs) and T2 systems. For each Transport Stream carried in a DVB-T2 system in the network, there shall be at least one T2_delivery_system_descriptor in the corresponding transport stream loop of the respective NIT sub-table. The descriptor reflects a mapping of a TS - heading the NIT's TS loop - to a data PLP, whereby the T2_system_id field might occur multiple times, via multiple instances of the descriptor, because a particular

combination of Transport Stream and data PLP may belong to different T2 systems. Within a network, several different Transport Streams may map to the same combination of T2_system_id and plp_id of the data PLP, for example when the same T2 System is used throughout a network and in different geographical areas different Transport Streams are used and mapped to the same data PLP.

If this descriptor is present in the NIT, the following definitions apply:

• The transport_stream_id and original_network_id announced within the transport stream loop of the NIT identify the Transport Stream that is carried by the PLP/T2 system pair identified with plp_id and T2_system_id in the descriptor.

NOTE 1: In the case of multiple PLPs in a T2 multiplex and in the presence of a common PLP, the corresponding TS is split into a data PLP, being referred to by the plp_id, and a common PLP. A corresponding re- assembly operation of the data PLP and common PLP on the receiver side is performed to recover the TS to be output by the receiver.

Table 128: T2 delivery system descriptor

Syntax Number of bits Identifier

T2_delivery_system_descriptor() { descriptor_tag _{8 uimsbf} descriptor_length _{8 uimsbf} descriptor_tag_extension _{8 uimsbf} plp_id _{8 uimsbf} T2_system_id _{16 uimsbf} if (descriptor_length > 4){ SISO/MISO _{2 bslbf} bandwidth _{4 bslbf} reserved_future_use _{2 bslbf} guard_interval _{3 bslbf} transmission_mode _{3 bslbf} other_frequency_flag _{1 bslbf} tfs_flag _{1 bslbf} for (i=0;i<N,i++){ cell_id _{16 uimsbf} if (tfs_flag == 1){ frequency_loop_length _{8 uimsbf} for (j=0;j<N;j++){ centre_frequency _{32 uimsbf}

Syntax Number of bits Identifier } } else{ centre_frequency _{32 uimsbf} } subcell_info_loop_length _{8 uimsbf} for (k=0;k<N;k++){ cell_id_extension _{8 uimsbf} transposer_frequency _{32 uimsbf} } } } )

Semantics for the T2 delivery system descriptor:

plp_id: This 8-bit field identifies uniquely a PLP within the T2 system, identified with the T2_system_id. The term is defined in EN 302 755 [47].

T2_system_id: This 16-bit field identifies uniquely the T2 system within the DVB network (identified by network_id). The term is defined in EN 302 755 [47].

The remaining part of this descriptor, immediately following the T2_system_id field, may be present at most once per T2 system, because the parameters are uniquely applicable to all Transport Streams carried over a particular T2 system. The presence or absence of that part can be derived from the descriptor length field. In the absence of the remaining part this length equals 0x04, otherwise a larger value applies.

SISO/MISO: This 2-bit field indicates the SISO/MISO mode according to table 129. Table 129: Signalling format for SISO/MISO mode

SISO/MISO Description

00 SISO 01 MISO 10 reserved for future use 11 reserved for future use

bandwidth: This 4-bit field indicates the bandwidth in use according to table 130. Table 130: Signalling format for the bandwidth

Bandwidth Bandwidth value

0000 8 MHz 0001 7 MHz 0010 6 MHz 0011 5 MHz 0100 10 MHz 0101 1,712 MHz

0110 to 1111 reserved for future use

Table 131: Signalling format for each of the guard interval values

guard_interval Guard interval values

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

transmission_mode: This 3-bit field indicates the FFT size of the signals transmitted within the associated cell according to table 132.

Table 132: Signalling format for transmission mode/FFT size

transmission_mode Description 000 2k mode 001 8k mode 010 4k mode 011 1k mode 100 16k mode 101 32k mode

110 to 111 reserved for future use

other_frequency_flag: This 1-bit flag indicates whether other frequencies (non-TFS case) or other groups of frequencies (TFS case) are in use. The value 0 (zero) indicates that the set of frequencies (non-TFS case) or the set of groups of frequencies (TFS case) included in the descriptor is complete, whereas the value 1 (one) indicates that the set is incomplete.

tfs_flag: This 1-bit flag indicates whether a TFS arrangement is in place or not. It shall be coded according to table 133. Table 133: Signalling format for the TFS arrangement

tfs_flag Description

0 No TFS arrangement in place 1 TFS arrangement in place

cell_id: This 16-bit field uniquely identifies a cell, as defined in EN 302 755 [47].

NOTE 2: cell_id = 0x0000 indicates that no cell_id is assigned. In this case information for different cells can still be provided by means of multiple instances of the cell loop.

frequency_loop_length: This 8-bit field indicates the total length in bytes of the following loop that enumerates two to six centre frequencies belonging to the TFS arrangement associated with the named cell_id and its parameters. This loop is present only in the case of a TFS arrangement in place, otherwise only a single frequency per cell will be provided with a single instance of the centre_frequency parameter.

centre_frequency: This 32-bit field indicates the frequency value in multiples of 10 Hz. The coding range is from minimum 10 Hz (0x00000001) up to a maximum of 42 949 672 950 Hz (0xFFFFFFFF).

subcell_info_loop_length: This 8-bit field indicates the total length in bytes of the following loop that indicates the frequencies used in subcells.

cell_id_extension: This 8-bit field is used to identify a sub-cell within a cell.

transposer_frequency: This 32-bit field indicates the centre frequency that is used by a transposer in the sub-cell indicated. It is encoded in the same way as the centre_frequency field.