Type 0 Extension 1 - mattpascoe135/dab GitHub Wiki

#Extension 1 - Basic sub-channel organization The Extension 1 of FIG type 0 (FIG 0/1) defines the basic sub-channel organization. Each sub-channel is described explicitly by its start address (in the range 0 to 863 CUs) and (either explicitly or implicitly) by the size of the sub-channel and the error coding protection mechanism employed. The structure is shown in figure 22.

Two forms of signalling the sub-channel size and error protection are used. The first is a shorter form which is used for service components employing the Unequal Error Protection (UEP) profiles given in clause 11.3.1. In this case, the UEP index is signalled explicitly and the sub-channel size can be implicitly derived from it. The second form requires the sub-channel size and error protection to be signalled explicitly. In this case, eight options for defining these parameters are allowed; only the first two are defined and are used for Equal Error Protection (EEP) according to clause 11.3.2.

UEP profiles are designed for audio at bit-rates indicated in table 6, but the use of UEP profiles for other applications is not excluded. EEP profiles may be used for audio as well as for data (see also clauses 11.3.1 and 11.3.2). In particular, UEP profiles are not defined for audio bit-rates 8 kbit/s, 16 kbit/s, 24 kbit/s, 40 kbit/s and 144 kbit/s. For these audio bit-rates, EEP profiles should be used.

Type 1

##Header Structure ###SubChId (Sub-channel Identifier) This 6-bit field, coded as an unsigned binary number, shall identify a sub-channel.

###Start Address This 10-bit field, coded as an unsigned binary number (in the range 0 to 863), shall address the first Capacity Unit (CU) of the sub-channel.

###Short/Long form This 1-bit flag shall indicate whether the short or the long form of the size and protection field is used, as follows:

`0: short form`

`1: long form.`

Table 6: Sub-channel size for audio service components as a function of the audio bit rate and the protection level (short-form application)

###Short form:

  • Table switch: this 1-bit flag shall indicate whether table 6 is signalled or there is some other use of the table index field, as follows:

    0: table 6

    1: reserved for future use of the table index field.

  • Table index: this 6-bit field, coded as an unsigned binary number, contains an index which shall identify one of the 64 options available for the sub-channel size and protection level. For table 6, the net data rate associated with each index is given. Six of the possible combinations of protection level and rate are not provided and are indicated by an "x".

###Long form:

  • Option: this 3-bit field shall indicate the option used for the long form coding. Two options (000 and 001) are defined to provide Equal Error Protection as defined in clause 11.3.2. The remaining options are reserved for future use.

    In the case of option 000, the following parameters are defined (see clause 11.3.2):

  • Protection level: this 2-bit field shall indicate the protection level as follows:

    00: protection level 1-A

    01: protection level 2-A

    10: protection level 3-A

    11: protection level 4-A.

    The associated convolutional coding rate is given in table 7.

Table 7: Sub-channel size for data at different coding rates, as a function of the data rate 8 n kbit/s (where n is an integer ≥ 1)

  • Sub-channel size: this 10-bit field, coded as an unsigned binary number (in the range 1 to 864), shall define the number of Capacity Units occupied by the sub-channel. Table 7 shows the number of CUs required for all permissible data rates, in multiples of 8 kbit/s, for the four protection levels defined.

In the case of option 001, the following parameters are defined (see clause 11.3.2):

  • Protection level: this 2-bit field shall indicate the protection level as follows:

    00: protection level 1-B

    01: protection level 2-B

    10: protection level 3-B

    11: protection level 4-B. The associated convolutional coding rate is given in table 8.

  • Sub-channel size: this 10-bit field, coded as an unsigned binary number (in the range 1 to 864), shall define the number of Capacity Units occupied by the sub-channel. Table 8 shows the number of CUs required for all permissible data rates, in multiples of 32 kbit/s, for the four protection levels defined

Table 8: Sub-channel size for data at different coding rates, as a function of the data rate 32 n kbit/s (where n is an integer ≥ 1)

##Field Structure