Page 770 - 5G Basics - Core Network Aspects

2 Transport aspects

NOTE 2 – The example applies to DMT symbols in the normal operation interval (NOI). The bit loadings in the RMC
tone set (RTS) may be different in the RMC symbol than in the data symbols.
NOTE 3 – In the discontinuous operation interval (DOI), the pre-ordered tone table t1 is identical to the original tone
ordering table t.

If SRA changes the number or indices of 0-bit subcarriers or 1-bit subcarriers, tables t' and b' shall be
recalculated from the updated table b and the original table t. Upon FRA, table t' shall not be recalculated,
and the ordering of table b' shall not change (see clause 13.3.1.1).
Trellis coding is performed according to the re-ordered bit allocation table b' and re-ordered tone table t'
(see clause 10.2.1.3). Constellation mapping is performed according to the re-ordered tone table t', with
the number of bits per subcarrier as defined by the original bit allocation table b (see clause 10.2.1.4).
Following reception of the tables br and gr, the transmit FTU shall calculate, according the same rules
described above for the table b and g, a re-ordered bit allocation table br' and a re-ordered tone table tr'
from the original tables br and first NSCR entries of the pre-ordered table t1. During the RMC symbol, trellis
coding of the LRMC RMC bits is performed according to the re-ordered bit allocation table br' and a
re-ordered tone table tr'. Constellation mapping is performed according to the re-ordered tone table tr',
with the number of bits per subcarrier as defined by the original bit allocation table br (see clause 10.2.1.4).
Both the transmit and the receive FTUs shall also calculate, according the same rules described above for
the table b and g, a re-ordered bit allocation table bd' and a re-ordered tone table td' from the original
tables b and last NSC-NSCR entries of table t1. During the RMC symbol, trellis coding of the LDR data bits is
performed according to the re-ordered bit allocation table bd' and a re-ordered tone table td'.
Constellation mapping is performed according to the re-ordered tone table td', with the number of bits per
subcarrier as defined by the original bit allocation table b (see clause 10.2.1.4).
10.2.1.3 Trellis coding

The trellis encoder shall use block processing of Wei's 16-state 4-dimensional trellis code (see Figure 10-7).
For data symbols, the LD bits associated with a normal data frame shall be loaded onto one data symbol.
Trellis encoder encodes the incoming LD bits into LD' bits, matching the re-ordered bit allocation table b'.
The values of LD and LD' relate as:

 NCONEBIT 
 NCUSED  
L ' b '  b  L  ceiling  2   4
 i
D
 i
D
 2  

 
where NCUSED is the number of subcarriers actually used for data transmission (with bi > 0). The added
4 bits are to return the trellis to the zero state at the end of the symbol, as described in clause 10.2.1.3.2.
The ratio (LD'-LD)/LD determines the overhead introduced by the trellis code.
For RMC symbols, the LR bits associated with an RMC data frame shall be loaded onto one RMC symbol.
Trellis encoder first encodes the incoming LRMC bits that carry the RMC data into LRMC' bits, matching the
re-ordered bit allocation table bRMC'.
The values of LRMC and LRMC' relate as:



'
L RMC '  b RMC i   b RMC i  L RMC  ceiling  NCUSED RMC   4
 2 
where NCUSEDRMC is the number of subcarriers actually used for transmission of RMC bits (with bRMC-i > 0) ,
and bRMC-i is the bit allocation on the RMC subcarriers. The added 4 bits are to return the trellis to the zero
state at the end of the RMC part of the RMC symbol.

NOTE – bRMC is referred to as br in clause 10.2.1.2.
Further, the trellis encoder encodes the incoming LDR bits into LDR' bits, matching the re-ordered bit
allocation table bDR'. If the number of non-zero entries in bDR’ is greater or equal to 4, the values of LDR and

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