5.2 Code block segmentation and code block CRC attachment
38.2123GPPMultiplexing and channel codingNRRelease 17TS
5.2.1 Polar coding
The input bit sequence to the code block segmentation is denoted by 
, where 
.
if 
Number of code blocks: 
;
else
Number of code blocks: 
end if
;
for 
to 
;
end for
for 
to 
;
end for
;
for 
to 
for 
to 
;
;
end for
The sequence 
is used to calculate the CRC parity bits 
according to Clause 5.1 with a generator polynomial of length 
.
for 
to 
;
end for
end for
The value of 
is no larger than 1706.
5.2.2 Low density parity check coding
The input bit sequence to the code block segmentation is denoted by 
, where 
. If 
is larger than the maximum code block size 
, segmentation of the input bit sequence is performed and an additional CRC sequence of 
bits is attached to each code block.
For LDPC base graph 1, the maximum code block size is:
– 
.
For LDPC base graph 2, the maximum code block size is:
– 
.
Total number of code blocks C is determined by:
if 
Number of code blocks: 
else
Number of code blocks: 
.
end if
The bits output from code block segmentation are denoted by
, where 
is the code block number, and 
is the number of bits for the code block number 
.
The number of bits 
in each code block is calculated as:
;
For LDPC base graph 1,
.
For LDPC base graph 2,
if 
;
elseif 
;
elseif 
;
else
;
end if
find the minimum value of 
in all sets of lifting sizes in Table 5.3.2-1, denoted as 
, such that 
, and set 
for LDPC base graph 1 and 
for LDPC base graph 2;
The bit sequence 
is calculated as:
;
for 
to 
for 
to 
;
;
end for
if 
The sequence 
is used to calculate the CRC parity bits 
according to Clause 5.1 with the generator polynomial 
.
for 
to 
;
end for
end if
for 
to 
— Insertion of filler bits
;
end for
end for