LDPC code block desegmentation and CRC decoding
concatenates the input code block segments
err] = nrCodeBlockDesegmentLDPC(
cbs into a single output
blk of length
blklen. The function
validates the data dimensions of the input
cbs based on the specified
base graph number
bgn and output block length
blklen. The function removes any filler bits and type-24B cyclic
redundancy check (CRC) bits present in the input
cbs. The output
err is the result of the type-24B CRC decoding (if applicable). This
process is the inverse of the low-density parity-check (LDPC) code block segmentation
specified in TS 38.212 Section 5.2.2  and implemented in
Back-to-Back LDPC Code Block Segmentation and Desegmentation
Perform code block segmentation of a random sequence of binary input data.
bgn = 1; blklen = 10000; cbs = nrCodeBlockSegmentLDPC(randi([0 1],blklen,1),bgn);
When the base graph number is 1, segmentation occurs whenever the input length is greater than 8448. The input data of length 10000 is split into two code block segments of length 5280. The code block segments have filler bits and CRC attached.
ans = 1×2 5280 2
Concatenate the code block segments.
[blk,err] = nrCodeBlockDesegmentLDPC(cbs,bgn,blklen);
The concatenated result is of the same size as the original input with CRC and filler bits removed.
blkSize = size(blk)
blkSize = 1×2 10000 1
Verify if the CRC decoding was successful by checking the error vector.
err = 1x2 uint32 row vector 0 0
Display Index Mapping of LDPC Code Block Desegmentation
Create a matrix representing two code block segments. Each element contains the linear index of that element within the matrix.
cbs = reshape([1:10560]',,2);
Concatenate the code block segments using the specified base graph number and output block length.
bgn = 1; blklen = 10000; blk = nrCodeBlockDesegmentLDPC(cbs,bgn,blklen);
To see how the input maps onto the output, plot code block segment indices relative to the corresponding indices in the concatenated input. In each code block segment, the last 280 bits represent CRC and filler bits. These additional bits are removed from the recovered data.
plot(blk); xlabel('Code Block Bit Indices'); ylabel('Recovered Data Bit Indices'); title('Code Block Desegmentation Operation');
cbs — Code block segments
Code block segments, specified as a real matrix. A matrix with only one column corresponds to one code block segment without CRC bits appended. If you specify a matrix with more than one column, each column in the matrix corresponds to a separate code block segment with type-24B CRC bits appended. In both cases, the code block segments can contain filler bits.
bgn — Base graph number
Base graph number, specified as
blklen — Output block length
blk — Concatenated data block
empty vector | real column vector
err — CRC error
empty vector | vector of nonnegative integers
CRC error, returned as one of these values:
Vector of nonnegative integers — If
cbshas more than one column,
errcontains the CRC error bits obtained from decoding the type-24B CRC bits in each code block segment. The length of
erris equal to the number of code block segments (number of columns in the input
 3GPP TS 38.212. “NR; Multiplexing and channel coding.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network.