nrULSCH

Apply UL-SCH encoder processing chain

Description

The nrULSCH System object™ applies the uplink shared channel (UL-SCH) encoder processing chain to one or two transport blocks. The UL-SCH encoding process consists of cyclic redundancy check (CRC), code block segmentation and CRC, low-density parity-check (LDPC) encoding, rate matching, and code block concatenation. The object implements these aspects of TS 38.212 [1]:

• Sections 6.2.1: Transport block CRC attachment

• Sections 6.2.2: LDPC base graph selection

• Sections 6.2.3: Code block segmentation and code block CRC attachment

• Sections 6.2.4: Channel coding of UL-SCH

• Sections 6.2.5: Rate matching

• Sections 6.2.6: Code block concatenation

To apply the UL-SCH encoder processing chain:

1. Create the nrULSCH object and set its properties.

2. Call the object with arguments, as if it were a function.

To learn more about how System objects work, see What Are System Objects?

Creation

Syntax

encUL = nrULSCH

encUL = nrULSCH(Name,Value)

Description

encUL = nrULSCH creates a UL-SCH encoder System object.

encUL = nrULSCH(Name,Value) creates the object with properties set by using one or more name-value pairs. Enclose the property name inside quotes, followed by the specified value. Unspecified properties take default values.

Example: For example, nrULSCH('MultipleHARQProcesses',true) creates the object and enables multiple hybrid automatic repeat-request (HARQ) processes.

Properties

Unless otherwise indicated, properties are nontunable, which means you cannot change their values after calling the object. Objects lock when you call them, and the release function unlocks them.

If a property is tunable, you can change its value at any time.

For more information on changing property values, see System Design in MATLAB Using System Objects.

MultipleHARQProcesses — Enable multiple HARQ processes

0 or false (default) | 1 or true

Enable multiple HARQ processes, specified as one of these values:

• 0 (false) — The object uses a single HARQ process.

• 1 (true) — The object uses multiple HARQ processes, at most 32.

In both cases, to enable retransmissions when a failure occurs, the object buffers the input data.

Data Types: logical | double

CBGTransmission — Enable support for CBG-based transmission

0 or false (default) | 1 or true

Since R2025a

Enable support for transmission based on code block groups (CBGs), specified as one of these values:

• 0 (false) — Disable support for CBG-based transmission. The object uses transmission based on transport blocks (TBs).

• 1 (true) — Enable support for CBG-based transmission. The object takes an additional input argument, cbgtiIn, that specifies CBG transmission information used with the current transmission. If the number of rows in cbgtiIn is 1, the processing is equivalent to the TB-based transmission.

Data Types: logical | double

TargetCodeRate — Target code rate

0.5137 (default) | real number

Target code rate, specified as a real number in the interval (0, 1). The default value corresponds to 526/1024.

Tunable: Yes

Data Types: double

LimitedBufferRateMatching — Enable limited buffer rate matching

false (default) | true

Enable limited buffer rate matching, specified as false or true. When set to false, the size of the internal buffer used for rate matching is the full coded length of each code block. When set to true, you can specify the size of the internal buffer used for rate matching by setting the LimitedBufferSize property.

Tunable: Yes

Data Types: logical

LimitedBufferSize — Limited buffer size

25344 (default) | positive integer

Limited buffer size used for rate matching, specified as a positive integer. The default value corresponds to 384×66, which is the maximum coded length of a code block. The default value implies no limit on the buffer size.

Tunable: Yes

Dependencies

To enable this property, set LimitedBufferRateMatching to true.

Data Types: double

UniformCellOutput — Enable cell output format

0 (default) | 1

Since R2024a

Enable cell output format, irrespective of the number of codewords, specified as one of these logical values:

• 0 (false) — This option corresponds to the default behavior of the object in which the codedBits output is returned as a column vector for a single codeword or as a cell array for two codewords.

• 1 (true) — The object returns codedBits as a cell array irrespective of the number of codewords.

Data Types: logical | double

TransportBlockSizesPerProcess — Transport block sizes per each HARQ process

1-by-2 array of nonnegative integers | 32-by-2 array of nonnegative integers

Since R2025a

Transport block sizes per each HARQ process, returned as one of these values:

• 1-by-2 array of nonnegative integers for a single HARQ process (MultipleHARQProcesses = false)

• 32-by-2 array of nonnegative integers for multiple HARQ processes (MultipleHARQProcesses = true)

The array rows correspond to HARQ processes. The two array columns correspond to the two possible transport blocks.

This property accounts for the transport blocks that you load into the encoder using the setTransportBlock function.

Data Types: double

Usage

Syntax

codedBits = encUL(mod,nLayers,outlen,rv)

codedBits = encUL(___,harqID)

codedBits = encDL(___,cbgtiIn)

[___,cbgtiOut] = encDL(___)

Description

codedBits = encUL(mod,nLayers,outlen,rv) applies the UL-SCH encoder processing chain to one or two transport blocks. The object returns the encoded, rate-matched, and concatenated code blocks as one or two codewords of length outlen. Before you call this object, you must load the transport blocks into the object by using the setTransportBlock object function. mod specifies the modulation scheme. nLayers specifies the number of transmission layers. rv specifies the redundancy version of the transmission.

codedBits = encUL(___,harqID) specifies the HARQ process number harqID used with the current transmission in addition to the input arguments in the previous syntax. To use this syntax, set the MultipleHARQProcesses property to true. When the property is set to false, the object uses HARQ process number 0.

codedBits = encDL(___,cbgtiIn) specifies the CBG transmission information used with the current transmission in addition to the input arguments in any of the previous syntaxes. To use this syntax, set the CBGTransmission property to true. (since R2025a)

[___,cbgtiOut] = encDL(___) also returns the CBG transmission information after the encoding in addition to the input and output arguments in any of the previous syntaxes. (since R2025a)

Input Arguments

mod — Modulation scheme

'pi/2-BPSK' | 'QPSK' | '16QAM' | '64QAM' | '256QAM' | string array (since R2024a) | cell array of character vectors (since R2024a)

Modulation scheme, specified as 'pi/2-BPSK', 'QPSK', '16QAM', '64QAM', '256QAM', a string array, or a cell array of character vectors. This modulation scheme determines the modulation type and number of bits used per modulation symbol. For two transport blocks, the modulation scheme applies to both blocks. Alternatively, you can specify different modulation schemes for each transport block by using a string array or a cell array of character vectors.

Modulation Scheme	Number of Bits Per Symbol
'pi/2-BPSK'	1
'QPSK'	2
'16QAM'	4
'64QAM'	6
'256QAM'	8

Data Types: char | string

nLayers — Number of transmission layers

integer from 1 to 8

Number of transmission layers, specified as an integer from 1 to 8. For nLayers > 4, the object expects two transports blocks.

Data Types: double

outlen — Output codeword length

nonnegative integer | 1-by-2 vector of nonnegative integers (since R2024a)

Output codeword length, in bits, specified as a nonnegative integer or a 1-by-2 vector of nonnegative integers. If you specify outlen as a scalar, the object applies scalar expansion when processing two transport blocks. To specify a different codeword length for each transport block, specify outlen as a vector.

The actual output length is a multiple of the product of the number of bits per symbol and the number of transmission layers. For example, for 64-QAM and 1 transmission layer, if you specify 16 for outlen, the actual output length is 6x1x3 = 18.

Data Types: double

rv — Redundancy version

integer from 0 to 3 | 1-by-2 vector of integers from 0 to 3 (since R2024a)

Redundancy version, specified as one of these options:

• Integer from 0 to 3 — Use this option to specify the redundancy version for a single transport block.

• 1-by-2 vector of integers from 0 to 3 — Use this option to specify the redundancy version for two transport blocks.

Data Types: double

harqID — HARQ process number

0 (default) | integer from 0 to 31

HARQ process number, specified as an integer from 0 to 31. To specify a value other than 0, set the MultipleHARQProcesses object property to true.

Data Types: double

cbgtiIn — CBG transmission information

N-by-1 or N-by-2 array of binary values

Since R2025a

CBG transmission information used in the current transmission, specified as an N-by-1 or N-by-2 binary array. N is the maximum number of CBGs defined by the higher-layer parameter maxCodeBlockGroupsPerTransportBlock. Alternatively, N can also be 1, in which case the object uses TB-based transmission. Array values 1 and 0 indicate whether the corresponding CBG in the corresponding transport block is present or absent in the current transmission, respectively.

The array columns correspond to transport blocks. If you specify an N-by-1 column vector in case of two transport blocks (nLayers > 4), the object applies the same CBG information to both transport blocks. If you specify an N-by-2 array in case of one transport block (nLayers <= 4), the object ignores the second column.

Note

To use this argument, set the CBGTransmission property to true.

Data Types: double

Output Arguments

codedBits — One or two UL-SCH codewords

binary column vector | cell array of two binary column vectors (since R2024a)

One or two UL-SCH codewords, returned as a binary column vector or a cell array of two binary column vectors. A codeword is the encoded, rate-matched, and concatenated code blocks obtained by processing one transport block. Specify the length of the codewords by using the outlen input argument.

Data Types: int8

cbgtiOut — CBG transmission information after transmission

N-by-1 or N-by-2 array of binary values

Since R2025a

CBG transmission information after the transmission, returned as an N-by-1 or N-by-2 binary array. In object calls that specify the cbgtiIn input, N is the number of rows in cbgtiIn. In all other calls, N is 1. Array values 1 and 0 indicate whether the corresponding CBG in the corresponding transport block has been transmitted or not in the current transmission, respectively.

For one transport block (nLayers <= 4), cbgtiOut has the same size as cbgtiIn. For two transport blocks (nLayers > 4), cbgtiOut is of size N-by-2, irrespective of the size of cbgtiIn.

Data Types: double

Object Functions

To use an object function, specify the System object as the first input argument. For example, to release system resources of a System object named obj, use this syntax:

release(obj)

Specific to nrULSCH

getTransportBlock	Get transport block from UL-SCH or DL-SCH encoder
setTransportBlock	Load transport block into UL-SCH or DL-SCH encoder

Common to All System Objects

step	Run System object algorithm
clone	Create duplicate System object
isLocked	Determine if System object is in use
release	Release resources and allow changes to System object property values and input characteristics
reset	Reset internal states of System object

Examples

Connect UL-SCH Encoder and Decoder Back to Back

Generate a random sequence of binary values corresponding to one transport block of length 5120.

trBlkLen = 5120;
trBlk = randi([0 1],trBlkLen,1,'int8');

Create and configure an UL-SCH encoder System object with the specified target code rate.

targetCodeRate = 567/1024;
encUL = nrULSCH;
encUL.TargetCodeRate = targetCodeRate;

Load the transport block into the UL-SCH encoder.

setTransportBlock(encUL,trBlk);

Call the encoder with 64-QAM modulation scheme, 1 transmission layer, an output length of 10,240 bits, and redundancy version 0. The encoder applies the UL-SCH processing chain to the transport block loaded into the object.

mod = '64QAM';
nLayers = 1;
outlen = 10240;
rv = 0;
codedTrBlock = encUL(mod,nLayers,outlen,rv);

Create and configure an UL-SCH decoder System object.

decUL = nrULSCHDecoder;
decUL.TargetCodeRate = targetCodeRate;
decUL.TransportBlockLength = trBlkLen;

Call the UL-SCH decoder on the soft bits representing the encoded transport block. Use the configuration parameters specified for the encoder. The error flag in the output indicates that the block decoding does not have errors.

rxSoftBits = 1.0 - 2.0*double(codedTrBlock);
[decbits,blkerr] = decUL(rxSoftBits,mod,nLayers,rv)

decbits = 5120×1 int8 column vector

   1
   1
   0
   1
   1
   0
   0
   1
   1
   1
   0
   1
   1
   0
   1
      ⋮

blkerr = logical
   0

Verify that the transmitted and received message bits are identical.

isequal(decbits,trBlk)

ans = logical
   1

UL-SCH Encoding with Multiple HARQ Processes

Generate a random sequence of binary values corresponding to one transport block of length 5120.

trBlkLen = 5120;
trBlk = randi([0 1],trBlkLen,1,'int8');

Create and configure an UL-SCH encoder System object for use with multiple HARQ processes.

encUL = nrULSCH;
encUL.MultipleHARQProcesses = true;

Load the transport block into the UL-SCH encoder, specifying HARQ process number 2.

harqID = 2;
setTransportBlock(encUL,trBlk,harqID);

Call the encoder with QPSK modulation scheme, 3 transmission layers, an output length of 10,002 bits, and redundancy version 3. The encoder applies the UL-SCH processing chain to the transport block loaded into the object for HARQ process number 2.

mod = 'QPSK';
nLayers = 3;
outlen = 10002;
rv = 3;
codedTrBlock = encUL(mod,nLayers,outlen,rv,harqID);

Verify that the encoded transport block has the required number of bits.

isequal(length(codedTrBlock),outlen)

ans = logical
   1

References

[1] 3GPP TS 38.212. “NR; Multiplexing and channel coding.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network.

[2] 3GPP TS 38.211. “NR; Physical channels and modulation.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network.

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

See System Objects in MATLAB Code Generation (MATLAB Coder).

GPU Arrays

Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™. (since R2025a)

The nrULSCH System object supports GPU arrays with these usage notes and limitations:

• To return the codedBits output on the GPU, specify the transport block as a gpuArray (Parallel Computing Toolbox) object in the setTransportBlock function call.

For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Version History

Introduced in R2019a

R2025a: Enable support for CBG-based transmission

The nrULSCH object adds support for CBG-based transmission. To enable this support, set the CBGTransmission object property to true, then call the object with additional CBG transmission-related input and output arguments.

R2025a: Obtain transport block sizes

Use the TransportBlockSizesPerProcess read-only property to obtain the transport block sizes per each HARQ process.

R2025a: GPU array support

The nrULSCH System object adds support for GPU arrays. For more information, see GPU Arrays.

R2024b: LimitedBufferRateMatching and LimitedBufferSize properties become tunable

The LimitedBufferRateMatching and LimitedBufferSize properties are now tunable.

R2024a: Release 18 support for two-codeword encoding

The object adds support for two-codeword encoding, as defined in Release 18 of TS 38.211 Section 6.2.

R2024a: Configure format of outputs

To return the codedBits output as a cell array irrespective of the number of codewords, set the UniformCellOutput property to true.

R2023a: Release 17 updates for 32 HARQ processes

The object now supports up to 32 HARQ processes.