lteULSCHDecode

Uplink shared channel decoding

Syntax

[trblkout,blkcrc,stateout] = lteULSCHDecode(ue,chs,trblklen,cwin,statein)

Description

[trblkout,blkcrc,stateout] = lteULSCHDecode(ue,chs,trblklen,cwin,statein) returns the information bits trblkout decoded from the input soft LLR codewords data cwin. The UL-SCH decoder includes channel deinterleaver, rate recovery, turbo decoding, block concatenation and CRC calculations. The function also returns the type-24A transport block CRC decoding result in blkcrc and the HARQ process decoding state in stateout. The initial HARQ process state can be input via the optional statein parameter. The function is capable of processing both a single codeword or pairs of codewords, contained in a cell array, for the case of spatial multiplexing schemes transmitting two codewords. The type of the return variable trblkout is the same as input cwin. If cwin is a cell array containing one or two codewords, trblkout returns a cell array of one or two transport blocks. If cwin is a vector of soft data, trblkout returns a vector too. If decoding a pair of codewords, pairs of modulation schemes and RV indicators are required to be defined in the associated parameter fields below. This function only decodes the information bits, but supports the presence of UCI data, CQI, RI, and HARQ-ACK, in the input codeword. UCI should be demultiplexed then decoded separately.

Strictly speaking, because all the fields in structure ue are optional, it is legal for this parameter to be an empty structure.

Multiple codewords can be parameterized by two different forms of the chs structure. Each codeword can be defined by separate elements of a 1-by-2 structure array, or the codeword parameters can be combined together in the fields of a single scalar, or 1-by-1, structure. Any scalar field values apply to both codewords and a scalar NLayers is the total number. See UL-SCH Parameterization for more details.

trblklen is an input vector (one or two elements in length) defining the transport block lengths that the input code blocks should be rate recovered and decoded to.

cwin is an input parameter containing the floating point soft LLR data of the codewords to be decoded. It can either be a single vector or a cell array containing one or two vectors. If the latter, then all rate matching calculations assume that the pair were transmitting on a single PUSCH, distributed across the total number of layers defined in chs, as per TS 36.211 [1].

statein is an optional input structure array (empty or one or two elements) which can input the current decoder buffer state for each transport block in an active HARQ process. If statein is not an empty array and it contains a non-empty field CBSBuffers then this field should contain a cell array of vectors representing the LLR soft buffer states for the set of code blocks at the input to the turbo decoder i.e. after explicit rate recovery. The updated buffer states after decoding are returned in the CBSBuffers field in the output parameter stateout. The statein array would normally be generated and recycled from the stateout of previous calls to lteULSCHDecode as part of a sequence of HARQ transmissions.

trblkout is the output parameter containing the decoded information bits. It is either a single vector or a cell array containing one or two vectors, depending on the class and dimensionality of cwin.

blkcrc is an output array (one or two elements) containing the result of the type-24A transport block CRC decoding for the transport blocks.

stateout, the final output parameter, is a one element structure array containing the internal state of each transport block decoder in the fields CBSBuffers, CBSCRC, blkcrc.

The stateout array would normally be reapplied via the statein variable of subsequent lteULSCHDecode function calls as part of a sequence of HARQ retransmissions.

Examples

Decode UL-SCH

Generate and decode 2 transmissions (RV=0 then RV=2) as part of a single codeword HARQ process for the A3-3 FRC.

Initialize one subframe of an FRC A3-3 transmission. Create a codeword with RV = 0. Turn logical bits into 'LLR' data. Initialize the decoder states for the first HARQ transmission. The returned decState contains the decoder buffer state for each transport block for an active HARQ process.

nsf = 1;
frc = lteRMCUL('A3-3');
trBlkLen = frc.PUSCH.TrBlkSizes(nsf);
trBlkData = randi([0,1],trBlkLen,1);

frc.PUSCH.RV = 0;
cw = lteULSCH(frc,frc.PUSCH,trBlkData);

cw(cw == 0) = -1;

decState = [];
[rxTrBlk,~,decState] = lteULSCHDecode(frc,frc.PUSCH,trBlkLen,cw,decState);

Create a second retransmitted codeword with RV = 2. Turn logical bits into 'LLR' data. The previous transmission decoder buffer state, decState, is used as part of the sequence of active HARQ transmissions.

frc.PUSCH.RV = 2;
cWord = lteULSCH(frc,frc.PUSCH,trBlkData);

cWord(cWord == 0) = -1;

rxTrBlk = lteULSCHDecode(frc,frc.PUSCH,trBlkLen,cWord,decState);

Input Arguments

ue — UE-specific settings

scalar structure

UE-specific settings, specified as a scalar structure with the following fields. Because all the fields in structure ue are optional, this parameter can be an empty structure.

Parameter Field	Required or Optional	Values	Description
CyclicPrefixUL	Optional	'Normal' (default), 'Extended'	Cyclic prefix length.
Shortened	Optional	0 (default), 1	Option to shorten the subframe by omitting the last symbol, specified as 0 or 1. If 1, the last symbol of the subframe is not used. For subframes with possible SRS transmission, set Shortened to 1 to maintain a standard compliant configuration.

Data Types: struct

chs — UL-SCH related parameters

scalar structure

UL-SCH related parameters, specified as a scalar structure with the following fields.

Parameter Field	Required or Optional	Values	Description
Modulation	Required	'QPSK', '16QAM', '64QAM', '256QAM'	Modulation scheme associated with each transport block, specified as a character vector, or if there are two blocks, as a cell array of character vectors or string array.
NLayers	Optional	1 (default), 2, 3, 4	Number of transmission layers. (total or per codeword)
RV	Required	0, 1, 2, 3	Redundancy version indicators, specified as a vector of 1 or 2 indicators.
QdCQI	Optional	nonnegative scalar integer	Number of coded channel quality information (CQI) symbols (Q’_CQI)
QdRI	Optional	Nonnegative scalar integer 0 (default)	Number of coded symbols for RI (Q’_RI)
QdACK	Optional	nonnegative scalar integer 0 (default)	Number of coded ACK symbols (Q'_ACK)
NTurboDecIts	Optional	Scalar integer 5 (default)	Number of turbo decoder iteration cycles

Data Types: struct

trblklen — Transport block length

numeric vector

Transport block length, specified as a numeric vector (one or two elements in length) defining the transport block lengths that the input code blocks should be rate recovered and decoded to.

Data Types: double

cwin — Soft LLR codeword data

numeric column vector | cell array of one or two column vectors

Soft LLR codeword data, specified as a numeric column vector or a cell array of one or two column vectors. This argument contains the floating point soft LLR data of the codeword or codewords to be decoded. It can either be a single vector or a cell array containing one or two vectors. If a cell array, all rate matching calculations assume that the pair were transmitting on a single PUSCH, distributed across the total number of layers defined in chs, as specified in [1].

Data Types: int8 | cell

statein — Initial HARQ process state

optional | structure array

Initial HARQ process state, specified as a structure array. It can be empty or have one or two elements, which can input the current decoder buffer state for each transport block in an active HARQ process.

Data Types: double

Output Arguments

trblkout — Decoded information bits

numeric vector | cell array

Decoded information bits, returned as a numeric vector or cell array. trblkout contains decoded transport data blocks. It is either a single vector or a cell array containing one or two vectors, depending on the class and dimensionality of cwin.

Data Types: double | cell

blkcrc — Type 24A transport block CRC decoding result

0 or 1

Type 24A transport block CRC decoding result, returned as 0 or 1.

Data Types: logical

stateout — HARQ process decoding state

structure | structure array

HARQ process decoding state, returned as a one-element structure array. It contains the internal state of each transport block decoder. It contains the following parameter fields.

Parameter Field	Description	Values	Data Type
CBSBuffers	LLR soft buffer states for the set of code blocks associated with a single transport block. The buffers are positioned at the input to the turbo decoder, or after explicit rate recovery.	Cell array of numeric vectors	cell
CBSCRS	Type-24B code block set CRC decoding results	Numeric vector	int8
BLKCRC	Type-24A transport block CRC decoding error	One- or two-element numeric vector	logical

References

[1] 3GPP TS 36.211. “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network. URL: https://www.3gpp.org.

Version History

Introduced in R2014a