nrPUSCHDescramble

Perform PUSCH descrambling

Since R2019a

Syntax

cw = nrPUSCHDescramble(in,nid,rnti)

cw = nrPUSCHDescramble(in,nid,rnti,nrapid)

cw = nrPUSCHDescramble(___,xInd,yInd)

Description

cw = nrPUSCHDescramble(in,nid,rnti) returns a column vector of soft bits resulting from the inverse operation of physical uplink shared channel (PUSCH) scrambling from TS 38.211 Section 6.3.1.1 [1]. in is a vector of scrambled soft bits, nid is the scrambling identity, and rnti is the radio network temporary identifier (RNTI) of the user equipment (UE). When you use this syntax, the function descrambles only the data bits because the placeholder bit locations for any uplink control information (UCI), if present, are unknown in this case.

cw = nrPUSCHDescramble(in,nid,rnti,nrapid) specifies random access preamble index nrapid to initialize the scrambling sequence for msgA on PUSCH, as defined in Release 16 of TS 38.211 Section 6.3.1.1.

cw = nrPUSCHDescramble(___,xInd,yInd) specifies UCI placeholder X bit locations xInd and UCI placeholder Y bit locations yInd in addition to the input arguments in any of the previous syntaxes. The inputs xInd and yInd are 1-based column vectors within the codeword and indicate the respective placeholder locations.

Examples

Perform PUSCH Descrambling

Create a random sequence of binary values corresponding to a codeword containing 3000 bits. Perform PUSCH scrambling initialized with the specified physical layer cell identity number and RNTI.

cw = randi([0 1],3000,1);
ncellid = 42;
rnti = 101;
scrambled = nrPUSCHScramble(cw,ncellid,rnti);

Modulate the scrambled data using 16-QAM modulation. Demodulate the result.

modulation = '16QAM';
sym = nrSymbolModulate(scrambled,modulation);
demod = nrSymbolDemodulate(sym,modulation);

Perform PUSCH descrambling of the demodulated symbols.

descrambled = nrPUSCHDescramble(demod,ncellid,rnti)

descrambled = 3000×1
1010 ×

   -1.6000
   -1.6000
    0.4000
   -0.4000
   -1.6000
    0.4000
    0.4000
   -0.4000
   -0.4000
   -0.4000
      ⋮

Perform hard decision on the soft metric.

rxcw = double(descrambled<0)

rxcw = 3000×1

     1
     1
     0
     1
     1
     0
     0
     1
     1
     1
      ⋮

Compare the result with the original codeword.

isequal(cw,rxcw)

ans = logical
   1

Perform PUSCH Descrambling with UCI Placeholder Indices

Create a codeword for 1 bit.

cw = [1 -2 -1 -1]';

Specify the scrambling identity as 100 and radio network temporary identifier as 65,350.

nid = 100;
rnti = 65350;

Perform PUSCH scrambling that is initialized with the UCI placeholder X and Y bit locations.

xind = find(cw == -1);
yind = find(cw == -2);
scrambled = nrPUSCHScramble(cw,nid,rnti);

Modulate the scrambled data using 16-QAM scheme. Demodulate the result.

modulation = '16QAM';
sym = nrSymbolModulate(scrambled,modulation);
demod = nrSymbolDemodulate(sym,modulation);

Perform PUSCH descrambling of the demodulated symbols.

descrambled = nrPUSCHDescramble(demod,nid,rnti,xind,yind)

descrambled = 4×1
1010 ×

   -1.6000
   -1.6000
   -0.4000
   -0.4000

Compare the result with the original codeword.

isequal(descrambled(1)<0,cw(1))

ans = logical
   1

Input Arguments

in — Approximate LLR soft bits

real column vector

Approximate log-likelihood ratio (LLR) soft bits, specified as a real column vector. Sign represents scrambled hard bit.

Data Types: double | single

nid — Scrambling identity

integer from 0 to 1023

Scrambling identity, specified as an integer from 0 to 1023. nid is higher layer parameter dataScramblingIdentityPUSCH, ranging from 0 to 1023, if the higher layer parameter is configured. Otherwise, nid is physical layer cell identity number NCellID, ranging from 0 to 1007. For more information, see TS 38.211 Section 6.3.1.1.

Data Types: double

rnti — RNTI of UE

integer from 0 to 65,535

RNTI of the UE, specified as an integer from 0 to 65,535.

Data Types: double

nrapid — Random access preamble index

[] (default) | integer from 0 to 63

Random access preamble index, specified as one of these values.

• [] — Use this value to indicate that the scrambling initialization does not consider msgA on PUSCH.

• Integer from 0 to 63 — Use this value to initialize the scrambling sequence for msgA on PUSCH, as defined in Release 16 of TS 38.211 Section 6.3.1.1.

Data Types: double

xInd — X placeholder indices of UCI

column vector of positive values

X placeholder indices of the UCI, specified as a column vector of positive values. When you specify this input, the function descrambles the input codeword, in, at all locations except the X placeholder locations. A value of [] indicates no X placeholder indices.

Data Types: double

yInd — Y placeholder indices of UCI

column vector of positive values

Y placeholder indices of the UCI, specified as a column vector of positive values. The input codeword, in, at the placeholder locations, yInd, is descrambled with the previous values of the scrambling sequence. A value of [] indicates no Y placeholder indices.

Data Types: double

Output Arguments

cw — Descrambled approximate LLR soft bits

numeric column vector

Descrambled approximate LLR soft bits, returned as a numeric column vector. Sign represents descrambled hard bit.

Data Types: double | single

References

[1] 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™.

Version History

Introduced in R2019a