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ltePSBCHPRBS

PSBCH pseudorandom binary scrambling sequence

Syntax

seq = ltePSBCHPRBS(ue,n)
seq = ltePSBCHPRBS(ue,n,mapping)

Description

example

seq = ltePSBCHPRBS(ue,n) returns a column vector containing the first n outputs of the PSBCH pseudorandom binary scrambling sequence (PRBS) for the specified UE settings structure.

The scrambling sequence generated should be applied to the coded PSBCH data carried by the associated subframe. The PRBS sequence generator used is initialized with cinit = ue.NSLID.

example

seq = ltePSBCHPRBS(ue,n,mapping) specifies the format of the returned sequence through the mapping input.

Examples

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Scramble a PSBCH codeword by generating the PSBCH pseudorandom binary sequence (PRBS) and applying an exclusive OR operation on the two sequences.

Create a UE configuration structure and SL-BCH codeword. Generate the required length of the PRBS and scramble the PSBCH codeword with the PRBS sequence using xor.

ue = struct('NSLID',2);
codeword = lteSLBCH(ue,ones(40,1));
psbchPrbs = ltePSBCHPRBS(ue,length(codeword));
scrambled = xor(psbchPrbs,codeword);

Descramble a received PSBCH codeword.

Scramble PSBCH Codeword

  • Create a UE configuration structure and SL-BCH codeword.

  • Generate the required length of the PRBS and scramble the PSBCH codeword with the PRBS sequence using xor.

  • Modulate the logical scrambled data.

ue = struct('NSLID',2);
codeword = lteSLBCH(ue,ones(40,1));

psbchPrbs = ltePSBCHPRBS(ue,length(codeword));
scrambled = xor(psbchPrbs,codeword);

txsym = lteSymbolModulate(scrambled,'QPSK');

Descramble Recovered Codeword

  • Add noise to transmitted symbols and demodulate received soft data.

  • Generate the PSBCH PRBS in signed form.

  • Descramble a vector of noisy demodulated symbols representing a sequence of soft bits. To do so, perform a pointwise multiplication between the PRBS sequence and the recovered data.

  • Compare the transmitted codeword to the recovered codeword.

rxsym = awgn(double(txsym),30,'measured');
softdata = lteSymbolDemodulate(rxsym,'QPSK');

scramblingSeq = ltePSBCHPRBS(ue,length(softdata),'signed');

descrambled = softdata.*scramblingSeq;

isequal(codeword,descrambled > 0)
ans =

  logical

   1

The transmitted codeword matches the hard decision on the descrambled data.

Input Arguments

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User equipment settings, specified as a parameter structure containing this field:

Physical layer sidelink synchronization identity, specified as an integer from 0 to 355. (NIDSL)

Data Types: double

Data Types: struct

Number of outputs, specified as a nonnegative integer.

Data Types: double

Output sequence formatting, specified as 'binary' or 'signed'.

  • 'binary' maps true to 1 and false to 0.

  • 'signed' maps true to –1 and false to 1.

Data Types: char

Output Arguments

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PSBCH pseudorandom scrambling sequence, returned as a column vector. seq contains the first n outputs of the physical sidelink broadcast channel (PSBCH) scrambling sequence.

  • When mapping is set to 'signed', then seq is a double column vector.

  • When mapping is set to 'binary', then seq is a logical column vector.

Data Types: logical | double

Introduced in R2016b

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