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ltePSCCHPRBS

PSCCH pseudorandom binary scrambling sequence

Syntax

seq = ltePSCCHPRBS(n)
seq = ltePSCCHPRBS(n,mapping)

Description

example

seq = ltePSCCHPRBS(n) returns a column vector containing the first n outputs of the PSCCH pseudorandom binary scrambling sequence (PRBS).

The scrambling sequence generated should be applied to the coded PSCCH data carried by the associated subframe. The PRBS sequence generator used is initialized with cinit = 510.

example

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

Examples

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

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

codeword = ones(288,1);
pscchPrbs = ltePSCCHPRBS(length(codeword));
scrambled = xor(pscchPrbs,codeword);

Descramble a received PSCCH codeword.

Scramble PSCCH Codeword

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

  • Modulate the logical scrambled data.

codeword = ones(288,1);
pscchPrbs = ltePSCCHPRBS(length(codeword));
scrambled = xor(pscchPrbs,codeword);

txsym = lteSymbolModulate(scrambled,'QPSK');

Descramble Recovered Codeword

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

  • Generate the PSCCH 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.

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

scramblingSeq = ltePSCCHPRBS(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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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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PSCCH pseudorandom scrambling sequence, returned as a column vector. seq contains the first n outputs of the physical control channel (PCCH) 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.

Introduced in R2016b

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