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wlanConstellationMap

Constellation mapping

Syntax

y = wlanConstellationMap(bits,numBPSCS)
y = wlanConstellationMap(bits,numBPSCS,phase)

Description

example

y = wlanConstellationMap(bits,numBPSCS) maps the input sequence bits using the number of coded bits per subcarrier per spatial stream, numBPSCS, to one of the following modulations:

  • BPSK, QPSK, 16QAM, or 64QAM, as per IEEE® 802.11™-2012, Section 18.3.5.8

  • 256QAM, as per IEEE 802.11ac™-2012, Section 22.3.10.9.1

  • 1024QAM, as per IEEE 802.11-16/0922r2

The constellation mapping is performed column-wise.

example

y = wlanConstellationMap(bits,numBPSCS,phase) rotates the constellation points counterclockwise by the number of radians specified in phase.

Examples

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Perform a 256QAM mapping, as defined in IEEE® 802.11ac™-2013 Section 22.3.10.9.1.

Create the sequence of data bits.

bits = randi([0 1],416,1,'int8');

Perform the constellation mapping on the data bits with a 256QAM modulation.

numBPSCS = 8;
mappedData = wlanConstellationMap(bits,numBPSCS);

The size of the output returned by this modulation equals the size of the input sequence divided by eight.

size(mappedData)
ans = 

    52     1

Perform a -BPSK mapping on a sequence of data bits as defined in IEEE® 802.11ad™-2012 Section 21.6.3.2.4.

Create the sequence of data bits.

bits = randi([0 1],512,1);

Perform the BPSK mapping on the data bits with a rotation of radians. Note that the size of the constellation rotation phase is equal to the size of input sequence.

numBPSCS = 1;
phase = pi*(0:size(bits,1)/numBPSCS-1).'/2;
mappedData = wlanConstellationMap(bits,numBPSCS,phase);

As we performed a BPSK mapping, the number of symbols per bit is one, therefore the size of the output is equal to the size of the original sequence.

size(mappedData)
ans = 

   512     1

Display the modulated signal constellation using the scatterplot function.

scatterplot(mappedData);

Perform BPSK and QBPSK demapping for different OFDM symbols for the VHT-SIG-A field by using a soft demodulation. The mapping is defined in IEEE® 802.11ac™-2013 Section 22.3.8.3.3 for the VHT-SIG-A field.

Create the sequence of data bits. Place the two OFDM symbols in columns.

bits = randi([0 1],48,2,'int8');

Perform constellation mapping on the data bits. Specify the size of constellation rotation phase as the number of columns in the input sequence. The first column is mapped with a BPSK modulation. The second column is modulated with a QBPSK modulation.

numBPSCS = 1;
phase = [0 pi/2];
mappedData = wlanConstellationMap(bits,numBPSCS,phase);

Display the modulated signal constellation by using the scatterplot function. The first plot shows the data after the BPSK modulation, and the second plot shows the QBPSK-modulated symbols.

scatterplot(mappedData(:,1))

scatterplot(mappedData(:,2))

Input Arguments

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Input sequence of bits to map into symbols, specified as a binary vector, matrix, or multidimensional array.

Data Types: double | int8

Number of coded bits per subcarrier per spatial stream, specified as log2(M), where M is the modulation order. Therefore, numBPSCS must equal:

  • 1 for a BPSK modulation

  • 2 for a QPSK modulation

  • 4 for a 16QAM modulation

  • 6 for a 64QAM modulation

  • 8 for a 256QAM modulation

  • 10 for a 1024QAM modulation

Example: 4

Data Types: double

Constellation rotation in radians, specified as a scalar, vector, or multidimensional array. The size of phase must be compatible with the size of the input bits. phase and bits have compatible sizes if, for each corresponding dimension, the dimension sizes are either equal or one of them is 1. When one of the dimensions of bits is equal to 1, and the corresponding dimension of phase is larger than 1, then the output dimensions have the same size as the dimensions of phase.

Example: pi*(0:size(bits,1)/numBPSCS-1).'/2;

Data Types: double

Output Arguments

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Mapped symbols, returned as a complex vector, matrix, or multidimensional array. y has the same size as bits, except for the number of rows, which is equal to the number of rows of bits divided by numBPSCS.

Extended Capabilities

Introduced in R2017b

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