# wlanReferenceSymbols

Find reference symbols of constellation diagram

## Description

example

refSym = wlanReferenceSymbols(mod) returns the reference symbols of the constellation diagram for the specified modulation scheme.

example

refSym = wlanReferenceSymbols(mod,phase) returns reference symbols with counterclockwise rotation for the specified modulation scheme.

refSym = wlanReferenceSymbols(cfg) returns the reference symbols used in the data field of a single-user (SU) transmission or a recovered high-efficiency (HE) transmission parameterized by the configuration object cfg.

example

refSym = wlanReferenceSymbols(cfg,userNumber) returns the reference symbols used in the data field for the user specified by userNumber in a multiuser (MU) transmission specified by MU configuration object cfg.

## Examples

collapse all

Fine reference symbols for a quadrature phase-shift keying (QPSK) modulation scheme and plot the resulting constellation.

Generate noisy QPSK symbols.

sym =  awgn(qammod(randi([0 3],100,1),4)/sqrt(2),20);

Find the reference symbols.

refSym =  wlanReferenceSymbols('QPSK');

Plot the constellation diagram.

figure;
plot(sym,'b.');
hold on;
plot(refSym,'ro');
title('Noisy QPSK Constellation with Reference Symbols');
legend('Noisy symbols','Reference symbols','Location','South');

Find reference symbols for a chosen modulation scheme and counterclockwise rotation.

Reference Symbols for $\frac{\pi }{2}$-BPSK

Specify a $\frac{\pi }{2}$-BPSK modulation scheme and a counterclockwise rotation of $\frac{\pi }{6}$.

mod = 'pi/2-BPSK';
phase =  pi/6;

Find the reference symbols for the chosen modulation and rotation.

refSym = wlanReferenceSymbols(mod,phase);

Display the reference symbols on a constellation diagram.

figure;
plot(refSym,'b*');
hold on;
title('Reference Symbols for $\frac{\pi}{2}$-BPSK','Interpreter','latex');
legend('Reference symbols');

Reference Symbols for $\frac{\pi }{2}$-16-QAM

Specify a $\frac{\pi }{2}$-16-QAM modulation scheme and a counterclockwise rotation of $\frac{\pi }{3}$.

mod = 'pi/2-16QAM';
phase =  pi/3;

Find the reference symbols for the chosen modulation and rotation.

refSym = wlanReferenceSymbols(mod,phase);

Display the reference symbols on a constellation diagram.

figure;
plot(refSym,'b*');
hold on;
title('Reference Symbols for $\frac{\pi}{2}$-16-QAM','Interpreter','latex');
legend('Reference symbols');

Plot the reference constellation for a user in a very-high-throughput (VHT) multiuser configuration.

Create a VHT-format configuration object, setting channel bandwidth, number of users, group identifier, number of transmit antennas, number of space-time streams, and modulation and coding schemes.

cfg = wlanVHTConfig('ChannelBandwidth','CBW20','NumUsers',2,'GroupID',2, ...
'NumTransmitAntennas',2,'NumSpaceTimeStreams',[1 1],'MCS',[8 4]);

Find the reference symbols for both users and plot the constellations.

refSym1 = wlanReferenceSymbols(cfg,1);
refSym2 = wlanReferenceSymbols(cfg,2);
figure;
plot(refSym1,'b*'); hold on
plot(refSym2,'ro');
title('Reference Constellations for Both Users')
legend('User 1','User 2','Location','bestoutside');

## Input Arguments

collapse all

Modulation scheme, specified as one of these values.

• 'BPSK' — Binary phase-shift keying (BPSK)

• 'pi/2-BPSK' — π/2-BPSK

• 'QPSK' — Quadrature phase-shift keying (QPSK)

• 'pi/2-QPSK' — π/2-QPSK

• '16QAM' — 16-point quadrature amplitude modulation (16-QAM)

• 'pi/2-16QAM' — π/2-16-QAM

• '64QAM' — 64-QAM

• 'pi/2-64QAM' — π/2-64-QAM

• '256QAM' — 256-QAM

• '1024QAM' — 1024-QAM

• '4096QAM' — 4096-QAM

Data Types: char | string

Counterclockwise rotation, in radians, specified as a real-valued scalar or real-valued row vector. To return reference symbols for different phases, specify phase as a row vector in which each element represents a chosen phase.

Data Types: double

Physical layer (PHY) format configuration, specified as one of these objects: wlanHESUConfig, wlanHEMUConfig, wlanHETBConfig, wlanHERecoveryConfig, wlanDMGConfig, wlanS1GConfig, wlanVHTConfig, wlanHTConfig, or wlanNonHTConfig.

Number assigned to user of interest, specified as a positive integer in the interval [1, Nu], where Nu is the number users in the transmission.

This argument is required when you specify the cfg input as an object of type wlanHEMUConfig, wlanS1GConfig, or wlanVHTConfig.

If cfg is a wlanHEMUConfig object, Nu is equal to the number of elements in the value of its User property. If cfg is a wlanS1GConfig or wlanVHTConfig object, Nu is equal to the value of its NumUsers.

#### Dependencies

This argument applies only when the cfg input is an object of type wlanHEMUConfig, wlanS1GConfig, or wlanVHTConfig.

Data Types: double

## Output Arguments

collapse all

Reference symbols of constellation diagram, returned as a complex-valued column vector.

Data Types: double
Complex Number Support: Yes

## Version History

Introduced in R2019a