QPSK = 4-PSK. Each symbol in QPSK consists of 2 bits.
MATLAB Script
clc;
clear all;
close all;
M = 4; % constellation size = 4
data = randi([0 (M-1)], 2520, 1);
Phase = 0;
QPSKData=pskmod(data,M,Phase);
scatterplot(QPSKData);
title('constellation diagram of qpsk')
clear all;
close all;
M = 4; % constellation size = 4
data = randi([0 (M-1)], 2520, 1);
Phase = 0;
QPSKData=pskmod(data,M,Phase);
scatterplot(QPSKData);
title('constellation diagram of qpsk')
Output
Constellation points are 1+0.j, 0+j, -1+0.j, 0-j