Communication System - QAM

 clear;

clc;
close;
T=3;//One Symbol period
t=0:0.01:T;// Sampling Matrix for one symbol period
f=1/T;// Carrier frequency (cycles per bit period)
I=[000001010011100101110111];//data stream giving tribits equivalent to 0,1,2,3,4,5,6,7
//Polar NRZ Converter
I_PNRZ=[]//empty matrix for Polar NRZ data
for n=1:length(I)
if I(n)==0 then
I_PNRZ=[I_PNRZ,-1]
else
I_PNRZ=[I_PNRZ,1]
end
end
I_Carrier=sqrt(2/T)*cos(2*3.14*f*t);// In phase carrier
Q_Carrier=sqrt(2/T)*sin(2*3.14*f*t);// Quadrature phase carrier
//Generation of 8-QAM Waveform
z=0;//Starting point of plot on x-axis
for n=1:3:length(I_PNRZ)
Q_Bit=I_PNRZ(n) //Set Q Bit Value
I_Bit=I_PNRZ(n)+1 //Set I Bit Value
C_Bit=I_PNRZ(n)+2//Set C Bit Value
if C_Bit==-1 then//Set PAM, Product of C with I or Q
QC=0.5*Q_Bit//Set half amplitude
IC=0.5*I_Bit//Set half amplitude
else
QC=Q_Bit//Set full amplitude
IC=I_Bit//Set full amplitude
end
subplot(3,1,1)//QC Plot
a=gca();
a.data_bounds=[0,-1.5;length(I_PNRZ),1.5];
a.x_location="origin";
a.grid=[1,1];
title('Q-PAM')
plot((t+z),Q_Carrier*QC);//Q_Carrier * Q-PAM (Q Balance Modulator)
plot((t+z),QC,'r');//Q-PAM Output
subplot(3,1,2)//IC Plot
a=gca();
a.data_bounds=[0,-1.5;length(I_PNRZ),1.5];
a.x_location="origin";
a.grid=[1,1];
title('I-PAM')
plot((t+z),I_Carrier*IC);//I_Carrier * I-PAM (I Balance Modulator)
plot((t+z),IC,'r');//I-PAM Output
subplot(3,1,3)//8-QAM Plot
a=gca();
a.data_bounds=[0,-1.5;length(I_PNRZ),1.5];
a.x_location="origin";
a.grid=[1,1];
title('8-QAM')
plot((t+z),(I_Carrier*IC)+(Q_Carrier*QC));//I-PAM + Q-PAM (Adder)
plot((t+z),I_Carrier,'r');//I Carrier for reference
plot(((t/3)+z),Q_Bit,'c');//Q Bit for reference
plot(((t/3)+1+z),I_Bit,'b');//I Bit for reference
plot(((t/3)+2+z),C_Bit,'m');//C Bit for reference
z=z+3;//Move starting point of plot on x-axis by 3 bits (1 symbol) period
end