% Lab 06
% WiCom_1
% By Kashif Shahzad
% 01-ET-31
% 3rd July 2004
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Frequency Hopping Spread Spectrum
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
clc
clear
% Generation of bit pattern
s=round(rand(1,25)); % Generating 20 bits
signal=[];
carrier=[];
t=[0:2*pi/119:2*pi]; % Creating 60 samples for one cosine
for k=1:25
if s(1,k)==0
sig=-ones(1,120); % 120 minus ones for bit 0
else
sig=ones(1,120); % 120 ones for bit 1
end
c=cos(t);
carrier=[carrier c];
signal=[signal sig];
end
subplot(4,1,1);
plot(signal);
axis([-100 3100 -1.5 1.5]);
title('\bf\it Original Bit Sequence');
% BPSK Modulation of the signal
bpsk_sig=signal.*carrier; % Modulating the signal
subplot(4,1,2);
plot(bpsk_sig)
axis([-100 3100 -1.5 1.5]);
title('\bf\it BPSK Modulated Signal');
% Preparation of 6 new carrier frequencies
t1=[0:2*pi/9:2*pi];
t2=[0:2*pi/19:2*pi];
t3=[0:2*pi/29:2*pi];
t4=[0:2*pi/39:2*pi];
t5=[0:2*pi/59:2*pi];
t6=[0:2*pi/119:2*pi];
c1=cos(t1);
c1=[c1 c1 c1 c1 c1 c1 c1 c1 c1 c1 c1 c1];
c2=cos(t2);
c2=[c2 c2 c2 c2 c2 c2];
c3=cos(t3);
c3=[c3 c3 c3 c3];
c4=cos(t4);
c4=[c4 c4 c4];
c5=cos(t5);
c5=[c5 c5];
c6=cos(t6);
% Random frequency hopps to form a spread signal
spread_signal=[];
for n=1:25
c=randint(1,1,[1 6]);
switch(c)
case(1)
spread_signal=[spread_signal c1];
case(2)
spread_signal=[spread_signal c2];
case(3)
spread_signal=[spread_signal c3];
case(4)
spread_signal=[spread_signal c4];
case(5)
spread_signal=[spread_signal c5];
case(6)
spread_signal=[spread_signal c6];
end
end
subplot(4,1,3)
plot([1:3000],spread_signal);
axis([-100 3100 -1.5 1.5]);
title('\bf\it Spread Signal with 6 frequencies');
% Spreading BPSK Signal into wider band with total of 12 frequencies
freq_hopped_sig=bpsk_sig.*spread_signal;
subplot(4,1,4)
plot([1:3000],freq_hopped_sig);
axis([-100 3100 -1.5 1.5]);
title('\bf\it Frequency Hopped Spread Spectrum Signal');
% Expressing the FFTs
figure,subplot(2,1,1)
plot([1:3000],freq_hopped_sig);
axis([-100 3100 -1.5 1.5]);
title('\bf\it Frequency Hopped Spread Spectrum signal and its FFT');
subplot(2,1,2);
plot([1:3000],abs(fft(freq_hopped_sig)));
评论0