www.pudn.com > FHSS_DSSS_CDMA.zip > freq_hopp_sprd_spctrm.m

% Lab 06 
% WiCom_2 
% By Kashif Shahzad  
% 01-ET-31 
% 3rd July 2004 
 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
% Frequency Hopping Spread Spectrum 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
clc 
clear 
 
% Generation of bit pattern 
s=round(rand(1,20));    % Generating 20 bits 
signal=[];   
carrier=[]; 
t=[0:10000];    
fc=.01; 
for k=1:20 
    if s(1,k)==0 
        sig=-ones(1,10001);    % 10001 minus ones for bit 0 
    else 
        sig=ones(1,10001);     % 10001 ones for bit 1 
    end 
    c=cos(2*pi*fc*t);    
    carrier=[carrier c]; 
    signal=[signal sig]; 
end 
subplot(2,1,1); 
plot(signal); 
axis([-1 200050 -1.5 1.5]); 
title('\bf\it Original Bit Sequence'); 
 
% BPSK Modulation of the signal 
bpsk_sig=signal.*carrier;   % Modulating the signal 
subplot(2,1,2); 
plot(bpsk_sig) 
axis([-1 200050 -1.5 1.5]); 
title('\bf\it BPSK Modulated Signal'); 
 
% FFT Plot of BPSK Modulated Signal 
figure,plot([1:200020],abs(fft(bpsk_sig))) 
title('\bf\it FFT of BPSK Modulated Signal'); 
 
% Preparation of Six carrier frequencies 
fc1=.01; 
fc2=.02; 
fc3=.03; 
fc4=.04; 
fc5=.05; 
fc6=.06; 
c1=cos(2*pi*fc1*t); 
c2=cos(2*pi*fc2*t); 
c3=cos(2*pi*fc3*t); 
c4=cos(2*pi*fc4*t); 
c5=cos(2*pi*fc5*t); 
c6=cos(2*pi*fc6*t); 
 
% Random frequency hopps to form a spread signal 
spread_signal=[]; 
for n=1:20 
    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 
figure,plot([1:200020],abs(fft(spread_signal))) 
 
% Transformation of a BPSK signal into a wider band 
freq_hopped_sig=bpsk_sig.*spread_signal; 
figure,plot([1:200020],abs(fft(freq_hopped_sig)))