how to switch off some of the subcarriers in an ofdm system using matlab programme???

[Alok Ranjan Samal]

sir, how to switchoff some of the subcarriers in an ofdm system in a matlab programme??????please reply.i need it urgently.thanks.

 

[albbg]

I think you can simply put 0 on the corresponding bin of the FFT,redistributing the signal on the remaining subcarriers.

 

[Alok Ranjan Samal]

thank you sir for your help. but when we are writing a programme of ofdm in matlab , we are taking the ifft of the whole signal instead of single subcarrier , so how to take individual subcarriers as zero.

 

[albbg]

In the OFDM the signal is built in the frequency domain, that is subcarrier by subcarrier, then you'll take the IFFT of the whole subcarriers assembly. Just don't assign the subcarriers you want to be off and put them to zero.

 

[Alok Ranjan Samal]

thank you sir for your help.............here the ofdm programme in matlab
n = 256;
x = randint(n,1);
M = 16;
k = log2(M);
xsym = bi2de(reshape(x,k,length(x)/k).','left-msb');

y = modulate(modem.qammod(M),xsym);

tu=3.2e-6;
tg=0.8e-6;
ts=tu+tg;n
nmin=0;
nmax=64;%total number of subcarriers
scb=312.5e3;%sub carrier spacing
fc=3.6e9;%carrier frequency
Rs=fc;
tt=0: 6.2500e-008:ts-6.2500e-008;
c=ifft(y,nmax);%IFFT
s=real(c'.*(exp(1j*2*pi*fc*tt)))


here , the ofdm is generated by taking the ifft as shown above.after this if i have to switch off some of the subcarriers let be switch off subcarriers from 52 to 60.then how to switchoff them?????

 

[albbg]

I think you have to see inside the function modulate()

 

[Alok Ranjan Samal]

thank you sir for giving your valuable time. but sorry sir, i did not get your answer.how can i change inside of the function modulate(), so that i can switch off the sequence of subcarriers which i want to switch off.