Clear Filters
Clear Filters

trying to reaccunting the subcarriers

1 view (last 30 days)
itsik
itsik on 18 May 2011
hello y'all!!! i got this code its a ofdm signal modulate by bpsk does any ones know how do i make the subcarriers 0:52 and not -1:26,1:26 ? i tried to change only the numbers but it make nothing.. thanks alot!!! and this is the code
clear all
nFFTSize =64 ;
% for each symbol bits a1 to a52 are assigned to subcarrier
% index [-26 to -1 1 to 26]
subcarrierIndex = [-26:-1 1:26];
nBit = 2500;
ip = rand(1,nBit) > 0.5; % generating 1's and 0's
nBitPerSymbol = 52;
nSymbol = ceil(nBit/nBitPerSymbol);
% BPSK modulation
% bit0 --> -1
% bit1 --> +1
ipMod = 2*ip - 1;
ipMod = [ipMod zeros(1,nBitPerSymbol*nSymbol-nBit)];
ipMod = reshape(ipMod,nSymbol,nBitPerSymbol);
figure(1)
plot(ipMod)
st = []; % empty vector
for ii = 1:nSymbol
inputiFFT = zeros(1,nFFTSize);
% assigning bits a1 to a52 to subcarriers [-26 to -1, 1 to 26]
inputiFFT(subcarrierIndex+nFFTSize/2+1) = ipMod(ii,:);
% shift subcarriers at indices [-26 to -1] to fft input indices [38 to 63]
inputiFFT = fftshift(inputiFFT);
outputiFFT = ifft(inputiFFT,nFFTSize);
% adding cyclic prefix of 16 samples
outputiFFT_with_CP = [outputiFFT(49:64) outputiFFT];
st = [st outputiFFT_with_CP];
end
close all
fsMHz = 20;
[Pxx,W] = pwelch(st,[],[],4096,20);
figure(2)
plot([-2048:2047]*fsMHz/4096,10*log10(fftshift(Pxx)));
xlabel('frequency, MHz')
ylabel('power spectral density')
title('Transmit spectrum OFDM (based on 802.11a)');

Answers (1)

Oleg Komarov
Oleg Komarov on 18 May 2011
subcarrierIndex = 0:52;
  2 Comments
itsik
itsik on 18 May 2011
no its not work i tried it
Oleg Komarov
Oleg Komarov on 18 May 2011
What do you mean no it's not it??

Sign in to comment.

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!