## FFT and IFFT in OFDM

Started by in Matlab DSP16 years ago

Can we use directly the FFT and IFFT functions in Matlab for OFDM simulation? I found IFFT(AWGN) will result in strange mean and variance. ...

Can we use directly the FFT and IFFT functions in Matlab for OFDM simulation? I found IFFT(AWGN) will result in strange mean and variance.

## ifft in matlab

Started by in Matlab DSP13 years ago 2 replies

i want to compute the ifft of the following data data=[0 1 1 0] in matlab it should return me a single value but it is giving me a...

i want to compute the ifft of the following data data=[0 1 1 0] in matlab it should return me a single value but it is giving me a column of values can anybody explain this to me and secondly how matlab carries out the ifft , how can it be done by hand to verify the result thanks

## FFT and IFFT

Started by in Matlab DSP18 years ago

Hi, I want to ask if I FFT an image, how can I recover the image using IFFT. I try to use it directly, but turn out some a totally...

Hi, I want to ask if I FFT an image, how can I recover the image using IFFT. I try to use it directly, but turn out some a totally bright picture. However, when i change the image to a very simple one, say only black and whit region, ifft can receover the image. I find out from

## ofdm simulation (ifft/fft) & NoiseVar

Started by in Matlab DSP16 years ago

Hi all, I have some problems in simulating the OFDM using matlab. I will list them one by one. 1). Normailsation of the signal after ifft...

Hi all, I have some problems in simulating the OFDM using matlab. I will list them one by one. 1). Normailsation of the signal after ifft & fft. Do we have to multiply by any factor after taking the ifft and fft in the matlab?. Please explain me about this for the OFDM symbol with Useful Subcarriers. 2). Finding the NoiseVariance in to create the

## FFT/IFFT functions in Maltab & DSP same?

Started by in Matlab DSP16 years ago

I'm currently doing a project on OFDM signal generation. I plan to write my codes in Matlab and later convert it into C and then download...

I'm currently doing a project on OFDM signal generation. I plan to write my codes in Matlab and later convert it into C and then download it into DSPs. My question is, when i use the fft/ifft functions that come with Matlab, when i convert it and download it into the DSP. Will it have any problem? Will the fft/ifft operation be same on the DSP?

## Why this particular code doesnt work?

Started by in Matlab DSP16 years ago 2 replies

sig=wavread('path to signal file'); reconstructed_sig=ifft(fft(sig)); subplot(2,1,sig); plot(sig); subplot(2,2.reconstructed_sig); plot(reconstructed_sig); i know that to analyse the fft of sig, the magnitude and phase spectra of it must be found.But why is the ifft-fft combination not working? What must i do so that i can reconstruct the original sig using ifft? Thanx in advance warrier

## csd ifft

Started by in Matlab DSP17 years ago

Hi, I compute the cross spectrum, using the CSD function, and I am trying to represent it in time-domain using IFFT (see...

Hi, I compute the cross spectrum, using the CSD function, and I am trying to represent it in time-domain using IFFT (see example below). But what I got in the y-axis is something strange or maybe not-normalized. Does anybody have tried it before ? How can I perfe

## problem with IFFT and sampling time

Started by in Matlab DSP16 years ago

Hi everybody, My problem is as follows: I get data from a fft analyser after numerous averaging in order to remove the noise. Now in...

Hi everybody, My problem is as follows: I get data from a fft analyser after numerous averaging in order to remove the noise. Now in order to use it i have to take the IFFT of this data in Matlab. But fft analyser(any) while taking fft take sampling frequency as 2.56 times the maximum frequency specified. But when IFFT is taken in matlab it will just do

## IFFT for OFDM

Started by in Matlab DSP18 years ago

I write this code to get IFFT for y but only spectrum drawn not time domain siganal ploted: t = -5:0.001:5; y1 =...

I write this code to get IFFT for y but only spectrum drawn not time domain siganal ploted: t = -5:0.001:5; y1 = sin(pi*(t+1))./(pi*(t+1)); y2 = sin(pi*(t+2))./(pi*(t+2)); y3 = sin(pi*(t+3))./(pi*(t+3)); y0 = sin(pi*t)./(pi*t); y11= sin(pi*(t-1))./(pi*(t-1));

## my first ofdm

Started by in Matlab DSP12 years ago

Hi guys this is "my first" ofdm code.could you tell me how it is and how to add the cyclic prefix? Another question is: in the function ifft...

Hi guys this is "my first" ofdm code.could you tell me how it is and how to add the cyclic prefix? Another question is: in the function ifft should i insert the IFFT SIZE? %--------1---------2---------3---------4---------5---------6---------7---------8 % OFDM Simulation clear all; close all; % % Basic OFDM system parameters % - choice of defaults or user selections % fprintf ('OFDM...

## Finding a Faster Way

Started by in Matlab DSP18 years ago 3 replies

Here is the code snipet i need help with... for i = 1:end_frame for j = 1:1024 fout(i,j) = ifft(Z(i,j)); end end As...

Here is the code snipet i need help with... for i = 1:end_frame for j = 1:1024 fout(i,j) = ifft(Z(i,j)); end end As you can see, if the end_frame is large, the for loop would take so long. What alternatives can I do? I've tried fout = ifft

## using IFFT in matlab

Started by in Matlab DSP20 years ago

I meet a problem which is to convert a signal from frequency domain into time domain. I tried to use IFFT to convert it but I did...

I meet a problem which is to convert a signal from frequency domain into time domain. I tried to use IFFT to convert it but I did not succeed. If you are interested, please see the following matlab code Thank you! function calculate_TimeVariation(N,OR,M,Dop_res,res_accu

## power spectral density

Started by in Matlab DSP13 years ago

? Please i need? help in PSD to compare between different methods of PAPR. When apply the following code not given the same plot as in your...

? Please i need? help in PSD to compare between different methods of PAPR. When apply the following code not given the same plot as in your paper . ? My Matlab code ? N = 256;????? % length of OFDM IFFT M = 16;?????? % number of QAM constellation BW=10;??????????? % in MHz txData= randint(N,1,M); txDataMod? = qammod(txData,M); ? txDataZpadIfft = sqrt(N)*ifft(txDataMod ,N); ...

## FFT and IFFT

Started by in Matlab DSP18 years ago

I have signal x = sin(2*pi*2*t) + sin (2*pi*5*t) + noise(0.1). Could any one tell me how to obtain signal y = x - noise(0.1) in time...

I have signal x = sin(2*pi*2*t) + sin (2*pi*5*t) + noise(0.1). Could any one tell me how to obtain signal y = x - noise(0.1) in time domain? I do not know how to use IFFT. Much appreciate for your help! Mb.

## general filtering

Started by in Matlab DSP16 years ago

Hello anyone can please explain me when filtering by FFT, what is the diference between filtering the normal spectrum and iFFT and...

Hello anyone can please explain me when filtering by FFT, what is the diference between filtering the normal spectrum and iFFT and filtering the power spectrum and then iFFT ? which one are best ? thanx

## mapping symbols onto carrier waves? ifft?

Started by in Matlab DSP14 years ago 1 reply

so i'm venturing into communications research and i'm stuck on how to change symbols into the time domain. i have modulated bits, say [0...

so i'm venturing into communications research and i'm stuck on how to change symbols into the time domain. i have modulated bits, say [0 1] which in bpsk is just -1 and 1. how do i take this data and put it on the time domain to be transmitted? it should just be a sine wave and then at one point be shifted over 180 degrees. it was my understanding that you throw the IFFT in there to accomp...

## frequency selective fading for OFDM

Started by in Matlab DSP16 years ago 1 reply

hii all, I am trying to make a simulation program for OFDM.My modulation technique is BPSK.after doing the mapping of original to ...

hii all, I am trying to make a simulation program for OFDM.My modulation technique is BPSK.after doing the mapping of original to BPSK signal space, I am taking say N of those symbols and performing IFFT(I conjugate and append my BPSK data set so as to obtain a real signal out of the IFFT block).Now my problem goes like this- 1) how do i m

## FFT / IFFT twiddle factor

Started by in Matlab DSP15 years ago

Hi all ,=20 I am trying to implement IFFT in vhdl . I tried to use the=20 matlab , but not sure how can i get the twiddle factor ....

Hi all ,=20 I am trying to implement IFFT in vhdl . I tried to use the=20 matlab , but not sure how can i get the twiddle factor . Is it=20 possible to get the twiddile factor in fixed point from matlab so that=20 i can use it in vhdl code directily? Thanks in advance. John=20 =20 =20

## Help with FFT and IFFT

Started by in Matlab DSP13 years ago 5 replies

Hi!! I am new to matlab so please bear with me. I don't understand the IFFT and FFT matlab functions. Here is the code i am...

Hi!! I am new to matlab so please bear with me. I don't understand the IFFT and FFT matlab functions. Here is the code i am using: [sig,fs]=wavread('aemixed.wav'); time=(1:length(sig))'/fs; figure(1) plot(time,sig) fsig1 = fft(sig,fs); Y=real((ifft(fsig1,length(sig)))); figure(3) plot(time,Y) What I don't understand is that Y and sig are not the same. Can someone please explain...

## OFDM PSD

Started by in Matlab DSP14 years ago 1 reply

hi all, i'm trying to plot ofdm normalized (dBr) psd after ifft function. i.e: carriers=NFFT.*ifft(tx); %plot normalized PSD i've tried...

hi all, i'm trying to plot ofdm normalized (dBr) psd after ifft function. i.e: carriers=NFFT.*ifft(tx); %plot normalized PSD i've tried pwelch(), psd() and their varients but my results do not match the theory. i'll appreciate some help on the subject. thanks.