## can the output of QAM be given directly to IFFT ?

Started by in Matlab DSP13 years ago 2 replies

I am doing a project regarding OFDM.I used 64 QAM to modulate the data . The output of QAM is complex. Can the complex output be given...

I am doing a project regarding OFDM.I used 64 QAM to modulate the data . The output of QAM is complex. Can the complex output be given directly to perform IFFT ?

## Problem with IFFT and FFT in Matlab

Started by in Matlab DSP10 years ago 2 replies

Hi, I am working on an OFDM system using Matlab. The bits received at the receiver have a constant error ( i.e., avg 200 bits out of 1000 are...

Hi, I am working on an OFDM system using Matlab. The bits received at the receiver have a constant error ( i.e., avg 200 bits out of 1000 are always wrong).. when I decreased no. of bits in a symbol to let say 49 and FFT length to 64, there was no error. It looks like that there is some error in the computation of IFFT/FFT bolcks by Matlab (maybe some rounding of the data by Matlab). I am unsu...

## 2D IFFT on array data to get angle of arrival

Started by in Matlab DSP15 years ago

Hi, Currently,I have an 10x10 array of channel impulse response data. I need to get spatial angle of arrival,azimuth and...

Hi, Currently,I have an 10x10 array of channel impulse response data. I need to get spatial angle of arrival,azimuth and elevation angle image information from array data. I am currently using 2 dimensional IFFT to do transform to angular domain. However,i am not sur

## IFFT in OFDM, real output requires conjugate symmetric

Started by in Matlab DSP14 years ago 1 reply

Hi, i've forgotten where i read about this but i know for OFDM, if i want the output of my IFFT to be real, i can only use half of...

Hi, i've forgotten where i read about this but i know for OFDM, if i want the output of my IFFT to be real, i can only use half of the subcarriers with the other half the complex conjugate mirror of the 1st half. It apparantly got to do with the properties of Fourier transform or something like that. I'm currently writing my report on OFDM. Can someone direct me to references or literature...

## y-axis of IFFT

Started by in Matlab DSP18 years ago 2 replies

I have a question. There is a signal which x-axis is freq. and y-axis is Power Spectrum Density. After convert this freq. domain...

I have a question. There is a signal which x-axis is freq. and y-axis is Power Spectrum Density. After convert this freq. domain signal to time domain(using IFFT), the x-axis is time, how about the unit in y- axis? Thank you.

## OFDM symbol genration - IIFT concept

Started by in Matlab DSP15 years ago 3 replies

Hi all I have basic question regarding OFDM symbol genration.IFFT is taken to genrate a OFDM symbol.that part is undersood. My...

Hi all I have basic question regarding OFDM symbol genration.IFFT is taken to genrate a OFDM symbol.that part is undersood. My question is that whether that IFFT taken is complex or real.i believe it is complex as the ouput is shown to be assymetrical.so if it is complex,the data to be transmitted also has to be complex. from where we fill

## Two Path Rayleigh Channel

Started by in Matlab DSP11 years ago

Hi Please see this code , I am confused how i added the two version of signal received from two Taps with one sample delay.Initially I have...

Hi Please see this code , I am confused how i added the two version of signal received from two Taps with one sample delay.Initially I have done IFFT of the signal with Four subcarriers.Please guide me. x=transdata1; taps=2; p1=1; p2=0.8; gain1=sqrt(p1/2)*[randn(1,length(x)) + j*randn(1,length(x))]; gain2=sqrt(p2/2)*[randn(1,length(x)) + j*randn(1,length(x))]; channel_ifft=ifft([gain1,ga...

## Unexpected oscillations in the impulse response

Started by in Matlab DSP12 years ago 1 reply

Hi all! My question is about getting the impulse response from the transfer function of a system. I have simulation data for the transfer...

Hi all! My question is about getting the impulse response from the transfer function of a system. I have simulation data for the transfer function of an LTI system. I make the data Hermitian symmetric so that when I do an IFFT on it, I get a real impulse response. So far so good. But the problem is the shape of the impulse response I get after the IFFT. It oscillates at the beginning, decays t...

## no of subcarriers in OFDM

Started by in Matlab DSP13 years ago 1 reply

I am doing a project related to OFDM. My doubt is whether the no of subcarriers and the IFFT size should be equal or not?

I am doing a project related to OFDM. My doubt is whether the no of subcarriers and the IFFT size should be equal or not?

## fast fourier code

Started by in Matlab DSP16 years ago 1 reply

hello everyone, i am performing fft,ifft & nested for loops on 21x1985 matrix. it is taking a lot of time. is there any...

hello everyone, i am performing fft,ifft & nested for loops on 21x1985 matrix. it is taking a lot of time. is there any function that i can use to do it faster. i'v heard of something called vectorization but couldnt find it anywhere. This is very urgent . tha

## Re: ofdm simulation (ifft/fft) & NoiseVar

Started by in Matlab DSP14 years ago

http://www.mathworks.com/matlabcentral/fileexchange/loadFile.do?objectId=6957 hi.. follow this link and download the m-fil... ofdm code is there... r u working in only ofdm... or u r workning on papr reduction also... thanku

## SC-FDE

Started by in Matlab DSP15 years ago

Dear all, I am simulating Single Carrier Frequency Domain Equalizer in AWGN Channel.. I used the QPSK BER curve and modified that to make...

Dear all, I am simulating Single Carrier Frequency Domain Equalizer in AWGN Channel.. I used the QPSK BER curve and modified that to make the SC-FDE. I am using 512 fft size and guard interval of 56. As awgn channel is used ,there is no operation in between the fft & ifft at the receiver. Should I do the zero padding at the transmitter?. If anyone

## using ifft in MATLAB

Started by in Matlab DSP17 years ago

I am having trouble getting the following problem to work-can anybody help me? problem:Obtain the 1024-point inverse FFT of...

I am having trouble getting the following problem to work-can anybody help me? problem:Obtain the 1024-point inverse FFT of a sequence of numbers whose imaginary parts are all zero, and the real parts are the following: b(1)=b(1023)=0.5 b(3)=b(1021)=0.1

## ofdm simulation

Started by in Matlab DSP12 years ago 2 replies

hi all I am simulatin ofdm using matlab,with 16QAM digital modulation. now my out put from QAM is a complex number.when i apply this to IFFT i...

hi all I am simulatin ofdm using matlab,with 16QAM digital modulation. now my out put from QAM is a complex number.when i apply this to IFFT i am still getting a complex number(i was hoping to get time varying signal). any help thanks

## PAPR calculation

Started by in Matlab DSP14 years ago

Dear All, I would highly appreciate if you share your thoughts on the correctness of the method for calculating PAPR value of OFDM signal as...

Dear All, I would highly appreciate if you share your thoughts on the correctness of the method for calculating PAPR value of OFDM signal as described below. I am using NRZ random bits as the random input data where the n point IFFT outputs are x1,x2..xn(complex values) for one OFDM symbol. peakpower=max(abs(x1).^2,abs(x2).^2,..abs(xn).^2) avgpower=sum((abs(x1).^2,abs(x2).^2..abs(xn).^2)/n

## Complex input to IFFT to generate real value signal

Started by in Matlab DSP15 years ago

The statement in the subject is refering to Erich Cosby's tutorial for OFDM. I'm simulating OFDM in Simulink with the aim of later...

The statement in the subject is refering to Erich Cosby's tutorial for OFDM. I'm simulating OFDM in Simulink with the aim of later converting it for a DSP. I use BPSK before the OFDM operation. With BPSK, all my binary inputs would be converted to either 1 or -1 in the IQ spectrum. In Simulink, the outputs contain very small values for the ima

Started by in Matlab DSP12 years ago

I have a question that has been bugging me fo rsome time and I am hoping someone here can help me get to the bottom of it. It is a zero padding &...

I have a question that has been bugging me fo rsome time and I am hoping someone here can help me get to the bottom of it. It is a zero padding & FFT issue. Here goes; If I take 2 random signals for deconvolution (say 1000 samples and 1500 samples long with same sampling time). If I zero pad both out to 4096, take FFTs, devide one by another, then take iFFT, I get a graph of one signal deconvo...

## BER for OFDM

Started by in Matlab DSP12 years ago

Hi, I'm trying to get the BER for OFDM system but the result is not correct. Can any one tell me what is the wrong in my program? Regards M....

Hi, I'm trying to get the BER for OFDM system but the result is not correct. Can any one tell me what is the wrong in my program? Regards M. Hussien This is my program clear all; close all; clc; % System Parameters N = 64; % length of OFDM IFFT M = 16; % number of QAM constellation points noz = N/4+1; % number Of Zeros GI ...

## Time Domain Response

Started by in Matlab DSP14 years ago 1 reply

Hi Guys, I have the stepped frequency data which is in the range 1GHz -3GHz (201 Frequency steps ; i.e. spacing 10MHz). I am using ifft...

Hi Guys, I have the stepped frequency data which is in the range 1GHz -3GHz (201 Frequency steps ; i.e. spacing 10MHz). I am using ifft (MATLAB command). I am getting 201 points in time domain. Q: What do the time samples (0-201) correspond to in terms of time units (seconds)? Thanks in advance Tron

## truncating the function and taking fft

Started by in Matlab DSP15 years ago

% Rectangular pulse,FFT shifted N=400; t=linspace(-10,10,2000); n=0:N-1;%index x = [zeros(1,220) ones(1,60)...

% Rectangular pulse,FFT shifted N=400; t=linspace(-10,10,2000); n=0:N-1;%index x = [zeros(1,220) ones(1,60) zeros(1,120)];%rectangular pulse % plot(n,x);axis([0 400 -0.5 1.5]);grid on xlabel('n');ylabel('x[n]');%pause; X = ifft(x,2000);%fourier transfo