Hello. In OFDM systems, there are CINR(carrier to interference and noise ratio) and SINR( signal to interference and noise ratio). Of course,...

Hello. In OFDM systems, there are CINR(carrier to interference and noise ratio) and SINR( signal to interference and noise ratio). Of course, the acronyms and its meanings are evident. But, in OFDM, why is CINR important? For example, is it a metric directly related with some specific performance criterion? I'd highly appreciate your comments. Thank you very much.

Hi all, I'm studying effect of phase noise on the BER performances for OFDM QAM Modulation. I found the SNR degradation due to the phase...

Hi all, I'm studying effect of phase noise on the BER performances for OFDM QAM Modulation. I found the SNR degradation due to the phase noise: D= 10/ln(10)*(1/60)*(4*pi*Beta*N/R)*SNR where N/R depends n the data rate and the number of OFDM sub-carrier But I don't really understand what is beta and its relationship with the LO curve in function of the frequency, for example -20 dB/dec.......

Hello group, It is my pleasure to be posting queries to this group again. My understanding of the presence of the cyclic prefix (CP) in an...

Hello group, It is my pleasure to be posting queries to this group again. My understanding of the presence of the cyclic prefix (CP) in an OFDM symbol is to: 1. Prevent inter-symbol interference in a FIR channel if the length of the CP is larger than the delay spread of channel. 2. Makes linear convolution "appear" as circular convolution over the duration of the useful period in the OF...

This is with reference to the white paper by TI entitled, "Power Line Modem with E-meter Platform", 2004 (i'm sorry i can't find the link to the...

This is with reference to the white paper by TI entitled, "Power Line Modem with E-meter Platform", 2004 (i'm sorry i can't find the link to the article) At the part where the paper decribes the Packet Format for the OFDM frames. It says that the data frames are grouped into blocks of 3 frames and each data frame in the block contains identical data but transmitted at different frequency. ...

Hello, I have maganged to simulate an OFDM system using Matlab. It works fine in AWGN channel and SNR vs BER curve matches the...

Hello, I have maganged to simulate an OFDM system using Matlab. It works fine in AWGN channel and SNR vs BER curve matches the theoretical one. But I have problem when I add Rayleigh to it (I get similar amount of BER for all SNR). I have used standard matlab functions to gerenate static flat fading: c=raylieghchan(); y = filter(c,ofdm_symbol); % the...

Hi everyone, I'm trying to understand OFDM and 64QAM, and am building some models in Matlab. There is something I cannot quite understand. I...

Hi everyone, I'm trying to understand OFDM and 64QAM, and am building some models in Matlab. There is something I cannot quite understand. I receive an OFDM Symbol (4us), strip the guard time off it , leaving me with a 3.2us time-domain signal .I then perform an FFT to get the 64QAM constellation. The problem I'm having is this; the decoded symbol will only have 48 data points, and some m...

Hi, I'm developing an OFDM system. In the transmitter I have taken 4 transmission symbols. Then zero padding is done according to IFFT size...

Hi, I'm developing an OFDM system. In the transmitter I have taken 4 transmission symbols. Then zero padding is done according to IFFT size and to get a real signal after IFFT, I have taken the symmetry of that. The problem is I'm not receiving the same transmitted symbol stream after doing FFT at the receiver (transmission channel is not included yet). Please correct my MATLAB code. ...

Hi, This has been a very informative forum while i have been working on this small simulation. I have a couple of questions now. 1) First I...

Hi, This has been a very informative forum while i have been working on this small simulation. I have a couple of questions now. 1) First I am simulating a simple uncoded 16-QAM OFDM system. I tried evaluate the performance of such a system in an AWGN channel and the results i have matches results of a single carrier system using 16 QAM in a AWGN channel. 2) Now I would like to study the ...

Hi, What is the performance difference of MMSE equalizer and ZF equalizer in a OFDM system. I have simulation 3 tap Rayleigh channel for QPSK...

Hi, What is the performance difference of MMSE equalizer and ZF equalizer in a OFDM system. I have simulation 3 tap Rayleigh channel for QPSK ODFM system and found out that both the equalizers give the same performance. But in Single carrier Frequency Domain Equalization, MMSE performs significantly better than ZF. Can anyone please advice me in this regard. Thanks in advance. _...

i have a basic question regarding MIMO OFDM. will it work for long distance communication like deep-space comm. or intercontinental...

i have a basic question regarding MIMO OFDM. will it work for long distance communication like deep-space comm. or intercontinental communication? and if not, why so? will it be due to different length of channels?

Hi All, I have a simple question that hope someone can explain it. What would be the time domain OFDM signal if you increase or decrease the...

Hi All, I have a simple question that hope someone can explain it. What would be the time domain OFDM signal if you increase or decrease the number of data tones/subcarriers e.g. increase from 135 to 220 data subcarriers? Why this change is observed? Thank you Regards, Suterr

Dear all, I have modeled a simple OFDM modem using MATLAB. The model works fine for AWGN channel, but when it comes to...

Dear all, I have modeled a simple OFDM modem using MATLAB. The model works fine for AWGN channel, but when it comes to flat fading it does not follow the theoretical curves. To implement the channel ( r = ax+n ) I generage "a" as following: a = sqrt(0.5) * sqrt(randn( 1, ofdm_sym_size) + j*randn( 1,ofdm_sym_size)); and after IFFT I multiply it to ...

Hi all!! I am performing LS & MMSE channel estimation in an OFDM system with the DVB-H parameters, where the pilots are not equally spaced as...

Hi all!! I am performing LS & MMSE channel estimation in an OFDM system with the DVB-H parameters, where the pilots are not equally spaced as the case with WIMAX. I am facing a severe problem as the BER of both MMSE and LS are identical. I am sure that the LS is correct and that the problem is with MMSE. I've tried everything to make a difference between them. The only successful attempt was to i...

Hi all, Could anyone help me understand some dsp things... 1) I'm trying to simulate LTE downlink channel. I use matlab lte...

Hi all, Could anyone help me understand some dsp things... 1) I'm trying to simulate LTE downlink channel. I use matlab lte toolbox. Everythings works fine in the absense of noise. Now I want to add some AWGN into my model. So the question is what are the typical values of SNR in dB for OFDM? for example SNR = 20dB is it low or high? Any links to read about this issue? 2) How to add...

Hi All I am simulating OFDM in MATLAB.. i have completed most of the part.. I have one doubt..i get complex signal to be transmitted that is...

Hi All I am simulating OFDM in MATLAB.. i have completed most of the part.. I have one doubt..i get complex signal to be transmitted that is real and imaginary... how do i pass such a signal through channel filter.. so as to simulate actual scenario of real world channel propagation.... should i pass the real part only Please help me on this sandeep

I want to calculate the BER performance for the case of Perfect Channel Information in OFDM. Below is the block diagram that I used: Binary...

I want to calculate the BER performance for the case of Perfect Channel Information in OFDM. Below is the block diagram that I used: Binary gen --> insert pilot --> zero padding ---> ifft ---> CP insertion --> conv. with CIR ---> Remove CP ---> Add AWGN noise --> rx The pilots will be used for channel estimation later. My question is: From (rx), how can I get the demodulated binary data?

hi all , Currently , i need to generate an Blind channel estimation in my OFDM system , but i am really not that understand about the blind...

hi all , Currently , i need to generate an Blind channel estimation in my OFDM system , but i am really not that understand about the blind channel estimation , for my understanding , i only know that we can use the training sequence from transmitted signal to estimate the channel.Ya , this is very very brief understanding. but frankly to say , i cant found any useful reference or source abo...

Hello, I have a question regarding the OFDM transmitter. In order to reduce the burden on the reconstruction filters, oversampling is used...

Hello, I have a question regarding the OFDM transmitter. In order to reduce the burden on the reconstruction filters, oversampling is used before feeding the data to the DAC. Oversampling, however, creates images of the baseband signal. To remove these images, low pass filters are placed after the rate up converter. These filters are FIR systems, and, when applied to the signal, "smudge" it...

i have simulated the MSE for channel estimate for different techniques for OFDM. But for LMMSE i am not getting the desired results. the MSE for...

i have simulated the MSE for channel estimate for different techniques for OFDM. But for LMMSE i am not getting the desired results. the MSE for LMMSE comes out to be better than transform domain LS and time domain LS for low SNR (like below 5 dB) but gets poor at higher snrs and approaches frequency domain LS at high SNRs like 40 dB. My simulation parameters are: symbol_length = 64; ...

i have simulated the MSE for channel estimate for different techniques for OFDM. But for LMMSE i am not getting the desired results. the MSE...

i have simulated the MSE for channel estimate for different techniques for OFDM. But for LMMSE i am not getting the desired results. the MSE for LMMSE comes out to be better than transform domain LS and time domain LS for low SNR (like below 5 dB) but gets poor at higher snrs and approaches frequency domain LS at high SNRs like 40 dB. My simulation parameters are: symbol_length = 64...