## Forums Search for: OFDM

## Conv. coding with ofdm in flat rayleigh

inHi all, I tried to simulate the bit error rate performance using bpsk with convolutional code: R=1/2, K=7, generator polynomials (133,171) in...

Hi all, I tried to simulate the bit error rate performance using bpsk with convolutional code: R=1/2, K=7, generator polynomials (133,171) in AWGN and the performance using bpsk ofdm with the code in AWGN. I got the same ber curve for both cases, which showed some advantage or gain after using the coding However, when I simulated the bpsk ofdm system using the conv. code in flat rayleigh, I ...

## Oversampling in OFDM

inHi, I have a question related with the OFDM transmitter. What is the commonly method to increase the sampling rate ? - Increasing the IFFT...

Hi, I have a question related with the OFDM transmitter. What is the commonly method to increase the sampling rate ? - Increasing the IFFT size and insert zero in the inpput ? or - Insert zero in the IFFT output and followed by interpolation filter ? What is the trade-off ? anyone can help ? Thanks. Buzz

## MATLAB OFDM Simulation

inDoes anyone know if there is a OFDM simulation in matlab is possible? If anyone has it, can you please share it with me. I have a final sem...

Does anyone know if there is a OFDM simulation in matlab is possible? If anyone has it, can you please share it with me. I have a final sem project that's due next week and am going crazy over this coding. SOS! Thanks.

## Sparse Channel Estimation in OFDM Systems

inHi, I am actually new in sparse signal processing and first trying to get the basics of the sparse signals. In OFDM systems the sparse channel...

Hi, I am actually new in sparse signal processing and first trying to get the basics of the sparse signals. In OFDM systems the sparse channel is estimated by using some sparse signal processing algorithms such as compressive sensing. Could anyone please explain me how to model the sparse channel/sparse signal in OFDM systems? What is the logic behind the sparse representation? Thanks i...

## awgn SNR in ofdm, sampling clock offset estimation

inHi 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...

## Assumptions to be made while simulating for a wireless channel

inDear comp.dsp, I am going to try to learn a bit more about the wireless channel (specifically using OFDM) by first creating a set of symbols...

Dear comp.dsp, I am going to try to learn a bit more about the wireless channel (specifically using OFDM) by first creating a set of symbols and perform a transmit and receive. It is a simple begining I want to make, and I will probably use GNU Octave and, later, when I do know the basics, shift to IT++. My doubts are: 1. Let us say I am going to use just BPSK over OFDM. Then, I can l...

## FFT or DFT with large N (for OFDM/DMT)

Hello, I have a question about the DFT that is used in OFDM and DMT. Emerging standards such as VDSL, DVB and Powerline allow transfrom ...

Hello, I have a question about the DFT that is used in OFDM and DMT. Emerging standards such as VDSL, DVB and Powerline allow transfrom sizes which can be as large as N = 1024, 2048 or 4096. Associated with this there is the problem of large peak to average ratio, clipping and non-linearities at the power amplifier. But there are methods to reduce these effects (see Tellado and Cioffi...

## Variance of the noise in OFDM

Hi, I am quite confused with the variance of the noise in the OFDM system. Should it be equal to N0 or N0/2? N0: Single sided noise power...

Hi, I am quite confused with the variance of the noise in the OFDM system. Should it be equal to N0 or N0/2? N0: Single sided noise power spectral density. Please help. Thanks.

## simple-minded OFDM question

inFrom what little I've read on OFDM, it seems that its claim to fame is its resistance to frequency-selective fading (at least I think that's the...

From what little I've read on OFDM, it seems that its claim to fame is its resistance to frequency-selective fading (at least I think that's the proper term - correct me if I'm wrong). That resistance comes via the multiple carriers. If one or two carriers fade, no problem - you've got a horde of others which are more than the coherence bandwidth away, so you still get a lot of usable data...

## OFDM: Mapping of Rayleigh SNR to AWGN SNR for BLER calculation

inDear all, Hi, I am trying to simulate the performance (block error rate) of ofdm over raylegih. My question is, how do I calculate SNR for...

Dear all, Hi, I am trying to simulate the performance (block error rate) of ofdm over raylegih. My question is, how do I calculate SNR for OFDM Rayleigh channel and map it to equivalent AWGN SNR so that I can calculate the block error rate ? I like to mention that I have already simulate AWGN block error rate (BLER) for different modulation and coding (MCS) combination. Difficulty arise...

## Tin can modulation, OFDM, PAPR

inAs was kindly suggested to me, I've been experimenting with OFDM for my TCP/IP over tin cans project. Since the modulation on the "wire" is...

As was kindly suggested to me, I've been experimenting with OFDM for my TCP/IP over tin cans project. Since the modulation on the "wire" is at baseband, and I'm using a sound card as a DAC, this means my signals are audible. When modulating a random bitstream, the resulting audio is full of popping noises. I have taken steps to ensure that no clipping is occurring, so these pops are really...

## Single carrier with frequency domain equalization (SCFDE)

inI have seen some paper demonstrating the benefit of SCFDE over OFDM, basically low PAPR performance, comparable complexity, improved performance...

I have seen some paper demonstrating the benefit of SCFDE over OFDM, basically low PAPR performance, comparable complexity, improved performance especially when convolutional code rate is high. But why we see many standards still using OFDM, but not SCFDE?

## Frame sync for OFDM under multipath environment

inHi Would like to know how to do frame synchronization in OFDM systems. Seems like many folks like to correlate a copy of what is received with...

Hi Would like to know how to do frame synchronization in OFDM systems. Seems like many folks like to correlate a copy of what is received with a delayed copy of itself, but this method is not robust esp in the presence of multipath. What is the best way? Thanks all.

## wimax synchronization

Hi, I'm working on ofdm synchronization with wimax now. is there any reading or paper can give a full insight view? I found it's quite...

Hi, I'm working on ofdm synchronization with wimax now. is there any reading or paper can give a full insight view? I found it's quite different with cdma synchronization, so i wonder know the key point in solving the synchronization in ofdm and sampling related. Thanks very much. Laron B. R.

## OFDM - cyclic prefix ?

inHow in OFDM the size and type of a cyclic prefix gets out? What characteristics of a liaison channel and a signal influence a prefix?

How in OFDM the size and type of a cyclic prefix gets out? What characteristics of a liaison channel and a signal influence a prefix?

## OFDM

inSirs, I have some questions on OFDM method 1) what is meant by orthogonality in frequency domain. I understand orthogonality in time...

Sirs, I have some questions on OFDM method 1) what is meant by orthogonality in frequency domain. I understand orthogonality in time domain 2) what is the significance of keeping the inter carrier seperation equal to 1/symbol time Thanks, Manish

## circular convolution or matrix multiplication

inHi, I'm currently doing project on OFDM based. I want to transmit my signal through a Rayleigh channel. assume that the received signal should...

Hi, I'm currently doing project on OFDM based. I want to transmit my signal through a Rayleigh channel. assume that the received signal should be y(t)=x(t)*h(t)+n(t) or Y(f)=X(f)H(f)+N(f). I understand that in order to get y(t), we need to do a convolution between x(t) and h(t). let say, after IFFT in OFDM part, then I change the signal into serial where the data is in time domain. Now, I don...

## How can i verify how many samples have i skipped (OFDM QUESTION)

inhi all DSP giants and experts, i am struggling on one problem..lemme share with you people.. Thanks...

hi all DSP giants and experts, i am struggling on one problem..lemme share with you people.. Thanks in advance for all answers its like this i have OFDM Symbols say 256 ifft which has a cylic prefix of 32 say a system is taking fft at some sample offset..i need to know..at what sample offset from start. the FLOW is like this step1-===...

## CCDF Plot of OFDM PAPR

inHi! I am looking for some help on how to calculate or plot CCDF of OFDM PAPR. A malab code or necessary lines of codes would be highly...

Hi! I am looking for some help on how to calculate or plot CCDF of OFDM PAPR. A malab code or necessary lines of codes would be highly appreciated. Thanks in advance for your generous help.

## OFDM PSD

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.