a mini question about the "sample sheme" of OFDM

Started by daor in comp.dsp14 years ago 6 replies

Hi all, I have a mini question and need yr help pls. It is simply about the understanding of sample scheme of OFDM. For convenience, the...

Hi all, I have a mini question and need yr help pls. It is simply about the understanding of sample scheme of OFDM. For convenience, the parameters of a OFDM system are presented as follows. .the sample period: T .FFT/IFFT point: N .the OFDM symbol period: N=B7T Then we obtain that, .the carrier spacing: 1/(N=B7T) .the frequency of the first "baseband" carrie...


OFDM Spectrum

Started by Shahin in comp.dsp14 years ago 2 replies

Hi, I'm trying to visualize the sub-carriers in my ofdm model. What I do is I generate a BPSK OFDM symbol and after IFFT I...

Hi, I'm trying to visualize the sub-carriers in my ofdm model. What I do is I generate a BPSK OFDM symbol and after IFFT I plot the FFT of transmitter output. I only get one Sinc graph not the overlapping sub-channels. Could you please correct me to get a proper view of sub-carriers? Best regards Shahin


OFDM

Started by kumic in comp.dsp13 years ago

Hi, i'm an undergraduate student doing some project on Stochastic Processes and i have a few questions on OFDM. There are few things that i...

Hi, i'm an undergraduate student doing some project on Stochastic Processes and i have a few questions on OFDM. There are few things that i don't quite understand and they are mainly in Digital Signal Processing domain (that is not my field of expertise). I'm writing code in MATLAB for transmitting data using sound and use OFDM modulation. Mathematically the transmitted multicarrier ...


LTE, FFT, OFDM

Started by Sharan123 in comp.dsp5 years ago 55 replies

Hello, In LTE specification, OFDM is implemented using FFT of sizes 128/256/512/1024/1536/2048. These correspond to Downlink bandwidth...

Hello, In LTE specification, OFDM is implemented using FFT of sizes 128/256/512/1024/1536/2048. These correspond to Downlink bandwidth of 1.4/3/5/10/15/20 MHz. I don't know how these N point FFT are selected for OFDM implementation. Let us take 1.4 MHz and 128 point FFT for example. 128 point FFT has N value of (2^N = 128) of 7. With a sub-carrier spacing of 15 KHz, this covers = 7*15 KH...


TDoA in OFDM

Started by ryujin_ssdt in comp.dsp13 years ago 5 replies

Does anyone know about or can refer to me any work/papers related to TDoA (Time Differential of Arrival) of OFDM signals?. I would like to...

Does anyone know about or can refer to me any work/papers related to TDoA (Time Differential of Arrival) of OFDM signals?. I would like to learn more about current and new algorithms for TDoA estimation that take advantage of the multi-carrier structure of OFDM. Thanks in advance...


Need help in understanding OFDM

Started by Rohith in comp.dsp13 years ago 1 reply

Hello Everyone, My name is Rohith and I recently started working on OFDM. I am trying to simulate 4 carrier OFDM system using QPSK...

Hello Everyone, My name is Rohith and I recently started working on OFDM. I am trying to simulate 4 carrier OFDM system using QPSK modulation. I am not sure if my current test model is correct or not. Could you please review this and let me know if I am doing anything wrong? Here is the link to my simulink model: http://rohithramnath.googlepages.com/home Thank you so much. Re...


OFDM-coherent

Started by Zeph80 in comp.dsp14 years ago

Im a little confused about how you employ coherent demod in OFDM. After the FFT at the receiver, how do I perform a coherent demodulation-dont I...

Im a little confused about how you employ coherent demod in OFDM. After the FFT at the receiver, how do I perform a coherent demodulation-dont I need a carrier for phase estimation in case of BPSK, QPSK etc. Also this is what coherent OFDM is, right?


AWGN channel in OFDM-System

Started by steffen in comp.dsp15 years ago 5 replies

Hallo everybody, I've just finished my OFDM-Simulation, but I'm still facing a little problem with the AWGN-function provided by Matlab. The...

Hallo everybody, I've just finished my OFDM-Simulation, but I'm still facing a little problem with the AWGN-function provided by Matlab. The transmitted OFDM-Signal s(k) consists of samples of the komplexe baseband signal. (As I've implemented a diskrete time OFDM-baseband-system). The channel should add white Gaussian noise n(k). An the resulting signal r(k) = s(k) + n(k) will than be process...


synchronization in OFDM and others...

Started by rifo in comp.dsp13 years ago 8 replies

Hello, I am wondering there is so much literature about carrier and timing recovery in communications*. However as far as I understand, OFDM...

Hello, I am wondering there is so much literature about carrier and timing recovery in communications*. However as far as I understand, OFDM uses a different approach in synchronization. My question is since OFDM is becoming more and more popular does this mean that these algorithms will cease to be used in future? * synchronization in software radios (chris dick, fred harris, michael ric...


Is low latency important in CFR of OFDM?

Started by fl in comp.dsp11 years ago 2 replies

Hi, all: I am interested in CFR of OFDM. I find some relavant paper mentioned low latency feature in the crest factor reduction (CFR) topic of...

Hi, all: I am interested in CFR of OFDM. I find some relavant paper mentioned low latency feature in the crest factor reduction (CFR) topic of OFDM. I don't understand the reason. It seems to me that several hundreds of microseconds delay is not a big issue. I don't know the specification of WiMax of the latency. Anyone can tell me that? I appreciate to any feedback on this. Thanks.


implementing rayleighchan in OFDM

Started by burky in comp.dsp13 years ago

Hi everbody, I am doing my M.SC thesis on the topic "ICI cancellation in OFDM". I have very limited time, if you can help me I will be...

Hi everbody, I am doing my M.SC thesis on the topic "ICI cancellation in OFDM". I have very limited time, if you can help me I will be grateful to you.... I can implement the OFDM structure in AWGN channel, it works very well.. But when i try to implement the system in a "rayleighchan", I obtain very bad BER results. -------------------------- N=3D256 ; % carriers GI=3DN/4;...


Simulation of symbol synchronization in a OFDM receiver

Started by Anonymous in comp.dsp14 years ago

Dear all I am doing a block for a OFDM receiver that receives as input the ofdm received signal and gives as output a rectangular signal...

Dear all I am doing a block for a OFDM receiver that receives as input the ofdm received signal and gives as output a rectangular signal (for synchronization) in which each pulse represents a peak in the autocorrelation function realised over the ofdm received signal. How can i define a threshold to detect this peak of the correlation function? Is there another way to do this? I will use di...


Can LDPC and Bit-loaded OFDM be combined efficiently?

Started by Anonymous in comp.dsp12 years ago 5 replies

Hi guys I have a question about the use of LDPC codes and different bit- loadings which naturally occur as part of a large number of...

Hi guys I have a question about the use of LDPC codes and different bit- loadings which naturally occur as part of a large number of OFDM systems (802.16e, for example). I have seem a few methods in the literature for using LDPC with multi-level (e.g. BICM, MLC, etc.) but none of them seem to tackle the problem I'm interested in. Specifically, consider two of the sub-carriers in an OFDM ...


OFDM Transmit diversity

Started by Shahin in comp.dsp13 years ago 3 replies

Hello, Assume you have 2 OFDM transmitters that are simultanously transmitting different data and the data is somehow coded (ie...

Hello, Assume you have 2 OFDM transmitters that are simultanously transmitting different data and the data is somehow coded (ie CDMA). After IFFT the ofdm symbol of each transmitter , X1 and X2, passes a freq. selective fading channel: Y = X1.G1 + X2.G2 + N My question is at the receiver, before or after the FFT, how to remove the effect G1 and G2 which are the fading coeffici...


OFDM in SystemC

Started by Rezwan in comp.dsp14 years ago

Does anyone has experience of using SystemC for OFDM based design. Please share your experience. I'm new in SystemC so not sure how to start. If...

Does anyone has experience of using SystemC for OFDM based design. Please share your experience. I'm new in SystemC so not sure how to start. If you know any good books/websites for OFDM in C/C++ please post here. kind regards, Rezwan


OFDM Simulink problem, SOS!

Started by Ant_Magma in comp.dsp15 years ago 13 replies

I'm simulating an OFDM transceiver to be later converted and implemented on a C6713 DSK. I'm currently facing a problem with the simulation and...

I'm simulating an OFDM transceiver to be later converted and implemented on a C6713 DSK. I'm currently facing a problem with the simulation and i'm at my wits end trying to figure out what is wrong. Thus i'm really hoping you guys can lend me some help otherwise i can't proceed anymore... Here are 2 pictures of my OFDM simlation in Simulink. Pic1 is the model with the convolutional enco...


FFT in OFDM

Started by srikoll in comp.dsp17 years ago 3 replies

hi all, I have a question regarding FFT in OFDM. why do we use FFT in OFDM systems? thanx.

hi all, I have a question regarding FFT in OFDM. why do we use FFT in OFDM systems? thanx.


OFDM symbol

Started by harishm in comp.dsp6 years ago 1 reply

Hi, I have a question on IFFT input in OFDM systems. Why center tone is always set to ZERO for IFFT input ? is it one method to reduce...

Hi, I have a question on IFFT input in OFDM systems. Why center tone is always set to ZERO for IFFT input ? is it one method to reduce PAPR in OFDM systems ? _____________________________ Posted through www.DSPRelated.com


BER in OFDM

Started by Kumar Appaiah in comp.dsp13 years ago 2 replies

Dear comp.dsp, Though I did try looking at the previous posts related to this, my question has not been answered. So, here goes: I have a...

Dear comp.dsp, Though I did try looking at the previous posts related to this, my question has not been answered. So, here goes: I have a simple OFDM+QPSK code wherein I use one symbol to estimate the channel and do the zero forcing (multiply by reciprocal of channel FFT) to get derotated QPSK symbols. Note that the data is uncoded and not interleaved. 1. BER for QPSK+OFDM in an AWGN ...


BPSK + OFDM over a very wideband channel

Started by lsw00kor in comp.dsp15 years ago 1 reply

Hello, everyone. I would like to discuss OFDM's robustnesss againt freq-selective channel. 1) I'm using BPSK( for some reasons, even though...

Hello, everyone. I would like to discuss OFDM's robustnesss againt freq-selective channel. 1) I'm using BPSK( for some reasons, even though mostly we use QPSK, or QAM..) on a very very wide channel. 2) I didn't employ a channel equalizer at the frontend before fft. 3) I, as a reference, followed Richard Van Nee's 'OFDM for wireless multimedia communications' to set the parameters: [1] wor...