ofdm | CrazyEngineers

ofdm
Member • Nov 21, 2008

ofdm

need a book related to orthogonal frequencu division multiplexing and peak to average power reductio ratio using convolution codes

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durga ch

Member • Nov 22, 2008

Hi OFDM,

Can you describe in brief what you are after?

Is it like you need detailed description of OFDM or you need to program to calculate peak to average power ratio of COFDM?

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sauravgoswami

Member • Nov 22, 2008

well,for wat u need that????hope its not for clearing your examination!!!

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ofdm

Member • Nov 23, 2008

i am doing a project . i need information regarding ofdm and peak to average power reduction ratio using convolution codes,and mat lab code for the same.

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durga ch

Member • Nov 24, 2008

hey buddy ..

let me see if I can help you out with the information you need !!
ok.

lemme give you a brief up of OFDM ( I am not sure how much you are familiar with it)

You can generate OFDM response either with normal system inplementation or signal implemetation.

In system analysis, you tend to mathematically derive the OFDM symbol charateristics and write a code for it.. This will not come more than say 40 llines..

where as in signal analysis model...you will be 'replicating ' the systems what you encounter while your OFDM signal is being trasmitted from your transmitter to reciever.

A OFDM system basically has a transmitter consisting of a encoder, modulator, IFFT . and reciever has a FTT,demodulation, decoder..

You need to be more clear on what information you are after 😀

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ofdm

Member • Nov 24, 2008

i have to work on system analysis ,have to write matlab code for ofdm and peak to average power mathematically and i have to show that tpeak to average power is reduced using convolution codes.
thank for helping me .

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durga ch

Member • Nov 24, 2008

hmmm...

So firslty ou should begin with the mathematical part of it..

once you derive the ouput symbols interms of input symbols , then its easy to assign values to input symbol and run your code to get the out.

you can do it in teo ways!
1.no encoding ie no convolutional coding and derive the t peak to average peak ratio.

2. use encoding and then derive the same ratio..

draw a comparison graph between both!

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Evelyn

Member • Feb 26, 2009

Hello..I'm Evelyn. I just join CE because I happen to see this group when I desperately searching for OFDM related project information hoping to solve my problem.

I'm doing my final year project on OFDM. I just get to build some models on reducing the Peak Average Power Ratio, PAPR.

I've built Uncoded OFDM, generator matrix model (encoder), lookup table model, and odd bit model. But those models do not works as desired. The result shown in the spectrum scope and vector scope display is weird.

I really hope whoever think they are able to help to share their valuable ideas on how to solve my problems.

Thanks..

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durga ch

Member • Mar 1, 2009

hey Evelyn,

I just saw the simulink simulation you did. I noticed that there is no cyclic prefix being added at Tx and then removed from Rx. Did you do this part?
Cyclic prefix formas a very important part of your simulation to over come ISI

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Evelyn

Member • Mar 1, 2009

Hi durga,

Thanks for checking my simulink model. Ya, didn't add in the cyclic prefix because I don't know how to build one. I cant see clearly the picture you embedded here. Can u send me the model of how to add in the cyclic model?
Thanks. 😀

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