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OFDM
Jun 4, 2004 2:32:10 GMT -5
Post by Pankaj on Jun 4, 2004 2:32:10 GMT -5
Actually I am working on Physical Layer Simulation of IEEE 802.16a Wireless MAN which uses OFDM in one of its methods.
One think which I still not able to understand is that first you told that we have many spikes in frequency domain of the different harmonics of OFDM carriers and afterwards you depicted them by different "Sinc" functions, HOW?
Pankaj
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OFDM
Jun 8, 2004 9:59:52 GMT -5
Post by charan langton on Jun 8, 2004 9:59:52 GMT -5
In Fig 13 of the OFDM tutorial, I show a time domain signal of the composite OFDM carrier. It has a lot of spikes because the many individual carriers can add up to a large amplitude instantenously. This is a time domain description.
In Figure 20, I show the frequency response. The frequency response of each of these OFDM carriers is exactly the same except for the center frequency. They have the sinc shape, since this is the frequency response of a square pulse multiplied by a sine wave, the process of modulation.
So there is no contradiction if you keep in mind that one is a time domain resonse (the peaky one) and the other the frequency response.
Charan Langton
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OFDM
Jun 30, 2004 0:08:19 GMT -5
Post by Pankaj on Jun 30, 2004 0:08:19 GMT -5
Sorry for late reply
First of all I was talking of spikes in fig 14b which are shown as sincs in fig 20
Also how come in digital domain you are talking about square pulse.
Please elaborate some more.
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OFDM
Jul 6, 2004 9:07:33 GMT -5
Post by charan langton on Jul 6, 2004 9:07:33 GMT -5
Hello Pankaj,
Sinc is a spectrum of a square pulse. It is a frequency domain description. The composite signal peaks occur in time domain. So althogh you can have a lot of well separated sinc functions in the frequency domain, they can add to create peaks in the time domain.
Charan Langton
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