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serimc
Joined: 07 Jan 2005
Posts: 18
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 30 Apr 2006 10:35 about ofdm and Orthogonal frequencies |
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Hi
I am looking for ofdm and try to understand but there are problems.
My questions:
How many signals can be Orthogonal to one signal?.I mean for example sin(x) is Orthogonal to cos(x).Are there any signals that orthoganal to these 2 signals.
In 2-d there can not be.(if wrong please correct it).
So can we say "A signal have only one Orthogonal signal".Is it true?
If so in ofdm modulation Can we say:
We can communicate only "2" peer in "one" frequency.So our gain is 2.
I am confused about ofdm and orthoganal signals.
I am looking for your answers.
Thanks.
Good works...
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Sal
Joined: 29 Nov 2005
Posts: 288
Helped: 36
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| 01 May 2006 6:34 about ofdm and Orthogonal frequencies |
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Hi
the concept of orthogonality is very simple, 2 signals are orthogonal if their crosscorrelation is zero and their autocorrelation is different from zero in the range there are defined.
Now about OFDM, it is even simpler, if you have 2 time (or frequency) limitted signals, they are orthogonal if they don7t overlap, The conditions in the previous paragraph can be verified very easily.
Cheers
Sal
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mro83
Joined: 06 Oct 2004
Posts: 227
Helped: 18
Location: Mashad
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| 01 May 2006 11:23 about ofdm and Orthogonal frequencies |
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as an example, sin(x) and cos(n.x) that are different in frequency, are orthogonal.
or, in Fourier Transform , any of exp(j*n*2*pi*f*t) 's are orthogonal so we can use the FT Theorem (u are rejecting FT Theory with ur sayings).
and asignal may have infinite orthogonal signals.
in OFDM, it is correct. In ONE freq. u have just 2 orthogonal signals but u use multiple signals with diferent frequencies.
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aelmh
Joined: 24 Mar 2006
Posts: 24
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| 01 May 2006 20:20 about ofdm and Orthogonal frequencies |
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| i think if you study wireless communication by molisch(chapter 19) you uderstand everything in OFDM.....
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aelems
Joined: 02 May 2006
Posts: 12
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| 02 May 2006 11:48 about ofdm and Orthogonal frequencies |
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| can someone help in writing matlab codes for OFDM
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thanhpv
Joined: 14 Jan 2006
Posts: 39
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| 03 May 2006 11:49 Re: about ofdm and Orthogonal frequencies |
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You can read the document
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aelmh
Joined: 24 Mar 2006
Posts: 24
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| 05 May 2006 9:52 about ofdm and Orthogonal frequencies |
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| what do you suggest as a good book in this subject?
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moustafahussein
Joined: 05 May 2006
Posts: 15
Helped: 1
Location: Alexandria, Egypt
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| 06 May 2006 23:20 Re: about ofdm and Orthogonal frequencies |
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About orthogonality, there is 2 concepts for it, the signal is said to be orthogonal in time and also said to be orthogonal in frequency.
But to do mulitcarrier transmission, you should chose only one of the previous.
What i recommend for OFDM is to read chapter 4 in this book: "Theory and Applications of OFDM and CDMA : Wideband Wireless Communications"
you can find its link over here: http://edaboard.com/viewtopic.php?t=159897&highlight=ofdm+cdma
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azaz104
Joined: 30 Aug 2005
Posts: 111
Helped: 7
Location: Jordan
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| 07 May 2006 21:53 Re: about ofdm and Orthogonal frequencies |
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you need to understand what does orthogonal mean...
go to this site:
http://mathworld.wolfram.com/OrthogonalFunctions.html
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polag
Joined: 13 Oct 2005
Posts: 32
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| 08 May 2006 10:50 Re: about ofdm and Orthogonal frequencies |
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hi.
I am a student, new to OFDM and supposed to be working on a project using OFDM. Please I need all there is to know about this technology.
Thanks.
Added after 15 minutes:
This material may be of help...
I just got it.
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