about ofdm and Orthogonal frequencies

[serimc]

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...

 

[Sal]

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

 

[mro83]

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.

 

[aelmh]

i think if you study wireless communication by molisch(chapter 19) you uderstand everything in OFDM.....

 

[aelems]

can someone help in writing matlab codes for OFDM

 

[thanhpv]

You can read the document

 

[aelmh]

what do you suggest as a good book in this subject?

 

[moustafahussein]

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:

 

[azaz104]

you need to understand what does orthogonal mean...
go to this site:

https://mathworld.wolfram.com/OrthogonalFunctions.html

 

[polag]

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.