How to investigate the OFDM symbol amplitude?

[jairusye]

Now I am using simulink to build the OFDM system, I have met a problem. In modulation when through the IFFT block, I got 256 point data which are all complex numbers, and I want to investigate the OFDM symbol amplitude, how shall I do next? Now I just accumulate the 256 point data, and calculate its absolute value, is it right?
Thank you for your help in advance.

 

[samuraign]

OFDM Help

if you want to test IFFT generate sine wave and check the o/p of IFFT(in time domain i.e IFFT output u will see impulses at the frequency of ur sine wave)

u can plot and check the result.

 

[firewood80]

Re: OFDM Help

Hi there,

I just want ask if somebody can help me explain what does modulation (QAM, BPSK) does in OFDM? If any, can you give something to refer to.

One more thing, i discover that different books have different arrangement of the process in OFDM, like the arragement of IFFT, Guard Insertion etc. Is it allowable?
does it has any effects?

 

[Naveed Alam]

Re: OFDM Help

Hi there,

I just want ask if somebody can help me explain what does modulation (QAM, BPSK) does in OFDM? If any, can you give something to refer to.

One more thing, i discover that different books have different arrangement of the process in OFDM, like the arragement of IFFT, Guard Insertion etc. Is it allowable?
does it has any effects?

when u use QAM or BPSK, ur resultant subcarriers (output of ifft block) differs. read some text for it.
ur 2nd question's answer is that because OFDM is used in different techniques, like DSL, WI-MAX and TV-Brodcasting so the arrangement will differ for different fields.

Naveed

Added after 16 minutes:

Now I am using simulink to build the OFDM system, I have met a problem. In modulation when through the IFFT block, I got 256 point data which are all complex numbers, and I want to investigate the OFDM symbol amplitude, how shall I do next? Now I just accumulate the 256 point data, and calculate its absolute value, is it right?
Thank you for your help in advance.

see, if
complex value = A+Bj
symbol amplitude= sqrt(sqr A + sqr B)

if you have done it then it is okay. if u have used any buil-in function which do the same, then it it is right.

Naveed

 

[mahankalisatish]

Re: OFDM Help

IN wimax a symbol is formed data carriers suppose if u have 128 point fft data carriers are 84 rest are guard carriers .