OFDM 4 QAM to OFDM 16 AQM

[zapata henao]

(Awaiting moderation)

[zapata henao]

(Awaiting moderation)

[nadzreen]

Hi,

I try to get constellation diagram for 16 QAM using OFDM 4 QAM example. (OptiSystem 14.2 Samples\Advanced modulation systems\OFDM systems\Direct Detection OFDM 4 QAM)
By using this example, I change the bit/symbol from 2 to 4 to get 16QAM.
But constellation diagram at OFDM demodulator is not correct.
Can some help to explain why cannot get correct 16 QAM constellation diagram?
And how to get the correct 16 QAM using this example? attached is the result for 4 bit/sym.

thanks

Attachments:

1. 

   4bitpersymbol.png
   

[Fauza Khair]

Hi Nadzreen, can you attach the your optisystem project file.osd ?

if you run the OFDM system with QAM modulation, you must configure the symbol rate and reference bit rate, not only on the QAM Modulator, but also on OFDM Modulator. After that, When you used the BER TEST set, there are many parameter sets that must changed.

[Fauza Khair]

I think, you must try this project.

I Hope this project can give you the solution. But this project not give us the BER Value.

On this project, we must change the configuration of the phase value on the Quadrature Demodulator for the variation of optical launch power (CW Laser) and optical fiber length so that we can the good constellation.

[Fauza Khair]

I’m sorry, I don’t know why i cannot attcah the .osd file in this reply.

would you like to give me the your email address ?

[nadzreen]

hi fauza,

go to below link to download my .osd file.
https://www.dropbox.com/s/q97blyhcu91488s/Direct%20Detection%20OFDM%204%20QAM-1.osd?dl=0

thanks.

[Fauza Khair]

Hi Nadzreen, please try this scheme if you want to know about the characteristic of direct detection mechanism.

Based on this simulation, you can find that The direct detection mechanism is not appropiate for high modulation e.g 16-QAM. The constellation is not good and have the High BER. You also using the high power for CW Laser, and you cand find the effect of the phase set and quadrature demodulator.

Attachments:

1. 

   BER-TEST-SET.png
   

2. 

   constellation.png
   

3. 

   picture.png
   

[nadzreen]

hi Fauza,

can you share the DD-OOFDM 16 QAM file via dropbox?

thanks

[Fauza Khair]

HI Nadzreen,
Could I have your email address, please ?

[hela Snoussi]

HI Fauza
I didn’t understand how to change the phase value of QM. could I have a scheme of DD OFDM 16 QAM please.
Regards

[Author]

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