Constellation diagram16-QAM OFDM based FSO link

[Verla Hersom]

(Awaiting moderation)

[Verla Hersom]

(Awaiting moderation)

[Verla Hersom]

(Awaiting moderation)

[Verla Hersom]

(Awaiting moderation)

[Rajveer Bhagat]

Hi everyone.

I want to simulate OFDM based FSO link using M-QAM modulation. I replaced optical fiber in OFDM modulator project file with FSO component. When I ran the project for 4-QAM scheme, the constellation of the received signal was good. But when i tried simulating 16-QAM by changing bits/symbol to 4, the constellation diagram became distorted. Can anyone please suggest what can be done to correct this. I think it has something to do with electric constellation visualizer properties

Attachments:

1. OFDM-Modulator.zip

[Ahmad Atieh]

Hello Rajveer,
I went through your project, you could simulate 16-QAM and obtain a proper constellation. However, you need to set properly the following:
1. the global parameter symbol rate must be 2.5Gsymbol/s due to using 4bits/symbol
2. The OFDM Demodulator reference bit rate should be Bit rate/4
3. The phase of the Quadrature Demodulator should be set at 185 deg

The constellation should looks like the attached file.
I recommend you using new OFDM components instead of the OFDM OS12 version. It is more flexible and has more capabilities.
Regards,
Ahmad

Attachments:

1. 

   16-QAM_Feb-19-2019.png
   

[Rajveer Bhagat]

Thank you sir for your help.

[Vamsi mohan]

Hi Sir

After making all the modifications suggested by you,
why the BER shows 1 and max-Q-factor as 0 ?

please reply
regards
Vamsy

[Vamsi mohan]

Hi Sir

After making all the modifications suggested by you,
why the BER shows 1 and max-Q-factor as 0 ?

please reply
regards
Vamsy

[Ahmad Atieh]

Dear Vamsy,
you need to email me your project as Zip file and let me know the version of OptiSystem that you use. My email is ahmad.atieh@optiwave.com.
Also, let me know if you have valid maintenance and support license.
Regards,
Ahmad

[Ahmad Atieh]

Dear Vamsy,
you need to email me your project as Zip file and let me know the version of OptiSystem that you use. My email is ahmad.atieh@optiwave.com.
Also, let me know if you have valid maintenance and support license.
Regards,
Ahmad

[Vamsi mohan]

Hi sir

The project is already attached in the first thread of this post

regards
Vamsy

[Vamsi mohan]

Hi sir

The project is already attached in the first thread of this post

regards
Vamsy

[Author]

Posts