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why BER is increasing with increasing SNR values?

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Usiddique

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Hi,

I have implemented very basic OFDM system to calculate BER. But BER is increasing as SNR increases.

Anyone can highlight the reason please??
 

Hi,

When SNR increase, the noise power level decrease. So, the BER must decrease also.

For ofdm modulation, every subcarrier is a separate transmitter with modulation corresponding to the mapping choice.

For example, if you are using BPSK mapping, you must get BER function equal to 1/2*erfc(sqrt(Eb/No)).

If you have problem with code, you can post it and i see if i can help you.

Regards,

Chaker
 
Hi Chaker,

Thank you very much. I am trying to debug the code if i couldnot I do post..


Regards,
usman
 

Hi,

I 'm working on a DVB -T chain .the BER decreases as SNR inceases until a specific value of SNR(17-18db) onwards this limit the BER increases as SNR increases.
Anyone can explain this please??
 

Hi Mejda,

Are you using matlab to simulate ?

It could be :
- a limited number of transmitted bits.
- your system is not stable.

Regards,

Chaker
 

Hi,
I m working with cocentric studio system and i simulate with matlab.In fact i have increased the number of simulated bits(from 1e7 to 1e8) to see this result!
sorry what do you mean by a non stable system?
 

Hi,

- With SNR between 17 and 18 dB and the DVB-T communication system contain a convolutionnal code and Reed solomon code to correct errors, you are supposed to get no error with only 1e7 to 1e8 transmitted bits.
- non stable system, that is mean not correct. Try to simulate without noise and check if your system decode with 0 error.
 

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