BER Test set and PRBS for OFDM

[–]

Hi all,
I was trying to know whether PRBS Generator and BER Test set works for OFDM systems. But when I tried to simulate the system using the PRBS generator relacing the BER Test set the system showed different results. Is it due to PRBS Generator’s inability to take into account the Training symbols inclusion in the system? Does it show different result from that of BER analyzer.

[alistu]

Hi Gokul,

If the results you are referring to are the ones shown by BER analyzer after you used PRBS generator, then the reason for the change in the results is that BER analyzer cannot take pilot and training symbols into account when calculating BER. In this case, there should not be any remarkable change in constellation diagram at the receiver.

Regards

[–]

Thank you alistu. So, what I can conclude is that I can’t use PRBS in OFDM system design when I use training or pilot symbols. Am I right alistu?

[alistu]

You’re welcome Gokul. You are right. As I mentioned previously, the BER analyzer does not take the training symbols and such factors into account and consequently, the results calculated by it cannot be very accurate. Otherwise, this has nothing to do with PRBS generator component itself. So I believe it would be more accurate to say that BER analyzer should not be used in such systems and BER test set should be used instead.

Regards

[Fady]

Hi Gokul, You should use the BER Test set for OFDM systems.

[–]

Thank you Fady for the information.

[Fady]

You are welcome!

[Ranjeet Kumar]

Hi Alistu sir,
I request you to explain that if i use OS12 (ofdm) modulator that is not having pilot and training symbols and OFDM modulator with pilot and training symbols, is it any difference between the results of both . if yes then how and why ,please explain it in details.
Here i have designed 4 user OFDM system with OS12 modulator , please would you upload osd file of corresponding file with OFDM modulator with pilot and training symbols or even suggest some steps so that i could get proper results(qfactor and BER).

[alistu]

Hi Ranjeet,

I remember Damian mentioning about using BER test set instead of BER analyzer on several occasions, once explaining the reason to be traning symbols, so I am not sure if BER analyzer can be used in the case you have mentioned. I’d use both to find out, though.

In order to use pilot symbols, you need to use OptiSystem 13 OFDM components. OS12 OFDM components do not have such capability. You can refer to the available OFDM examples in OptiSystem 13 samples where pilot and training signaling is used.

Regards

[Ranjeet Kumar]

Thank you Alistu sir,
I have both the design comprising OS12 and OFDM mod. of optisystem 13 or 14 version.
Would you please suggest me how could i connect OFDM mod. to corresponding OFDM demod. In case of Multi-user design .. either we should connect ofdm mod. to ofdm demod. one by one in case of pilot and training ports i.e using 4 pair of OFDM mod. demod. pair for 4 user of using 4 port OFDM mod. but in this case we have problem of connecting pilot and training port because in transmitter section we have one 4 ports OFDm mod. but in receiver end we four 1 port OFDM demod. ..
seeking for response.

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