Bit rate in Layout and BER test set of OFDM in example

[–]

Hi everyone,
I am confused with the DDO-OFDM system available in the example of Optisystem 14. There are two separate bit rate in the system. The Layout has bit rate of 10e+009 while the BER test set has 5e+009. Now my confusion is which one is the transmission bit rate. If I am using the system, at what rate am I transmitting the bits?

[prakash jat]

good question , same think for me

[Aabid Baba]

Hello Gokul,
If i read your questions right then I guess it is the layout bit rate which you have mentioned to be 10e+009 Gbps which is the rate you are transmitting your bits. Set Layout bit rate is eventually the bit rate or transmission rate of your system. So i think it is 10 Gbps you are transmitting your data.
regards

[–]

Thank you Mr. Prakash Jat.
Thank you Aabid Baba. Yes you got my question right. If I agree that, since the layout has 10e+009 as the bit rate, the transmission rate rate is 10e+009 then what does that in BER Test Set mean?

[Aabid Baba]

Hi Gokul,
you are welcome.
BER calculation is done using the BER test set. It means the number of errors are counted and therefore the number of bits transmitted has to be large enough to obtain the BER value estimated.
Please follow the link for further referral regarding the BER test set. it would give you an idea what BER test set is all about.

BER Calculation Using the BER Test Set

Regards

[alistu]

Hi all,

The bit rate of the generated bit sequence is determined by the component that generates it, and the layout parameters can merely be used in such a component, for example in script mode. So the overall bit rate is the one determined in BER which both generates the bit sequence and calculates BER.

Regards

[aasif bashir dar]

hi all,
i think alistu has point

the link attached by aabid has two snapshots on it , one with the peudo random sequence gennerator, where we can used layout properties in sript mode such as bit rate,

but the pic with BER TEST set does not contain the peudo random sequence gennerator.
please explain your reply #30602 in detail, so that i could understand.

with regards

[alistu]

BER test set does two tasks: Calculating BER and generating pseudo random bit sequence. In order to do the second task, the bit rate must be defined in the component itself (as in PRBS generator component). So the bit rate determined in the component itself is the bit rate it uses to generate the bit sequence.

Nonetheless, for OFDM systems there is a box stating “using OFDM” which can be checked. If it is checked and all the corresponding OFDM characteristics are defined according to OFDM components, the the bit rate (which Gokul has asked about) is calculated in the following way:

overall bit rate = bit rate defined in BER Test Set * (Maximum possible subcarriers / number of subcarriers in port)

So in Gokul’s example, the bit rate is 10e9 using the above formula. We could have easily not used script mode to refer to laouy parameters bit rate, so it doesn’t necessarily have anything to do with the layout parameters bit rate.

Regards

[Aabid Baba]

Thank you alistu,
The explanation was very good but could you please tell me using below formula, how did you get 10e009 ???

overall bit rate = bit rate defined in BER Test Set * (Maximum possible subcarriers / number of subcarriers in port)

i am not able to calculate it.
regards

[alistu]

You are welcome. Please see the following formula, which is the same as the formula I have used in my above comment but with the corresponding numbers instead of the terms:

overall bit rate = 5e9 * (1024/512) = 10e9

I have to mention that all of the parameters used in the above formula are defined in the BER test set.

Regards

[–]

Thank you Alistu, as usual you gave good response. I had same perception that the bit rate is determined by the component that generates it. Hence,the bit rate shown in BER Test Set is the bit rate of the system.

Now, what does the bit rate in Layout mean? Why is it half of that in BER Test Set? Can anyone explain it.
Thanks in advance.

[alistu]

You’re quite welcome Gokul. Actually the bit rate in layout parameters is twice the value defined in BER test set for the bit rate. The value in BER test set has been set in this way so that when the above formula for the calculation of bit rate is used (when “using OFDM” is checked and the corresponding parameters are defined), the overall bit rate would become the same as the one defined in overall layout parameters.

To make it simple, if you are using OFDM and want to check the box, the bit rate in BER test set should be set as:

BER test set bit rate = desired bit rate (which is usually the same as the bit rate in layout parameters) * (number of subcarriers in port/Maximum possible subcarriers)

Regards

[Aabid Baba]

Okay fine.
Thank you very much Alistu. Such a good help.

[alistu]

You’re welcome.

Regards

[aasif bashir dar]

hi all,
alistu what a great explanation., i appreciate your efforts.

thanku very much

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