need help with my project

[feras]

hello everybody,
i am working on LTE-ROF project and i did the simulation using optisystem 13 , i want to transmit the ofdm pilot symbol on the fiber with the data signal using wdm multiplexer but my work dose not work , and how i can see the eye diagram clearly .
can anyone help me please , and i will be thankful for all

[Damian Marek]

You cannot transmit the pilot tones down the fiber length because they will become distorted and essentially useless as a reference for the receiver. The output of the pilot tones on the OFDM Modulation should be directly connected to the OFDM Demodulation. This models the fact that in a real system the receiver knows the pilot tones beforehand and can adjust the detected pilot tone signal with the known pilot tones.

[feras]

thank you,
but if i can’t use the fiber to transmit the pilot signal how can i transmit it in reality

[Damian Marek]

Sorry I just saw this now must have missed this earlier. Looking at my explanation I don’t think it was clear.

The pilot tones and training sequence are in fact transmitted along with the signal. The top port that you connect directly to the OFDM demodulator is what the demodulator compares the received pilot/training symbols to. In a REAL system the receiver is programmed to know what pilot tone/training symbols it expects and compares it to the detected signal which is a combination of the overhead and the actual information.

In the simulation, as I mentioned the pilot tones/training symbols make up part of the transmitted signal, and the port coming out the top is the undistorted pilot and training sequence tones the receiver compares the detected signal too. This is perhaps a bit confusing, but this port should not be interpreted as a real signal but rather just a visual way to show that this particular modulator and that particular receiver are agreeing on the same pilot tone and training symbols.

Regards

[Ravil]

Hi feras,

According to your last question, I agree with second explanation given by Damian. The pilot signal is transmitted during the connection session. At the same time, this signal is known at the receiver as well and used for future comparison. Therefore, Multiple Input Multiple Output (MIMO) is allowed in these systems. For further details, I can refer you to a recommendation of ITU-T. Please, take a look at the following ITU-T recommendation: G Suppl.RoF.

[feras]

thank you very much for the explain Damian Marek and ravil ,
now i catch the idea .

[Ravil]

You are welcome, feras! As a forum member I am glad to give you my advice and recommendations. Good luck with your project and your work!

[Author]

Posts